I am trying to learn how to tune with HPT on my 05 cav. After beating my head against the wall because my VE mods weren't changing my AFRs like I had thought they would, I figured out that the Fuel Trim was countering the changes I was attempting.
So my questions are:
1. Is there a way to temporarly disable the corrective fuel trim for experiments?
2. Or should I just try to tune it to the point that I have negligable fuel trim?
3. Does advancing the timing cause leaner AFR's(causing the computer to bump the fuel trim)?
Thanks for any clues.
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Suffering from more imagination than sanity......
1. Yes, set your closed loop enable temp to something huge, like 255 degrees.
2. Yes, but don't pay a lot of attention to the short term trims, the long term ones are going to help you more, but only for cruising/closed loop operation, not for open loop
3. Not really, an air fuel ratio is an air fuel ratio, no matter where it burns, and the O2 sensor isn't determining the a/f based on ignition advance.
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Thanks for the response.
I'm going to go back and look at my previous logs to check LT trim. I just noticed that when I bumped up my timing, my ST trim started to mirror my O2 sensor reading. So I figured that the extra timing was causing the increased ST trim.
But that's why I'm experimenting, gotta learn sometime.
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Suffering from more imagination than sanity......
I do just want to add one thing...
The longer the fuel/air stays in the combustion chamber, the more it will burn, so it can slightly affect your a/f ratio on the reading side since there is less "raw" fuel going through the exhaust. This is only true up to the point of a complete burn, and obviously can work the other way as well.
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