Quote:
Originally Posted by dwarmenzerk
what would i expect with z06 mufflers, ziptie mod, new plugs/wires, and xpipe out of a4 c5? If its not much I dont see any use doing it, but if i can make a little bit more power then i may consider.. how often does something like this come around??
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When you increase the air in and air out on our cars the pcm needs to be reprogrammed.
The pcm is programmed for x amount of air, when you increase the air with an aftermarket filter or in your case removing the top of the filter box the car will run lean but the pcm using the MAF will adjust for this using the long term fuel trims.
Your LTFTs should run as close to 0 as possible, but with increased air they will run on the positive side. Running positive is adding fuel to make up for the lean condition in normal driving conditions which is refered to as closed loop.
Now you might say what's the big deal the pcm has adjusted for it.
The bad thing about pos. LTFTs is when you go into open loop or WOT (wide open throttle).
When the engine goes in to OL it uses a table and the recorded LTFTs to keep the AFR at a set point.
This is the power enrichment table which I like to set at about 12.8-13.0 AFR at WOT.
So when you have the PE table set for the optimum air fuel ratio the LTFTs if running positve will add extra fuel and make the engine run rich and impossible to keep consistant.