loosing power with afr 12.8-13.0 afr ?????

[NNBS]

Hi all
i have l92 truck with ls9 cam headers cai , it has this weird problem . i tuned it on the street with afr 12.8 and adjusted WOT timing to reach safely with no knock .then last week i dyno it
it produce 370bhp around 5400rpm lost all low end compared to stock ??? on dyno with pro tuner he said to me that these engine like more fuel . i return stock tune and AFR 11.8 and the truck shows crazy 440bhp on stock rich tune , adjusted the timing and got 495bhp .

as i know if you lean any engine to 12.8-13.0 N/A + some spark advance = power

any comments guys ??

[BigDaddyCool]

Hi all
i have l92 truck with ls9 cam headers cai , it has this weird problem . i tuned it on the street with afr 12.8 and adjusted WOT timing to reach safely with no knock .then last week i dyno it
it produce 370bhp around 5400rpm lost all low end compared to stock ??? on dyno with pro tuner he said to me that these engine like more fuel . i return stock tune and AFR 11.8 and the truck shows crazy 440bhp on stock rich tune , adjusted the timing and got 495bhp .

as i know if you lean any engine to 12.8-13.0 N/A + some spark advance = power

any comments guys ??

You can tune it any which way you want....... I had mine professional tuned ran 13.1 afr virtually..... ran like crap...... and made no power...... Go to the other end of the scale and add timing = a beast..... I think alot of it comes down to cylinder pressure and temps and that's what really seperates some engines and cars in terms of it they like it lean or rich..........

You can always use PE Enrichment Speed to get both results...... eg 1st gear gets to the limiter faster then 4th for example......... so in 1st gear 13.1 might be ideal, but in say 4th 12.5 all the way down to 11.16 might be better at the top end.

I think the best course of action with any car in my opinion is now to dyno it first............ see where the cam and engine makes power and how, then design your pe, maf/ve to reach set targets at certain spots on the dyno spots same with timing........

pe does not have to = what you are trying to command........ if it does great but you in many cases just need to deal with the characteristics of how the engine works.

Anyway.... I personally dont think lean is the answer. Every gear needs to be richer in the same spot then the last............ hence the factory settings alot of times......... it allows for this.

[NNBS]

Thanks alot for the replay . Now i well rent a dyno when ever i tune my car.

[Ben Charles]

Its bc people are tuning with AFR and there Stoich ratios are different than what they realize.

[Maxspeed96ct]

Wide bands at wot don't care what your stoich is - it will still display the proper a/f - they just convert lambda to the number 14.7 in most cases .
The tuning with lambda theory is very misunderstood