I've got a Silverado SS that I just put a 414 into, and when I took it the dyno, the tuner cannot get the AFR to stay where he wants it (12.8~13.0). He will make one pull, and it will be dead on, but then make another pull without touching the tune and the AFR will lean out to 15 or 16. When scanning the MAF during the pull, it will just all over the place, as much as 40~45 g/s throughout the entire pull. He thinks that there is an electrical problem or interference with the MAF. Is it normal for the MAF to fluctuate that much during a pull?
We have tried several MAFs, moved the MAF farther away from the intake, tried a stock truck intake tube with baffles in it, and nothing seems to make a difference.
The only thing I can say, the tuner did not adjust the P0101 max delta airflow or the MAP max error tables. The MAF and MAP codes were being thrown on the dyno, but I have since fixed that on my own and the MAF still acts the same way on the street when I log it. The tuner also did not disable STFTs during openloop, so I'm not sure if those could of been throwing the tune off that much or not. I have since also disabled STFT during open loop to try and figure out whats going on.
When I do back to back runs on the street, the O2s can be at .930mv for one run, then I can stop, do another run, and they will only be at .880mv. Seems kind of odd to me that they flucuate that much from back to back runs during openloop with both LTFT and STFTs disabled.
If anyone has any ideas, please post as I need to get this truck running ASAP. I've been to the tuner twice already with no luck.
Two log files are attached along with the tune. For both logs, the truck was locked into 2nd gear for the WOT pull. One log is with the stock truck intake tube on, the other log has a 4" intake tube with a K&N air filter on the end with the MAF right next to the filter.
Engine mods: Engine is a 414 (Iron block, 4" stroke), 246/252 .630/.635 +4 112 lsa cam, Edelbrock Pro Flow XT intake (http://www.edelbrock.com/automotive_...f-xt_ls1.shtml), 42lb GM Marine Injectors, 4" Intake tube (90* off of the intake and runs over to the fender with a K&N cone filter with the MAF attached to the Filter), AFR Heads ported by TEA, flow right at 340 at .600 lift, 1 7/8 LT Headers.