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I've read quite a few guides and used them together to make my opinion of the best method (may be putting it all together with a good amount of screenshots). My question is this.. Some guides say that you want your fuel trims between 0 and -5 and some say between 5 and -5. What is the reason for wanting your VE table to always be slightly rich vs as close to perfect (whether slightly rich or lean)?
Some one correct me if i'm wrong.
I think the logic behind it has to do with PE. When you enter PE and have a positive fuel trim, that fuel is added to the PE, making it richer. If the number is negative it will be ignored and PE will be closer to what is getting commanded.
I hope that helps.
fuel trims aren't really the best method in tuning part throttle can be helpful but a wideband and lambda is the best method by far.....I never run leaner than zero ...if you must look at fuel trims I always and tune all of the trim areas within 2% of each other and no more.......The fuel trims in the computer are there to compensate for minor differences in the std/factory calibrations and engine wear, they are not designed to be used as a BANDAID TUNING TOOL that allows you to forget about GETTING your VE tables right.....I always tune to get/achieve fuel economy/drivability and I always maintain that it is very important to ENSURE that the/your FUEL TRIMS ARE LESS THAN 2% everywhere, if the engine has to compensate for inaccurate tuning it will 100% overcompensate and use more fuel in a effort to keep it in a SAFE MODE......THESE fuel trims are carried over into W.O.T as the designers of the system decided that if the engine thought it had INCORRECT FUELING VIA FUEL TRIMS it should carry these over into the W.O.T fueling strategy to look after the engine....this boys has been one of the things that has created the MYTH that the engine needs to learn modifications that have been done- BASICALLY the PCM sees that a error has occurred and ties to correct/fix it - in a modified car TUNED CORRECTLY/PROPERELY THIS DOES NOT HAPPEN......JUST MY ADVICE AND OPINION AND EVERY SET UP IS DIFFERENT AND EVERY SET UP NEEDS A DIFFERENT FUELING STRATEGY IT MIGHT WORK FOR ONE BUT NOT THE OTHER JUST LIKE EVERY OTHER PARAMETER IE TIMING SOME NEED MORE AND SOME LESS CHEERS BRET