Why is Miata MPG So Awful?
Jack
"Karl Kittler" <soli...@ptd.net> wrote in message
news:3E0548D5...@ptd.net...
> Here's some things that seem obvious but
> may not be to check:
> Tire pressure, this is the biggest
> factor in poor mileage most of the time.
>
> Plugs, wires and timing.
> Large variations from stock, if you put
> 18" "inexpensive" wheels on, they are
> probably very heavy, hence poor mileage.
I got 15'' lo-pro tires @ $60/each -- that considered inexpensive? im not
too sure..
> Junk in the trunk. Excess weight will
> bring that number down quickly.
dont have much in there.. except for the extra tire
> Driving style. If you upshift when
> cruising in slow traffic, it will
> increase your numbers, and stay below
> 4000 rpm and avoid WOT if at all
> possible.
im sorry, what is WOT?
> If you're like me, WOT above 4000 rpm is
> why I bought a miata.
I usually shift up around 3000 - 3500 rpm, rarely do I go up to 4000 rpm
unless im on the freeway.
Another thing --
when im coming up to a red light, I shift to a lower gear to use the
engine to help the car stop.. Is this a good idea? The other way is to put
it in neutral and use my brakes to stop.. but when i do that it takes me
longer to stop... maybe weak brakes? How responsive is everyone else's
brakes? I get afraid that I might hit the car ahead of me by just using the
brakes.
-SK
tooloud
news:l4nN9.35179$3t6....@nwrddc03.gnilink.net...
>
> "tooloud" <nospa...@mchsi.com> wrote in message
> news:au4rt6$4c90l$1...@ID-121148.news.dfncis.de...
> > "HardwareLust" <cesl...@SPAMyahoo.com> wrote in message
> > news:Y89N9.77478$4W1....@nwrddc02.gnilink.net...
>
> > Why the premium? You're wasting your money, it's not doing anything for
> your
> > gas mileage, and there's actually talk that it can harm the engine if
your
> > car doesn't require it.
> >
>
> It seems to run better on Premium, and although I know it doesn't make a
> difference, I do get slightly better gas mileage on premium.
>
> Does Mazda recommend a particular gasoline for the 1.8L?
87-octane.
> And, how can premium gas harm your engine?
At least one auto manufacturer warns against the use of higher octane fuel
when it is not required. It seems that the unburned additives, used to slow
the fuel's burn rate, may actually form deposits in the combustion chamber.
--
tooloud
Remove nothing to reply...
Cliff Knight
less and it pings when it hot.
'90, # 4231, mfg 5/89
"tooloud" <nospa...@mchsi.com> wrote in message
news:au4rt6$4c90l$1...@ID-121148.news.dfncis.de...
> "HardwareLust" <cesl...@SPAMyahoo.com> wrote in message
> news:Y89N9.77478$4W1....@nwrddc02.gnilink.net...
> >
> > "Cliff Knight" <cli...@paladinmicro.com> wrote in message
> > news:D64N9.11455$0v3....@news.bellsouth.net...
> > > I get 28-30 mpg with my '90 1.6L -- that's good enough for me...
> > >
> > >
> > That ain't bad, but I get 33+ with my bone-stock '91 on premium. Of
> > course, that's mostly due to the 210 mile commute to work each day on
the
> > freeway. Now that I'm commuting 12 miles to the park-n-ride in my '99,
> I'm
> > back down to ~26 mpg.
>
> Why the premium? You're wasting your money, it's not doing anything for
your
> gas mileage, and there's actually talk that it can harm the engine if your
> car doesn't require it.
>
Cissy Brazil
>road trips
Same here....possible average of 33 MPG...freeway driving, particularly a long
drive with little variation in speed. Typical, I guess. Around town,
significanlty lower...like around 24-25 mpg, something like that. :-P
~Cissy
'90 Crystal White "one way or another" <ducking>
http://members.aol.com/ivamiata/Krikkit/index2.html
Lanny Chambers
"Jack" <no_of_yo...@yahoo.com> wrote:
> im sorry, what is WOT?
Wide Open Throttle. Also known as WFO (no, I won't explain that one).
> I usually shift up around 3000 - 3500 rpm, rarely do I go up to 4000 rpm
> unless im on the freeway.
Ah. If you've been doing this for years, your engine may be encrusted
with internal deposits. I redline mine all the time, and get 25 on
backroads, mostly in 3rd and 4th gears. At 80 mph on the highway, I'm
getting around 33 if it's not too windy, 34 with the top up. The car
gets flogged to 100+ mph at least monthly, to help keep it clean inside.
At 115k miles, my '94 runs like new and uses no oil. I'd hop into it
tomorrow for a trip to either coast, with no more preparation than
checking the tires.
Something is wrong with your Miata, Jack. Look into Motor Vac cleaning
(see your Yellow Pages). How old are your plugs and plugwires? Your air
filter element? Where's your timing set? Miatas are really robust, but
they do benefit from a little maintenance.
> How responsive is everyone else's
> brakes? I get afraid that I might hit the car ahead of me by just using the
> brakes.
Um...try pressing harder on the pedal. Miatas have great brakes,
powerful and easy to modulate, but the pedal action is not delicate. If
you really stand on it, you should be able lock all four wheels. Unlike
the typical sedan, the brakes are not overboosted and touchy.
Hard braking is a good thing to practice once in awhile. Find an empty
road and play. Learn threshhold braking, and you'll be amazed how
quickly a Miata can stop.
When was your brake fluid last flushed and changed? I like to do this
annually, to maintain the nice, solid pedal feel. Brake fluid absorbs
water from the air, and that causes a spongy pedal. The rear brakes
should be adjusted at every oil change, and the slider pins lubed to
prevent seizing.
You can let things slide and treat a Miata like a beater Chevy, but
don't expect the performance of a well-maintained sports car.
--
Lanny Chambers, St. Louis, USA
'94C
the alignment page:
http://www.hummingbirds.net/alignment.html
Leon van Dommelen
Miata Magazine at some time said something like, that the fuel system
of the Miata is optimized for the volatility of 87 octane fuel. Don't
know what it means, with fuel injectors.
Note that this only applies to the M1 Miatas.
Leon
--
Leon van Dommelen :) Bozo, the White 96 Sebring Miata .)
REMOVE THE "z"s -> domm...@zmiata.net www.dommelen.net
EXIT THE INTERSTATES (Jamie Jensen)
Leon van Dommelen
>BTW, I think the Miata's top-down Cd is probably a lot higher than
>0.35, probably well above 0.40.
Top up, 0.38. Top down 0.44. (Mazda wind tunnel). Most likely both
with pop-ups down. :)
Note however that a Miata is a low car, and drag coefficient is
per frontal area. So the actual drag is not as much as those
numbers would suggest. A Miata with a drag coefficient of 0.44
may have less actual drag than an SUV with 0.25. :)
Joe
"tooloud" <nospa...@mchsi.com> wrote in message
news:au4rt6$4c90l$1...@ID-121148.news.dfncis.de...
> "HardwareLust" <cesl...@SPAMyahoo.com> wrote in message
> news:Y89N9.77478$4W1....@nwrddc02.gnilink.net...
> >
> > "Cliff Knight" <cli...@paladinmicro.com> wrote in message
> > news:D64N9.11455$0v3....@news.bellsouth.net...
> > > I get 28-30 mpg with my '90 1.6L -- that's good enough for me...
> > >
> > >
> > That ain't bad, but I get 33+ with my bone-stock '91 on premium. Of
> > course, that's mostly due to the 210 mile commute to work each day on
the
> > freeway. Now that I'm commuting 12 miles to the park-n-ride in my '99,
> I'm
> > back down to ~26 mpg.
>
> Why the premium? You're wasting your money, it's not doing anything for
your
> gas mileage, and there's actually talk that it can harm the engine if your
> car doesn't require it.
>
Kevin Stevens
In article <emsN9.38478$KW2.1...@twister.austin.rr.com>,
"Jack" <no_of_yo...@yahoo.com> wrote:
> Another thing --
> when im coming up to a red light, I shift to a lower gear to use the
> engine to help the car stop.. Is this a good idea?
No. That technique is a 30 year old racing technique for saving brakes
when they were the weakest link and would fade to uselessness at a
moment's notice. The only reason for downshifting while stopping in a
modern (disk-brake) automobile is to sustain the ability to immediately
ACCELERATE at need. Or if you want to make racy vroom-vroom noises,
which I occasionally do. Sounded better in the Corvette, though. ;)
>The other way is to put
> it in neutral and use my brakes to stop.. but when i do that it takes me
> longer to stop... maybe weak brakes?
I do that a lot, but purists quite properly don't like it - the reason
having nothing to do with stopping but because if you have to accelerate
suddenly for some reason you can't. Typical behavior is to leave the
car in the gear it was approaching the stop and declutch when you get to
15mph or so.
> How responsive is everyone else's
> brakes?
If your brakes won't lock all four wheels at say 20mph with a hard stab
on them, they are seriously broken and unsafe and the car shouldn't be
driven until they are fixed. (They should actually be able to lock them
at a significantly higher speed, but I don't advise trying it except
under very controlled conditions.)
>I get afraid that I might hit the car ahead of me by just using the
> brakes.
You are just habituated to using engine compression. Look at it this
way - If you've performed the brake-locking test above, you know your
brakes can lock the wheels. That degree of braking is more than the car
can use to stop (you don't actually want to lock the wheels). So, if
the brakes alone can stop the car as fast as it can be stopped, how can
engine braking improve it? It can't, it's your use of the controls.
Work on your braking over a couple of weeks and you'll see - it's just
braking ;) a long-term habit. One exercise you can practise where it's
safe is to come to a stop with one side of the car on a painted line;
that wheel should lock up much quicker than the other side and it gives
you good feedback as to what's going on.
KeS
(Note below - to those about to get on my case about extremely
sophisticated use of engine braking during threshold braking to
selectively affect the rearwards brake bias - yes, I know what you're
talking about; yes, I use it sometimes under racing conditions; and no,
it's not relevant to this conversation.)
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hjarrett
drop a few miles per gallon at around 40,000 miles and immediately after
that an ignition wire failed. When I put new wires on the mileage jumped
right back up and has stayed there. I drive a mix of in town and Interstate
on a normal basis.
Hank J
"Jack" <no_of_yo...@yahoo.com> wrote in message
news:_j5N9.36002$6H6.9...@twister.austin.rr.com...
> 30 ? wow..
>
> what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
> but it seemed impossible
>
> did you change anything to improve the gas mileage?
>
> thanks
>
> -SK
>
> "hjarrett" <hjar...@hroads.net> wrote in message
> news:oI4N9.301$b_4....@sydney.visi.net...
> > That seems strange to me. I consistently get about 30MPG and a over
that
> on
> > road trips. I have a 94.
> > Hank (Of course I am the one with the oil leak problem and my OIL
mileage
> > was pretty bad!) J
> >
> > "Todd Kuzma" <tul...@TheRamp.net> wrote in message
> > news:3E04C45C...@TheRamp.net...
> > > I like small cars. I got a Miata because it was small and
> > > nimble. I was also hoping for good gas mileage but
> > > generally only received 25 mpg or so. It's light and has a
> > > relatively small displacement engine so why the poor mileage?
> > >
> > > I used to have a BMW so I looked up the latest figures on
> > > Edmunds:
> > >
> > > 2003 Miata
> > > 1.8 Liter 4-Cylinder
> > > 142 HP
> > > 2387 Pounds
> > > 23 mpg City/28 mpg Highway
> > >
> > > 2003 BMW 330i
> > > 3.0 Liter 6-Cylinder
> > > 225 HP
> > > 3285 Pounds
> > > 21 mpg City/30 mpg Highway
> > >
> > > The BMW weighs 900 pounds more, has an engine with 2 more
> > > cylinders and 1.2 liters of extra displacement, and offers
> > > 83 more horsepower yet offers similar mileage. Is the
> > > Bimmer motor that much better than the Miata?
> > >
> > > Even the heavier Mini Cooper and Cooper S offer much better
> > > economy:
> > >
> > > 2003 Mini Cooper
> > > 1.6 Liter 4-Cylinder
> > > 115 HP
> > > 2524 Pounds
> > > 28 mpg City/37 mpg Highway
> > >
> > > 2003 Mini Cooper S
> > > 1.6 Liter 4-Cylinder (Supercharged)
> > > 163 HP
> > > 2678 Pounds
> > > 24 mpg City/33 mpg Highway
> > >
> > > Todd Kuzma
> > > Heron Bicycles
> > > Tullio's Big Dog Cyclery
> > > LaSalle, IL 815-223-1776
> > > http://www.heronbicycles.com
> > > http://www.tullios.com
> > >
> >
> >
>
>
Jack
-SK
"Joe" <joec...@nospamearthlink.net> wrote in message
news:pjtN9.1576$ka5.1...@newsread1.prod.itd.earthlink.net...
Lanny Chambers
domm...@zmiata.net (Leon van Dommelen) wrote:
> A Miata with a drag coefficient of 0.44
> may have less actual drag than an SUV with 0.25. :)
And are we holding our collective breath for an SUV with a Cd of 0.25?
:-)
Per K. Nielsen
wrote:
>My 2001 pings like heck if I don't use premium so I use it also.
I thought the M2 had a built-in knock sensor?
--
Per K. Nielsen
Pixie - 94 Classic Red
I like curves!
Leon van Dommelen
>sorry, what does ping mean?
Autoignition. The fuel starts burning on its own before the flame
front from the spark plug hits it.
Frank Berger
are different things.
"Per K. Nielsen" <pnie...@image.dk> wrote in message
news:l8md0vs1ptu2jtl6e...@4ax.com...
Frank Berger
"Leon van Dommelen" <domm...@zmiata.net> wrote in message
news:c0oc0v4pgqapkjaim...@4ax.com...
My '96 always pings on 87, so I use 89. I thought that was basically what
is supposed to determine the decision.
pws
Lanny Chambers wrote:
> The rear brakes should be adjusted at every oil change, and the slider pins
> lubed to
> prevent seizing.
>
Every oil change? That means my rear brakes should have been adjusted 21 times by
now. I have adjusted mine three times in 50,000 miles and they work great. I like
a well maintained car and I consider the brakes to be the single most important
component to keep an eye on, but doing this adjustment every single oil change
seems excessive to me.
Pat
'96M
John Miller
> The rear brakes should be adjusted at every oil change, and the slider
> pins lubed to prevent seizing.
Lanny, aren't your rears self-adjusting? Mine are. ('96 USA model)
--
John Miller, N4VU
One father is more than a hundred schoolmasters.
-- George Herbert
Cliff Knight
gas used to advertise "anti-knock" additives. "Knocking" is also applied to
connecting rod bearing failures, usually big-end problems.
It's "pinking" for those on the other side of the pond...which is arguably a
more clear description of the sound when it's mild.
-cliff knight-
"Frank Berger" <Frank.D...@dal.frb.org> wrote in message
news:3e073477$4...@news.teranews.com...
Cliff Knight
> damspam...@rochester.rr.com (DM) wrote:
>
> >BTW, I think the Miata's top-down Cd is probably a lot higher than
> >0.35, probably well above 0.40.
>
> Top up, 0.38. Top down 0.44. (Mazda wind tunnel). Most likely both
> with pop-ups down. :)
>
> Note however that a Miata is a low car, and drag coefficient is
> per frontal area. So the actual drag is not as much as those
> numbers would suggest. A Miata with a drag coefficient of 0.44
> may have less actual drag than an SUV with 0.25. :)
>
This is quite true, also high[er] drag coefficient may be a factor of
aerodynamic design intended to increase downward force (and please, I'm not
suggesting the the Miata does this--although it may). For example, Indy and
Formula One cars can have a Cd of 0.6 or more (over 1.0) but they've got
powerful engines that use some (at times a LOT) of their power to keep that
puppy glued to the track at 200 mph.
-cliff knight-
L. Santer
around 35 mpg. That's not much fun though. A Geo Metro convertible
will probably get 35 mpg at 75 mph. That's not much fun either.
Hedonists have more fun.
Lanny Chambers
John Miller <NOS...@n4vu.com> wrote:
> Lanny, aren't your rears self-adjusting? Mine are. ('96 USA model)
No, and neither are yours. There's an Allen-headed manual adjuster
hidden beneath a 14mm plug in each rear caliper.
See: http://www.miata.net/garage/brakepad.html
John Miller
> No, and neither are yours. There's an Allen-headed manual adjuster
> hidden beneath a 14mm plug in each rear caliper.
Well, yes, that's what Mazda calls the "manual adjustment gear," and it's
used when R&R-ing the rear caliper. Fully documented in the factory
manual.
What I'm wondering is how the folklore got started that periodic
adjustments are necessary.
Just a couple of pieces of evidence:
- No periodic adjustment is called for in the factory manual
- When replacing rear pads on a car that has never had the manual
adjustment touched, it's still necessary to back out the screw several
turns. How did it get changed?
--
John Miller, N4VU
"The eleventh commandment was `Thou Shalt Compute' or `Thou Shalt Not
Compute' -- I forget which."
-- Epigrams in Programming, ACM SIGPLAN Sept. 1982
pws
Lanny Chambers wrote:
I thought that both the front and rear brake are self adjusting for pad
wear, but that the rear brakes need to be adjusted to allow for the
parking brake. Is this incorrect? If it is wrong, then why do the front
brakes lack this adjustment capability, and why have I seen rear pads
wear out evenly and work properly on other miatas despite never having
been adjusted?
Just curious,
Pat
'96M
Larry Gadbois
designed to deliver 140 hp on 87 octane. The 2001 and newer cars have VVT
and a higher compression ratio to generate that extra two horsepower (142 hp
on premium fuel).
Hmmmm..... what's wrong with this picture? Why is it that the 10AE model
will outrun the new ones. Why is it that the new owners have to pay 15% more
for their fuel.
Is the emission reduction due to a new engine design worth the increase in
octane requirement? Why didn't the miles per gallon improve on the new
models? Are the 2004 models really going to be another 200 pounds heavier?
Are heated power seats really necessary? Will the new Miata share the Ford
Focus platform? (Excuse me.... I just woke up from a nightmare!)
--
Larry
Remove ".nospam" from address to reply
***********
"Per K. Nielsen" <pnie...@image.dk> wrote in message
news:l8md0vs1ptu2jtl6e...@4ax.com...
Dave
then I am an easy driver and I have a 45 mile commute one way at 50 to 60
mph and only 3 stops.
Dave
2000 SE II
John Miller
> I thought that both the front and rear brake are self adjusting for pad
> wear,
Yes, that's right.
> but that the rear brakes need to be adjusted to allow for the
> parking brake. Is this incorrect?
That's correct. The rear (manual) adjustment is to take up slack in the
linkage between the parking brake handle and the brake pads.
As the pads wear, the caliper pistons' "home" position gets further and
further out in the cylinders, thus creating slack in the parking brake.
The adjustment is for the purpose of taking up that slack.
For people use their parking brakes occasionally, the system is
self-adjusting. But in any case, the adjustment is for the benefit of the
parking brake, not the service brakes.
--
John Miller, N4VU
Young men think old men are fools; but old men know young men are fools.
-- George Chapman
Frank
My 02 runs fine on the middle grade without spark knock or ping.
Frank
02 Laser Blue
"Larry Gadbois" <lgad...@earthlink.net.nospam> wrote in message
news:I_LN9.3289$b97.3...@newsread2.prod.itd.earthlink.net...
pws
John Miller wrote:
> That's correct. The rear (manual) adjustment is to take up slack in the
> linkage between the parking brake handle and the brake pads.
>
> As the pads wear, the caliper pistons' "home" position gets further and
> further out in the cylinders, thus creating slack in the parking brake.
> The adjustment is for the purpose of taking up that slack.
>
> For people use their parking brakes occasionally, the system is
> self-adjusting. But in any case, the adjustment is for the benefit of the
> parking brake, not the service brakes.
>
This is what I thought, which is why I was confused by Lanny's suggestion that
the adjustment should be made at every oil change. I was trying to figure out
how adjusting the parking brake would make a difference in the braking
performance of the car, unless the pads are dragging, in which case it would
obviously be beneficial to back the pads off of the rotors.
Pat
'96M
Leon van Dommelen
It is. Lowest that does not knock. Prolonged nonlight knock can
severely damage an engine.
You may want to try one of those anti-carbon treatments. They do
seem to help on my 96.
Larry Gadbois
10AE is the fastest U.S. model.
--
Larry
Remove ".nospam" from address to reply
***********
"Frank" <Hell...@Thanks.com> wrote in message
news:6NMN9.64201$Rt1.2...@twister.southeast.rr.com...
Leon van Dommelen
>
>"Leon van Dommelen" <domm...@zmiata.net> wrote in message
>news:81oc0vsicrmpf9bgj...@4ax.com...
>> damspam...@rochester.rr.com (DM) wrote:
>>
>> >BTW, I think the Miata's top-down Cd is probably a lot higher than
>> >0.35, probably well above 0.40.
>>
>> Top up, 0.38. Top down 0.44. (Mazda wind tunnel). Most likely both
>> with pop-ups down. :)
>>
>> Note however that a Miata is a low car, and drag coefficient is
>> per frontal area. So the actual drag is not as much as those
>> numbers would suggest. A Miata with a drag coefficient of 0.44
>> may have less actual drag than an SUV with 0.25. :)
>>
>
>This is quite true, also high[er] drag coefficient may be a factor of
>aerodynamic design intended to increase downward force (and please, I'm not
>suggesting the the Miata does this--although it may). For example, Indy and
>Formula One cars can have a Cd of 0.6 or more (over 1.0) but they've got
>powerful engines that use some (at times a LOT) of their power to keep that
>puppy glued to the track at 200 mph.
True. We aerospace engineers call that lift-induced drag, though
those *mechanical* engineers never got it into their heads
that lift is *up*. *We* would have F1 cars soaring above the
track! ;)
Somehow, (I have no data,) I doubt that the Miata produces much down
force for all that drag however. I would think it simply has the
aerodynamics of a brick. :)
Leon van Dommelen
>I've heard both terms used for pre-ignition,
Knock can cause pre-ignition by severely heating carbon deposits
and cause glowing deposits to break off ("wild ping") but normally
only ignites after the spark plug has already started the combustion.
I believe most people mean knock if they say "ping."
> detonation,
Car engines do not detonate. It is very hard to achieve detonation
even if you are really, really trying.
> etc. One brand of
>gas used to advertise "anti-knock" additives. "Knocking" is also applied to
>connecting rod bearing failures, usually big-end problems.
>
>It's "pinking" for those on the other side of the pond...which is arguably a
>more clear description of the sound when it's mild.
I always found the sound hard to describe. I certainly did not
recognize it from the descriptions I read when I heard it first.
But finding my knock sensor had been disconnected gave me a clue. :)
Leon
>"Frank Berger" <Frank.D...@dal.frb.org> wrote in message
>news:3e073477$4...@news.teranews.com...
>> I'm sure someone else will explain the difference, but pinging and
>knocking
>> are different things.
>>
>> "Per K. Nielsen" <pnie...@image.dk> wrote in message
>> news:l8md0vs1ptu2jtl6e...@4ax.com...
>> > On Mon, 23 Dec 2002 01:05:25 GMT, "Joe" <joec...@nospamearthlink.net>
>> > wrote:
>> >
>> > >My 2001 pings like heck if I don't use premium so I use it also.
>> >
>> > I thought the M2 had a built-in knock sensor?
>> > --
>> > Per K. Nielsen
>> > Pixie - 94 Classic Red
>> > I like curves!
>>
>>
>
--
Leon van Dommelen
>The knock sensor was added in '99. The 2000 was the last Miata that was
>designed to deliver 140 hp on 87 octane. The 2001 and newer cars have VVT
>and a higher compression ratio to generate that extra two horsepower (142 hp
>on premium fuel).
>
>Hmmmm..... what's wrong with this picture? Why is it that the 10AE model
>will outrun the new ones. Why is it that the new owners have to pay 15% more
>for their fuel.
So that they do not look cheap compared to S2000 and BMW Z4 owners? ;)
>Is the emission reduction due to a new engine design worth the increase in
>octane requirement?
It seems somewhat unfair to us Miata owners if you see what SUV owners
get away with. ;)
> Why didn't the miles per gallon improve on the new models?
Who cares about MPG on a Miata?
OK. OK, enough already, I have seen the thread.
> Are the 2004 models really going to be another 200 pounds heavier?
>Are heated power seats really necessary? Will the new Miata share the Ford
>Focus platform? (Excuse me.... I just woke up from a nightmare!)
Good. Using such a flimsy and unsafe platform would be outrageous,
since a *sturdy* Ford Explorer platform is readily available to
raise the Miata a safe distance from the ground and support its
increased weight at the same time.
Leon ;)
Jimmer50
Snow?
No excuses....it wasn't designed to be a snow car. It'll do it (I'm a daily
driver and have 10 winters of snow experience)
but it doesn't do it well. Were tennis shoes designed for the snow?
The Miata wasn't designed to get fabulous gas milage either. They'd have to
take away a lotl of the things we appreciate about this car in order to gain a
few mpg's.
Matthew Russotto
Jack <no_of_yo...@yahoo.com> wrote:
>30 ? wow..
>
>what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
>but it seemed impossible
I get over 30 on highway driving with real (non-RFG) gas. With
diluted RFG gas, 27 is the ceiling. 25 is my typical mileage in mixed
driving (with RFG shit-gas). When I've taken it to the racetrack, you
could watch the gauge drop if you dared take your eyes off the track..
--
Matthew T. Russotto mrus...@speakeasy.net
"Extremism in defense of liberty is no vice, and moderation in pursuit
of justice is no virtue." But extreme restriction of liberty in pursuit of
a modicum of security is a very expensive vice.
Matthew Russotto
HardwareLust <cesl...@SPAMyahoo.com> wrote:
>
>
>My tips: Use your cruise control as much as possible. And, drive slower! 5
>mph less doesn't make that much difference. I know, it only takes about 6
>minutes off my 109 mile commute. Lower rpm = less gas.
My '91 mileage didn't seem to change much between 55 and 75. Over
80mph and mileage dropped like a stone, though.
Matthew Russotto
Leon van Dommelen <domm...@zmiata.net> wrote:
>
>Miata Magazine at some time said something like, that the fuel system
>of the Miata is optimized for the volatility of 87 octane fuel. Don't
>know what it means, with fuel injectors.
It means exactly nothing, as volatility within the grade varies from
summer to winter and from region to region.
Matthew Russotto
Frank Berger <Frank.D...@dal.frb.org> wrote:
>I'm sure someone else will explain the difference, but pinging and knocking
>are different things.
They're two different sounds which result from the same two
conditions. IIRC, one of those two conditions tends to
result in one sound (though it can result in either), but the other
can result in either one depending on the severity.
The two conditions:
Detonation: Part of the fuel-air mixture explodes before the
flame-front from the spark hits it (but after the spark)
Pre-ignition: The entire fuel-air mixture explodes prior to the
spark.
The two sounds:
Knock: Sounds like marbles being shaken in a coffee can.
Ping: Onomotaopeoic. A clear metallic "ping" sound.
Knock occurs with less-severe detonation; you can hear it by
deliberately lugging the engine (e.g. accelerating while in too-high a gear)
Ping occurs with more-devere detonation, and IME with pre-ignition. I
once accidentially set my Miata to 18 degrees rather than the 14 I was
trying for, and got a couple of very obvious pings on the test drive.
Note, however, that no one is consistent about the terminology of the
two conditions.
Matthew Russotto
>even if you are really, really trying.
Oh yeah, wiseguy? Try filling a cylinder of a Chevy small-block
with water while it's running at redline. It'll detonate all right...
Jack
> My '91 mileage didn't seem to change much between 55 and 75. Over
> 80mph and mileage dropped like a stone, though.
i shud stop going 90 then :)
-Sk
Lanny Chambers
russ...@grace.speakeasy.net (Matthew Russotto) wrote:
> My '91 mileage didn't seem to change much between 55 and 75. Over
> 80mph and mileage dropped like a stone, though.
Same here. Your ears tell you when the lousy aerodynamics gets really
nasty. That, and watching the hood bulge upward.
Cliff Knight
I don't know if I'd go as far as "brick", my '90 with less than 100 RWHP
gets up to 100+ mph reasonably well--of course the frontal area is quite
small so total drag is low(ish).
And watch those ME slams! <g>
-cliff knight-
BSME MIT '73
Cliff Knight
"Jimmer50" <jimm...@aol.com> wrote in message
news:20021223212331...@mb-fc.aol.com...
Bingo!
It was/is not intended to be an economy car, nor an off-road vehicle
(whether your in the woods, at the beach, or "off" the road because of a
layer of snow and ice 'tween you and same.
It was/is intended to be relatively inexpensive, simple, and fun to drive,
and I think it (at least the NA's) meets that criteria quite well!
-cliff knight-
Michael Verive
> need to. :-)
And faster, too!
Mike Verive
mve...@peoplepc.com
Leon van Dommelen
>In article <3e073477$4...@news.teranews.com>,
>Frank Berger <Frank.D...@dal.frb.org> wrote:
>>I'm sure someone else will explain the difference, but pinging and knocking
>>are different things.
>
>They're two different sounds which result from the same two
>conditions. IIRC, one of those two conditions tends to
>result in one sound (though it can result in either), but the other
>can result in either one depending on the severity.
>
>The two conditions:
>Detonation: Part of the fuel-air mixture explodes before the
>flame-front from the spark hits it (but after the spark)
That would be called auto-ignition. Detonation would be the
flame front itself moving at excessive speed. And Chevy engines
and Miata engines do not detonate. Chevy engines explode when
you fill them with water, and Miata engines with aftermarket goodies
do if you keep the ignition on too long without running the engine.
>Pre-ignition: The entire fuel-air mixture explodes prior to the
>spark.
I thought it means that it *somewhere* ignited before the spark,
not that *all* of it must be gone at that time.
>The two sounds:
>
>Knock: Sounds like marbles being shaken in a coffee can.
>
>Ping: Onomotaopeoic. A clear metallic "ping" sound.
>
>Knock occurs with less-severe detonation; you can hear it by
>deliberately lugging the engine (e.g. accelerating while in too-high a gear)
>
>Ping occurs with more-devere detonation, and IME with pre-ignition. I
>once accidentially set my Miata to 18 degrees rather than the 14 I was
>trying for, and got a couple of very obvious pings on the test drive.
>
>Note, however, that no one is consistent about the terminology of the
>two conditions.
Detonation and auto-ignition have clear and different definitions.
However, in the far, far, past people erroneously assumed that
detonation occurred. While flow visualizations subsequently
showed that auto-ignition and not detonation occurred, the
car community at large apparently never got the update. Most people
who write books simply copy the previous books, propagating previous
mistakes until kingdom come.
Matthew Russotto
Leon van Dommelen <domm...@zmiata.net> wrote:
>russ...@grace.speakeasy.net (Matthew Russotto) wrote:
>
>>In article <3e073477$4...@news.teranews.com>,
>>Frank Berger <Frank.D...@dal.frb.org> wrote:
>>>I'm sure someone else will explain the difference, but pinging and knocking
>>>are different things.
>>
>>They're two different sounds which result from the same two
>>conditions. IIRC, one of those two conditions tends to
>>result in one sound (though it can result in either), but the other
>>can result in either one depending on the severity.
>>
>>The two conditions:
>>Detonation: Part of the fuel-air mixture explodes before the
>>flame-front from the spark hits it (but after the spark)
>
>That would be called auto-ignition. Detonation would be the
>flame front itself moving at excessive speed. And Chevy engines
>and Miata engines do not detonate. Chevy engines explode when
>you fill them with water, and Miata engines with aftermarket goodies
>do if you keep the ignition on too long without running the engine.
Unless you have a reference (one which has to do with automobiles and
not aircraft), I'll keep using the terms I'm using; everyone seems to
have different terms for the various conditions. I've never heard of
the flame front moving with excessive speed.
>>Pre-ignition: The entire fuel-air mixture explodes prior to the
>>spark.
>
>I thought it means that it *somewhere* ignited before the spark,
>not that *all* of it must be gone at that time.
Yeah, I was imprecise; the difference between this and the previous
condition is that the ignition starts before the spark.
Leon van Dommelen
>In article <c02h0v4no2d3cest5...@4ax.com>,
>Leon van Dommelen <domm...@zmiata.net> wrote:
>>russ...@grace.speakeasy.net (Matthew Russotto) wrote:
>>
>>>In article <3e073477$4...@news.teranews.com>,
>>>Frank Berger <Frank.D...@dal.frb.org> wrote:
>>>>I'm sure someone else will explain the difference, but pinging and knocking
>>>>are different things.
>>>
>>>They're two different sounds which result from the same two
>>>conditions. IIRC, one of those two conditions tends to
>>>result in one sound (though it can result in either), but the other
>>>can result in either one depending on the severity.
>>>
>>>The two conditions:
>>>Detonation: Part of the fuel-air mixture explodes before the
>>>flame-front from the spark hits it (but after the spark)
>>
>>That would be called auto-ignition. Detonation would be the
>>flame front itself moving at excessive speed. And Chevy engines
>>and Miata engines do not detonate. Chevy engines explode when
>>you fill them with water, and Miata engines with aftermarket goodies
>>do if you keep the ignition on too long without running the engine.
>
>Unless you have a reference (one which has to do with automobiles and
>not aircraft),
There is a well known text book from an MIT ME Professor on automotive
theory that has a valid discussion in the combustion chapter, including
pointing out the error. There are also some research monographs
explaining how people originally thought the fuel inside cars really
detonates. I looked the above up in the Stanford Library in response
to another thread in this group some years ago. I remember writing down
the references in a file folder, but not where I left the file folder. :)
If I remember, I'll try to look around the office for the folder when
I am back.
We also had a seminar speaker who reported the tremendous difficulty
in achieving detonation in a *hydrogen oxygen* mix! ;) I asked
him specifically about detonation in cars. He answered that he had
been told it is auto-ignition, not detonation. Yes, I think he was
an aerospace engineer working for NASA. ;)
> I'll keep using the terms I'm using; everyone seems to
>have different terms for the various conditions.
Anybody need more information on how incorrect info survives
after scientists showed it bull half a century or so ago? ;)
> I've never heard of
>the flame front moving with excessive speed.
Well, it is Christmas eve. And asking for a reference is a
good skeptical attitude. Have a nice Christmas! :)
Greg Esres
My engine book (by some John Lumley) says "Knocking was formerly
called detonation, but that is now reserved for steady-state
combustion situations in which the flame front propagates at
supersonic speeds (when the flame front propogates at subsonic speeds,
it is called deflagration.)"
Do you think that true "detonation" is what occurs in piston aircraft
engines, or is that autoignition, based on the above definition?
BRUCE HASKIN
Deflagrate, or Deflagration, is the burning at a given rate, ie. a rate
under about 4,000 meters per sec.
Auto gas is given additives to control that speed.
Detonation occures above that rate. (I have seen speedes of 12.000
meters using Hydrozine fuel mixtures) Oh and that will put a crank
shafts right out on the track in no time at all !!! <G>
That is an explosion. Most commercial explosives run about 6,000 to
8,000 MPS. M6 Military Blasting caps run about 9,000 MPS.
"Deflagration" at the "proper time" is normal.
"Detonation" occuring in a combustion chamber of a gasoline engine is
the "uncontrolled"expantion and most of the time is the result of too
much heat. (Blowers of some type !) or too lean a mixture, agin, too
much heat. It can and will send a jet of hot gas down the side of a
piston, the size of your little finger in no time at all and we all know
that, "ain't a good thing" <G>
I just saw a Miata engine (with a S/C) that just ate the pistons! One
piston had the top of the piston blown out down to the first ring & bent
up about 1/4" into the combustion chamber. All the other pistons were
pitted down in the valve area about 1/16 to 1/8". I can't say for sure,
but it looks like low fuel pressure caused a lean mixture.
Well so much for that.
Bruce RED '91
Boeing Security
"Lanny Chambers" <la...@hummingbirds.net> wrote in message
news:lanny-E4C48C....@newssvr11-ext.news.prodigy.com...
> In article <4yHN9.62$re1...@tornadotest1.news.pas.earthlink.net>,
> John Miller <NOS...@n4vu.com> wrote:
>
> > Lanny, aren't your rears self-adjusting? Mine are. ('96 USA model)
>
> No, and neither are yours. There's an Allen-headed manual adjuster
> hidden beneath a 14mm plug in each rear caliper.
>
> See: http://www.miata.net/garage/brakepad.html
Leon van Dommelen
>Well, I think we need to call things by their correct name.
>
>Deflagrate, or Deflagration, is the burning at a given rate, ie. a rate
>under about 4,000 meters per sec.
That would be burning *below* a given limiting rate, not *at*
given rate.
>Auto gas is given additives to control that speed.
Are you claiming auto gas burns at 4,000 m/sec??
And that the additives are *not* to resist auto-ignition, which
has nothing to do with speed?
>Detonation occures above that rate. (I have seen speedes of 12.000
>meters using Hydrozine fuel mixtures) Oh and that will put a crank
>shafts right out on the track in no time at all !!! <G>
No doubt it will. The question is whether detonation occurs in
automotive engines with normal fuels. My sources say it does not.
>That is an explosion. Most commercial explosives run about 6,000 to
>8,000 MPS. M6 Military Blasting caps run about 9,000 MPS.
>
>"Deflagration" at the "proper time" is normal.
>
>"Detonation" occuring in a combustion chamber of a gasoline engine is
>the "uncontrolled"expantion
Whose's definition is that, and what does it mean? How is it different
from auto-ignition?
> and most of the time is the result of too
>much heat. (Blowers of some type !)
Blowers of some kind add oxygen, not necessarily much heat.
> or too lean a mixture, agin, too
>much heat.
My sources listed a long list of factors that promote knock, not just
heat.
> It can and will send a jet of hot gas down the side of a
>piston, the size of your little finger in no time at all and we all know
>that, "ain't a good thing" <G>
>
>I just saw a Miata engine (with a S/C) that just ate the pistons! One
>piston had the top of the piston blown out down to the first ring & bent
>up about 1/4" into the combustion chamber. All the other pistons were
>pitted down in the valve area about 1/16 to 1/8". I can't say for sure,
>but it looks like low fuel pressure caused a lean mixture.
Do you have evidence this was caused by detonation instead of
pre-ignition?
Leon van Dommelen
><<Detonation and auto-ignition have clear and different definitions.>>
>
>My engine book (by some John Lumley) says "Knocking was formerly
>called detonation, but that is now reserved for steady-state
>combustion situations in which the flame front propagates at
>supersonic speeds (when the flame front propogates at subsonic speeds,
>it is called deflagration.)"
If that is the John Lumley I took Turbulence from at Cornell,
I think he is an aerospace engineer. ;) Anyway, my sources,
monographs from researchers in the field, said different;
they said that knocking was formerly *mistaken* for detonation,
which is quite a different statement than that of your John
Lumley. In other words, people really believed the flame front
would propagate at supersonic speeds. (Which is what autoignition
would look like if you did not have the accuracy to see that the
flame front is separate from the farthest burning regions.)
>Do you think that true "detonation" is what occurs in piston aircraft
>engines, or is that autoignition, based on the above definition?
I do not work in the field and can only cite from others who do,
and they were likely not concerned with aircraft engines. But given
the difficulty people claim of achieving detonation even if they want
it, I would surely guess it to be auto ignition.
Greg Esres
think he is an aerospace engineer. ;) >>
Same man! The book jacket merely says "Professor of Engineering,
Sibley School of Mechanical and Erospace Engineering, Cornell
University."
<<they said that knocking was formerly *mistaken* for detonation,
which is quite a different statement than that of your John Lumley.
>>
Yes it is. Hmmm. Guess I'll have to hold that question in the back
of my mind as I read further.
Leon van Dommelen
>Same man! The book jacket merely says "Professor of Engineering,
>Sibley School of Mechanical and Erospace Engineering, Cornell
>University."
While he is well known and respected in turbulence theory, I did
not know he was a particular expert in automotive theory. I guess
I did not keep in touch since then. :)
BRUCE HASKIN
I said, "Well I think we should call things by their correct name."
What I show is that there is a "speed is Meters Per Second" that has
been picked by the Explosives world that divides "Deflagration" and
"Detonation".
AND !! they just had to pick a spot & that is where it is. It's as
simple as that! (4,000 MPS)
"Gasoline" (burns !) Avgas, auto gas, boat gas..... and on & on. I said
that auto-gas "Deflagrates".
( I did not mention at what speed, but said "Auto gas is given additives
to control that speed" . I did not mention what additives or how they
control the speed, or what other things that they will control.
(The mian differance between "grades" of gas is the "speed" that the
mixture burns = "Deflagratoin". The higher the grade the slower it will
Deflagrate. SO, auto-gas will Deflagrate at many differant speeds.)
Oh & yes, that is called the "flame front" in ref. to the speed that the
burning mixture expands.
Your Question is, .."whether automotive engines with normal fuels."
Well, I think if we knew what "normal fuel" was and the exact contant
was, Your sources may be correct. However we get contaminated fuel many
times and just don't know it. We have a refinery up North of us that
makes our gas and they have screwed it up many times! We have had every
thing from jet fuel to heating oil mixed in & some just plain crud. The
contaminates will cause Detonation if combined with "high, hot mixtures"
I think you will agree that the "act of compressing the air" that a
Turbo or a JR type supercharger produces "heat". If they don't people
are wasting a lot of money on "intercoolers" and "JR liquid intercooling
systems". The higher the boost the more the heat, right ??
(almost last,) Leon I know you have aircraft in your background . Would
you go look up "ADI" (anti detonant injection) used on "ALL" large, high
HP piston aircraft engines & see what the word is on that type of
system. I know in our "Air Racing" world, that Race built Rolls Royce
engines at 3000 RPM & 120" MP, that if the ADI fails, it costs over
$120,000 to fix it! (and that's why we watch the "induction air temp" ,
"cyl head temp." & BMEP,(brake mean effective pressure), like a hawk!
While you are at it look at : Av grades 115/145,
100/130 & 80/87 and why they are, what they are.
<G> "this is not a test" , but it may put some light on the subject.<G>
Let's not link "pre-ignition" that you can hear, with detonation, that
you can almost NEVER hear until it has done the damage that it is going
to cause.
Yes, high combustion chamber pressure at normal cyl. temps., bad gas,
too much advance in ignition and carbon "hot spots" can & will cause
"pre-ignition" and it "pings" or makes a rapid loud clicking sound .
Hee, Hee, Hee, this is not a contest & no test at the end of the year,
Leon <G>
Bruce RED '91
Leon van Dommelen
>Nope Leon, that's not what I said!
Maybe not. *What* you say, if anything, is unclear.
>( I did not mention at what speed, but said "Auto gas is given additives
>to control that speed" .
Incorrect. Auto gas is given additives to resist auto-ignition, not
to change flame front speed.
>I think you will agree that the "act of compressing the air" that a
>Turbo or a JR type supercharger produces "heat". If they don't people
>are wasting a lot of money on "intercoolers" and "JR liquid intercooling
>systems". The higher the boost the more the heat, right ??
Irrelevant what I agree or not agree to w.r.t. heat.
*Your* statement was that only the heat promotes auto ignition.
Which I pointed out was incorrect. If you have evidence that
*only* heat causes auto ignition, go publish it and show the
experts wrong.
>(almost last,) Leon I know you have aircraft in your background . Would
>you go look up "ADI" (anti detonant injection) used on "ALL" large, high
>HP piston aircraft engines & see what the word is on that type of
>system.
I did. A search on "anti detonant injection auto-ignition" turns
up http://www.turbodynamics.co.uk/water.htm which shows clearly
that many people still use the incorrect term "detonation" when
they really mean auto-ignition.
If you have *any* reasonably authorative reference that shows that
detonation and *not* auto-ignition occurs in any piston engine,
let's have it. Otherwise you are just wasting my time.
[mega snip of remarks for which what is being asserted is unclear,
as is how it relates to the issues at hand.]
BRUCE HASKIN
First of all, I didn't post the things I did, to waste your time.
I'm sure you have the background to back up all the things that you say.
I started out by saying that there was a differance between Detonation
and Deflagration AND it is only the speed of the occurrence. (a speed
less than 4,000 MPS and a speed more than 4,000 MPS.).
It looks to me like you call all of this auto-ignition. I can live with
that, "new school vs old school".
You do however (as I see in your posts), contend that Detonation is no
longer a term that is used with gasoline engines. ..... I guess it's the
old story of, if it walks like a Duck and talks like a Duck, it's a
Duck! (but some will still say "no", it's a "Mallard".)
It was nice to see the ref. you showed about Aquamist Water Injection.
As it states at the start :
"aquamist ERL's latest generationof water-injection equipment. The main
function of these systems is to suppress detonation caused by high
temperature and pressure developedwithin the combustion chamber when the
effective compression ratio has been taken byond the auto-ignition point
by eather a turbo or a supercharger."
It looks like you disagree with this because you do not agree that the
terms Deflagration & Detination are defined as, above 4000 MPS and below
4,000 MPS and they cause different things to happen.
That is not a slam, just a differ of terms, I guess.
I do not have the web ability to fwd. this to you, so if you can just
hang with me I try to relay the info..
Taken from "Department of The Air Force, AF Manual 51-9", "Aircraft
Performance Engineering for reciprocating engines",
page: 154 , under the heading of, "The Engine Does Not Detonate - The
Charge Mixture Detonates"
COL. 2, first paragraph.:
".........; it is the charge mixture that detonates. The visual picture
of what happens has been obtained in a laboratory by high-speed motion
pictures, taken at 200,000 - frames per second through a quartz glass
window opening on a combustion chamber. ........"
------
(Note here:, it goes on to explain how the mixture gets to this point.)
------
"It is easy to look at this picture and say, "that's it", but still
takes the laboratory technition to analyze just what happened. His
report is that, as the mixture passes through the engine induction
system, it undregoes successive increases of temperature - first,
because of supercharging, then because of cylinder compression, and
finaly from the heating and squeezing of the unburned portion of the
charge (end zone) by the advancing flame fronts during combustion. If
thruogh these successive heating stages the final "end zone" tempreature
is greater than the kindling point of the charge, as determined by the
fuel grade and mixture strength, all of the unburned charge undergoes
spontaneous
( NOTE HERE: this is Leons "auto-ignition")
combustion and explodes."
( NOTE HERE: "explodes" = Detonation, or over 4,000 MPS)
"This results in an abnormal and uncontrolled rate of pressure, which
takes place with sufficient rapidity to set up waves within the
combustion chamber. These waves travelat supersonic" (page 155)
"velocity under the temperature conditions in the cylinder and cause
the "ping" or "knock" that is heard."
Col. 2.page 155:
"As detonatin becomes heavier. it's ugly nature asserts itself. The
hammer blows on the piston, chamber domes, and valves erode the surfaces
and causr fatigue failures These show up as cracked cylinder heads,
broken spark plugs, dished piston heads and dimpled exhaust valves"
"............. Even this degree of this detonation may not be apparent
on the flight deck until tha failure takes place."
It goes on and on, but this is where I am coming from on this subject.
Page 155 even comes with a picture of a piston with damage on it like I
said I saw on the JR supercharged Miata that had failed.
I hope this didn't waste any body's time. <G>
Leon and I are talking about the same thing, he just has a different
word for it <G>
The book also mentions preignition, but we all know that is from an
"incondecent point" in the chamber.
Happy New Year Leon <G>, I just need to stop and see you some time. I
think we could have a good time talking. My son is going to move to
Veldosta (sp) ? Moddy AFB Ga. when he comes back from "the Sand Box"
(F15E Strike Eagle pilot) to be a fighter instructor, in T-38C's. In the
summer. I'll look you up.
Bruce RED '91
Leon van Dommelen
>I started out by saying that there was a differance between Detonation
>and Deflagration AND it is only the speed of the occurrence. (a speed
>less than 4,000 MPS and a speed more than 4,000 MPS.).
>
>It looks to me like you call all of this auto-ignition. I can live with
>that, "new school vs old school".
No. Neither has anything to do with auto-ignition. Auto ignition
is when regions *before* the flame front start burning by themselves.
(Without the flame front hitting them.) The flame front moves
at the normal subsonic speed, whatever that may be.
The flame front is propagating away from the spark plug at normal
speed and regions, typically near the wall ignite before the flame
front hits them.
>You do however (as I see in your posts), contend that Detonation is no
>longer a term that is used with gasoline engines.
I do not. I said detonation is a thing that people no longer believe
*happens* in automotive engines. As far as I understand the references
I read.
>It was nice to see the ref. you showed about Aquamist Water Injection.
>As it states at the start :
>"aquamist ERL's latest generationof water-injection equipment. The main
>function of these systems is to suppress detonation caused by high
>temperature and pressure developedwithin the combustion chamber when the
>effective compression ratio has been taken byond the auto-ignition point
>by eather a turbo or a supercharger."
>It looks like you disagree with this because you do not agree that the
>terms Deflagration & Detination are defined as, above 4000 MPS and below
>4,000 MPS and they cause different things to happen.
Incorrect. (And I would think deflagration and detonation are
defined as subsonic and supersonic combustion, and that 4000 mps
is just a ball park number someone (AF?) gave for average engines.)
The point is that auto-ignition has nothing to do with flame front
speed since it occurs in unburned regions not at the flame front.
My point in mentioning the above reference is that the author uses
the term "detonation" when he means the completely different concept
of auto-ignition.
And the fact that cross searching detonation and auto-ignition produces
only this. Searching for "detonation" produces zillions of references,
but *none* of these has a discussion how it is different from auto-
ignition and when detonation would occur instead of auto-ignition.
I conclude that *all* of these zillions of authors use detonation
when they mean auto-ignition, and guess that many of them, like you,
may think the flame front really goes supersonic.
>Taken from "Department of The Air Force, AF Manual 51-9", "Aircraft
>Performance Engineering for reciprocating engines",
From what year does the research in this publication date, (check
the references), and is it a scientific document or a flight training
manual?
Learning to fly a Cessna 152 did not turn me into a decent pilot, but
it *did* teach me that the science in flight training books is
absolutely horrible lies. :)
>page: 154 , under the heading of, "The Engine Does Not Detonate - The
>Charge Mixture Detonates"
People deny both.
>COL. 2, first paragraph.:
>".........; it is the charge mixture that detonates. The visual picture
>of what happens has been obtained in a laboratory by high-speed motion
>pictures, taken at 200,000 - frames per second through a quartz glass
>window opening on a combustion chamber. ........"
My references said that people initially *thought* the flame front
moved at excessive speeds because early experiments could not
distinguish the flame front as being separate from the auto-ignition
zones, so it looked to them that the *flame front* leaped to the
auto-ignition zones, which would of course produce excessive speeds
for the flame front. (Infinite speeds, in fact. Poor Albert.)
>fuel grade and mixture strength, all of the unburned charge undergoes
>spontaneous
>
>( NOTE HERE: this is Leons "auto-ignition")
NOTE HERE: This is untrue. The mixture right in front of the flame
front *does not* undergo spontaneous combustion. Pockets of
mixture near the walls away from the flame front start to burn.
> combustion and explodes."
>
>( NOTE HERE: "explodes" = Detonation, or over 4,000 MPS)
I am unsure that explodes is the same as detonates. But auto-ignition
is not detonation.
>"This results in an abnormal and uncontrolled rate of pressure, which
>takes place with sufficient rapidity to set up waves within the
>combustion chamber. These waves travelat supersonic" (page 155)
Um, the question is whether *flame fronts* propagate at supersonic
speeds. A compression wave of any decent strength *will* propagate
at supersonic speeds, absolutely no objection from me.
>"velocity under the temperature conditions in the cylinder and cause
>the "ping" or "knock" that is heard."
>
>Col. 2.page 155:
>
>"As detonatin becomes heavier. it's ugly nature asserts itself. The
>hammer
Present in many internal combustion engines, I am sure. :)
> blows on the piston, chamber domes, and valves erode the surfaces
>and causr fatigue failures
My sources say auto-ignition causes non-design stresses since the
burning pattern is not as designed, and more importantly, destroys
the cooling boundary layers existing near the walls in a cylinder
under normal conditions, allowing excessive heat to get at the
surfaces and also allowing carbon deposits on those same walls to
start glowing; eventually glowing carbon particles can detach and
ignite the mixture before the spark plug does (wild ping, or
pre-ignition). Not a word about hammers in the combustion chamber,
though.
> These show up as cracked cylinder heads,
>broken spark plugs, dished piston heads and dimpled exhaust valves"
>"............. Even this degree of this detonation may not be apparent
>on the flight deck until tha failure takes place."
>
>It goes on and on, but this is where I am coming from on this subject.
>
>Page 155 even comes with a picture of a piston with damage on it like I
>said I saw on the JR supercharged Miata that had failed.
How did you measure that the flame front propagated at 4000+ m/s? :)
>Leon and I are talking about the same thing, he just has a different
>word for it <G>
No.
>The book also mentions preignition, but we all know that is from an
>"incondecent point" in the chamber.
No, I don't. What is incondecent point, anyway? As stated
above, my sources blame pre-ignition on pieces of glowing carbon
breaking off the walls and igniting the mixture when they get out
of the protective wall boundary layers.
>Happy New Year Leon <G>,
Happy new year, Bruce. :)
> I just need to stop and see you some time. I
>think we could have a good time talking. My son is going to move to
>Veldosta (sp) ? Moddy AFB Ga.
I think it is Valdosta, and Moody, but I do not keep up with it very
well. We do not have much contact since students from GA would have
to pay out-of-state tuition. I did have some Air Force types in Panama
City (Florida, not Panama) in my graduate classes.
> when he comes back from "the Sand Box"
>(F15E Strike Eagle pilot) to be a fighter instructor, in T-38C's. In the
>summer. I'll look you up.
Do. After Valdosta, Tallahassee will be Gotham City. :)
BRUCE HASKIN
you say. (:-) I think it comes from a "glowing light bulb" , are they
not "hot glowing items, an incandecant light bulb ? <G> or have they
changed the name of that too?<G>
Finding the speed ? ball park, (AF) ? No!
The way the Explosive Lab at the Edgewood Arsenal (U.S. Gov.) Md. did
it, (when I did some consulting there) is with high speed photography
and glass tubes. It was very easy to see the shock wave progress. It
would be a bit difficult to have an auto-ignition occure under that
condition.
Deflagration and Detonation come fom the Explosive side of the science
world.
(I spent 11 years in the Explosive world for Rocket Research Corp. and a
sub-company of theirs, Explosives Corp. of America. I was a concultant
to the Army Special Forces in "clandestine warfare and improvised
weapons")
Defligration and Detonation.
There is a definition of these two terms in the explosive science
world as I have ref. and it is 4,000 MPS, below and above that speed.
One is burning and the other is an explosion.
HOWEVER, I will yeld to you and your, .. :-) auto-ignition. Because I
know what you are saying & how it is applied. In the NEW world, what you
are saying in correct and I know that is what you are telling the new
kids :-)
Now, about the world being "flat", .................. :-)
I'll come see you when I'm down that way. (is it up or down, I can't
remember)
It's been fun Leon. See ya.
Bruce RED '91
BRUCE HASKIN
"auto-ignition" ? ....... and is that a "high speed" or "low speed"
diesel ? It must be a "low speed" cause a "high speed" uses a glow plug!
hee, hee, hee. but that would be an incandesent, wouldn't it ?
see ya Leon, <G>
Bruce RED '91
Leon van Dommelen
>The way the Explosive Lab at the Edgewood Arsenal (U.S. Gov.) Md. did
>it, (when I did some consulting there) is with high speed photography
>and glass tubes. It was very easy to see the shock wave progress. It
>would be a bit difficult to have an auto-ignition occure under that
>condition.
This is what my references did. And they observed auto-ignition.
Also, I am confused about you saying the "shock wave progress".
We are talking about the *flame front* progressing. Shock waves
*always* progress supersonically.
When was the date of your experiments? More importantly, do you
know about an actual report of those experiments in a scientific
journal?
DM
>There is a well known text book from an MIT ME Professor on automotive
>theory that has a valid discussion in the combustion chapter, including
>pointing out the error.
Probably referring to John B. Heywood, the text is "Internal
Combustion Engine Fundamentals". On my X-mas "to read" list ;-)
Leon van Dommelen
I believe that is it. I am planning to order it myself, since
I see coming that eventually I end up as the college SAE advisor.
I am a mathematical aerospace engineer, but reading this group for
years has given me a tremendous amount of actual knowledge about
cars. ;) I have no doubt I now know a lot more about cars than any
other professor in my department.
The other thing I really need is a very authorative and exhaustive
reference on tires. :)
BRUCE HASKIN
from Edgewood, they could be found. All done in the mid to late 1960's
for the ARMY. Many were done to study "Shape Charge" results. I don't
know if you have info. on how that works, but here is a short look.
Take a "wine bottle" and remove the "neck" so you have a "cylinder" and
a cone at the bottom. Now load the cyl. with explosives with a value of
1 1/2 X the dia.of the cyl., above the top, of the top of the cone.
You now have a bottle full of explosives and the top of the explosive is
1 & 1/2 the dia. of the bottle, above the top of the cone, (OK)?
When you set off the explosive, the shock wave of the event is like the
waves if you drop a rock into weter. ( I know you know this but, I need
to set up the picture) Part of the wave will move out and break the
sides of the bottle, but the wave will still go down the cyl. of the
bottle at some rate (<G> above 4'000 MPS, we hope) When the shock wave
contacts the top of the cone, it will invert the cone (in the same
direction the wave in moving) but it will "concentrate" the wave into a
point. As the cone continues to invert, the shock wave in now a "high
speed point" and when it is completely extended out the bottom of the
bottle, it is a "Very sharp pointed concentration of energy" ...AT
"X",000 MPS and will "cut", "punch" or what ever you are using it for .
This is how you penatrate Armor Plate, (or Hee, bank vault doors).
You can see that the higher speed of the shock wave, the more power in
the "point" and the deeper the penetration .
Now we come to, Detonation & Deflagration !!!
Deflagration (under 4,000 MPS, " WILL NOT "!, cut or punch! , because it
is just burning,
The speed must be over 4,000 MPS to be a Detonation and have the "shock
wave" powerful enough to do damage !
If the explosive does not boost its self to Detonation , (or what we
call "high order" it will deflagrate and just leave a black spot <G>)
GRIN..... I hope this didn't waste your time Leon, it's kind'a long.
When you have some time to play, look into , "Shape charges", It is fun
stuff and it might suprise you on how it can be used.
see ya later.
Bruce RED '91
Leon van Dommelen
>Yes Leon, I'm sure that some where in the "deep depths" of the U.S.Gov.
>from Edgewood, they could be found.
Hum. I'll skip.
[snip]
I am interested in how it was established that the shock wave in the
model piston engine you were talking about was a flame front, and not
just a shock wave. And what the fuel was, and to what pressure the air
fuel mixture was precompressed before ignition was initialized.
>Deflagration (under 4,000 MPS, " WILL NOT "!, cut or punch! , because it
>is just burning,
>
>The speed must be over 4,000 MPS to be a Detonation and have the "shock
>wave" powerful enough to do damage !
Actually, I am not particularly interested in piercing armor. :)
Also, I do not believe that 4000 m/sec can mean much too:
1) It is a simple fact that a shock that moves at 4,000 m/sec
through atmospheric air is a very different shock from a shock
that moves at 4,000 m/sec through air inside a cylinder that
has first been compressed with a 9 or so compression ratio.
2) I have never heard of any physical law that makes 3,999 m/sec
fundamentally different from 4,001 m/sec. Especially in gasses
where the physical speed I do know of, the speed of sound, is
different with temperature.
Grant Edwards
>
>>sorry, what does ping mean?
>
> Autoignition. The fuel starts burning on its own before the flame
> front from the spark plug hits it.
And, when it does that, it starts to sound sort of like a deisel
engine. Which isn't to surprising, I guess.
--
Grant Edwards grante Yow! I've been WRITING
at to SOPHIA LOREN every 45
visi.com MINUTES since JANUARY 1ST!!
Matthew Russotto
Grant Edwards <gra...@visi.com> wrote:
>In article <9j4e0vsun3gb721al...@4ax.com>, Leon van Dommelen wrote:
>>
>>>sorry, what does ping mean?
>>
>> Autoignition. The fuel starts burning on its own before the flame
>> front from the spark plug hits it.
>
>And, when it does that, it starts to sound sort of like a deisel
>engine. Which isn't to surprising, I guess.
Ping in the miata, IME, is a "bright" metallic sound. Knock could be
compared to a diesel engine sound.
Leon van Dommelen
>In article <3e10ae1d$0$22191$a186...@newsreader.visi.com>,
>Grant Edwards <gra...@visi.com> wrote:
>>In article <9j4e0vsun3gb721al...@4ax.com>, Leon van Dommelen wrote:
>>>
>>>>sorry, what does ping mean?
>>>
>>> Autoignition. The fuel starts burning on its own before the flame
>>> front from the spark plug hits it.
>>
>>And, when it does that, it starts to sound sort of like a deisel
>>engine. Which isn't to surprising, I guess.
>
>Ping in the miata, IME, is a "bright" metallic sound. Knock could be
>compared to a diesel engine sound.
You are right. I was assuming knock was meant instead of (wild) ping.
Pahsons - Smile when you think of me
> I like small cars. I got a Miata because it was small and
> nimble. I was also hoping for good gas mileage but
> generally only received 25 mpg or so. It's light and has a
> relatively small displacement engine so why the poor mileage?
>
> I used to have a BMW so I looked up the latest figures on
> Edmunds:
>
> 2003 Miata
> 1.8 Liter 4-Cylinder
> 142 HP
> 2387 Pounds
> 23 mpg City/28 mpg Highway
94 Protege
1.8 4cly
125 hp
2359 pounds
Consistent 37+mpg and he beats on it
Way more then what it's supposed to.
Could be in the way my dad tunes it
My 95 Protege only gets about 20-22mpg, could be in the way I tuned it.
That has the 92hp engine...
I would expect better drag out of one of those, but some other posts have
said otherwise. I'm actually shocked that Edmunds has the stick listed as
only 23/29 mpg.
--
This is the way we bash the skull
Bash the skull, bash the skull
This is the way we bash the skull
And don't bother mourning!
Some Everquest player on Portal
DHW
When running premium unleaded I get 28mpg when I run regular I get 22/23mpg.
The tires make a difference also. After I ate up my stock turanzas in under
10k miles I changed to a harder compound on the replacements(treadwear
rating 140 to 340) which gives a little increase in mileage like 1 or 2 mpg
on average but im not as sticky anymore. To help calcualte mpg better I also
try and use the same station and pump every time which helps to get a more
accurate calc.
If i were to tune it down and goto steel 14in rims with tires from a
geometro i could probably get high 30s. But then again if I wanted a high
mileage commuter car I would gotten a geometro.
"Pahsons - Smile when you think of me" <Asle...@lelola.asszzn.com> wrote
in message news:Xns92F6657E...@204.127.202.16...
Pahsons, new and improved with special XY-87
> But then again if I wanted a high
> mileage commuter car I would gotten a geometro.
And how does that relate to what I said?
Just curious
motopix21
The Turanzas are terrible!
"DHW" <dwi...@cox.net> wrote in message
news:J0gT9.7471$mg1.9...@news1.east.cox.net...
tooloud
>
> When running premium unleaded I get 28mpg when I run regular I get
22/23mpg.
Why would you ever use regular gas in the car? IIRC, the variable-valve
timing models require premium.
> The tires make a difference also. After I ate up my stock turanzas in
under
> 10k miles I changed to a harder compound on the replacements(treadwear
> rating 140 to 340) which gives a little increase in mileage like 1 or 2
mpg
> on average but im not as sticky anymore. To help calcualte mpg better I
also
> try and use the same station and pump every time which helps to get a more
> accurate calc.
>
> If i were to tune it down and goto steel 14in rims with tires from a
> geometro i could probably get high 30s.
I doubt it.
> But then again if I wanted a high
> mileage commuter car I would gotten a geometro.
<snip>
--
tooloud
Remove nothing to reply...
DHW
And yes, if i really wanted to I could make a miata get high 30s for gas
mileage. But it wouldnt be much fun to drive. Ya know like a geo metro.
Sometimes Premium Fuel just isnt available when you have a quart of gas left
in your tank.
The metro comment means everything.
"DHW" <dwi...@cox.net> wrote in message
news:J0gT9.7471$mg1.9...@news1.east.cox.net...
tooloud
news:LAEU9.17323$H76.1...@news1.east.cox.net...
> I put a sticker on it, it goes much faster now
>
> And yes, if i really wanted to I could make a miata get high 30s for gas
> mileage. But it wouldnt be much fun to drive. Ya know like a geo metro.
I still say that's pushing it.
> Sometimes Premium Fuel just isnt available when you have a quart of gas
left
> in your tank.
I live in the rural Midwest and did my share of travelling in an '89 Taurus
SHO that required premium fuel and can't recall ever having the slightest
problem finding premium fuel. Even if that had happened, octane booster is
readily available in virtually any convenience store I've run across.
Leon claims to have had trouble finding premium fuel, but he also takes 12k
mile trips on a whim it seems.
> The metro comment means everything.
<snip>
Leon van Dommelen
>> Sometimes Premium Fuel just isnt available when you have a quart of gas
>left
>> in your tank.
>
>I live in the rural Midwest and did my share of travelling in an '89 Taurus
>SHO that required premium fuel and can't recall ever having the slightest
>problem finding premium fuel.
You must have traveled at sea level. 89 is the highest available
in *major* parts of the US even where the elevation is only
a few thousand feet. The Dealer Alternative in *Colorado* complains
about it, forget about midwest states such as New Mexico, Kansas,
Utah, ...
> Even if that had happened, octane booster is
>readily available in virtually any convenience store I've run across.
I have bought a bottle once, but have not tried it whether it works.
I am somewhat leery of it.
>Leon claims to have had trouble finding premium fuel,
No, Leon claims that there are *large* regions in the US were you
*cannot* find over 89 octane *regardless of the trouble*. And that
outside the US, there are regions were you cannot find 85 octane
within the driving distance of a tank of gas.
>but he also takes 12k
>mile trips on a whim it seems.
And he *really* will try every single gas station on those trips
before disabling his SC or when hoping to enable it again.
tooloud
news:upq62vkapsm6sn3in...@4ax.com...
> "tooloud" <nospa...@mchsi.com> wrote:
>
> >> Sometimes Premium Fuel just isnt available when you have a quart of gas
> >left
> >> in your tank.
> >
> >I live in the rural Midwest and did my share of travelling in an '89
Taurus
> >SHO that required premium fuel and can't recall ever having the slightest
> >problem finding premium fuel.
>
> You must have traveled at sea level. 89 is the highest available
> in *major* parts of the US even where the elevation is only
> a few thousand feet. The Dealer Alternative in *Colorado* complains
> about it, forget about midwest states such as New Mexico, Kansas,
> Utah, ...
>
> > Even if that had happened, octane booster is
> >readily available in virtually any convenience store I've run across.
>
> I have bought a bottle once, but have not tried it whether it works.
> I am somewhat leery of it.
What did you do with the bottle you purchased?
FWIW, I lent my '89 SHO to my father one day with explicit instructions to
pump 91 octane into the car if he needed fuel. He nodded his head, then
returned the car with the engine running like crap. He said he couldn't
figure out why the engine was running like that, until I pointed out the gas
receipt reading "87 octane" he had left lying on the floor. I put in some
octane booster and the car came back to life in a few miles.
> >Leon claims to have had trouble finding premium fuel,
>
> No, Leon claims that there are *large* regions in the US were you
> *cannot* find over 89 octane *regardless of the trouble*. And that
> outside the US, there are regions were you cannot find 85 octane
> within the driving distance of a tank of gas.
Yeah, I remember the discussion. We must visit different places, as I've
taken trips out west and out east and never had any problems. Certainly
people in those large regions purchase vehicles that sometimes require
premium fuel; what do these folks do at fill-up time? I mean, otherwise
you're essentially saying that there are large regions of the US in which no
one can own a newer BMW or Mercedes or Acura or Porsche.
> >but he also takes 12k
> >mile trips on a whim it seems.
>
> And he *really* will try every single gas station on those trips
> before disabling his SC or when hoping to enable it again.
>
> Leon
>
> --
> Leon van Dommelen :) Bozo, the White 96 Sebring Miata .)
> REMOVE THE "z"s -> domm...@zmiata.net www.dommelen.net
> EXIT THE INTERSTATES (Jamie Jensen)
--
Pahsons, new and improved with special XY-87
> You must have traveled at sea level. 89 is the highest available
> in *major* parts of the US even where the elevation is only
> a few thousand feet. The Dealer Alternative in *Colorado* complains
> about it, forget about midwest states such as New Mexico, Kansas,
> Utah, ...
So I should be happy that 93 and 94 octane is available around me?
Leon van Dommelen
>premium fuel; what do these folks do at fill-up time? I mean, otherwise
>you're essentially saying that there are large regions of the US
Large, but only a small fraction of the US lives there.
> in which no
>one can own a newer BMW or Mercedes or Acura or Porsche.
The idea is that the lower air density at higher altitudes allows you
to use lower octane gas than you would at sea level. (So far for the
poor souls that believe that knock only depends on intake temperature.)
Because of the thinner air, there is less oxygen in the cylinder, so
tendency to auto-ignite is reduced. That is probably largely OK
for a normally aspirated car, but maybe somewhat less for a
supercharger. It is simply no good for a turbo, since a turbo pretty
much compresses the air to what it wants, regardless how thin it was
initially.
So, if you have a normally aspirated car or a supercharged one, you
might be relatively safe using the lower octane fuel available at
higher altitudes. But one difficulty is that I found that the parts
where the most you can get is 89 or 90 extend *well below 2000 ft*
in altitude, producing *heavy* knock in Bozo with the supercharger
enabled. Of course, only a very small fraction of the population
lives in those areas.
As far as the particular cars you mention above, they seem to be
expensive enough to have a good knock sensor with enough range to
prevent the engine from melting down if lower octane is used,
though maybe power, drivability, emissions, gas consumption,
etc. might be adversely affected by too low octane gas.
In any case, there are parts of the US I definitely would *not*
want to own a car that *really* needs 93 octane at sea level,
even if it is normally aspirated. If I lived in *large* parts (by
area) of the US, I also would not want to own any car for which
the warranty is void if you use less than 93 octane regardless
of height.
Todd Kuzma
nimble. I was also hoping for good gas mileage but
generally only received 25 mpg or so. It's light and has a
relatively small displacement engine so why the poor mileage?
I used to have a BMW so I looked up the latest figures on
Edmunds:
2003 Miata
1.8 Liter 4-Cylinder
142 HP
2387 Pounds
23 mpg City/28 mpg Highway
2003 BMW 330i
3.0 Liter 6-Cylinder
225 HP
3285 Pounds
21 mpg City/30 mpg Highway
The BMW weighs 900 pounds more, has an engine with 2 more
cylinders and 1.2 liters of extra displacement, and offers
83 more horsepower yet offers similar mileage. Is the
Bimmer motor that much better than the Miata?
Even the heavier Mini Cooper and Cooper S offer much better
economy:
2003 Mini Cooper
1.6 Liter 4-Cylinder
115 HP
2524 Pounds
28 mpg City/37 mpg Highway
2003 Mini Cooper S
1.6 Liter 4-Cylinder (Supercharged)
163 HP
2678 Pounds
24 mpg City/33 mpg Highway
Todd Kuzma
Heron Bicycles
Tullio's Big Dog Cyclery
LaSalle, IL 815-223-1776
http://www.heronbicycles.com
http://www.tullios.com
Jack
mpg.... kinda sad aint it?
when both cars in the garage, you cant even see my car, the damn camry is so
big.
"Todd Kuzma" <tul...@TheRamp.net> wrote in message
news:3E04C45C...@TheRamp.net...
DM
>I like small cars. I got a Miata because it was small and
>nimble. I was also hoping for good gas mileage but
>generally only received 25 mpg or so. It's light and has a
>relatively small displacement engine so why the poor mileage?
I can't really answer that. It seems it *should* have better. Part
is likely due to the aggressive gearing. Also, while a very small
frontal area, any convertible, including the Miata, has a poor drag
coefficient. Still, this shouldn't impact the city MPG number very
much. The engine isn't that impressive that it should have such poor
numbers. Does it generally due better in the real world vs the tests?
Your experience seems to indicate not, but depends on the driving
conditions.
hjarrett
road trips. I have a 94.
Hank (Of course I am the one with the oil leak problem and my OIL mileage
was pretty bad!) J
"Todd Kuzma" <tul...@TheRamp.net> wrote in message
news:3E04C45C...@TheRamp.net...
Cliff Knight
"Todd Kuzma" <tul...@TheRamp.net> wrote in message
news:3E04C45C...@TheRamp.net...
Cliff Knight
I have a 1200 cc Yamaha V-Max that weighs around 500 lbs--I get 30-45 mpg
with that.
"Todd Kuzma" <tul...@TheRamp.net> wrote in message
news:3E04C45C...@TheRamp.net...
Lanny Chambers
Todd Kuzma <tul...@TheRamp.net> wrote:
> I like small cars. I got a Miata because it was small and
> nimble. I was also hoping for good gas mileage but
> generally only received 25 mpg or so. It's light and has a
> relatively small displacement engine so why the poor mileage?
The Miata is geared pretty low, for snappy acceleration with a dated,
not-very-torquey engine, and the body was designed for looks, not
aerodynamic efficiency; its coefficient of drag is terrible, something
like 0.35. It also runs rather rich under full throttle, and if this is
your habit, it will be reflected in your mileage.
My '94 has recorded between 9 and 37 mpg, according to how it was
driven. Average has been around 29 mpg. If you have less fun, you'll get
better mileage, and if mileage is more important than fun you bought the
wrong car.
Here's my take: I'll never spend enough on gas to cover the
maintenance-cost difference between a Miata and the next-most-fun car
(much less the purchase price), so why should I worry about its mileage?
It's capable of going much farther on a tank of gas than I care to drive
without stopping, so range is not an issue.
The main problem is that a Miata makes you want to drive more than you
need to. :-)
--
Lanny Chambers, St. Louis, USA
'94C
the alignment page:
http://www.hummingbirds.net/alignment.html
Jack
what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
but it seemed impossible
did you change anything to improve the gas mileage?
thanks
-SK
"hjarrett" <hjar...@hroads.net> wrote in message
news:oI4N9.301$b_4....@sydney.visi.net...
Jack
> need to. :-)
a-men :)
HardwareLust
"Cliff Knight" <cli...@paladinmicro.com> wrote in message
news:D64N9.11455$0v3....@news.bellsouth.net...
> I get 28-30 mpg with my '90 1.6L -- that's good enough for me...
>
>
course, that's mostly due to the 210 mile commute to work each day on the
freeway. Now that I'm commuting 12 miles to the park-n-ride in my '99, I'm
back down to ~26 mpg.
Karl Kittler
miata, but why in general mpg is going
downhill compared to 10 years ago. But I
admit, the miata is not, and does not
claim to be a gas conscious car unlike
so many others.
I had a 87 CRX, it got 44 mpg at a
weight similar to the miata.
When I bought my miata, I used to get
about 28, 50% highway, by time, 80% by
miles. I just recently had the engine
replaced because of the dreaded
crankshaft problem and my timing was
off, hence with the same daily drive, my
mpg was down to 14, because I could only
drive in 3rd most of the time. Fifth was
only good if I was going downhill and
over 5000 rpm, which was nearly
impossible to achieve. Now with the new
engine out of a 92, it's about 26.
Here's some things that seem obvious but
may not be to check:
Tire pressure, this is the biggest
factor in poor mileage most of the time.
Plugs, wires and timing.
Large variations from stock, if you put
18" "inexpensive" wheels on, they are
probably very heavy, hence poor mileage.
Junk in the trunk. Excess weight will
bring that number down quickly.
Driving style. If you upshift when
cruising in slow traffic, it will
increase your numbers, and stay below
4000 rpm and avoid WOT if at all
possible.
If you're like me, WOT above 4000 rpm is
why I bought a miata.
FWIW, I have an 82 Kawasaki GPz ~650lbs
w/ rider 60 bhp, I can get anywhere from
52 mpg to 23, depending on how I drive
it. 35 mph in fifth, vs 85+ in third,
respectively.
--
"WARNING: Armed with a dangerous mind"
Fruit Pie the Magician
"Jack" <no_of_yo...@yahoo.com> wrote:
> 30 ? wow..
>
> what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
> but it seemed impossible
>
> did you change anything to improve the gas mileage?
>
> thanks
>
> -SK
You can save some weight by removing the driver. ;-)
Alex Rodriguez
>
>
>I like small cars. I got a Miata because it was small and
>nimble. I was also hoping for good gas mileage but
>generally only received 25 mpg or so. It's light and has a
>relatively small displacement engine so why the poor mileage?
Convertibles have more aero drag. Also in a fun car like a Miata,
you are more likely to drive in a spirited manner that uses more
gas.
--------------
Alex
DM
>The question should not be why the
>miata, but why in general mpg is going
>downhill compared to 10 years ago. But I
>admit, the miata is not, and does not
>claim to be a gas conscious car unlike
>so many others.
Okay, let's address that :-)
First, the average number is going down primarily because of the mix
of vehicles. More than half of the new US passenger vehicle purchases
today are "trucks" (SUV's, pickups, minivans). And the mix for the
Big 3 is much higher, 62% trucks. Chrysler sells 65% trucks, and
that's even with the car-bias they get from the Daimler side.
If you looked truck now vs truck then, I think (though I don't have
the numbers to back it up), they've gone up on average. But they
aren't going to compete with small-midsize cars, so the total average
declined.
If you looked at car now vs car then, I'm not sure if it has gone up
or down. In general, big engine MPG has gotten better, but there are
a lot more big engine, high hp cars than their were 15 years ago.
Typical mid-compact family sedan now is offered with 200-240 hp (!).
15 years ago, only the top-line sports cars competed. "Econoboxes"
now weigh 2500-2900 lbs with 2.0-2.4L engines. 15 years ago, they
were 1.6-1.8L and 2000-2400 lbs.
We seem to prefer larger, heavier, more feature-laden, more "safety"
equipment, and more power. Even with technology's inevitable
advancement, it can only do so much to keep pace.
BTW, I think the Miata's top-down Cd is probably a lot higher than
0.35, probably well above 0.40.
Leon van Dommelen
>30 ? wow..
>
>what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
>but it seemed impossible
>
>did you change anything to improve the gas mileage?
Mileage depends strongly on rpm. Keep rpm low. Don't know
optimum speed but it might be something like 55 in 5th.
Lanny, did you not do "best milage" runs?
Leon
--
tooloud
news:Y89N9.77478$4W1....@nwrddc02.gnilink.net...
Why the premium? You're wasting your money, it's not doing anything for your
gas mileage, and there's actually talk that it can harm the engine if your
car doesn't require it.
Lanny Chambers
domm...@zmiata.net (Leon van Dommelen) wrote:
> Lanny, did you not do "best milage" runs?
Once. That accounted for my sole example of 37.4 mpg. I was miserable,
not exceeding 2500 rpm for several hours. Never again.
I came in second. The winner got 43 mpg(!) with a 1.6. His car has
probably still not forgiven him, the swine.
HardwareLust
"tooloud" <nospa...@mchsi.com> wrote in message
news:au4rt6$4c90l$1...@ID-121148.news.dfncis.de...
> "HardwareLust" <cesl...@SPAMyahoo.com> wrote in message
> news:Y89N9.77478$4W1....@nwrddc02.gnilink.net...
> Why the premium? You're wasting your money, it's not doing anything for
your
> gas mileage, and there's actually talk that it can harm the engine if your
> car doesn't require it.
>
It seems to run better on Premium, and although I know it doesn't make a
difference, I do get slightly better gas mileage on premium.
Does Mazda recommend a particular gasoline for the 1.8L?
And, how can premium gas harm your engine?
HardwareLust
"Jack" <no_of_yo...@yahoo.com> wrote in message
news:_j5N9.36002$6H6.9...@twister.austin.rr.com...
> 30 ? wow..
>
> what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
> but it seemed impossible
>
> did you change anything to improve the gas mileage?
>
> thanks
>
> -SK
My tips: Use your cruise control as much as possible. And, drive slower! 5
mph less doesn't make that much difference. I know, it only takes about 6
minutes off my 109 mile commute. Lower rpm = less gas.
Kevin Stevens
In article <wbnN9.35181$3t6....@nwrddc03.gnilink.net>,
"HardwareLust" <cesl...@SPAMyahoo.com> wrote:
> "Jack" <no_of_yo...@yahoo.com> wrote in message
> news:_j5N9.36002$6H6.9...@twister.austin.rr.com...
> > 30 ? wow..
> >
> > what can I do to improve my mileage? I get about 23-25.. 30 was my goal,
> > but it seemed impossible
Gimme a break - I get 18-20mpg in my '93. Exactly what my Tahoe gets;
guess I'm driving them differently! ;)
KeS
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