Can you get faster acceleration by using less throttle?
- Thread starter Jotun
- Start date
None. Because I've never test driven a car where going from 80% to 100% throttle when accelerating actually results in it "slowing down", decided that that was fine, bought the car and then perhaps several months later decided that no actually the mapping really is broken and unacceptable and gone to a rolling road station and shoved the skilled operator out of the way and done the mapping myself.
So because you haven't driven a modern petrol turbo that has this issue then it doesn't exist?
It won't happen on a Normally aspirated unless it is silly rich at the top end.
To the clever folk in here, what effect exactly does altering throttle body size have on throttle response? In my Colt for example, unless you are at high rpm's and really gunning it, there is no discernible difference between using half throttle or wide open. Over on the owners forum a bunch of people hark on about fitting bigger throttle bodies from GSR's and Evo's and how it makes it better. Better how I don't quite know.
The way I see it when you are at low rpm the engine can only inhale so much air so opening the throttle beyond a certain point becomes pointless as the small throttle opening is no longer the limiting factor. Now surely if you had a larger throttle body then the same amount of opening will allow more flow and thus the usable amount of pedal travel will become smaller? Or am I waaaaaaaay off the mark?
The way I see it when you are at low rpm the engine can only inhale so much air so opening the throttle beyond a certain point becomes pointless as the small throttle opening is no longer the limiting factor. Now surely if you had a larger throttle body then the same amount of opening will allow more flow and thus the usable amount of pedal travel will become smaller? Or am I waaaaaaaay off the mark?
How many are affected? 1%? 10%? Knowing this would be useful going forward IMO...
almost all turbo cars will run a conservative map from the factory (i.e. rich at the top end) as they would rather get no complaints of blown engines and not quite squeeze out the last horsey to please the 0.001% of people that will notice.
my 200sx was running aroung 10:1 in the top end and that was pretty standard for those cars. next stage if i hadnt sold it would have been a remap to iron out the fuel/air ratio. which would have probably given another 10+ Bhp and better fuel economy!
Although equally i never found it faster to press the throttle progressively. i think that foot to the floor would give faster turbo spool anyway.
my 200sx was running aroung 10:1 in the top end and that was pretty standard for those cars. next stage if i hadnt sold it would have been a remap to iron out the fuel/air ratio. which would have probably given another 10+ Bhp and better fuel economy!
Although equally i never found it faster to press the throttle progressively. i think that foot to the floor would give faster turbo spool anyway.
Soldato
- Joined
- 23 Oct 2002
- Posts
- 2,562
- Location
- Edinburgh/Southampton
One is 3rd person the other 1st/2nd person I think? Don't actually know the technical descriptions of correct English just have picked up over the years what is right and what is wrong....
CORRECT:
The car was driven quickly
I drove the car quickly
She drove the car quickly
WRONG:
My mate driven real quick away from cops like
I driven that thing well quick
If we had drove more fast we would not 'ave been nicked pal
When you say "top end" are you referring to throttle opening or RPM?
as well as checking the ve tables for how much fuel to inject and what ignition advance to use, the ECU will use the TPS sensor to determine how quickly you pressed the pedal down. it will inject addtional fuel as an 'acceleration pulse' if that is incorrectly timed, then you might see the car pull better when not floored.
on an n/a car, if the TB is oversized, it can cause poor(er) acceleration at WOT as the gas speed drops off as the air comes in through a hole that is just too big. Also, with a larger throttle butterfly, you loose some of the ability to make minor adjustments to the throttle.
not forgetting mind, that on modern petrol engines pressing the throttle pedal just moves a potentiometer that gives a reading to the ECU and then the actual butterfly is moved to a point that the ECU deciedes using a stepper motor.
on an n/a car, if the TB is oversized, it can cause poor(er) acceleration at WOT as the gas speed drops off as the air comes in through a hole that is just too big. Also, with a larger throttle butterfly, you loose some of the ability to make minor adjustments to the throttle.
not forgetting mind, that on modern petrol engines pressing the throttle pedal just moves a potentiometer that gives a reading to the ECU and then the actual butterfly is moved to a point that the ECU deciedes using a stepper motor.
I know I only drive a 1.6 with 98BHP but I find it responds better to smooth acceleration rather than very harsh throttle input, and I find I can make better progress if I pay more attention to how smoothly I accelerate rather than just stamping on it and hoping for the best.
Might be entirely psychological and unrelated to what you guys are talking about but, meh. Just thought Id throw that in.
Might be entirely psychological and unrelated to what you guys are talking about but, meh. Just thought Id throw that in.
Deleted member 66701
Deleted member 66701
Maximum engine power is usually made between 12.6:1 and 13:1 AFR (i.e. rich of stoichmetric). Boosted cars (turbo and supercharger) typically run richer than this to supress detonation, not because it produces more power.
Back to the original question - on a modern fuel injected engine, maximum power (and hence maximum acceleration) will be achieved at full throttle. On a well mapped engine, flooring the throttle shouldn't induce any hesitation as the accel enrich will take care of that.
If anyone is interested, here is my fuel table (RPM vs TPS) for my 2.1 Pinto on TB's.
You can see maximum fuel is being injected @ 6500rpm @ full throttle (200 TPS ADC).
Here you can see the AFR target table (i.e. the AFR the ECU is aiming for at any given engine speed/TPS position).
You can see it aims for 12.6:1 AFR at full throttle, max revs. It cruises @ 14.6:1 (cruise sites have actually been approved upon since this tune). This AFR target table (at least on accel - not cruise) has been verified on an engine dyno as being the best for power on this engine.
Last edited by a moderator:
yeah what others said here, with carbs yes, but EFI, the computer will let the max amount of fuel into cylinders to give best possible power
I guess a badly mapped car could benenfit from less throttle... as running rich would reduce power
I guess a badly mapped car could benenfit from less throttle... as running rich would reduce power
needs a remap
, but I guess it could be just the way it's designed in that stamping down hard will always mess up mixture, and no remap could fix it.Deleted member 66701
Deleted member 66701
Running rich produces maximum power.
Running stocih is best for emmissions.
Running lean is best for economy.
The first graph I was shown on my college "Electroninc engine control and mapping" course was:-
Running rich produces maximum power.
Running stocih is best for emmissions.
Running lean is best for economy.
The first graph I was shown on my college "Electroninc engine control and mapping" course was:-
I thought running slightly lean gives more power.. but at expense of burning hole in piston or burning valves (as less fuel to cool engine means it runs hotter)
Tuners I thought ran slightly lean at track to give a power advantage..
I remember the guy who mapped my bike said he could extract more power by going leaner, but it's not a good idea for reliability, maybe I've muddled it up though... this is why people who mess with maps without getting it properly setup risk engine meltdown, unless they run rich for safety
Maybe it was all based on manufacturers specced air / fuel ratio, which would still make your graph correct
Last edited: