Cars is feels slower at WOT as oppose to partial throttle

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Sep 9, 2003 | 07:04 PM

#41

2KxSEx

Thread Starter

Senior Member

Joined: Apr 2001

Posts: 456

I like your theory spirilis! I really hope you guys find the problem if that's what we can call it. Good thing I made this thread.

Later

Sep 10, 2003 | 04:48 AM

#42

SteVTEC

Dyno plot says I have the most area under the Administrator curve

Joined: Jul 2001

Posts: 7,064

Quote:

Originally Posted by spirilis

I think it's possible, if the fuel system is clogged/dirty or otherwise not pumping fuel quite as much as it should, that the Closed-Loop fuel trim ends up richer than open-loop (i.e. at open-loop, the mixture is too lean due to a fault in the fuel system, thus in Closed-Loop it compensates by using positive fuel trim values)... thus flooring it would run LEAN, not RICH, and backing off would put it back into positive fuel trim (Open Loop = fuel mixture computed from MAFS/ECT/IAT/etc, then in Closed Loop it uses Fuel trim values which define a percentage + or - open loop's mixture)
An OBD-II sensor scan tool might shed some light into that scenario, if it exists...

I think you might have some of your terms switched around.

Closed-loop = normal driving, stoich mixture, active feedback from sensors.
Open-loop = >90% throttle, rich mixture, no feedback from sensors.

If the fuel system is a bit clogged as you suggest, all of the sensors in the system will work to compensate for that during closed-loop normal driving and keep the mixture where it's supposed to be for emissions. If it can't, you'll get an SES light.

If flooring it (open-loop) was running leaner, then the engine would have even more power since it normally runs very rich in open-loop. Guys lean out their fuel with S-AFCs on the dyno just for this reason. These guys are saying they have less power, not more.

Sep 10, 2003 | 06:42 AM

#43

spirilis

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From: New Market, MD

I think I had my terms correct, but I was misunderstanding the purpose of open-loop (didn't know it intentionally runs rich in open-loop, I figured it just computed fuel delivery to match stoich as close as possible based off inputs from MAFS/ECT/IAT/etc, without the accuracy of having an O2 sensor to tell it whether it was correct)