Closed Loop Fuel Trims at idle & low rpms

[TURBODAWG]

+8% means the ECU is adding 8% fuel to the mixture to achieve stoichometric that it is trying to achieve. So your global compensation is causing the duty cycle too be too low. So the ECU is compensating by adding fuel. So you would need to make the global adjustment LESS negative to ~ -32% . That should get you a good starting point.

Brian

[SuperHatch]

Sounds good, thats what I thought but I wanted to make sure.... It would also explain why the car stumbles on a cold start, I believe the mixture is too lean.

- Steve

[Magnumpsi]

hey so can someone give me an overview of how the ecutek or techtom softwares deal with rescaling. i'm under the impression there is actually a function in the software specifically to address this. so how does it work? is it the same as a global open loop reduction in fueling? because on the other hand it really doesn't _sound_ that simple



There is an injector scaling in the software that just allows you to adjust the injector dead time. To say that no one has tested 1000cc injectors is just false. Like 8urvtec said Rich has and there are a dozen other guys out there that have done it. Can it control them effectively, i would say yes and no, but if you are using 1000ccs and Ecutek i think that you are either using too big of an injector or it is time to rethink your engine managment.
Mitch

[trinydex]

there's two ways. you can first adjust injector dead time and dwell time.

and then after you've done that you can adjust the globals further.

[AlwaysinBoost]

Originally Posted by trinydex

how much range does the stft have?

24%

[gogoevo]

Originally Posted by AlwaysinBoost

24%

thats right its around 20%

[ez76]

Originally Posted by TURBODAWG

+8% means the ECU is adding 8% fuel to the mixture to achieve stoichometric that it is trying to achieve. So your global compensation is causing the duty cycle too be too low. So the ECU is compensating by adding fuel. So you would need to make the global adjustment LESS negative to ~ -32% . That should get you a good starting point.

if it is adding 8% more fuel, and the global reduction is currently -40% (60% of baseline), then wouldn't the proper global reduction be (60% * 1.08) - 100% = -35.2% rather than -32%?

[blkdinan]

Back to the orignal Question...I’m going to go out on a limb. Question, with the engine at full load what is your injector duty cycle? When using an AEM or other stand alone system, larger injectors are necessary because of the limited duty cycle you can produce. The stock computer does not have these limitations. Also when power is applied to the injector there is a delay. It is only a few milliseconds, but it is the time it takes for a magnetic field to be produced, and then for that field to physically open the injector. This time varies with different injectors but should be considered when tuning injectors that large. You may find that you don’t need such a large injector. There is a tremendous amount of information on how to calculate proper injector size on the web. A good starting point is at Turbobygarrett.com. We have tested 720cc injectors with a static fuel pressure of 45psi with a 1-1 regulator. At 44 psi intake pressure and 7,800 RPM the injectors were at 82% duty cycle Producing AFR's in the mid 11's. This was done on a 2.0 with a Cosworth head 272 cams GT4094 turbo .84 hot side. And a custom tuned ECU.