Question for expert tuners

[ViperGMC]

Anyone seeing a difference in A/F between the left/right bank while the car is cold. I’m seeing a 2 point leaner condition in left bank until the care gets to about 185 or so, after that they even out. I changed all the injectors and no change so that rules them out. All plugs firing, so that is not the problem either. Maybe the car has always done it, just never had a wide band on both sides when it was stock. Anyway maybe some one else has seen this issue before.

Maybe the cold walls are grabbing the spray and the chamber is not getting good atomization until it warms up???

 

[Racer Robbie]

Not to sound like a smart ass but why worry about it. What really counts is that the A/F is correct once the engine has fully warmed up. My viper runs richer on the drivers side when it is first started too. One should always let your engine warm up completely before you drive it.

Robbie.

 

[ViperGMC]

I have pretty much stopped really worrying about it, but everyone loves a good mystery. I am beginning to conclude that it is related to the stuff in my glove box. He is why. This same observation was made with different O2 sensors, different injectors, different sparkplugs, different valves, different heads, different piston/rings, different wheels, different brakes, different coolant and different upholstery on the seats. The only thing I did not change was the stuff in my glove box. So, one must conclude that the junk is the culprit.

The car runs great so it’s not holding me back, just curious though.

 

[britospeed]

The reason to worry about it is you could have hot and cold cylinders on one bank and all though you AFR on that bank might be good you could still damage a piston in the hot cylinder. In a forced induction app. it is even more critical. Go buy an EGT and check cylinder by cylinder just to be on the safe side. Or don't worry about it as Racer Robbie suggested.

 

[Racer Robbie]

As ViperGMC said his condition is only when the engine is cold. He never mentioned that he had a blower or turbo, therefor I stand by what I said in that I would not worry about it as long as he lets the car warm up completely in the driveway. I agree with you, freeflyer, concerning a forced induction car as it is critical to have it right.

 

[Ooomph]

I don't think our Vipers have them but my Mustang has a smog pump that cycles a small portion of the richer, fuel-heavy exhaust found at startup back through to the intake again to reduce emissions. Perhaps the lower a/f ratio can be explained if we do infact have a smog pump that is physically tied to that bank.

I think that if we did [have a smog pump] we would see lower a/f ratio's based on the fact that a small portion of the combustible a/f mixture is being contributed directly from the exhaust. Just food for thought.

 

[DAMN YANKEE]

925 RWHP....time to ask...."what manifold"

 

[GR8_ASP]

Warm up completely before driving? I do not think so. Just drive reasonable during the warm-up period. That way more than just the coolant warms up. Idling the engine oil, transmission, differential, etc. will stay cold.

 

[Viper X]

Hey GMC,

Do you have an AEM running your engine?

I had a similar experience and concern with my AEM Paxton car. Simple answer: It was tuning and the way the cold enrichment program was set up. DC straightened it out for me.

I also had some issues early on with A/F ratio imbalance due to a poorly designed fuel system. I have now solved both issues.

If you have a stock computer, oh well.....

Dan