Maximum acceleration
john
What do all y'all do when you need maximum acceleration, eg after
stopping at a red light on a de-restricted dual carriageway?
To get up to a target cruising speed as quickly as possible, is it better
to rev close to the redline in each gear before changing up, or to change
up at the point of maximal torque (ie 3500 rpm)?
Haven't found any good answers to this on Google.
Cheers,
John
Roger Mills
john <jo...@nospam.com> wrote:
There isn't a universally correct answer to your question because it depends
on the shape of the engine torque curve and on the gearing. But, in general,
it's best to go up to somewhere near the max *power* speed (which is higher
than max torque speed) because the thrust at the wheels (and hence
acceleration) usually reduces when you change to a higher gear even though
you're moving back to a point of higher engine torque.
You clearly wish to maximise thrust (or torque at the driving axle). In
order to work out how to do that, you need to plots graphs of drive axle
torque vs roadspeed in each of the gears, and to see where the curves
intersect - if indeed they do. [1] The intersection points are where you
change gear. If they *don't* intersect (and they don't always, unless the
gears are closely spaced) you hang onto the lower gear until you run out of
revs. Not all the thrust at the contact patch is available to accelerate the
vehicle, of course, because you first have to deduct aerodynamic drag and
rolling resistance - but these are dependent on roadspeed, and not on which
gear you're in, so they don't affect the optimisation of gearchange point.
[1] For the sake of simplicity, you can ignore gearbox (in-)efficiency but,
in practice, it's slightly more complicated than that because you sometimes
need to take account of the fact that the efficiency of the gearbox may not
be the same in all gears.
--
Cheers,
Roger
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Mike Barnes
>What do all y'all do when you need maximum acceleration, eg after
>stopping at a red light on a de-restricted dual carriageway?
I've only done this once, but the procedure is: cancel ESP, foot on
brake pedal, move gear selector to Sport, floor accelerator, disengage
handbrake, wait for the revs to stabilise, foot off brake.
--
Mike Barnes
Mortimer
news:Lq9UIyMZ...@g52lk5g23lkgk3lk345g.invalid...
And what if you've got a manual gearbox? ...
Harry Bloomfield
Engage brain in sport mode lol
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
Conor
Look up the specifications of your engine. You want to know the
powerband.
Accelerate til you reach the revs at the top of the powerband and change
up gear to one that puts you at the bottom of it - you might find that
actually being a block change 2 up, such as 2nd to 4th.
In the absence of that you want two figures:
RPM of Max Torque
RPM of Max BHP.
On a petrol, you'll find the torque and BHP figures to be similar.
Change up at the RPM for the BHP and try to change so it drops to around
2500-3000.
On a diesel, change up when you hit the revs for the max BHP and try to
change up to a gear that puts you at the figure for the max torque.
As in the first example, you may find it is a block change up of two
gears.
--
Conor
www.notebooks-r-us.co.uk
I'm not prejudiced. I hate everybody equally.
Mike Barnes
>> john <jo...@nospam.com>:
>>>What do all y'all do when you need maximum acceleration, eg after
>>>stopping at a red light on a de-restricted dual carriageway?
>>
>> I've only done this once, but the procedure is: cancel ESP, foot on
>> brake pedal, move gear selector to Sport, floor accelerator, disengage
>> handbrake, wait for the revs to stabilise, foot off brake.
>
>And what if you've got a manual gearbox? ...
He asked me what *I* did, and I told him. He didn't ask me to speculate
on what others might do.
--
Mike Barnes
Silk
> Hey
>
> What do all y'all do when you need maximum acceleration, eg after
> stopping at a red light on a de-restricted dual carriageway?
Most of us are grown ups and have moved on from such immature behavior.
Bod
Wait for the lights to turn green first.
Bod
Dr Zoidberg
"john" <jo...@nospam.com> wrote in message
news:hilbnh$fm9$1...@speranza.aioe.org...
> Hey
>
> What do all y'all do when you need maximum acceleration, eg after
> stopping at a red light on a de-restricted dual carriageway?
>
--
Alex
Harry Bloomfield
> Most of us are grown ups and have moved on from such immature behavior.
Where is your competitive spirit :-)
NM
What are you going to do in the seconds, or maybe only milliseconds,
you save?
DavidR
> Hey
>
> What do all y'all do when you need maximum acceleration, eg after
> stopping at a red light on a de-restricted dual carriageway?
Usually, sit and watch the people at the front of the grid perform a slow
drag race.
> To get up to a target cruising speed as quickly as possible, is it better
> to rev close to the redline in each gear before changing up, or to change
> up at the point of maximal torque (ie 3500 rpm)?
The physics says to do whatever maximises power. But why don't you try both
methods you suggest? (Or are you asking this because you can't drive?)
john
> "john" <jo...@nospam.com> wrote
>> To get up to a target cruising speed as quickly as possible, is it
>> better to rev close to the redline in each gear before changing up, or
>> to change up at the point of maximal torque (ie 3500 rpm)?
>
> The physics says to do whatever maximises power.
Unfortunately there is no power display on my dashboard - only rpm.
> But why don't you try
> both methods you suggest? (Or are you asking this because you can't
> drive?)
I can't drive and simultaneously operate a stopwatch precisely.
Nick Finnigan
>
> I can't drive and simultaneously operate a stopwatch precisely.
You don't need to. Just start at the same red light on a de-restricted
dual carriageway and note the point on the road where you reach cruising speed.
(You will have noticed that you get lots of different answers and no way
to choose which is correct unless you are familiar with the posters).
Conor
says...
Use a HPE powered Ford Anglia, MK1/2 Escort or Capri instead of a
motorbike.
OG
Plan ahead by stopping 10 metres back from the line, start on red-amber and
give yourself a flying start as the light turns green.
NM
> In article <himoi6$5d...@news.eternal-september.org>, Dr Zoidberg
> says...
>
>
>
> > "john" <j...@nospam.com> wrote in message
> >news:hilbnh$fm9$1...@speranza.aioe.org...
> > > Hey
>
> > > What do all y'all do when you need maximum acceleration, eg after
> > > stopping at a red light on a de-restricted dual carriageway?
>
> > Use my motorbike instead of the car.
>
> Use a HPE powered Ford Anglia, MK1/2 Escort or Capri instead of a
> motorbike.
>
> --
> Conorwww.notebooks-r-us.co.uk
>
> I'm not prejudiced. I hate everybody equally.
Why? He wants to go fast, no need to lumber him with the weight of a
tin box to drag along.
Silk
Tin? How many cars do you know are made of tin?
Silk
> on 14/01/2010, Silk supposed :
>> Most of us are grown ups and have moved on from such immature behavior.
>
> Where is your competitive spirit :-)
I'm competitive in that I want to be a good driver. Traffic light drag
races have nothing to do with good driving.
Silk
Why stop in the first place. I always try to anticipate traffic lights
to avoid stopping at all. It means I rarely have to come to a complete
stop, even in heavy traffic.
NM
Colloquial 'tin', most of one of my cars is plastic, I like plastic,
it dosen't rust.
NM
I have been doing that for years, I learned it driving a heavy truck,
saves fuel.
Bod
Yes, I always try to anticipate light changes in the same way.
Bod
Mortimer
news:7rb1n4...@mid.individual.net...
Likewise. Occasionally by slowing down I can avoid coming to a complete
rest, but usually even by coming off the power early and slowing down more
gradually using engine braking, I still find that I have to stop because the
lights still haven't gone green and/or the cars in front haven't yet got up
to my speed by the time I arrive at the lights. Still, it's nice when it
*does* work out.
If I do have to stop, and I'm the first car, I tend to stop short and set
off on the red and amber so I'm crossing the line as they go green - it's
particularly satisfying when there's a powerful car on my left which has to
set off from rest because they always look gobsmacked to be overtaken by a
little Pug!
Harry Bloomfield
> I have been doing that for years, I learned it driving a heavy truck,
> saves fuel.
Plus saving lots of wear and tear - and is the best way to get away
from the lights fast, if you must. A rolling start easily beats a
standing start.
DavidR
>> "john" <jo...@nospam.com> wrote
>>> To get up to a target cruising speed as quickly as possible, is it
>>> better to rev close to the redline in each gear before changing up, or
>>> to change up at the point of maximal torque (ie 3500 rpm)?
>>
>> The physics says to do whatever maximises power.
>
> Unfortunately there is no power display on my dashboard - only rpm.
No need for a power display. If the matter is so important to you, you
should have stayed awake during science lessons.
>> But why don't you try
>> both methods you suggest? (Or are you asking this because you can't
>> drive?)
>
> I can't drive and simultaneously operate a stopwatch precisely.
If you compare your two suggestions you don't need a stopwatch.
Dr Zoidberg
"Conor" <co...@gmx.co.uk> wrote in message
news:MPG.25b9a8f02...@news.eternal-september.org...
> In article <himoi6$5di$1...@news.eternal-september.org>, Dr Zoidberg
> says...
>>
>> "john" <jo...@nospam.com> wrote in message
>> news:hilbnh$fm9$1...@speranza.aioe.org...
>> > Hey
>> >
>> > What do all y'all do when you need maximum acceleration, eg after
>> > stopping at a red light on a de-restricted dual carriageway?
>> >
>> Use my motorbike instead of the car.
>
> Use a HPE powered Ford Anglia, MK1/2 Escort or Capri instead of a
> motorbike.
>
Not that I *have* a 600cc sports bike or could get close to it's theoretical
0-60 time , mined-ewe
--
Alex
Silk
> No need for a power display. If the matter is so important to you, you
> should have stayed awake during science lessons.
It sounds like he should have stayed awake during all lessons.
Brimstone
"Silk" <m...@privacy.net> wrote in message
news:hiqk4n$ufb$1...@speranza.aioe.org...
You're being uncommonly charitable, are you ill or something?
Brimstone
"DavidR" <cure...@4bidden.org.uk> wrote in message
news:7rbjve...@mid.individual.net...
> "john" <jo...@nospam.com> wrote in message
>> DavidR wrote:
>>> "john" <jo...@nospam.com> wrote
>
>>>> To get up to a target cruising speed as quickly as possible, is it
>>>> better to rev close to the redline in each gear before changing up, or
>>>> to change up at the point of maximal torque (ie 3500 rpm)?
>>>
>>> The physics says to do whatever maximises power.
>>
>> Unfortunately there is no power display on my dashboard - only rpm.
>
> No need for a power display. If the matter is so important to you, you
> should have stayed awake during science lessons.
>
More like he should have gone to school in the first place.
Silk
No, thanks for asking.
Ray Keattch
At least 50% of drivers appear to be doing this already.
--
MrBitsy
Harry Bloomfield
> At least 50% of drivers appear to be doing this already.
..and the other 49% keep on drifting forward, past the line and into
the area intended for bikes.
NM
Ian Dalziel
How many tin boxes are made of tin?
--
Ian D
Ed Chilada
wrote:
>Hey
>
>What do all y'all do when you need maximum acceleration, eg after
>stopping at a red light on a de-restricted dual carriageway?
While the lights are on red, I usually do a couple of wheelspins just
to put some tracks of rubber down. I find it helps with the traction
when the lights change.
Silk
All of them.
Ian Dalziel
Really?
Not tinplate, then?
--
Ian D
NM
You are right, I have never seen a tin box, We all made tinplate boxes
at school in metalwork and the 'tins' that we refer to are really
tinplated food containers or more probably nowerdays aluminium or
aluminium alloy even plactic but still called tins. Referring to cars
as tin boxes has been colloquial as long as I can remember, before
the war most cars were coachbuilt bodywork AFAIK there has never been
a tinplated steel car (toys aside) so I wonder how the common term tin
box came about in reference to car usually it's implied as a
derogatory reference.
Brimstone
"NM" <nik.m...@mac.com> wrote in message
news:483bcf07-0350-474f...@r24g2000yqd.googlegroups.com...
Probably because tin and tin plated products were always viewed as being
cheap and nasty so if one wished to be rude about someone's car it became a
"tin box".
Roger Mills
NM <nik.m...@mac.com> wrote:
> Referring to cars
> as tin boxes has been colloquial as long as I can remember, before
> the war most cars were coachbuilt bodywork
As kids, we used to say:
"A bit of tin, a bit of board,
is all that goes to make a Ford!"
Remember it?
--
Cheers,
Roger
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Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!
Silk
> In an earlier contribution to this discussion,
> NM<nik.m...@mac.com> wrote:
>
>> Referring to cars
>> as tin boxes has been colloquial as long as I can remember, before
>> the war most cars were coachbuilt bodywork
>
> As kids, we used to say:
>
> "A bit of tin, a bit of board,
> is all that goes to make a Ford!"
>
> Remember it?
Most of us weren't around during the war, so have no idea what you're on
about.
Roger Mills
Nor was I - but that little ditty persisted well into the 1950's - when
there still plenty of pre-war cars around.
NM
> In an earlier contribution to this discussion,
>
> > Referring to cars
> > as tin boxes has been colloquial as long as I can remember, before
> > the war most cars were coachbuilt bodywork
>
> As kids, we used to say:
>
> "A bit of tin, a bit of board,
> is all that goes to make a Ford!"
>
> Remember it?
Now you come to mention it I think so.
The early pressed steel bodied Vauxhalls used to rot at an
unbelievable rate and I think were responsible for the expression "As
rotten as a pear" but the metal 'tin' dosen't rust thus it's
application to an item that does is odd.
Roger Mills
As an aside, the early Vauxhall Victors (late 50's) had a reputation for
breaking the wrap-around windscreen if you jacked up one front corner,
because the body twisting stiffness was so low.
Coming back to tin, wasn't the Model T Ford also known as a Tin Lizzie?
Brimstone
"Roger Mills" <watt....@googlemail.com> wrote in message
news:7rgbog...@mid.individual.net...
> Coming back to tin, wasn't the Model T Ford also known as a Tin Lizzie?
Yes.
Silk
> Coming back to tin, wasn't the Model T Ford also known as a Tin Lizzie?
And due to confusion with Irish pronunciation, became Thin Lizzy and the
rest is history.