So I took the car to the track last night for the first time, I wasn't expecting too much with the EB Porting heads being on the small side for my 13.5:1 385 with E85, (185cc, stock size undercut valves, and stock intake manifold). I am on the stock rear still so I left the line soft (2.0 60') only running best of 8.1 @ 91.3. Looked at the datalog from that run and the MAP reading stayed a steady 54.3 from the idle up to the track, through the run, and after. LTFT were reading lean as well, 137-160 idle and down track. STFT were more normal 124-131/131-144 (still lean on one side).

Would a bad MAF cause the off fuel trims and also account for the poor mph at the track? I also have more surging/stumbling at low rpms as well.

 

You mean MAP right?

 

Yes sorry, MAP, Manifold Absolute Pressure sensor, lol. It's not throwing a code but the reading stays constant, and low/partial throttle is rough.

 

AFAIK the stock GM programming uses it mostly for verification but it's definitely reading very wrong. I don't know enough about the programming to say it'll fix your problems but it won't hurt them.

 

I can't help with your tuning question, but I would say 91.5 mph in the 1/8th with a 2.0 sixty foot and 8.1 time is very good. When you leave slow/soft like that to save your stock rearend then you don't have as much track to build MPH. I bet once you have a stronger rear and can leave at more RPM (& hook) then you'll get some 1.6 sixties or better and very low 7's along with a few more mph. I'd be happy with that.

 

sounds like your map sensor maybe bad. you should see it vary with changes to the throttle. depending on were your located you should be seeing kpa in the 90's at wot and at idle it should be a lower value. the kpa at idle will vary for different engines so i can give you a solid number.

 

A new MAP sensor fixed it, runs better now and actually commanding correct timing. It was at 42-46* timing through the run, and apparently only at 44-48% throttle in 1st, short shifting into 2nd at 5400, so I would hope there's more in it.