Can you get faster acceleration by using less throttle?

tuners I thought ran slightly lean at track to give a power advantage..
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I wouldn't be giving any of those tuners my cash in that case.

What is probably confusing is that tuners will "lean out" an engine to make more power - however the engine will still be rich - I.e. they'll take it from the "safe" manufacturers rich setting of say 12.2:1 afr to a "leaner" setting of 12.6:1 - so they are correct - they have leaned out the engine AND gained power but the engine is still running rich (as in < 14.7:1 afr).
 
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Dont forget the effect of the spark. The different fuel ratios burn very differently in terms of peak pressures so the timing needs to change to suit that. This is where a std calibration running long term fuel trims from closed loop lambda feedback can move the fuelling around a bit with no adjustment to the ignition map.
 
amigafan2003 said:
I wouldn't be giving any of those tuners my cash in that case.

What is probably confusing is that tuners will "lean out" an engine to make more power - however the engine will still be rich - I.e. they'll take it from the "safe" manufacturers rich setting of say 12.2:1 afr to a "leaner" setting of 12.6:1 - so they are correct - they have leaned out the engine AND gained power but the engine is still running rich (as in < 14.7:1 afr).
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ahh I get it thanks :), so they run 'leaner' rather than 'lean'

i guess the manu's running richer than optimal for safety is why remappers can extract some nice gains from a lot of cars.. ? (even normally aspirated)
 
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I've heard that running leaner gives better power. Running rich certainly doesn't. I've heard people with forced induction cars say their cars felt really fast just before melting a piston.
 
And from the graph you can also see why a chipped or remapped engine returns better fuel economy, even though it's actually making more power :-)
 
I've heard that running leaner gives better power. Running rich certainly doesn't.
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Read my post - "running leaner" does generally give more power but that's a different statement than "running lean".

I've heard people with forced induction cars say their cars felt really fast just before melting a piston.
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Well, running at 12.6:1 afr on a turbo engine will make more power than running at 10:1 but it's still running RICH but it is leaner than reconmened (but still RICH - do I have to say it again?). Running 10:1 on a turbo car won't make as much power but it will stop the pistons melting :-)
 
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On the standard turbo, my old Rover turbo used to run 10-11 AFR on full throttle/boost over 5000rpm.
 
My MR2 runs slightly rich, only under 10.0 after 6.3k
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On the standard turbo, my old Rover turbo used to run 10-11 AFR on full throttle/boost over 5000rpm.
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Exactly correct (as long as the MR2 is a turbo).

You do lose a little bit of power (over the 12.6:1 afr ideal) and your fuel economy will suffer (who has a petrol turbo car for fuel economy though?) BUT at least your engine will be in one peice by the end of a run.
 
Plus by running rich im told I get flames out the exhaust.
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This is true - hence the bottom right hand of my map set to overfuel - nice big flame when I part throttle at 6k rpm :-) Makes my LC1 wideband go nuts though.

Scared the bejesus out of the students when we had it on the college rollers! When it was on the engine dyno the flames came out of the extractor fan in the wall and someone from the biology lab called the fire brigade!
 
I don't have my carbs jetted up properly yet and it will pull better at 3/4 throttle than wide open until about 5000rpm when I can open her up properly. Runs out very lean by the sound of it.

Should be able to just whack it open and it'll pull though.
 
amigafan2003 said:
Scared the bejesus out of the students when we had it on the college rollers! When it was on the engine dyno the flames came out of the extractor fan in the wall and someone from the biology lab called the fire brigade!
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backfires through the intake system causing the carbon firbe plenmum to explode would scare them more.

I had a LC-1, dunno where it is now. Did a great job on my DTA S60 I fitted to my Rover turbo. Massive difference in drivability when you got the fuelling right, plus full throttle was cleaner and obviously more powerful.

A lot of OEMs overfuel purely to keep the plugs cool, as I mentioned in my previous post. They need hot plugs to avoid plug fouling in traffic etc, and full throttle fuel economy is not their biggest concern.

The BMW N54 3.0 twin turbo is interesting, because it is direct injection it never goes below Lambda 1.
 
I don't have my carbs jetted up properly yet and it will pull better at 3/4 throttle than wide open until about 5000rpm when I can open her up properly. Runs out very lean by the sound of it.

Should be able to just whack it open and it'll pull though.
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There we go - at full throttle you're running lean, which drops power. Shouldn't happen with properly jetted carbs. When you jet them properly for max power you'll probably find you'll run super rich at low throttle/rpm and it'll be a dog cruising - that's the trouble with carbs - they are a massive compromise unless it's a sbl on an anaemic and small engine.

Powerwise - throttle bodies and carbs both have the potential to make the same power and torque but the TB's will behave much better across the rev range and return much better mpg - they also wont have the bad warmup/cold start characteristics of carbs (anyone who has experienced carb icing will know where I'm coming from).
 
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backfires through the intake system causing the carbon firbe plenmum to explode would scare them more.
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Inlet reversion will never happen on my engine due to the cam profile (massive lift, short duration).
 
amigafan2003 said:
There we go - at full throttle you're running lean, which drops power. Shouldn't happen with properly jetted carbs. When you jet them properly for max power you'll probably find you'll run super rich at low throttle/rpm and it'll be a dog cruising - that's the trouble with carbs - they are a massive compromise unless it's a sbl on an anaemic and small engine.

Powerwise - throttle bodies and carbs both have the potential to make the same power and torque but the TB's will behave much better across the rev range and return much better mpg - they also wont have the bad warmup/cold start characteristics of carbs (anyone who has experienced carb icing will know where I'm coming from).
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On the contrary, DCOEs have 4 jets for idle, low running, mid running, top running and acceleration enrichment on flip of the throttle. Won't be a dog at low revs at all. Top jets are fine so my suspicious eye is on the emulsion tube leaning out the mixture.
 
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