E38 LS3 question

[67LS3]

one of our projects is a 61 vette with a gm ls3 crate engine. has a fast harness with a gm ecm. it is loaded with a stock 08 vette tune and runs extremely rich and backfires through the exhaust above 3000 rpm?? the only difference between the 08 vette and our setup is a little better flowing exhaust due to no cats and maybe a little better breathing intake setup. we have tried everything. we are new to the tuning game and are learning but are both gm certified on fuel injection back in the obd1 days. it has been a while. what do we need to check? also we are not getting any codes. the car runs almost perfectly with the maf unplugged but wont rev past 4000 unplugged. this is a chassis that has not hit the street yet. does the ecm need to learn??

[Redline Motorsports]

How do you know you are running rich? Do you have wide band o2 in the exhaust?

The E38 is pretty smart, and quick and on a stock motor should work seemless. Where is the MAF located relative to the throttle body? Is the MAF installed properly? I assume you are using a custom intake system pre-throttle body?

What are your fuel trims overall?

Howard

[67LS3]

rich? the exhaust makes your eyes burn and your clothes smell. no wideband o2 just the stock ones. after the tb is a 4 inch elbow 90 degree coupler with a 4 inch dia by 8 inch length tube with a k&n filter. the maf is @ two inches past the coupler in the straight tube.

[67LS3]

how far from the tb should the maf be installed?

[Redline Motorsports]

I assume that the car has no cats. Despite what people think no cats and the car still smells like exhaust. This is why a WB is needed. If the car is going into closed loop, the PCM will be pulling the AFR to stioch which is 14.7. Even at 14.7 the car can still "smell" rich. What are your fuel trims at idle??

The new style MAF's are very sensitive to airflow changes and a custom inlet system like yours will most certainly screw up the MAF tranfer function in that calibration. If I am understanding the inlet plumbing, there is a 90 degree turn before the straight to the MAF? If so that 90 can create turbulence that will drive the PCM nuts in calculating airflow.

If you can, send me the current file and send me a data long of idle and cruise area (3000-5000 hrtz). Log (rpm, maf hrtz, LTFT bank 1 and bank 2, KR, spark advance, coolant, IAT, o2 voltage bank 1 and 2, E38 dyn/cyl air).

Send it to howard@redline-motorsports dot net

Howard

[67LS3]

Howard, sent you an e-mail. Thanks

[Redline Motorsports]

Did you resolve this?

Howard

[gmh308]

Ditto?

[ringram]

Im in the process of tuning mine mafless and it runs like crap it shows its running real rich. I think the VVE values are way too high so when the Maf is unplugged it runs too rich. Check your AFR you might find thats the problem.