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Hey all I had a quick question for the experts. Recently did an engine swap into my 1974 2002. It's a 1998 m44 4 cylinder with a supercharger running a rrfpr for fuel management. The engine runs great at idle and light driving with ltft averaging around +6-7 and stft sitting + - 5 percent or so. When I put my foot into it the stft dives to the -20 range and then recovers when I let off. I don't have a great understanding of fuel trims but would like to get this sorted. What are your thoughts on what is going on here? Thanks guys sorry for the long post just wanted to get the info out there.
Ian83 post=49100Hey all I had a quick question for the experts. Recently did an engine swap into my 1974 2002. It's a 1998 m44 4 cylinder with a supercharger running a rrfpr for fuel managemanagemet
Your rising rate fuel regulator is adding too much fuel pressure when the boost pressure rises.
You could try adjusting the regulator pressure setting downwards to reduce the put the fuel trims slightly negative at idle to stop the fuel trims maxing out under boost
But uising this type of afermarket fuel pressure regulator is bodge. junking it and going up a size in injectors might work. I would look for advice on it from one make BMW forum but as always with one make forums do a sanity on any advice offered.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
"when I put my foot into it", I am assuming you are talking about wide open throttle? I have to be honest, I've never looked at trims or much cared about them at WOT or heavy acceleration. Maybe I am missing a tool I could be using for the acceleration period? But for sure at wide open throttle, we don't want to be at shoich, so trim numbers are invalid (can I say that?)
This makes sense to me, I will back off the rising rate regulator and bring idle trim slightly negative and see if that will get wot closer to where it should be.
Thanks for the reply, I am just watching the trims as I drive in generic obd2 mode live data. I would not be concerned if the wot did not seem to drag the ltft's down with spirited driving. I am going to try to reduce the rrfp regulator and will report back.
What's the Loop status while the trims are at -20%? If it's Open, then I'd be careful about making changes to the fuel delivery based on those numbers.
Are you running an AFR sensor? Or, would it be possible to get one and check the actual lambda during heavier loads?
I am a novice with obd2 operations but I believe it is running closed loop based on the o2 sensor values bouncing around. (This is an assumption I made and could be wrong)
I backed off the rising rate regulator but saw no change in my trim values. I am confused. Thinking this regulator may be trash.
