PDA

View Full Version : Turbo LS4 odd dma grams/cyl problem with mass air on the dyno



MattS
January 17th, 2011, 01:21 PM
I have an 07 monte carlo E67 os# 12609256 cal# 12605843 with a LS7x stlye head billet bocked turbocharged set up. The engine rips on open loop speed density, I have the virtual ve tuned spot on to 210 kpa and estimated beyond that (about 18 psi at my altitude). I reinstall the maf (customer wants traction control and this os has no patch), it is a blow through Lingenfelter 4 inch set up, scaled the maf on the dyno in simulated road. I ended up installing a maf screen to help smooth out the air flow in the maf. I had the maf set up correct below 50% throttle (up to about 280 grams/sec) and made a power pull on the dyno, that is when I has the odd problem show up. The engine leaned out untill it hit about 3770 rpm then the dma grams/cyl jumped in seven frames from .76 to 1.03 with almost no change in maf g/s, engine rpm, or map kpa. the odd thing is the maf was spot on at the same g/s at light throttle. If i richen up the wot maf at the 130-260 g/s range it is super rich any where else besides wot. I have attached several logs the first log #7 is of one of the maf dials on the dyno, all seems good and normal. log #21 is of the problem look at frames 2050 to 2057. Log #24 shows another power pull back in speed density frame 3300-3867 you can see the af is right on. (if found out later that the kr was caused by a slipping transmission) I have included a copy of the tune, any help would be great.9701970297039704