LS1Silverado05

iTrader: (41)

After chasing what appeared to be a lean issue to exhausting lengths (Blocked EGR, cleaned MAF, New plugs, wires, intake gaskets, new fuel filter etc) , I started on Calibrating the MAF. This car is a stock car with exception of a Walbro pump and someone has descreened the MAF. I was seeing 18% AFR error at idle with a commanded 12.5. After applying the % correction to the idle cells in the airflow/hz table, my error was -1 to 1. So the correction appeared to take hold, however my question is, does that sound possible without a physcial motor problem or air leak? I am new to tuning but 18% off at idle just seems high on an un-modified car on a stock tune (verified).

Please give me your thoughts on % error and what is a reasonable error to see while dialing in tables. I dont want to just dump fuel on top of a problem, but if it sounds possible without a problem being present I will continue my MAF Cal.

Thanks

Chevy406

iTrader: (12)

If you don't have vacuum or exhaust leaks then give the engine the fuel it wants.

LS1Silverado05

iTrader: (41)

Thanks for the reply... Yeah it sure doesnt appear to have any exhaust leaks or vacuum leaks. But it idles a little bit rough which makes me think there is. Then again maybe it idle rough because its busy correcting.

Chevy406

iTrader: (12)

I recently tuned a '99 Corvette that was pretty much stock. It required a lot of MAF adjustment to drop the fuel trims. I couldn't find a vacuum leak so I modified the table as required. I don't know if it was a replacement MAF sensor that had a different calibration or what.

LS1Silverado05

iTrader: (41)

Ahh ok. Maybe im banging my head against the wall for nothing. Just assumed that was way off for a stock car. RPMs are steady at 850-900 too so I wouldnt think I have a vacuum leak or I would be having a higher idle too?

Ill keep tuning on this MAF a bit. Any advice on what AFR to shoot for at idle?

outkast6991

iTrader: (34)

wouldn't stoich be a good target on a stock car?

LS1Silverado05

iTrader: (41)

Well thats my assumption yeah.. Just wanted to see if there were other schools of thought.

I only have it commanding the 12.5 for simplicity of tuning the MAF across the board for the moment...

BLK02WS6

iTrader: (2)

There would be your problem...

LS1Silverado05

iTrader: (41)

Think so? Will it be fine once I re-calibrate? Or should I be sourcing a replacement?

Is that proof that it flows more? LOL. Albeit not smooth flow?

BLK02WS6

iTrader: (2)

No, it flows different, not more - the screen is there to take away turbulence so the readings are smoother and flow is even across the cross section of the MAF. You can try to recalibrate it and as long as you get a smooth table and smooth readings, that's fine. If it gives you fits, I would get another. BTW a stock screened MAF is good up to around 450 rwhp before it becomes a restriction - been proven many times...

LS1Silverado05

iTrader: (41)

Im with ya... I was kind of being a smartass, Ive never prescribed to the de-screen idea.

After some tweaking I got my errors to dial in some.... far from finished but...