I have 1.8T Audi A4. I just upgraded to a ATP GT28RS turbo kit. With a tuned ECU my air fuel ratio is still pretty high. I talked to a couple shops and they're saying that air fuel ratios up to 12.5:1 are still okay. I always thought that air fuel ratios should be in the elevens for turbo charged cars. Does anyone know what an caceptable air fueld ratio is under wide open throttle?
Posts: 2931
Joined: 7/18/2006 From: six zero seven, NY Status: offline
12.5:1 is still on the rich side of stochiometric and is probably OK, but running in the 11s is safer just because you've got the extra cooling effect of the additional fuel being injected, not to mention if you had a momentary injector stumble, you have more headroom for safety between the AF ratio you're running, and a lean AF ratio which could cause damage. To adjust this, if you're using an MBC, just dial the boost back a hair.
Thnx for the post. The only thing here is that the chip is supposed to be good for even more boost than I'm running now. I'm running 18 PSI, and the tune is supposed to be good up to 21 PSI.
Posts: 2931
Joined: 7/18/2006 From: six zero seven, NY Status: offline
If the chip has the maps to handle that level of boost, then chances are you could do it. If it required bigger injectors, you'd have a different program. But, the higher you boost, the closer to stochiometric (and then lean beyond that) you will get. Also, just to keep in mind, remember that the more you boost, the more fuel you have to have, so your injectors will be running a higher and higher "on" percentage. The closer you get to their limit, the more potentially damaging a sputter on an injector would be. Keep a safe margin just for longevity's sake. I wouldn't run the ragged limit of what your map is set up for - it leaves you no headroom for any burps or hiccups in the fuel delivery under boost.
I know what you mean, but this at 18 PSI the AFR is in the 13's and 14's upon lifting. This means that AFR would get even leaner if I stayed in it all the way to redline.
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Air Fuel Ratio - 
