What are the Ltrims after a head and cam install?
04-04-2004, 06:47 PM
#1
What are the Ltrims after a head and cam install? I'm trying to figure out if my MAF is bad.
After you install a head & cam package on a M6 car, about what should the Ltrims be at with no tuning?
I am seeing between +10 - +17 for the average when driving around and they 'lock' at around +4 at WOT. I went to the trouble of putting my stock MAF ends with the screen still in it back on the car to get these readings.
I know how to adjust to lower the Ltrims (IFR Table) but just need to know if these numbers are correct for a completly stock MAF with heads & cam.
Cam specs are - 230 230 .575 .575 114 lsa (Custom TR Cam)
Thanks in advance guys...
Bill
After you install a head & cam package on a M6 car, about what should the Ltrims be at with no tuning?
I am seeing between +10 - +17 for the average when driving around and they 'lock' at around +4 at WOT. I went to the trouble of putting my stock MAF ends with the screen still in it back on the car to get these readings.
I know how to adjust to lower the Ltrims (IFR Table) but just need to know if these numbers are correct for a completly stock MAF with heads & cam.
Cam specs are - 230 230 .575 .575 114 lsa (Custom TR Cam)
Thanks in advance guys...
Bill
04-04-2004, 07:33 PM
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those numbers actually sound pretty good after a head cam swap. as long as the maf is reading and reacting properly i would trust it. maybe spray it with a little brake cleaner if your worried (be careful). inspect the three variable resistors for contaminants and insure they are intact at both ends. if all looks good i would trust the maf. what are your trims at idle? 25? whats the maf read at idle? 1.1-1.4?
04-04-2004, 07:41 PM
#3
Before I put the stock ends back on, I cleaned the MAF with alcohol and Q-Tips, VERY carefully and then after it dried, I sprayed it with CRC Electrical Contact cleaner.
The Ltrims get close to +17 - +21 at idle, but I've heard, that you can't always trust it on a cammed car at idle.
The maf at idle (850 rpms) reads about 1.2 lbs/min I think...
The Ltrims get close to +17 - +21 at idle, but I've heard, that you can't always trust it on a cammed car at idle.
The maf at idle (850 rpms) reads about 1.2 lbs/min I think...
04-04-2004, 08:07 PM
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those numbers at idle sound great. i would imagine your maf is fine.
P.S. the reason you "cant trust" a cammed engine at idle is because of valve overlap of a radical cam. exdended valve overlap allows unused o2 molecules to travel down the exhast stream. this causes the o2 sensors to relay a lean condition to the pcm. which intern jacks the fuel trims through the roof. unfortunately the only fix for that is to up the idle.
P.S. the reason you "cant trust" a cammed engine at idle is because of valve overlap of a radical cam. exdended valve overlap allows unused o2 molecules to travel down the exhast stream. this causes the o2 sensors to relay a lean condition to the pcm. which intern jacks the fuel trims through the roof. unfortunately the only fix for that is to up the idle.