Manifold Absolute Pressure sensor. A sensor used to meter air flow into the intake indirectly by measuring plenum pressure. This sensor is not as pre...
Subject: Re: tuning questions by djxib on 2013/5/6 12:12:06
Quote:
bam wrote: I really appreciate the comments, feedback here, otherwise one feels lost in the woods!!
I will try your suggestion on the PE, I was going to change it but for now I will leave it alone and do another data log first.
One question I have is; why the two 02 sensors? My 08 Grand Prix only has one located back of where the two manifolds join into one. The timing, map readings, temp readings are all the same for both banks of the engine,if so then why change the fueling. I can still see the split BLM's (although I have not logged since smoothing the VE tables, they may have improved but I doubt it) I am thinking this is because of the hot cam (112 lobe separation) and the LT1 intake short runners?? If I am right the problem is enhanced by having 2 02 sensors which are always trying to compensate for the reversion in the intake and constantly fighting against themselves. Andy any thoughts, have you been able to eliminate or improve on the split BLM issue with these motors?
Ahh - split BLMs. The curse of LT1 hot-rodders everywhere.
Firstly - 2 x O2 sensors allows for more fine tuning of the feedback to the ECM. In batch fire systems like 92 and 93 vettes it can adjust for general imbalance per bank. However it really comes useful for individual cylinder trims in 94 (95?) and later cars, - I'm told that the O2's are fast enough to allow the ECM to trim fuel per cylinder.
Split BLM's seem to have a lot of theories - many people have had success by fiddling with the VE table, IAC ports, throttle adjustment screw.. or even finding imbalances in the per-cylinder idle holes deep within the intake. I run my car in open loop all the time - I have a wideband gauge hooked up so I can see AFR, and it completely fixed the 'cam surge'. Not sure if I have any advice for you except that I chased my split BLMs on and off for 6 years before going open loop.
