Is an in-line six better than a V-6?
WÇY
engines. However, most posts state that an in-line 6 is a better
solution.
Why should a 6 in-line be a better option? It seems to me that a V-6
would mean a more compact engine, a shorter crankshaft , two heads and
-possibly- two camshafts. An V-6 should not be necessarily cheaper
unless a longer crankshaft would be much more expensive.
Feedback, please
WÇY
Robert Hancock
first and second-order vibrations. A 60-degree V6 has a second-order
imbalance, and a 90-degree V6 has both a first and second-order imbalance
(unless it uses a balance shaft system). Therefore an inline-6 will be
inclined to produce less engine vibration.
--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hanc...@nospamshaw.ca
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"WÇY" <WÇY...@czerny.labs> wrote in message
news:1i774v8rpnochanfv...@4ax.com...
bka...@snotmail.com
<WÇY...@czerny.labs> wrote:
A V-6 is great until you have to work on them! Hours to change spark plugs
instead of minutes.
--
To Email me, change snot to hot
KenG
KenG
Brent P
> Why should a 6 in-line be a better option? It seems to me that a V-6
> would mean a more compact engine, a shorter crankshaft , two heads and
> -possibly- two camshafts. An V-6 should not be necessarily cheaper
> unless a longer crankshaft would be much more expensive.
I6 has better balance (cept for a V12) and is naturally smooth. It also is a
great configuration for generating torque. Note that heavy duty diesel
engines are generally I6 configuration.
Dave Baker
>From: tetraet...@yahoo.com (Brent P)
>Date: 08/02/03 01:04 GMT Standard Time
>Message-id: <nIY0a.24475$iG3.3394@sccrnsc02>
Let's say we take two engines of identical capacity. A straight 6 and a V6.
Same bore, stroke, valve sizes and port shape, cam profile, induction and
exhaust systems. Why would the straight 6 produce any more power or torque than
the V6?
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
You're a big man but you're in bad shape. With me it's a full time job. Now
behave yourself. (Michael Caine in Get Carter)
Brent P
>>I6 has better balance (cept for a V12) and is naturally smooth. It also is a
>>great configuration for generating torque. Note that heavy duty diesel
>>engines are generally I6 configuration.
> Let's say we take two engines of identical capacity. A straight 6 and a V6.
> Same bore, stroke, valve sizes and port shape, cam profile, induction and
> exhaust systems. Why would the straight 6 produce any more power or torque than
> the V6?
Rather than rehash this over... see:
WÇY
wrote:
This was very helpful. Thanks for the answers and for the link.
WÇY
Huw
"KenG" <Ke...@ec.rr.com> wrote in message
news:3E445332...@ec.rr.com...
> Additionally in-line sixes normally have more main bearings
> KenG
That's because they have a long crank which would be prone to flex
without additional support.
Huw
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Huw
"Robert Hancock" <hanc...@nospamshaw.ca> wrote in message
news:iyX0a.208447$Yo4.8...@news1.calgary.shaw.ca...
> One advantage of an inline-6 is that they are inherently balanced
for both
> first and second-order vibrations. A 60-degree V6 has a second-order
> imbalance, and a 90-degree V6 has both a first and second-order
imbalance
> (unless it uses a balance shaft system). Therefore an inline-6 will
be
> inclined to produce less engine vibration.
>
True to an extent, although V6's can have offset journals to regain
balance. Inline 6 is also prone to vibration and most have a torsional
damper or harmonic balancer, often built into the crank belt pulley.
These are sometimes prone to failure, a symptom of which is throwing
fan belts and ultimately a sheared crank.
Huw
"Brent P" <tetraet...@yahoo.com> wrote in message
news:nIY0a.24475$iG3.3394@sccrnsc02...
Six cylinder engines are generally less torquey than a [same design]
four. Look at any low end heavy straight six and compare it with a
high end four of equal power from the same manufacturer and nine times
out of ten you will find that the four will have significantly higher
specific maximum torque and probably a higher torque rise plus the
likelihood of a greater range of 'constant power' or power bulge.
C. E. White
The amount of miss information in that thread was astounding. I am not
an expert on engines but I do think in general the following points are
true -
Inline 6
- For
- inherently balanced, leads to smoother operation
- uncomplicated block and head castings allows well formed water
jackets
- intake and exhaust tracts can be designed for optimum flow (more
important with FI)
- exhaust headers can easily be designed for optimum flow
- crankshaft load is spread out over 7 bearings which allows smaller
diameter bearings (less friction per bearing)
- easy to achieve good rod ratio
- against
- long and heavy for a given displacement
- long crankshaft is susceptible to torsional and longitudinal
vibration problems
V-6
- For
- compact package
- short rigid block
- short rigid crankshaft
- lighter for a given displacement
- against
- not inherently balanced (particularly 90 degree deigns)
- achieving evenly spaced firing requires complicated crank
(particularly 90 degree design)
- higher loads on bearings
- restricted room for intake runners (particularly 60 degree designs)
It is my belief that for relatively slow revving engines, an inline six
is a great design. However it is difficult to package in automobiles.
V-6s are better for high revving situations. They also have packaging
advantages - particularly for front wheel drive cars.
Regards,
Ed White
Brent P
> balance. Inline 6 is also prone to vibration and most have a torsional
I6's are naturally balanced in 1st,2nd,and except for a negilable fequency
in the 3rd order.
Brent P
> four.
Wrong. See the thread I referenced with the URL to google.
> Look at any low end heavy straight six and compare it with a
> high end four of equal power from the same manufacturer and nine times
> out of ten you will find that the four will have significantly higher
> specific maximum torque and probably a higher torque rise plus the
> likelihood of a greater range of 'constant power' or power bulge.
Wrong again. I6s get up to peak torque early and stay there. This
is why the configuration is the choice for heavy duty engines. the
catapiller web site will show this.
For your comparison, Even the 250cid I6 in my '73 crippled with a 1bbl
carb and single exhaust still has 200lb-ft of torque that comes on at
1600rpm. I find 4 cylinder cars to be torqueless by comparision. (even
those that have it, it doesn't come on until higher in the rpm band)
Dave Baker
>Message-id: <gg11a.31927$vm2.15419@rwcrnsc54>
Primarily misinformation as with most usenet threads. The answer is that power
and torque depend on air processing ability and if the engines are identical in
that respect as well as rod/stroke ratio etc then there is no inherent reason
why one would produce a different power curve to the other.
The amount of energy that gets lost due to primary and secondary balance
vibration is neglible. A 1hp motor driving a hammer via a cam mechanism would
produce more than an auto engine does. As vibration eventually turns into heat
you'd end up with melted engine mounts if the magnitude of these losses was in
any way material.
The major real world issue with V engines versus inline ones is the firing
interval which affects the interaction of exhaust and inlet gas dynamics
between cylinders i.e pulse tuning. Obviously the firing interval is dependent
on the V angle but can be further modified by any offset of the crank pins.
Provided the exhaust and inlet lengths, diameters and inter cylinder couplings
are designed with the firing interval in mind then these effects can also be
compensated for to a large extent.
It finally boils down to packaging. Truck engines are traditionally inline
because those are easier and cheaper to make and length and mass are not a
major issue. Auto engines have tighter packaging contraints. Inline 6's are
used in RWD configurations but not in FWD simply because of length issues. V
engines are used in racing e.g. F1 because the number of cylinders per litre
required for optimum performance exclude inline ones.
To say that one design is inherently more "torquey" or "powerful" than another
is to ignore the fact that the air processing ability of a cylinder is not
dependent on its position in 3 dimensional space.
Steve
Advantages of an I-6:
-Perfect "natural" balance
-Can have 7 main bearings each conrod bearing carried between two mains
-Easy service in most RWD engine layouts (and FWD if care is taken to
put frequently serviced items on one side of the engine.
Disadvantages of an I-6:
-overall length, harder to fit in FWD layout
Advantages of a v6:
- Compact length, ideal for FWD
- can be made based on existing v8 engines
Disadvantages of a v6:
- Harder to service in FWD layout (at least 3 plugs are going to be on
the "back" side.
- Best balance (for 60 degree engines) only occurs when crank pins are
splayed, weakening crank
- The ONLY way to balance a 90-degree v6 (the kind that can share parts
with a v8) is to use splayed crank pins, weakening the crank
- 4 main bearings
- No matter what you do, never as perfectly balanced as an I6
In summary, all of the I6's advantages are related to performance, all
of a v6's advantages are related to packaging.
Steve
>
> Let's say we take two engines of identical capacity. A straight 6 and a V6.
> Same bore, stroke, valve sizes and port shape, cam profile, induction and
> exhaust systems. Why would the straight 6 produce any more power or torque than
> the V6?
Well, given that you CANNOT have identical induction and exhaust
systems, its a silly question :)
But assuming you magically could do so, then power output would indeed
be identical, but the I6 would have better balance. If you add balance
shafts to the v6, then its net power output would be less than the I6
because of added parasitic losses.
SoCalMike
> In article <3e452...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>
> > Six cylinder engines are generally less torquey than a [same design]
> > four.
>
> Wrong. See the thread I referenced with the URL to google.
>
> > Look at any low end heavy straight six and compare it with a
> > high end four of equal power from the same manufacturer and nine times
> > out of ten you will find that the four will have significantly higher
> > specific maximum torque and probably a higher torque rise plus the
> > likelihood of a greater range of 'constant power' or power bulge.
>
> Wrong again. I6s get up to peak torque early and stay there. This
> is why the configuration is the choice for heavy duty engines. the
> catapiller web site will show this.
cummins too, right?
>
> For your comparison, Even the 250cid I6 in my '73 crippled with a 1bbl
> carb and single exhaust still has 200lb-ft of torque that comes on at
> 1600rpm. I find 4 cylinder cars to be torqueless by comparision. (even
> those that have it, it doesn't come on until higher in the rpm band)
my '75 MG was quite torquey. doesnt the bore vs stroke ratio have something
to do with this?
JazzMan
>
> In article <3e452...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>
> > Six cylinder engines are generally less torquey than a [same design]
> > four.
>
> Wrong. See the thread I referenced with the URL to google.
>
> > Look at any low end heavy straight six and compare it with a
> > high end four of equal power from the same manufacturer and nine times
> > out of ten you will find that the four will have significantly higher
> > specific maximum torque and probably a higher torque rise plus the
> > likelihood of a greater range of 'constant power' or power bulge.
>
> Wrong again. I6s get up to peak torque early and stay there. This
> is why the configuration is the choice for heavy duty engines. the
> catapiller web site will show this.
>
I would have thought that torque is a function of cylinder pressure,
piston area, and crank rod journal radius from crank centerline
(there's got to be a simpler way to describe the crank radius?).
Looking at the geometry, it would also seem that a longer connecting
rod would have an effect as well. Then, the more cylinders that the
piston area is divided into, the greater the average torque, all
other variables being the same. Comparing the torque of an L6 and a
V6 and saying that the cylinder configuration is the only determinant
is irrelevant. There are so many other variables that need to be
considered. Seems to me that a long-stroke 12 cylinder 5 litre motor
would have way more torque than a short stroke oversquare-bored
6 cylinder 5 litre motor, assuming cam timing, CR, combustion chamber
design, etc. were all equivalent.
JazzMan
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Steve
> True to an extent, although V6's can have offset journals to regain
> balance. Inline 6 is also prone to vibration
Actually its not. As another poster pointed out, an I6 lacks either
first or second-order harmonic imbalance. A v6 AT BEST has second-order
imbalance (60-degree engine w/ splayed crankpins) and AT WORST has
primary imbalance (v6 with out splayed crankpins). And the mere presence
of splayed crankpins noticeably weakens any crankshaft design so that
you have to add weight to get the strength back.
>and most have a torsional
> damper or harmonic balancer, often built into the crank belt pulley.
So does every v6 thats worth a plug nickel. So does every ENGINE thats
worth a plug nickel, frankly. Quite a few very small I4s are out there
running around without torsional balancers, but they're all low-end
junkers, in my opinion.
Steve
> Six cylinder engines are generally less torquey than a [same design]
> four.
Bullfeathers. Where do people come up with this garbage? The I6, V12
(basically a pair of I6s), flat 12 (another pair of I6s), I8, and v8 are
all better basic designs (for various reasons unrelated to packaging)
than the V6 or I4.
Huw
Funny that most do need that balancer then. When it fails, the
operator cannot generally feel the vibes but they are bad enough to
turn or throw fan belts in a very short time. Hardly 'negligible or
most makers wouldn't bother with the balancer.
Huw
"Dave Baker" <pumar...@aol.comma> wrote >
> To say that one design is inherently more "torquey" or "powerful"
than another
> is to ignore the fact that the air processing ability of a cylinder
is not
> dependent on its position in 3 dimensional space.
>
In general I agree with you and Mr White, so you must be correct LOL.
Huw
> In article <3e452...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>
> > Six cylinder engines are generally less torquey than a [same
design]
> > four.
>
> Wrong. See the thread I referenced with the URL to google.
The thread does not demonstrate this to satisfaction. The reason that
the four in my generalised example outperforms the torque output of a
six is that it is generally turbo and intercooled while the equivelent
power six of the same design and cylinder dimension [the same engine
family] is either naturally aspirated or mildly turbocharged only. It
is a question of the ability to burn efficiently and process the air
and fuel.
>
> > Look at any low end heavy straight six and compare it with a
> > high end four of equal power from the same manufacturer and nine
times
> > out of ten you will find that the four will have significantly
higher
> > specific maximum torque and probably a higher torque rise plus the
> > likelihood of a greater range of 'constant power' or power bulge.
>
> Wrong again. I6s get up to peak torque early and stay there. This
> is why the configuration is the choice for heavy duty engines. the
> catapiller web site will show this.
The Cat web site will confirm what I said. The only engines that give
a relevant comparison are the Perkins/Cat 1000 series in their
extensive range. For medium and heavy diesels you are reading the
torque curve from the wrong side of the chart. Torque rise is measured
from rated engine speed down to specific maximum torque and expressed
in percentage terms. Modern Cat engines, especially the engines above
10 litres are renouned for massive torque rise [but there is no
comparison to an equivalent four cylinder unless you have found one].
This means that, reading from the left, as you appear to favour, the
torque drops off rapidly with rising revs. What this means, of course,
is that maximum power at rated speed actually increases as revs drop
and only drops back below that of the rated speed after an engine
revolution drop of up to 30% of its whole operating range. They
actually produce engines which produce the same power at 1400erpm as
at 2100erpm with a torque rise, within that range, in excess of 50%.
>
> For your comparison, Even the 250cid I6 in my '73 crippled with a
1bbl
> carb and single exhaust still has 200lb-ft of torque that comes on
at
> 1600rpm. I find 4 cylinder cars to be torqueless by comparision.
(even
> those that have it, it doesn't come on until higher in the rpm band)
But here you are not comparing like with anything like.
Duncan Wood
thats the desired characterestic for most CAT applications. You lose quite a
lot of peak power though.
Brent P
> "Brent P" <tetraet...@yahoo.com> wrote in message
>> I6's are naturally balanced in 1st,2nd,and except for a negilable fequency
>> in the 3rd order.
> Funny that most do need that balancer then. When it fails, the
> operator cannot generally feel the vibes but they are bad enough to
> turn or throw fan belts in a very short time. Hardly 'negligible or
> most makers wouldn't bother with the balancer.
The harmonic balancer on the front of my I6 is negligible.
But since you are going to press the issue and won't look at the cite
Here it is:
From "The Design and Tuning of Competition Engines"
By Philip H. Smith, 5th ed, 1971.
Page 137 (Chapter 5, Crankshaft Design and Engine
Balance) Under the heading "Six-cylinder engines"
"The conventional six-in-line is similar to the
corresponding four, in that it comprises two
threes in looking-glass formation with the cranks
1-6,2-5,and 3-4 in the same phasing, at 120 deg.
angles between pairs. It is thus possible, as
in the four, to distribute the firing intervals
acceptably along the shaft; with the usual order
of 1-5-3-6-2-4, this means that alternate
cylinders fire from the centre pair of cylinders 3 and
4 to the outers, in turn, at each 120 deg of crankshaft
rotation"
<...>
"It will be evident that the primary forces are fully
balanced in this type. As two pistons come to rest
at each one-sixth of a revolution, the primary force
has a frequency of three times the rev/min, while the
secondaries have twice this frequency. The latter
are also balanced, as will be ascertained from a
study of piston accelerations, except for a minor
unbalanced third-order frequency which can be
disregarded."
Brent P
>> For your comparison, Even the 250cid I6 in my '73 crippled with a 1bbl
>> carb and single exhaust still has 200lb-ft of torque that comes on at
>> 1600rpm. I find 4 cylinder cars to be torqueless by comparision. (even
>> those that have it, it doesn't come on until higher in the rpm band)
> my '75 MG was quite torquey. doesnt the bore vs stroke ratio have something
> to do with this?
If I recall correctly it does.
Brent P
> rod would have an effect as well. Then, the more cylinders that the
> piston area is divided into, the greater the average torque, all
> other variables being the same. Comparing the torque of an L6 and a
> V6 and saying that the cylinder configuration is the only determinant
> is irrelevant.
No said it was.
Huw
"Steve" <n...@spam.thanks> wrote in message
news:3E454ED5...@spam.thanks...
> Huw wrote:
>
> > Six cylinder engines are generally less torquey than a [same
design]
> > four.
>
> Bullfeathers. Where do people come up with this garbage?
Reading actual engine spec sheets, both manufacturers and OECD test
reports, and from extensive testing of medium/heavy engines on
dynamometers to map power and torque curves and match them to official
tests actually.
Huw
"Duncan Wood" <free...@dmx512.co.uk> wrote in message
news:b23m8l$mm5$1$8300...@news.demon.co.uk...
Brent P brought up the Caterpillar association. He had obviously not
read the spectrum of spec sheets at all thoroughly. Or at least not
comprehended what he had read.
The reason that this high torque rise engine characteristic is now so
popular is because of the constant power. Consider a crawler hauling a
ripper through a clay pit at rated speed and near full power. It
suddenly hits a very compacted area that demands much more power to
haul through. In a conventional engine with little constant power
range and a moderate torque rise of,say, 20%, then as the vehicle hits
this hard patch, the engine power [and forward speed] decreases and so
does the power to pull through.
Now consider the Cat with constant power with almost the same power at
1200erpm as at 2100erpm. As the crawler hits the hard patch the engine
revs fall against the rising torque, but as the engine revs [and
therefore the forward speed] drops to just over half of the original,
the power requirement to pull through also drops to near half BUT the
engine power available does NOT drop, rather it remains constant. The
result is that such engines do not drop revs to that extent and hold
revs at a higher level thus increasing productivity and reducing wear
and tear and gearchanges. In practice these engines are almost
impossible to stall and the advantages apply equally to haulage and
other applications.
The disadvantage is that while specific fuel consumption is low, the
actual fuel consumption can be quite high due to there being
relatively little advantage [other than some efficiency gain] to be
had from throttling back and using lower revs.
Brent P
> The thread does not demonstrate this to satisfaction. The reason that
> the four in my generalised example outperforms the torque output of a
> six is that it is generally turbo and intercooled while the equivelent
> power six of the same design and cylinder dimension [the same engine
> family] is either naturally aspirated or mildly turbocharged only. It
> is a question of the ability to burn efficiently and process the air
> and fuel.
If one engine is turbo charged and the other isn't, then the comparison
isn't even. It's like saying a 1975 V8 with single exhaust, air pump,
primative catalyst, and 2bbl carb is worse than a modern 4 cylinder turbo
with all the bells and whistles means V8 suck... that's what you are
doing here.
>> Wrong again. I6s get up to peak torque early and stay there. This
>> is why the configuration is the choice for heavy duty engines. the
>> catapiller web site will show this.
> The Cat web site will confirm what I said. The only engines that give
> a relevant comparison are the Perkins/Cat 1000 series in their
> extensive range. For medium and heavy diesels you are reading the
> torque curve from the wrong side of the chart. Torque rise is measured
> from rated engine speed down to specific maximum torque and expressed
> in percentage terms. Modern Cat engines, especially the engines above
> 10 litres are renouned for massive torque rise [but there is no
> comparison to an equivalent four cylinder unless you have found one].
> This means that, reading from the left, as you appear to favour, the
> torque drops off rapidly with rising revs. What this means, of course,
> is that maximum power at rated speed actually increases as revs drop
> and only drops back below that of the rated speed after an engine
> revolution drop of up to 30% of its whole operating range. They
> actually produce engines which produce the same power at 1400erpm as
> at 2100erpm with a torque rise, within that range, in excess of 50%.
In other words, figures don't lie but liars figure. You are playing
around with the numbers to create a different impression. any IC
engine will show some drop off in torque once beyond the peak, that's
why it's the peak. But notice the flat, almost horizontal line
at the peak, that's what I was describing.
>> For your comparison, Even the 250cid I6 in my '73 crippled with a 1bbl
>> carb and single exhaust still has 200lb-ft of torque that comes on at
>> 1600rpm. I find 4 cylinder cars to be torqueless by comparision.
>> (even those that have it, it doesn't come on until higher in the rpm band)
> But here you are not comparing like with anything like.
And your turbo 4 comparo is ?
Brent P
> Primarily misinformation as with most usenet threads. The answer is that power
> and torque depend on air processing ability and if the engines are identical in
> that respect as well as rod/stroke ratio etc then there is no inherent reason
> why one would produce a different power curve to the other.
Then BMW is using I6s for what? Marketing purposes?
Dave Baker
>Date: 08/02/03 18:31 GMT Standard Time
>Message-id: <3E454CF...@spam.thanks>
>
>
>>
>> Let's say we take two engines of identical capacity. A straight 6 and a V6.
>> Same bore, stroke, valve sizes and port shape, cam profile, induction and
>> exhaust systems. Why would the straight 6 produce any more power or torque
>than
>> the V6?
>
>Well, given that you CANNOT have identical induction and exhaust
>systems, its a silly question :)
>
Of course you could have identical induction and exhaust systems - by the
simple expedient of not having any cylinders linked. That's commonplace on
induction systems anyway with individual chokes (DCOE) or throttle bodies for
each cylinder that are not interconnected in any way. In fact that's the
accepted performance solution compared to linked plenum manifolds.
Exhaust systems are normally linked of course via the manifold but individual
pipes for each cylinder would be quite simple and not even that unusual. My
Honda 550 for example had 4 pipes and 4 silencers rather than a 4 into 1
manifold like most engines. Drag engines and aero engines often use the same
arrangement.
I have covered pulse tuning from linked gas flows in a separate post but my
point here was to demonstrate that the physical arrangement of the cylinders
into a V or inline configuration has no primary bearing on their ability to
flow air or produce power.
I am still waiting for someone who believes that inline sixes are somehow
inherently "torquier" than V6's to supply some mathematical or physical
explanation of why that could possibly be.
I won't be holding my breath because such an explanation will not be
forthcoming.
Dave Baker
>Date: 08/02/03 20:19 GMT Standard Time
>Message-id: <HDd1a.38502$Ec4....@rwcrnsc52.ops.asp.att.net>
Is that comment meant to prove something? VW, GM, Ford are using V6s for what?
Marketing purposes?
Huw
> In article <3e455...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>
> > "Brent P" <tetraet...@yahoo.com> wrote in message
>
> >> I6's are naturally balanced in 1st,2nd,and except for a negilable
fequency
> >> in the 3rd order.
>
> > Funny that most do need that balancer then. When it fails, the
> > operator cannot generally feel the vibes but they are bad enough
to
> > turn or throw fan belts in a very short time. Hardly 'negligible
or
> > most makers wouldn't bother with the balancer.
>
> The harmonic balancer on the front of my I6 is negligible.
What the heck does that mean? It is either there and effective or it
is not. It is certainly there and effective on most straight sixes. I
never claimed that it was not needed on a V, only that it IS needed on
a straight six, so demonstrating that there ARE out of balance forces
acting upon it and that it is not acurate to say that it is naturally
balanced.
If it can be disregarded, then why have the harmonic balancer on most
straight six engines? LOL.
Huw
> In article <3e455...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>
> > The thread does not demonstrate this to satisfaction. The reason
that
> > the four in my generalised example outperforms the torque output
of a
> > six is that it is generally turbo and intercooled while the
equivelent
> > power six of the same design and cylinder dimension [the same
engine
> > family] is either naturally aspirated or mildly turbocharged only.
It
> > is a question of the ability to burn efficiently and process the
air
> > and fuel.
>
> If one engine is turbo charged and the other isn't, then the
comparison
> isn't even. It's like saying a 1975 V8 with single exhaust, air
pump,
> primative catalyst, and 2bbl carb is worse than a modern 4 cylinder
turbo
> with all the bells and whistles means V8 suck... that's what you are
> doing here.
Of course the comparison is even. A four litre Thousand Series
Perkins/Cat compared to a six litre 1000 Series six of the same bore
and stroke and identical horsepower. You cannot find a more equal
comparison because apart from the blower and cylinder numbers the
engines are otherwise identical down to the same horsepower exactly.
Look them up in a specific application where a choice of those two
engines is given as a power pack and you will find the four cylinder
provides more absolute torque. This is most common with comparisons
between four and six of equal design and power from most manufacturers
having the same result. There may be exceptions but I cannot think of
any offhand.
You have obviously not checked the torque curves for the range of
engines for which you provided a reference, namely Caterpillar, whose
main engine ranges lie above 10litres and which increasingly are
specified with 'high torque rise' engines. These typically produce a
curve with a sharp decline in torque as revs rise.
That you do not understand this or the concepts involved is obvious.
That you have not noticed the scales used and the typical 35%+ torque
rise of typical modern Cat engines is surprising.
>
> >> For your comparison, Even the 250cid I6 in my '73 crippled with a
1bbl
> >> carb and single exhaust still has 200lb-ft of torque that comes
on at
> >> 1600rpm. I find 4 cylinder cars to be torqueless by comparision.
> >> (even those that have it, it doesn't come on until higher in the
rpm band)
>
> > But here you are not comparing like with anything like.
>
> And your turbo 4 comparo is ?
It certainly is. Exactly the same design and cylinder capacity, even
down to identical combustion chambers, cannot be more similar, even
down to the horsepower. The only difference being a blower and cooler
to increase the air charge to enable more fuel to be burnt to provide
the same horsepower as the otherwise identical six.
There are very many similar examples and the overwhelming majority of
fours produce more torque than the alternative sixes used in the same
applications. Fact.
Duncan Wood
"Huw" <hedydd[nospam]@tiscali.co.uk> wrote in message
news:3e456...@mk-nntp-2.news.uk.tiscali.com...
>
> "Brent P" <tetraet...@yahoo.com> wrote in message
> news:ugd1a.37096$be.24815@rwcrnsc53...
> > In article <3e455...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
> >
> > > "Brent P" <tetraet...@yahoo.com> wrote in message
> >
> > >> I6's are naturally balanced in 1st,2nd,and except for a negilable
> fequency
> > >> in the 3rd order.
> >
> > > Funny that most do need that balancer then. When it fails, the
> > > operator cannot generally feel the vibes but they are bad enough
> to
> > > turn or throw fan belts in a very short time. Hardly 'negligible
> or
> > > most makers wouldn't bother with the balancer.
> >
> > The harmonic balancer on the front of my I6 is negligible.
>
> What the heck does that mean? It is either there and effective or it
> is not. It is certainly there and effective on most straight sixes. I
> never claimed that it was not needed on a V, only that it IS needed on
> a straight six, so demonstrating that there ARE out of balance forces
> acting upon it and that it is not acurate to say that it is naturally
> balanced.
>
>
It's normally a harmonic damper to eliminate the harmonics in the crank
itself.
Duncan Wood
> Of course the comparison is even. A four litre Thousand Series
> Perkins/Cat compared to a six litre 1000 Series six of the same bore
> and stroke and identical horsepower. You cannot find a more equal
> comparison because apart from the blower and cylinder numbers the
> engines are otherwise identical down to the same horsepower exactly.
> Look them up in a specific application where a choice of those two
> engines is given as a power pack and you will find the four cylinder
> provides more absolute torque. This is most common with comparisons
> between four and six of equal design and power from most manufacturers
> having the same result. There may be exceptions but I cannot think of
> any offhand.
>
>
Yeah but one of those is a turbocharged engine , the other isn't. For the
naturally aspirated engines the BMEP is the same for the 4 cylinder & the 6
cylinder engines.
Brent P
>>> Primarily misinformation as with most usenet threads. The answer is thatpower
>>> that respect as well as rod/stroke ratio etc then there is no inherent reason
>>> why one would produce a different power curve to the other.
>>Then BMW is using I6s for what? Marketing purposes?
> Is that comment meant to prove something? VW, GM, Ford are using V6s for what?
> Marketing purposes?
No, it's a question. Why pay for an inline 6 where a cheaper to build
engine should do if air processing ability is what matters?
You went through a post claiming that vibration and arragement of cylinders
were irrelevant. If the air processing ability is what is relevant and
configuration was irrelevant, then practically every car on the
road would have an inline 4 cylinder engine of some sort. Why pay for 6
or 8 pistons, etc all those extra parts, all those extra machining
operations, for what could be done with less?
A luxury or performance car should just have a larger displacement 4
cylinder. There were huge displacement 4 cylinder cars early on in
automotive history. If it is irrelvant, then the need for anything but a
4 cylinder vanishes. It's inline so it meets the cheap to make
requirement, it's got the packaging requirements down, regardless of
application. One can make a 4 cylinder have the same 'air processing
ability' so there shouldn't be anything else cept for marketing then,
correct?
Or do different configurations have advantages over one another beyond
manufacturing and packaging but in performance?
Huw
Which can be bad enough to break the crank in the long term if
unchecked by the balancer. I recognise of course that the throwing of
fan belts and early crank failure when a nose balancer goes bad is as
much due to the balancer going bad in an out of balance state rather
than any other force acting upon the crank.
Huw
The turbocharger does not endow the engine with more torque. The
figures do not lie, most comparisons of medium/heavy engines from the
same engine family and of the same horsepower will result in a higher
maximum torque figure for the four cylinder. Check it out in specific
applications which give a choice. Simple ones may be applications used
in tractors, which frequently offer the choice. Also possibly gen
sets, although these would not have high torque rise engines, not that
that is relevant I don't suppose.
JazzMan
>
>
> I am still waiting for someone who believes that inline sixes are somehow
> inherently "torquier" than V6's to supply some mathematical or physical
> explanation of why that could possibly be.
>
> I won't be holding my breath because such an explanation will not be
> forthcoming.
>
For once you and I agree. Torque is a geometry function, and a
V6 with the same stroke, displacement, and crank radius will
have the same torque as an L6 with matching geometry. Want to
talk about torque? How about the P&W Wasp engine? 28 cylinder
radial, lots of torque. Maybe radial engines have more torque
than inline or V engines? (lol!)
Dave Baker
>Message-id: <Dhe1a.34477$2H6.388@sccrnsc04>
>
>In article <20030208152747...@mb-fc.aol.com>, Dave Baker wrote:
>>>> Primarily misinformation as with most usenet threads. The answer is
>thatpower
>>>> and torque depend on air processing ability and if the engines
>areidentical in
>>>> that respect as well as rod/stroke ratio etc then there is no inherent
>reason
>>>> why one would produce a different power curve to the other.
>
>>>Then BMW is using I6s for what? Marketing purposes?
>
>> Is that comment meant to prove something? VW, GM, Ford are using V6s for
>what?
>> Marketing purposes?
>
>No, it's a question. Why pay for an inline 6 where a cheaper to build
>engine should do if air processing ability is what matters?
>
>You went through a post claiming that vibration and arragement of cylinders
>were irrelevant. If the air processing ability is what is relevant and
>configuration was irrelevant, then practically every car on the
>road would have an inline 4 cylinder engine of some sort. Why pay for 6
>or 8 pistons, etc all those extra parts, all those extra machining
>operations, for what could be done with less?
A completely different topic. The thread is about any inherent advantage of
different six cylinder engine layouts with same sized cylinders. I have no
interest in being drawn off topic down a side turning into something as
simplistic as why ants can lift many times their own body weight and elephants
can't jump. I still await an answer to my previous primary question.
Dave Baker
>Date: 08/02/03 20:12 GMT Standard Time
>Message-id: <3e456...@mk-nntp-2.news.uk.tiscali.com>
>
>
>"Brent P" <tetraet...@yahoo.com> wrote in message
>news:ugd1a.37096$be.24815@rwcrnsc53...
>> In article <3e455...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>>
>> > "Brent P" <tetraet...@yahoo.com> wrote in message
>>
>> >> I6's are naturally balanced in 1st,2nd,and except for a negilable
>fequency
>> >> in the 3rd order.
>>
>> > Funny that most do need that balancer then. When it fails, the
>> > operator cannot generally feel the vibes but they are bad enough
>to
>> > turn or throw fan belts in a very short time. Hardly 'negligible
>or
>> > most makers wouldn't bother with the balancer.
>>
>> The harmonic balancer on the front of my I6 is negligible.
>
>What the heck does that mean? It is either there and effective or it
>is not. It is certainly there and effective on most straight sixes. I
>never claimed that it was not needed on a V, only that it IS needed on
>a straight six, so demonstrating that there ARE out of balance forces
>acting upon it and that it is not acurate to say that it is naturally
>balanced.
The balancer has nothing to do with primary or secondary out of balance forces.
It is there to suppress torsional vibrations which exacerbate with increasing
crank length.
Dave Baker
>Message-id: <3e457...@mk-nntp-2.news.uk.tiscali.com>
>The turbocharger does not endow the engine with more torque.
That's its inherent primary function and the entire reason for operating an
induction system at above atmospheric pressure. Maybe you are meaning something
other than what you write but if so I can't fathom what.
Huw
NVH.
>
> A luxury or performance car should just have a larger displacement 4
> cylinder. There were huge displacement 4 cylinder cars early on in
> automotive history.
Low compression, low NVH.
If it is irrelvant, then the need for anything but a
> 4 cylinder vanishes. It's inline so it meets the cheap to make
> requirement, it's got the packaging requirements down, regardless of
> application. One can make a 4 cylinder have the same 'air processing
> ability' so there shouldn't be anything else cept for marketing
then,
> correct?
>
> Or do different configurations have advantages over one another
beyond
> manufacturing and packaging but in performance?
>
Only in NVH.
Mercedes make fours and sixes in both inline and V formation. Both are
used in their modern cars and trucks but the preference is for shorter
engines in cars due to a larger potential crumple zone available for a
given hood length.
They have dropped the six cylinder alternative in the new Mercedes
tractor and use fours up to 190 hp where the normal point for sixes
to find favour is around 115 horsepower. Of course, in these cases
there may be a packaging and stability advantage to the extra length
of a six which does not apply to the Unimog.
There is certainly more of a marketing advantage for BMW in their
straight sixes than any practical one. They do however make
exceedingly good engines in both straight and V configurations. Their
four and six diesels are certainly the best of their type and about to
get even better.
Brent P
> If it can be disregarded, then why have the harmonic balancer on most
> straight six engines? LOL.
You need another source? fine. Bosch Automotive handbook, 4th ed, page
390.
Free forces Free moments
1st order 2nd order 1st order 2nd order
In-line 4 0 0 3^.5*F1*a 3^.5F2*a
In-line 6 0 0 0 0
JazzMan
>
> In article <20030208152747...@mb-fc.aol.com>, Dave Baker wrote:
> >>> Primarily misinformation as with most usenet threads. The answer is thatpower
> >>> and torque depend on air processing ability and if the engines areidentical in
> >>> that respect as well as rod/stroke ratio etc then there is no inherent reason
> >>> why one would produce a different power curve to the other.
>
> >>Then BMW is using I6s for what? Marketing purposes?
>
> > Is that comment meant to prove something? VW, GM, Ford are using V6s for what?
> > Marketing purposes?
>
> No, it's a question. Why pay for an inline 6 where a cheaper to build
> engine should do if air processing ability is what matters?
>
> You went through a post claiming that vibration and arragement of cylinders
> were irrelevant. If the air processing ability is what is relevant and
> configuration was irrelevant, then practically every car on the
> road would have an inline 4 cylinder engine of some sort. Why pay for 6
> or 8 pistons, etc all those extra parts, all those extra machining
> operations, for what could be done with less?
>
There's so many variables here. Sigh. More pistons for a given
displacement means more cost, more engineering, more manufacturing,
etc. A Model T had 4 cylinders because in those days a larger
number of cylinders was much, much more expensive to make. There
were cars with straight 8s, too, but those were high-end and exotic
cars. Yes, marketing has as much to do as actual design. An L6
is naturally balanced, so it's easy to market it as a "naturally"
powerful engine. Maybe not as powerful as the Cosworth 4 banger
used in Formula 1 with over 1,000 HP, or not as powerful as the
monster V8 engines used to push dragsters down the quarter mile.
Manufacturers tend to use the engines that they've had success
with. So BMW has a good L6, so they use it. So what? Chevrolet
and Ford both have excellent V8 designs that have withstood the
test of time over the last half a century. Heck, even the
venerable 2.5 Duke motor got pretty good after they added the
counterbalance shafts. Nowadays, engine technology is so good
that the number and configuration of cylinders almost doesn't
matter as much as it used to. VW's coming out with a W8, now
that's different for a car application. Wasn't there a radial
in the Hudson Hawk?
The whole argument about which engine configuration is better
is starting to look like a bunch of guys standing around and
yelling "My engine's better than your engine" to each other.
They all have their good and bad points, which decide how
they're used, packaged, and yes, marketed.
JazzMan
> A luxury or performance car should just have a larger displacement 4
> cylinder. There were huge displacement 4 cylinder cars early on in
> automotive history. If it is irrelvant, then the need for anything but a
> 4 cylinder vanishes. It's inline so it meets the cheap to make
> requirement, it's got the packaging requirements down, regardless of
> application. One can make a 4 cylinder have the same 'air processing
> ability' so there shouldn't be anything else cept for marketing then,
> correct?
>
> Or do different configurations have advantages over one another beyond
> manufacturing and packaging but in performance?
--
Brent P
> Of course the comparison is even.
comparing a naturally asperated engine to a turbo charged or supercharged
engine is not even. Because one can take in alot more air per unit time.
> You have obviously not checked the torque curves for the range of
> engines for which you provided a reference, namely Caterpillar, whose
> main engine ranges lie above 10litres and which increasingly are
> specified with 'high torque rise' engines. These typically produce a
> curve with a sharp decline in torque as revs rise.
I have. Provide the URL to what you call a sharp curve.
>> > But here you are not comparing like with anything like.
>> And your turbo 4 comparo is ?
> It certainly is. Exactly the same design and cylinder capacity, even
> down to identical combustion chambers, cannot be more similar, even
> down to the horsepower. The only difference being a blower and cooler
> to increase the air charge to enable more fuel to be burnt to provide
> the same horsepower as the otherwise identical six.
It's clear you don't understand why a turbo makes the comparison
invalid. A turbo compresses air, allowing it to pump more air per
revolution and effectively makes the engine work as one with a higher
displacement. You might as well compare a 4 liter to 2 a liter than to
compare two engines of the same displacement with one with a turbo
and other not.
Huw
"Dave Baker" <pumar...@aol.comma> wrote >
> The balancer has nothing to do with primary or secondary out of
balance forces.
> It is there to suppress torsional vibrations which exacerbate with
increasing
> crank length.
>
As ever you are spot on. Just testing to see who actually knows
something and who's bullshitting.
Huw
"Dave Baker" <pumar...@aol.comma> wrote in message
news:20030208162814...@mb-fc.aol.com...
> >Subject: Re: Is an in-line six better than a V-6?
> >From: "Huw" hedydd[nospam]@tiscali.co.uk
> >Date: 08/02/03 21:09 GMT Standard Time
> >Message-id: <3e457...@mk-nntp-2.news.uk.tiscali.com>
>
> >The turbocharger does not endow the engine with more torque.
>
> That's its inherent primary function and the entire reason for
operating an
> induction system at above atmospheric pressure. Maybe you are
meaning something
> other than what you write but if so I can't fathom what.
>
Um yes! What I meant was that the turbo allows more fuel to be burnt
efficiently for a given swept volume which in fact does endow the
engine with more torque but it would not necessarily mean more maximum
torque than a six of equal maximum horsepower. What this does not
explain is why the blown four of same horsepower as the six from the
same family usually [but probably not always] produces more torque
than the six. It cannot be a coincidence that this is commonly the
case. It may be down to efficiency and pumping losses. Or have you
another explanation. It is not likely to be due simply because one is
four and one is six is it. The difference is commonly in the order of
around 2.5% to 5% more maximum torque
Huw
but they do share exactly the same basic design and Fastram combustion
chambers and individual cylinder swept volume. The turbo allows the
smaller displacement four to produce the same horsepower as the six
but the maximum torque produced is favourable to the four cylinder.
The same can be seen if you compare modern Powerstar and Saran engines
in the same way.
Brent P
Brent P
> I have covered pulse tuning from linked gas flows in a separate post but my
> point here was to demonstrate that the physical arrangement of the cylinders
> into a V or inline configuration has no primary bearing on their ability to
> flow air or produce power.
> I am still waiting for someone who believes that inline sixes are somehow
> inherently "torquier" than V6's to supply some mathematical or physical
> explanation of why that could possibly be.
> I won't be holding my breath because such an explanation will not be
> forthcoming.
From "The Design and Tuning of Competition Engines"
By Philip H. Smith, 5th ed, 1971.
Page 129 (Chapter 5, Crankshaft Design and Engine
Balance) Under the heading "Six-cylinder engines"
"the question then is to decide on the layout of engine which will
give good balance, as well as regular firing intervals, the later being
obviously desirable in the interests of smooth delivery of torque."
page 137:
"The conventional six-in-line is similar to the
corresponding four, in that it comprises two
threes in looking-glass formation with the cranks
1-6,2-5,and 3-4 in the same phasing, at 120 deg.
angles between pairs. It is thus possible, as
in the four, to distribute the firing intervals
acceptably along the shaft; with the usual order
of 1-5-3-6-2-4, this means that alternate
cylinders fire from the centre pair of cylinders 3 and
4 to the outers, in turn, at each 120 deg of crankshaft
rotation"
This alone would make the 90 degree V6 with it's firing
intervals inferior to the I6. However the 60 degree V6 will
retain the inline's 120deg. interval, but has the free moments
of the first and second order that the I6 doesn't. (Page 390-391,
bosch automotive handbook details what these moments are mathematically)
I simply find it hard to believe that these free momements
and forces of various configurations have no effect what-so-ever
on power and torque outputs. Especially when they are corrected
by damping techniques which add to the internal losses of the engine.
(more mass to move) I would like to see it proven mathematically
that such changes aren't going to reduce the power output when
compared to an equal engine of another layout that doesn't suffer
from these.
Brent P
> You need another source? fine. Bosch Automotive handbook, 4th ed, page
> 390.
> Free forces Free moments
> 1st order 2nd order 1st order 2nd order
In-line 4 0 4*F2 0 0
> In-line 6 0 0 0 0
Made a mistake, put inline 3 down, instead of 4, it's corrected above.
Dave Baker
>Message-id: <3e457bea$1...@mk-nntp-2.news.uk.tiscali.com>
>
>
>"Dave Baker" <pumar...@aol.comma> wrote in message
>news:20030208162814...@mb-fc.aol.com...
>> >Subject: Re: Is an in-line six better than a V-6?
>> >From: "Huw" hedydd[nospam]@tiscali.co.uk
>> >Date: 08/02/03 21:09 GMT Standard Time
>> >Message-id: <3e457...@mk-nntp-2.news.uk.tiscali.com>
>>
>> >The turbocharger does not endow the engine with more torque.
>>
>> That's its inherent primary function and the entire reason for
>operating an
>> induction system at above atmospheric pressure. Maybe you are
>meaning something
>> other than what you write but if so I can't fathom what.
>>
>
>Um yes! What I meant was that the turbo allows more fuel to be burnt
>efficiently for a given swept volume which in fact does endow the
>engine with more torque but it would not necessarily mean more maximum
>torque than a six of equal maximum horsepower. What this does not
>explain is why the blown four of same horsepower as the six from the
>same family usually [but probably not always] produces more torque
>than the six. It cannot be a coincidence that this is commonly the
>case. It may be down to efficiency and pumping losses. Or have you
>another explanation. It is not likely to be due simply because one is
>four and one is six is it. The difference is commonly in the order of
>around 2.5% to 5% more maximum torque
>
>Huw
Ok, I understand the point now. I'll paraphrase and elaborate. Take two engines
of identical cylinder geometry, cam profile, induction and exhaust flow, and
pulse tuning (or eliminate pulse tuning by keeping to separate pipes). Make one
a straight 4 cylinder and the other a straight 6 of consequently 50% greater
displacement. Volumetric and mechanical efficiencies will be the same. Prima
facie the two engines will produce identically shaped torque/litre curves. In
other words the torque curve of the 6, when scaled down by 1/3 would overlap
the torque curve of the 4 at all rpm points.
(There is a small proviso to the above because of the lack of torsional
rigidity of the crankshaft (and possibly also camshaft) of the 6. To achieve
the same rigidity, and therefore timing of cylinder events, as in the 4 the
crank/cam would have to be made more massive per unit length which would lead
to a greater moment of inertia per litre. In a laboratory environment this
could be compensated for by making the 4 cylinder crank heavier than it need
be. Torsional crank dampers of the same power absorption/litre would also have
to be fitted. Anyway I digress)
Now apply forced induction to the 4 and increase boost pressure until the peak
horsepower rises 50% to match the output of the 6. The variables that have now
been introduced are the adiabatic and compressor efficiencies of the
turbo/super charger and the flow losses in the induction and exhaust system at
higher mass flow rates.
Most processes suffer from a law of diminishing returns. To generate 50% more
peak horsepower will require a little more than 50% extra manifold pressure
because of these efficiency losses. At lower rpm, and mass air flow rates, the
extent of these losses will not be so high. In other words the boost required
to achieve the required 50% increase in peak horsepower could lead to a
slightly larger than 50% increase in torque at progressively lower rpm.
All of these factors could be compensated for by tailoring the boost pressure
map slightly at different rpm. Without knowing the exact details of the
implementation that the manufacturer chose to employ it probably isn't safe to
assume any inherent advantage of a 4 cylinder over a 6 based on examination of
torque curves of geometrically similar engines without a full laboratory
analysis to preserve similarities of all relevant factors.
Ray
> Or do different configurations have advantages over one another beyond
> manufacturing and packaging but in performance?
No. In a purely theoretical world, an engine of X displacement
could make Y torque, irrelevant of # of cylinders, location, # of
camshafts, etc. etc. An engine is just an air/gasoline pump, all that
matters is that in a certain of gasoline is a certain amount of energy.
In the _real_world_, it IS a YES, because it's really about:
1)Money: Aluminum heads are better than cast iron heads, but cost more.
Inline 6 blocks are "simple", but imagine making sure the deck of a
straight 6 block is level - that's a long distance to be made square.
(etc. etc...)
2)Packaging: Straight 6's are naturally well balanced, but try
fitting one under the hood of a Honda Accord.
3)Marketing: People associate higher #s of cylinders with "better."
4)Expected Application: Do you think the guys who design the I6
that goes in the BMW M3 and the guys who were tweaking the GM 2.8 V6
for use in a minivan were going after the same HP/torque/RPM/Cost
targets?
5)Efficiency. Some engines just ... well ... suck. They
are not very good at converting gasoline to HP. Some are.
I also think a lot of it is the companies have a "favourite"
layout that fits in the cars they build and engineers who have
experience working with that design.
So, which 6 is better? It depends. :) Whose engines are you
comparing? What is your criteria for "better?"
If you're looking for cheap and durable, it's hard to beat the
old Dodge slant-6. If you're looking for a lot of power or a
light engine, look elsewhere...
Ray
Dave Baker
>Date: 08/02/03 22:14 GMT Standard Time
>Message-id: <Rif1a.39373$Ec4....@rwcrnsc52.ops.asp.att.net>
Now were getting a little closer to it. The statement "I find it hard to
believe" is a quantum leap forward from the assertion "An inline 6 is a better
torque producer than a V6". (I paraphase rather than go back through many
posts)
The "smoothness" of torque delivery that Smith refers to is a function of
evenly spaced firing intervals and a desirable element in a road car as regards
the perception of engine quality and exhaust note. That smoothness also
improves with increasing cylinder number and smaller firing interval. Uneven
impulses of torque delivery don't alter the total torque ouput per unit time
though if we consider many engine cycles.
The damping techniques are actually likely to absorb more power on an inline
six rather than a V because of the torsional rigidity problems of long
crankshafts. Any "wind up" in the crank or camshaft will also lead to errors in
the timing of cylinder events (piston motion, valve opening, ignition firing
etc) and these can have consequences that lead to real world differences in
power output between the two engine types that a purely hypothetical laboratory
analysis of airflow considerations could ignore.
Finally, pulse tuning must always be considered in a real world engine and the
spacing of the cylinder events is a factor in this. I don't want to reiterate a
previous post unecessarily though.
Brent P
> Uneven
> impulses of torque delivery don't alter the total torque ouput per unit time
> though if we consider many engine cycles.
Which is why I then quoted the bosch handbook. If it's uneven, an energy
storage device must be used, ie, flywheel. These things are not loss free.
> The damping techniques are actually likely to absorb more power on an inline
> six rather than a V because of the torsional rigidity problems of long
> crankshafts. Any "wind up" in the crank or camshaft will also lead to errors in
> the timing of cylinder events (piston motion, valve opening, ignition firing
> etc) and these can have consequences that lead to real world differences in
> power output between the two engine types that a purely hypothetical laboratory
> analysis of airflow considerations could ignore.
The question is wether the any twist, angular deflection in the crank
offset what is lost to balance out the free momements and/or forces
of other configurations. Not to mention the energy lost by those forces
and moments. A suffiently torisonally rigid crank (not necesscarily bigger
due to material and manufacturing techniques) could solve any angular
deflection issue for the inline without any penalty to the rotating mass.
I still haven't seen anything that what is lost with making a
configuration that isn't naturally balanced smooth or what is lost
energy wise through vibration is insignificant or made up due to
losses that naturally balanced configurations have that the one's that
aren't don't. I've seen it declared, but no cites or mathematical
proof of such.
> Finally, pulse tuning must always be considered in a real world engine and the
> spacing of the cylinder events is a factor in this. I don't want to reiterate a
> previous post unecessarily though.
In which case, the inline 6 is clearly better than the 90 degree V6, the
60 degree is more debatable. Configuration simply isn't something that
can be disregarded, if it could, there would be things like 50 degree
V8s and the like. bank angles determined by packaging requirements. But
the degree between cylinder firings is important. To both smoothness
and the final output of the engine. If configuration were really, truely
irrelevant to the final output I would expect to see a great deal more
variation in piston configuration, especially with V engines.
Duncan Wood
> 60 degree is more debatable. Configuration simply isn't something that
> can be disregarded, if it could, there would be things like 50 degree
> V8s and the like. bank angles determined by packaging requirements. But
> the degree between cylinder firings is important. To both smoothness
> and the final output of the engine. If configuration were really, truely
> irrelevant to the final output I would expect to see a great deal more
> variation in piston configuration, especially with V engines.
>
>
though.
Dave Baker
>Message-id: <Owg1a.38987$tq4.3077@sccrnsc01>
>
>In article <20030208180138...@mb-fc.aol.com>, Dave Baker wrote:
>
>> Uneven
>> impulses of torque delivery don't alter the total torque ouput per unit
>time
>> though if we consider many engine cycles.
>
>Which is why I then quoted the bosch handbook. If it's uneven, an energy
>storage device must be used, ie, flywheel. These things are not loss free.
Well there is no "requirement" to use a flywheel for any reason. Certainly it
is desirable to achieve smooth idle characteristics regardless of eveness of
firing interval but a race engine would remove every scrap of rotating inertia
possible. The spacing of the firing intervals of a non uniformly firing v6 are
still closer together than those of a straight 4 so I see no extra requirement
to add flywheel mass. It boils down to the smoothness of idle that the
manufacturer believes his customers want.
Under steady state dynamometer conditions the flywheel mass would not show up
as a loss anyway. Only under acceleration would it absorb energy. This
shouldn't affect the debate on torque production at the root of this thread.
>
>> The damping techniques are actually likely to absorb more power on an
>inline
>> six rather than a V because of the torsional rigidity problems of long
>> crankshafts. Any "wind up" in the crank or camshaft will also lead to
>errors in
>> the timing of cylinder events (piston motion, valve opening, ignition
>firing
>> etc) and these can have consequences that lead to real world differences in
>> power output between the two engine types that a purely hypothetical
>laboratory
>> analysis of airflow considerations could ignore.
>
>The question is wether the any twist, angular deflection in the crank
>offset what is lost to balance out the free momements and/or forces
>of other configurations. Not to mention the energy lost by those forces
>and moments. A suffiently torisonally rigid crank (not necesscarily bigger
>due to material and manufacturing techniques) could solve any angular
>deflection issue for the inline without any penalty to the rotating mass.
>
>I still haven't seen anything that what is lost with making a
>configuration that isn't naturally balanced smooth or what is lost
>energy wise through vibration is insignificant or made up due to
>losses that naturally balanced configurations have that the one's that
>aren't don't. I've seen it declared, but no cites or mathematical
>proof of such.
I think the burden of proof is on the proponent of the premise that inline 6s
are better engines than V6s rather than the respondent.
>
>> Finally, pulse tuning must always be considered in a real world engine and
>the
>> spacing of the cylinder events is a factor in this. I don't want to
>reiterate a
>> previous post unecessarily though.
>
>In which case, the inline 6 is clearly better than the 90 degree V6, the
>60 degree is more debatable.
"Clearly better" is again open to debate until the engine requirements are
specified. Pulse tuning benefits apply over fairly narrow rpm bands and there
are always trade offs at other rpms. Road engines often have unequal length
induction and exhaust runners anyway to spread the effects of pulse tuning and
avoid peaks and troughs in the torque curve. On that basis an engine that is
not ideally suited to pulse tuning is at no disadvantage.
On a race engine it may well be that evenly spaced firing intervals help pulse
tune a very specific rpm band at peak power but whether this improves overall
performance depends on the spread of torque required, the number of gears and
the detrimental effects on power at rpms below peak.
Configuration simply isn't something that
>can be disregarded, if it could, there would be things like 50 degree
>V8s and the like. bank angles determined by packaging requirements. But
>the degree between cylinder firings is important. To both smoothness
>and the final output of the engine. If configuration were really, truely
>irrelevant to the final output I would expect to see a great deal more
>variation in piston configuration, especially with V engines.
There are some very unusual and quite successfuly applied bank angles on V
engines that at least throw doubt on the necessity of even firing intervals for
good performance. The Audi/VW VR6 engine has a 15 degree included angle between
banks in what is essentially a common block with a single cylinder head.
The TVR V8 engine 2v per cylinder engine that they designed in house to replace
the Rover/Buick V8 has a 72 degree angle if I recall correctly but a web search
would no doubt answer that.
The common crank configuration of American V8s doesn't allow the pulse tuning
that flat plane cranks of the Ferrari and race engine type but doesn't seem any
the worse for that. The sound is certainly much nicer :)
Chas Hurst
>
> In which case, the inline 6 is clearly better than the 90 degree V6, the
> 60 degree is more debatable. Configuration simply isn't something that
> can be disregarded, if it could, there would be things like 50 degree
> V8s and the like. bank angles determined by packaging requirements. But
> the degree between cylinder firings is important. To both smoothness
> and the final output of the engine. If configuration were really, truely
> irrelevant to the final output I would expect to see a great deal more
> variation in piston configuration, especially with V engines.
>
>
There are truly a vast number of V configuration engines. You are simply not
aware of them. In the 20s Vittorio Jano design the 15 deg V4 for Lancia. It
had one head and two main bearings. It was a gem. That architecture is
repeated in the current V6 of VW. Which has been evolved into what VW calls
a W8. In the 60s Ferarri experimented with a number of V6 & V8 using angles
of 65, 70, 90, 105 and more. The same is true today with the F1 V10 engines.
There are requirements other than smoothness and power. The chief one being
the use of existing tooling. And the ease of producing tooling at 90 deg.
And sometimes power outweighs smoothness, as in the current CART and IRL V8
engines. These have a single plane crankshaft (normal street V8 is a 2 plane
crankshaft) that allows a more efficient and tidy exhaust system that
produces more power.
The reasons for a particular configuration are what is relevent.
Regards
Chas Hurst
Steve
> I am still waiting for someone who believes that inline sixes are somehow
> inherently "torquier" than V6's to supply some mathematical or physical
> explanation of why that could possibly be.
Hell, man, someone already thinks FOURS are inherently torquier than
sixes of either configuration. Nothing surprises me here :-)
I agree, there's no fundamental reason that identical size, bore/stroke,
cam, and everything else V- and I-type engines should have different
torque curves or power output. But because of the mechanical concessions
that have to be made to create a v6, it always comes down to packaging
versus performance (and performance includes things like inherent
balance, lack of parasitic loss from balance shafts, and absence of
splayed crankpins.) V6 engines exist for packaging, and the sacrifices
made are actually fairly minimal for a 60-degree design.
Steve
>
>
> The turbocharger does not endow the engine with more torque.
Thats gotta count right up there with Parker's "torque=work" statement.
A turbocharger most definitely increases available torque, because it
increases the amount of fuel/air mixture that can be burned on each
power stroke, and therefore increases BMEP.
Put an engine on a dyno and measure the torque at 2000 RPM with the
turbocharger operational. Then open the wastegate and re-measure the
torque at 2000 RPM and tell me that its the same while keeping a
straight face!
Steve
> Dave Baker wrote:
>
>
>>I am still waiting for someone who believes that inline sixes are somehow
>>inherently "torquier" than V6's to supply some mathematical or physical
>>explanation of why that could possibly be.
>>
>>I won't be holding my breath because such an explanation will not be
>>forthcoming.
>>
>
>
> For once you and I agree. Torque is a geometry function, and a
> V6 with the same stroke, displacement, and crank radius will
> have the same torque as an L6 with matching geometry. Want to
> talk about torque? How about the P&W Wasp engine? 28 cylinder
> radial, lots of torque. Maybe radial engines have more torque
> than inline or V engines? (lol!)
Lots of horsepower, too (up to about 4000 in some versions). And its
air-cooled, so maybe air-cooled engines have more horsepower than liquid
cooled ones. :-)
Steve
>> If configuration were really, truely
>>irrelevant to the final output I would expect to see a great deal more
>>variation in piston configuration, especially with V engines.
>>
>>
>
> It's fairly irrelevant to power output, it's massively relevant to NVH
> though.
>
>
As are other subtlties of design. Compare the NVH of a 90-degree v8 with
a conventional (for v8s since the 30s) crank with 90-degree spaced
journals to the NVH of an identical v8 fitted and timed with a "flat"
(180-degree) crank as was mandated in IRL (or was it CART- I always get
the vacuum cleaner/rollerskate racing series confused ;-) a couple of
years ago. You can get about the same power out of the flat crank, but
at the expense of having to ruggedize everything on the car to survive
the eye-blurring vibration. And in that case, its not even a question of
one being even-firing and the other not, its all in the dynamic balance
of the rotating/reciprocating masses.
Steve
>
>>In article <3e452...@mk-nntp-2.news.uk.tiscali.com>, Huw wrote:
>>
>>>balance. Inline 6 is also prone to vibration and most have a
>>
> torsional
>
>>I6's are naturally balanced in 1st,2nd,and except for a negilable
>
> fequency
>
>>in the 3rd order.
>>
>
>
> Funny that most do need that balancer then.
You don't seem to understand the function of a harmonic balancer.
Although SOME engines have it asymmetrically waited to complete the
basic engine balance (examples I'm familiar with: cast-crank Mopar 360,
Mopar 440-6, and cast-crank Mopar 400), in MOST engines it is pefectly
symmetric and contributes NOTHING to first- and second-order imbalances
(Mopar 318, 340, 383, 440 (forged crank), countless Fords and Chevies,
Pontiacs, Buicks, and others as well).
What it does do in ALL of these engines is control crankshaft TORSIONAL
oscillation. ALL engines are subject to this oscillation, and while it
is possible to get away without a harmonic balancer on low-power,
low-speed engines with very short crankshafts, it is not advisable for
long-term longevity in ANY engine.
Chas Hurst
"Steve" <n...@spam.thanks> wrote in message
news:3E45D99C...@spam.thanks...
As are other subtlties of design. Compare the NVH of a 90-degree v8 with
> a conventional (for v8s since the 30s) crank with 90-degree spaced
> journals to the NVH of an identical v8 fitted and timed with a "flat"
> (180-degree) crank as was mandated in IRL (or was it CART- I always get
> the vacuum cleaner/rollerskate racing series confused ;-) a couple of
> years ago. You can get about the same power out of the flat crank, but
> at the expense of having to ruggedize everything on the car to survive
> the eye-blurring vibration. And in that case, its not even a question of
> one being even-firing and the other not, its all in the dynamic balance
> of the rotating/reciprocating masses.
>
It was the IRL that allowed-mandated ( I'm not sure which) the single plain
crank. But you have it backwards. The exhaust note from the 2 plane crank
vibrated the electronics to hell. When they switched to the single plane
crank-viola! The single plane crank has been used for decades in designed
for competition engines. CART has always used (V8) engines with a flat
crank.
Regards
Chas Hurst
Brent P
> "Brent P" <tetraet...@yahoo.com> wrote in message
>> 60 degree is more debatable. Configuration simply isn't something that
>> can be disregarded, if it could, there would be things like 50 degree
>> V8s and the like. bank angles determined by packaging requirements. But
>> the degree between cylinder firings is important. To both smoothness
> There are truly a vast number of V configuration engines. You are simply not
> aware of them.
I am aware of all sorts of designs that died out, have tiny niche
applications. But one would expect far more variation than what exists,
far more to have survived.
Brent P
>>In article <20030208180138...@mb-fc.aol.com>, Dave Baker wrote:
>>
>>> Uneven
>>> impulses of torque delivery don't alter the total torque ouput per unittime
>>> though if we consider many engine cycles.
>>Which is why I then quoted the bosch handbook. If it's uneven, an energy
>>storage device must be used, ie, flywheel. These things are not loss free.
> Well there is no "requirement" to use a flywheel for any reason.
Didn't say there was. Said an energy storage device must be used in
the context of evening out the impluses.
>>I still haven't seen anything that what is lost with making a
>>configuration that isn't naturally balanced smooth or what is lost
>>energy wise through vibration is insignificant or made up due to
>>losses that naturally balanced configurations have that the one's that
>>aren't don't. I've seen it declared, but no cites or mathematical
>>proof of such.
> I think the burden of proof is on the proponent of the premise that inline 6s
> are better engines than V6s rather than the respondent.
It's been shown that these forces and imbalances exist. You asserted
they are insignificant. WHY?
I say the inlines are better because these imblances and losses do
not exist. You say they are insignificant, what is the basis for this
assertion?
Brent P
>>In article <20030208180138...@mb-fc.aol.com>, Dave Baker wrote:
>>
>>> Uneven
>>> impulses of torque delivery don't alter the total torque ouput per unittime
>>> though if we consider many engine cycles.
>>Which is why I then quoted the bosch handbook. If it's uneven, an energy
>>storage device must be used, ie, flywheel. These things are not loss free.
> Well there is no "requirement" to use a flywheel for any reason.
Didn't say there was. Said an energy storage device must be used in
the context of evening out the impluses.
>>I still haven't seen anything that what is lost with making a
>>configuration that isn't naturally balanced smooth or what is lost
>>energy wise through vibration is insignificant or made up due to
>>losses that naturally balanced configurations have that the one's that
>>aren't don't. I've seen it declared, but no cites or mathematical
>>proof of such.
> I think the burden of proof is on the proponent of the premise that inline 6s
> are better engines than V6s rather than the respondent.
It's been shown that these forces and imbalances exist. You asserted
Dave Baker
>Message-id: <Gtm1a.44400$HN5.1...@rwcrnsc51.ops.asp.att.net>
I've already explained why in a previous post. I can in fact think of five
empirical explanations of why they aren't significant but I'm not going to let
you turn your assertion round at this stage and do your work for you. You
explain why they are significant to a level that can be measured as a loss of
bhp such as to support your assertion that an inline 6 is a measurably better
torque producing engine than a v6.
I'll remind you of your assertions.
"It [Inline 6] also is a great configuration for generating torque."
"Wrong again. I6s get up to peak torque early and stay there."
When asked to mathematically or empirically justify your assertions in these
debates you seem to rely on a standard tactic of saying "well you explain why
I'm wrong then and if you can't then I must be right".
I'm not letting you off the hook of what you yourself started. Define how the
primary or secondary balance forces of a V engine create losses that are
sufficient to justify your position that a geometrically similar I6 produces
more torque. If you can't then just retract the assertion.
Huw
"Steve" <n...@spam.thanks> wrote in message
Dave has it about right on this one after a short explanation from me.
The turbo is just a pump that pushes more air into the cylinders and
in the case I illustrated, allows a four cylinder of the same family
and otherwise same design as a six to produce the same horsepower for
a valid comparison. In most cases [all that I am familiar with] the
four cylinder engine produces more peak torque and logically has a
higher torque rise than the six. Remember that they produce the same
maximum horsepower at the same revs. I do not venture an opinion on
why this should be so, just a simple observation of a common
phenomenon within many engine families.
Duncan Wood
"Huw" <hedydd[nospam]@tiscali.co.uk> wrote in message
news:3e463...@mk-nntp-2.news.uk.tiscali.com...
& the 6 cylinder turbo do the same thing, it's a function of the turbo, not
the number of cylinders
Huw
"Duncan Wood" <free...@dmx512.co.uk> wrote > >
> >
>
> & the 6 cylinder turbo do the same thing, it's a function of the
turbo, not
> the number of cylinders
>
>
Could be but many of the low end sixes are also turbocharged and still
lack the torque. You may be correct though, however I fail to see why
just adding a turbo would increase low end torque and increase torque
rise for the same maximum horsepower from the same design engine
albeit from fewer cylinders.
Huw
"Steve" <n...@spam.thanks> wrote in message
> Dave Baker wrote:
>
> > I am still waiting for someone who believes that inline sixes are
somehow
> > inherently "torquier" than V6's to supply some mathematical or
physical
> > explanation of why that could possibly be.
>
> Hell, man, someone already thinks FOURS are inherently torquier than
> sixes of either configuration. Nothing surprises me here :-)
>
I do not 'think' this. I observe it daily from just reading and
measuring the engine output data from single engine families where
fours and sixes have the same maximum horsepower. There may be all
kinds of reasons why this is a common phenomenon. That it *is* a
common phenomenon within an engine family is not in doubt AFAICS.
engit
>
> The thread does not demonstrate this to satisfaction. The reason that
> the four in my generalised example outperforms the torque output of a
> six is that it is generally turbo and intercooled while the equivelent
> power six of the same design and cylinder dimension [the same engine
> family] is either naturally aspirated or mildly turbocharged only. It
> is a question of the ability to burn efficiently and process the air
> and fuel.
How does intercooling & turbocharging a 4-cylinder to boost power affect
it's gas consumption rate (i.e. fuel efficiency) ? I ask this because you
mention increased burn efficiency.
Huw
"engit" <engit_...@hotmail.com> wrote in message
news:0Hv1a.621066$F2h1....@news01.bloor.is.net.cable.rogers.com...
In general, within an engine family, there is usually a small
advantage in favour of the turbocharged smaller capacity [fewer
cylinders] engine. There can be a huge difference when comparing any
engine family with a different engine family.
Emission regulations have had a recent impact on medium diesels. Many
Tier1 compliant off-road engines are at the borderline of acceptable
consumption and commonly are up to 10% less efficient than prior
designs. I believe and hope that redesigns and electronics needed to
meet Tier11 rules will bring consumption back to former levels while
enhancing torque. An unfortunate side effect seems to be that some
direct injection diesels will become harder to start and rough running
when cold unless mechanical remedies [such as intake air heaters] are
put in place.
Brent P
>>It's been shown that these forces and imbalances exist. You asserted
>>they are insignificant. WHY?
>>I say the inlines are better because these imblances and losses do
>>not exist. You say they are insignificant, what is the basis for this
>>assertion?
> I've already explained why in a previous post. I can in fact think of five
> empirical explanations of why they aren't significant but I'm not going to let
> you turn your assertion round at this stage and do your work for you. You
> explain why they are significant to a level that can be measured as a loss of
> bhp such as to support your assertion that an inline 6 is a measurably better
> torque producing engine than a v6.
In other words, you can demand, and I can't.
> I'll remind you of your assertions.
> "It [Inline 6] also is a great configuration for generating torque."
> "Wrong again. I6s get up to peak torque early and stay there."
And it is.
And they can, and do.
The numerous engines using this configuration are proof of that.
These two statements are not the fictious 'all other factors equal'
condition, because all other factors are rarely equal. It seems some
want to take them that way, but have various ways of declaring 'equal'.
> I'm not letting you off the hook of what you yourself started. Define how the
> primary or secondary balance forces of a V engine create losses that are
> sufficient to justify your position that a geometrically similar I6 produces
> more torque. If you can't then just retract the assertion.
And this is a third topic, not related to the other two statements.
But regardless of what I calculate, I am sure you'll just declare that
the value is not sufficient in your mind, or redefine 'the all other
factors equal clause' again. But it seems I am the only one providing
any cites or doing any actual work in this thread, everyone else is
just spouting their assertions without bothering to cite any sources.
But anyway, page 384 bosch handbook
"The external effects, consisting of free forces or moments
impart movement to the engine. This is then transmitted to the engine
supports in the form vibrations."
This means energy (that could be useful work, hp, torque output)
is being lost by those configurations with free forces or
momements. So already, not matter how small, the V6 is
losing energy that the I6 is not. So now it's only a question
of degree, how much better is an I6.
For a 90 degree V6, M1 = 3^.5 * F1 * a
M1 = free moment of the first order, F1 = mo * r * w^2 * cos alpha
mr = rotating mass, crank mass + (2/3)*connecting rod mass
mo = oscillating mass, piston mass + (1/3)*connecting rod mass.
a = crank shaft length per throw (best I can describe the figure)
alpha = crank angle.
w = engine speed
r = radius, connecting rod connection to center of crank.
M1 = 3^.5 * mo * r * w^2 * cos alpha * a
(kg * m / s^2) * m
W = .5*I*w^2 (I = sum(mass*radius^2)) torque = I*angular_accel=M1
angular acceleration = (dw/dt)
How much is being lost to this free moment of interia?
Energy lost = .5* M1 = .866 * mo * r * w^2 * a * cos alpha
So what do we want to use? say 1kg for mo, 5in (.127m) for r and a,
3000 rpm = 314 rad/s say 15 deg for alpha, numbers are all arbitary.
energy = 1331 J
The question is that significant? what rate is this loss at? everytime
the engine fires, 6 times (6 cyl) every 4 revs. 3000rpm = .83 rev/s
3/2 firings per rev => 1.25/s 1331J * 1.25/s= 1664W = 2.2hp
So I would estimate, somewhere around 2hp give or take a bit, provided
I didn't make any mistakes. Seems measurable to me.
Dave Baker
>Message-id: <Yhx1a.51332$vm2.28493@rwcrnsc54>
3000 rpm = 50rev/s. You've divided by 3600 for seconds per hour not seconds per
minute. Slap forehead and say "buggrit" a few times :)
50 x 1.5 x 1331 would mean 99825W or 134 bhp if the proceeding calculations
were correct which they aren't.
Ok, good try and applause for the attempt at ploughing through some complicated
maths but you can't take a moment calculation at an arbitrary crank angle and
turn that into an energy loss.
I'll say again. The energy losses due to vibration are negligible. There is no
actual way of calculating them in simplistic terms because that requires
knowledge about how the masses of the engine and supporting structure really
move. There has to be movement for work to be done and that movement depends on
resonant frequencies, stiffness of materials, damping and a whole shed load of
things which can't just be derived from any simple formula.
Vibration can be effectively damped by correctly designed mountings. If the
energy loss into the mountings was material they would get hot. Given the mass
of an average engine mounting, a few pounds of steel and rubber, if the energy
loss was even 1kw the mounts would soon melt.
let's run through what we've established so far in the search for support to
the generic premise that an I6 is in some way a better torque or power producer
than a V6
1) The geometry of the bore, stroke, rod length, chamber shape, cam profile and
other engine fundamental dimensions can't be a factor because they can be made
the same in an I6 or V6 for test purposes.
2) Firing interval can be the same in a 60 degree v6 and in another
configuration it only means uneven torque impulses rather than any change in
total torque applied over time.
3) Pulse tuning can be eliminated by using separate induction and exhaust
runners or coupling a 60 degree V6 in the same way as an I6.
4) Torsional crank problems are worse in an I6 so if they are a factor they
can't support the premise.
5) We end up left with vibration as the last straw to clutch to and that
appears incapable of support.
The simple fact is an engine will produce a torque curve dependent on how it is
designed and tuned not on where the cylinders are located in space. Cam
duration, compression ratio, valve size, port area, induction and exhaust flow
are what matter. Perhaps you've come across some I6s tuned in a specific way
that have led you to the premise that they behave in a fundamentally different
way to a V6. They don't.
The premise fails and I think this thread has now exhausted my interest.
Ray
> 1) The geometry of the bore, stroke, rod length, chamber shape, cam profile and
> other engine fundamental dimensions can't be a factor because they can be made
> the same in an I6 or V6 for test purposes.
<snip>
> The simple fact is an engine will produce a torque curve dependent on how it is
> designed and tuned not on where the cylinders are located in space. Cam
> duration, compression ratio, valve size, port area, induction and exhaust flow
> are what matter. Perhaps you've come across some I6s tuned in a specific way
> that have led you to the premise that they behave in a fundamentally different
> way to a V6. They don't.
>
What about a really spaced out V6? Two banks wide, but as long as
an I-6? <grin> I think people are reading too much into this...
What about the Porsche V6 you'll find in all the 911's? It's a
very "flat" V, but that is the point I think you're trying to make -
cylinder arrangement is really irrelevant in the grand scheme of things
as far as theoretical power production is concerned.
Brent P
> 3000 rpm = 50rev/s. You've divided by 3600 for seconds per hour not seconds per
> minute. Slap forehead and say "buggrit" a few times :)
it happens....
> 50 x 1.5 x 1331 would mean 99825W or 134 bhp if the proceeding calculations
> were correct which they aren't.
> Ok, good try and applause for the attempt at ploughing through some complicated
> maths but you can't take a moment calculation at an arbitrary crank angle and
> turn that into an energy loss.
I know the arbitrary numbers could end up with a flawed estimation, but that
just means the numbers are chosen poorly, which I fully accept.
> I'll say again. The energy losses due to vibration are negligible.
You assert, so I ask why?
I've put together the best estimation I can from the texts I have
available to me at 3am on a sunday morning. There is a loss going
on. I don't have any texts that plunge further into the issue and
pieced it together from what I do have.
Engine design is primarily centered around just canceling out the
vibrations rather than a determination of the energy lost. Because all
factors are rarely equal, and just by doing something else (valves,
induction, etc etc) can be made up for. The engines simply aren't made
equal in reality, so nobody seems to wish to bother with what become
irrelevant calculations.
> There is no
> actual way of calculating them in simplistic terms because that requires
> knowledge about how the masses of the engine and supporting structure really
> move. There has to be movement for work to be done and that movement depends on
> resonant frequencies, stiffness of materials, damping and a whole shed load of
> things which can't just be derived from any simple formula.
Yes I know. There are alot of holes in the handbook equations and I
tried to piece them together as best I can to get from a to b.
> Vibration can be effectively damped by correctly designed mountings.
After internal measures are taken to cancel out the forces and moments.
> If the
> energy loss into the mountings was material they would get hot. Given the mass
> of an average engine mounting, a few pounds of steel and rubber, if the energy
> loss was even 1kw the mounts would soon melt.
Two reasons why that is false 1) Engines can use mechanical means within the
engine to create forces and moments of the about same magitude
in the opposite direction. It would have an energy loss due to the
motion of whatever masses were used but it wouldn't have materials
absorbing the energy as the forces would be canceled before hand.
2) for the remainder, the engine,drivetrain, exhaust, etc all still move,
however the vibrations are isolated by the mounts. IE, not absorbed,
simply not transfered, the energy disipated as movement.
For instance, the I4 in the winter beater has what can be a nasty
vibration at idle with alot of electrical load if the exhaust isn't
hanging right. So long as the exahust pipe at the muffler is held off
the car dead axle (for lack of a better term for the structure between
the two rear wheels on a FWD) it's barely preceptable. There is no
path of transmission. But I know the vibration didn't go away, it's
just not annoying me.
> let's run through what we've established so far in the search for support to
> the generic premise that an I6 is in some way a better torque or power producer
> than a V6
> 1) The geometry of the bore, stroke, rod length, chamber shape, cam profile and
> other engine fundamental dimensions can't be a factor because they can be made
> the same in an I6 or V6 for test purposes.
Which is fictious, as all factors are not equal. I don't recall making a
claim to this set of conditions, if something apeared to be it was
not my intent.
> 2) Firing interval can be the same in a 60 degree v6 and in another
> configuration it only means uneven torque impulses rather than any change in
> total torque applied over time.
And I have stated that.
> 3) Pulse tuning can be eliminated by using separate induction and exhaust
> runners or coupling a 60 degree V6 in the same way as an I6.
> 4) Torsional crank problems are worse in an I6 so if they are a factor they
> can't support the premise.
Or we can assume a stiffer crank for the I6 due to material or
manufacturing process, or both the same based on one that is sufficently
stiff to render it negligable for the I6, which will be past the point
of diminishing returns for the V6. Like I said, all other factors are
hardly equal.
> 5) We end up left with vibration as the last straw to clutch to and that
> appears incapable of support.
Again, you are applying this from piston-arragement-only, which I was
not, as all other factors are never equal. But even if it were, we know
that energy is lost through this. It's only a question of degree.
> The simple fact is an engine will produce a torque curve dependent on how it is
> designed and tuned not on where the cylinders are located in space. Cam
> duration, compression ratio, valve size, port area, induction and exhaust flow
> are what matter.
And I didn't say those weren't the over-riding factors. They are. Nobody
claimed that all I6s are better than all V6s.
> The premise fails and I think this thread has now exhausted my interest.
You haven't shown anything that supports your assertion that the free
moments are insignificant. You put it forth as an assertion, and that
is how it's been. I've shown they exist, and if we hold to an all
other factors equal (which they really aren't), it's a negative on
the V6 configuration.
Brent P
> 3000 rpm = 50rev/s. You've divided by 3600 for seconds per hour not seconds per
> minute. Slap forehead and say "buggrit" a few times :)
it happens....
> 50 x 1.5 x 1331 would mean 99825W or 134 bhp if the proceeding calculations
> were correct which they aren't.
> Ok, good try and applause for the attempt at ploughing through some complicated
> maths but you can't take a moment calculation at an arbitrary crank angle and
> turn that into an energy loss.
I know the arbitrary numbers could end up with a flawed estimation, but that
just means the numbers are chosen poorly, which I fully accept.
> I'll say again. The energy losses due to vibration are negligible.
You assert, so I ask why?
I've put together the best estimation I can from the texts I have
available to me at 3am on a sunday morning. There is a loss going
on. I don't have any texts that plunge further into the issue and
pieced it together from what I do have.
Engine design is primarily centered around just canceling out the
vibrations rather than a determination of the energy lost. Because all
factors are rarely equal, and just by doing something else (valves,
induction, etc etc) can be made up for. The engines simply aren't made
equal in reality, so nobody seems to wish to bother with what become
irrelevant calculations.
> There is no
> actual way of calculating them in simplistic terms because that requires
> knowledge about how the masses of the engine and supporting structure really
> move. There has to be movement for work to be done and that movement depends on
> resonant frequencies, stiffness of materials, damping and a whole shed load of
> things which can't just be derived from any simple formula.
Yes I know. There are alot of holes in the handbook equations and I
tried to piece them together as best I can to get from a to b.
> Vibration can be effectively damped by correctly designed mountings.
After internal measures are taken to cancel out the forces and moments.
> If the
> energy loss into the mountings was material they would get hot. Given the mass
> of an average engine mounting, a few pounds of steel and rubber, if the energy
> loss was even 1kw the mounts would soon melt.
Two reasons why that is false 1) Engines can use mechanical means within the
engine to create forces and moments of the about same magitude
in the opposite direction. It would have an energy loss due to the
motion of whatever masses were used but it wouldn't have materials
absorbing the energy as the forces would be canceled before hand.
2) for the remainder, the engine,drivetrain, exhaust, etc all still move,
however the vibrations are isolated by the mounts. IE, not absorbed,
simply not transfered, the energy disipated as movement.
For instance, the I4 in the winter beater has what can be a nasty
vibration at idle with alot of electrical load if the exhaust isn't
hanging right. So long as the exahust pipe at the muffler is held off
the car dead axle (for lack of a better term for the structure between
the two rear wheels on a FWD) it's barely preceptable. There is no
path of transmission. But I know the vibration didn't go away, it's
just not annoying me.
> let's run through what we've established so far in the search for support to
> the generic premise that an I6 is in some way a better torque or power producer
> than a V6
> 1) The geometry of the bore, stroke, rod length, chamber shape, cam profile and
> other engine fundamental dimensions can't be a factor because they can be made
> the same in an I6 or V6 for test purposes.
Which is fictious, as all factors are not equal. I don't recall making a
claim to this set of conditions, if something apeared to be it was
not my intent.
> 2) Firing interval can be the same in a 60 degree v6 and in another
> configuration it only means uneven torque impulses rather than any change in
> total torque applied over time.
And I have stated that.
> 3) Pulse tuning can be eliminated by using separate induction and exhaust
> runners or coupling a 60 degree V6 in the same way as an I6.
> 4) Torsional crank problems are worse in an I6 so if they are a factor they
> can't support the premise.
Or we can assume a stiffer crank for the I6 due to material or
manufacturing process, or both the same based on one that is sufficently
stiff to render it negligable for the I6, which will be past the point
of diminishing returns for the V6. Like I said, all other factors are
hardly equal.
> 5) We end up left with vibration as the last straw to clutch to and that
> appears incapable of support.
Again, you are applying this from piston-arragement-only, which I was
not, as all other factors are never equal. But even if it were, we know
that energy is lost through this. It's only a question of degree.
> The simple fact is an engine will produce a torque curve dependent on how it is
> designed and tuned not on where the cylinders are located in space. Cam
> duration, compression ratio, valve size, port area, induction and exhaust flow
> are what matter.
And I didn't say those weren't the over-riding factors. They are. Nobody
claimed that all I6s are better than all V6s.
> The premise fails and I think this thread has now exhausted my interest.
You haven't shown anything that supports your assertion that the free
Paul J Johnson
"WÇY" <WÇY...@czerny.labs> wrote in message
news:1i774v8rpnochanfv...@4ax.com...
> Many manufacturers have turned from in-line 6-cylinder engines to V-6
> engines.
Cos of the amount of yanks who keep buying FWD V6 minivans rather
than I6 BMWs?
> However, most posts state that an in-line 6 is a better
> solution.
Yup - cos most posters aspire to the BMW!
Don't confuse popularity with technical superiority.
--
PJ
SoCalMike
back to the question then...
why did chevy decide to go with a straight 6?
given their parts-bin mentality, wouldnt it have made more sense for them to
design a torquey V6 so they could use it in other cars, etc?
maybe they plan on building a BMW-type sports car and using it in that
eventually?
Steve
> It was the IRL that allowed-mandated ( I'm not sure which) the single plain
> crank. But you have it backwards. The exhaust note from the 2 plane crank
> vibrated the electronics to hell. When they switched to the single plane
> crank-viola! The single plane crank has been used for decades in designed
> for competition engines. CART has always used (V8) engines with a flat
> crank.
>
> Regards
> Chas Hurst
I'm not talking about exhaust vibration, I'm talking about inherent
mechanical imbalance. The whole reason that virtually all V8s went to
90-degree cranks decades ago is better inherent balance. The 180-degree
crank has as bad inherent balance (worse, actually!) than an inline 4.
Its ONLY advantage is that combustion strokes always alternate between
banks, wheras 90-degree cranks fire a pair of cylinders on each bank
sequentially. Thats what gives a 90-degree crank v8 that wonderful
"burble" that no other engine has.
Steve
> Dave has it about right on this one after a short explanation from me.
> The turbo is just a pump that pushes more air into the cylinders and
> in the case I illustrated, allows a four cylinder of the same family
> and otherwise same design as a six to produce the same horsepower for
> a valid comparison. In most cases [all that I am familiar with] the
> four cylinder engine produces more peak torque and logically has a
> higher torque rise than the six. Remember that they produce the same
> maximum horsepower at the same revs. I do not venture an opinion on
> why this should be so, just a simple observation of a common
> phenomenon within many engine families.
>
A turbocharger does essentially the same thing to an engine as
increasing its displacement. It allows it to process more air/fuel per
turn of the crank. Comaparing a non-turbo 6 engine to a turbo 4 engine
and claiming that the 4 "produces more torque" is specious. It is not
the "4" part that produces the torque, its the "turbo" part.
If what you were saying were true, then we could expect a Dodge 3.9L v6
to produce more torque than a 5.2L v8 using the same size/shape
cylinders (it does not). We could expect the Chevy 4.2L v6 to produce
more torque than the 5.7L v8 that uses the same shape cylinders (it does
not). We could expect the Jeep 3.7L v6 to produce more torque than the
4.7L v8 using the same cylinders (it does not). We could expect the
Detroit Diesel 3-71 to produce more torque than the 6-71 (all the many
permutations of the -71 engine use the same cylinder geometry) it does
not. Need I go on?
Steve
> How does intercooling & turbocharging a 4-cylinder to boost power affect
> it's gas consumption rate (i.e. fuel efficiency) ? I ask this because you
> mention increased burn efficiency.
>
>
>
It greatly increases thermal efficiency by using recovered exhaust heat
to do a large portion of the compression of the intake air prior to
ignition or fuel-injection. This is yet another reason that it is
completely invalid to compare a turbo 4 to a N/A 6 and then make claims
about the relative torque output of the engine as being "due to the
number of cyinders".
If you don't care about efficiency so much, then you can get the same
result at the crankshaft just by increasing displacement or (within
limits) static compression ratio.
Also, you can't draw too many generalizations about turbo spark-ignition
(gasoline) engines from the design and operation of turbo
compression-ignition (diesel) engines. The diesel can take much more
advantage of a high boost pressure and improved heat recovery because
there is no danger of detonation in a diesel. There is less need for
intercooling (aftercooling, to be pedantic) for the same reason. High
inlet air temperature on a diesel does not do catastrophic damage like
high inlet charge temperature on a spark-ignition engine can.
Richard Bell
>Brent P wrote:
>
>> Or do different configurations have advantages over one another beyond
>> manufacturing and packaging but in performance?
>
>No. In a purely theoretical world, an engine of X displacement
>could make Y torque, irrelevant of # of cylinders, location, # of
>camshafts, etc. etc. An engine is just an air/gasoline pump, all that
>matters is that in a certain of gasoline is a certain amount of energy.
>
>
>In the _real_world_, it IS a YES, because it's really about:
>1)Money: Aluminum heads are better than cast iron heads, but cost more.
>Inline 6 blocks are "simple", but imagine making sure the deck of a
>straight 6 block is level - that's a long distance to be made square.
>(etc. etc...)
Making something straight and level is one of the easiest things to do,
just look at the pyramids (tedious too, but they took the pains). The
tricky bits are curves that are not circular. If you can make the
cylinder bores parallel and the main journal bearings coaxial, machining
a level deck is the last of your worries. The I6 has the bonus that the
operation is only done once, not twice, on a simpler jig.
Chas Hurst
"Steve" <n...@spam.thanks> wrote in message
That"ONLY" advantage is the exact reason why designed for racing V8s use a
flat crank. The exhaust system can be configured with one bank into a
collector. A 2 plane crank requires mixing cylinder from both banks, and
results in an untidy or more likely, impossible exhaust system. The
designers of racing engines are willing to trade the imbalance for more
power. The burble of a 90 deg V8 turns into a destructive blare at 9000rpm.
In the early years of the IRL, the engines had (by rule) a 2plane crank.
They sounded like enraged Harley-Davidsons and were described as
"acoustically ugly". When the rule was changed a few years ago, every engine
builder switched to a flat crank. They now sound like kazoos. The are more
parameters to be considered than inherent balance.
Huw
"Steve" <n...@spam.thanks> wrote in message
Rubbish. The turbo is just an air pump. A means to an end. The end
being more power from a given displacement.
>
> If what you were saying were true, then we could expect a Dodge 3.9L
v6
> to produce more torque than a 5.2L v8 using the same size/shape
> cylinders (it does not).
I suspect it does not produce equal horsepower either. My example
does.
We could expect the Chevy 4.2L v6 to produce
> more torque than the 5.7L v8 that uses the same shape cylinders (it
does
> not). We could expect the Jeep 3.7L v6 to produce more torque than
the
> 4.7L v8 using the same cylinders (it does not). We could expect the
> Detroit Diesel 3-71 to produce more torque than the 6-71 (all the
many
> permutations of the -71 engine use the same cylinder geometry) it
does
> not. Need I go on?
>
>
No. You have amply demonstrated your lack of understanding.
Huw
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Brian Evans
The only significant advantage that I've been able to think of that a V-6
has over an I6 is the V-6 is shorter - and that's what counts when you make
an engine that has to fit into a transverse mounting position. To me, the
I6 and the V6 are equal as far as power and torque potential, and the I6 has
a significant advantage as far as vibration is concerned. With some intake
setups, the V-6 may have an advantage (think single carb I6 and mixture
distribution issues), but the mechanical FI Mercedes I6 that I had was a
superb engine.
I'd buy an I6 any day, over a V6.
Brian
"Paul J Johnson" <no...@nowhere.tv> wrote in message
news:b2763o$9ak$1...@sparta.btinternet.com...
Steve
> "Steve" <n...@spam.thanks> wrote in message
> news:3E47C9CE...@spam.thanks...
>
> engine
>
>>and claiming that the 4 "produces more torque" is specious. It is
>
> not
>
>>the "4" part that produces the torque, its the "turbo" part.
>
>
> Rubbish. The turbo is just an air pump. A means to an end. The end
> being more power from a given displacement.
>
So do you still believe that if you have a turbocharged engine running
on a dynomometer, that if you walk over and open the wastegage the
engine will continue to maintain the same torque?
I say AGAIN, the fact that you observed that a turbo 4 produces more
torque than a N/A 6 is due to the presence of the TURBO, not due to the
absence of two cylinders.
Huw
"Steve" <n...@spam.thanks> wrote in message
> Huw wrote:
> > "Steve" <n...@spam.thanks> wrote in message
> > news:3E47C9CE...@spam.thanks...
> > > Comaparing a non-turbo 6 engine to a turbo 4
> >
> > engine
> >
> >>and claiming that the 4 "produces more torque" is specious. It is
> >
> > not
> >
> >>the "4" part that produces the torque, its the "turbo" part.
> >
> >
> > Rubbish. The turbo is just an air pump. A means to an end. The end
> > being more power from a given displacement.
> >
>
>
> So do you still believe that if you have a turbocharged engine
running
> on a dynomometer, that if you walk over and open the wastegage the
> engine will continue to maintain the same torque?
Of course it will suffer from a lack of oxygen which will not allow
all the energy in the fuel to be used efficiently. I cannot see that
this has any bearing on the arguement.
>
> I say AGAIN, the fact that you observed that a turbo 4 produces more
> torque than a N/A 6 is due to the presence of the TURBO, not due to
the
> absence of two cylinders.
>
>
But apart from fewer cylinders and the addition of a turbo to allow
identical maximum power, the engines are the same apart from more
maximum torque from the four cylinder.
To recap. The four cylinder will produce more maximum specific torque
than the identical design, identically powered six of equal individual
cylinder capacity and dimension/design. You cannot find a more similar
comparison, yet in all cases I can think of the four produces more
torque than the six. Of course one would always expect less peak
torque from a substantially less powerful engine, which is what you
are arguing. No surprise there to any halfwit!
As an aside, the four is usually more responsive and sharp, lower
inertia. Also the four, within a single family, is more often than
not, more economical to a measurable degree than the six.
The figures do not lie. There may be many reasons for this, not least
the poor thermal efficiency and higher pumping loss of a mildly rated
engine. Certainly the sixes that I am thinking of are far more
competitive and efficient at higher rates of tune. A six in these
engine families might vary from 100hp at the low end to 250hp in turbo
intercooled form and from 450Nm torque to nearly 1500Nm from the same
engine capacity. Specific fuel consumption will be at a low of
230g/kW/h [at most efficient point in rev range] for the least
efficient member of the family, to around 200g/kW/h for the best.
Steve
> "Steve" <n...@spam.thanks> wrote in message
>>I say AGAIN, the fact that you observed that a turbo 4 produces more
>>torque than a N/A 6 is due to the presence of the TURBO, not due to
>
> the
>
>>absence of two cylinders.
>>
>>
>
>
> But apart from fewer cylinders and the addition of a turbo to allow
> identical maximum power, the engines are the same apart from more
> maximum torque from the four cylinder.
Which is enough to INVALIDATE ANY COMPARISON. That's the whole point,
and if THAT isn't clear to "any halfwit" (your phrase) then I don't know
what would be clear.
Richard Bell
>Huw wrote:
>> "Steve" <n...@spam.thanks> wrote in message
>> news:3E47C9CE...@spam.thanks...
>> > Comaparing a non-turbo 6 engine to a turbo 4
>>
>> engine
>>
>>>and claiming that the 4 "produces more torque" is specious. It is
>>
>> not
>>
>>>the "4" part that produces the torque, its the "turbo" part.
>>
>>
>> Rubbish. The turbo is just an air pump. A means to an end. The end
>> being more power from a given displacement.
>>
>
>
>So do you still believe that if you have a turbocharged engine running
>on a dynomometer, that if you walk over and open the wastegage the
>engine will continue to maintain the same torque?
You are fighting a losing battle. A vocal majority of posters on this
newsgroup do not firmly grasp thermodynamics and believe that the only
method of increasing the power of an IC engine is to ram more fuel through
it, while being blythely oblivious to the fact that increasing the
compression ratio boosts power by wasting less fuel.
Do not bother explaining how turbine driven compressor increases both the
compression and expansion, while an accessory driven pump only increases
compression, so that the turbocharged engine always produces more torque
than a supercharged engine running the same boost.
I confidently believe that these posters think that a 5l V8 with a 4-1
compression ratio must produce as much power as a 5l V8 with a 10-1 ratio,
as the carburator of the high compression engine cannot pull any more fuel
into the engine than the low compression engine (both are normally
aspirated).