This is the transfer function of the MAFT. As Shawn says the WOT switch does not affect anything below about 8Khz or I should say it does but it's so little it's not noticable. Looking at a A/F ratio curve with different WOT settings you can't see any difference below 8Khz.

 

Ok, that is starting to make more sense to me. Because my feeling was that the PCM would know if you tried to fool it all the time, and just add more fuel at WOT as well.

Now let me make sure I have the basics right...

If you are telling the PCM that there is less air flowing, than actually is - then you are leaning the engine - correct? Because the PCM is shooting fuel at a lower rate than it should according to it's tables, since it thinks there is less air in there.

This also tells the PCM that the engine isn't under as high a load as it actually is, and it advances the timing a little. Which is good for performance, as long as you don't get detonation.

That all makes sense to me.

Why adjust the BASE at all though?

The only thing that would make more sense to me, would be to install a MAFT-like device that actually read the Throttle Position and based it's operation on that.

Then, there would be no long-term fooling of the PCM. You could only trick the PCM at - say - 85% throttle and higher. Or whatever the PCM considers full enrichening mode. (Anyone know that threshold?)

Seems like a better - and less complex - way to do that.

The PCM would NEVER know what was going on at all, because as you say, it doesn't look at O2 sensors at WOT.

Any thoughts?


[Modified by Tom Steele, 12:20 AM 7/14/2002]

 

Correct. Sounds backwards, but thats the effect.

Correct. This is why you can add larger injectors, which the PCM isnt calibrated for, then use the MAFT to report a lesser load. In the end your getting the fuel you need, and timing advance.

You want to adjust BASE (during non-wot operation) to get your fuel trims at or below 0 so it isnt adding a component at WOT. Remember that anytime you change the BASE setting, the PCM has to spend some time adjusting before the trims will settle in. WOT setting on the MAFT can be changed on the fly for WOT tuning. But again, you want to get BASE to force 0 or negative trims, before moving WOT off 0. And you may not even need to take WOT off 0.

I agree, that would have been a better way to do it. With LS1edit out now, its probably not cost effective for someone to do it now.

80% is the documented threshold. Whether it picks off the TPS sensor or not tho, you still need to adjust the base setting to get the fuel trims where you want. You would just want to use the TPS pick, for the transistion of the signal if further fine tuning was needed.




[Modified by kewlbrz, 12:32 AM 7/14/2002]

 

Excellent mod! :reddevil