I'm hoping this isn't too dumb of a question...

It seems to me that there is a throttle position where "max acceleration" is reached, and any further depression of the gas pedal produces no noticeable benefit. For example, flooring the gas at 20mph in second gear doesn't seem to make it go any faster than ~3/4 throttle. So first of all, is my observation accurate? Next, if it is correct, what is happening with the fuel delivery when I'm at WOT at low RPM? Is it just dumping unburnable fuel into the engine and out my tailpipe, or is the computer smart enough to only inject an appropriate amount of gas for the airflow and engine speed it's running?

Does that make any sense?

 

I am not sure what your question is, but here is an answer.

The ECM has pre-programmed fuel and spark maps. It uses input from the throttle position sensor, the IAT, the ECT, the RPM, etc. to determine approrpaite A/F ratios throught out the range of normal driving. Stoiciometric A/F is 14.7:1 on an absolute basis, but in fact varies across the range of RPM. AT WOT, the ECM does do some special things on all cars (dumps the EGR, cuts out the A/C clutch, etc.) but it doesn't all of sudden let go of all control. Otherwise, the engine would go too rich, and you would lose fuel and power. Most dyno tunings I have been involved in actually leaned out the engine at higher RPM, as most mfrs go pig rich to protect the engines, and allow for idiot drivers driving up hills in 6th gear in 110 deg temps. This is really a tricky area on my Cobra, which has no knock sensor. That is why taking the engine up about a point leaner at WOT yielded so much peak power, while pushing mroe spark at lower RPM yielded a lot more torque.

Fact is, there is not much to gain on the S2000 in these areas without significant re-engineering of fuel and air enrichment strategies, i.e. forced induction or NOS.

 

Thanks RR, that's kinda what I was getting at. I was basically wondering if, when I stomp on the gas in a situation where more gas won't help, that extra gas simply blows out my tailpipe, or if the computer is smart enough not to inject the unnecessary gas in the first place.

 

Keep in mind that the 'gas' pedal is really the throttle pedal.

There is a cable connecting it to the butterfly valve in the throttle body. That valve controls how much air the engine gets. The ECU then controls how much fuel and timing to allow, based on a bunch of factors, including the throttle position, intake air temp, etc.

BTW, the throttle cable can get too tight or too loose, in which case you could wind up moving the pedal quite a ways before the butterfly is moved at all, or worse, you could have the pedal to the floor and not have the butterfly open all the way.

Ted

 

or could it be that when the pedal itself is pushed down 3/4 it is already at WOT?

 

Oh yeah, that was part of the point I was trying to make. Thanks!