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Rich AFRs, pinging at light load


New member
May 18, 2003
Santiago de Chile
Ok so I replaced my M46 with a Getrag 265, and the engine is a 9:8:1 CR squirter block. I cranked up the boost to 13 psi but the AFRs are still at 10:1 @ WOT. (it goes to 10:1 from 7 psi on, stock fuel system LH 2.2) Though I can hear some little pinging during the transition from vacuum to boost and light load that then dissapears when LH starts putting more fuel. (static advance at 10 deg.) It seems that it will never lean out.

2 questions:

1) I can I continue to increase the boost to say 15 psi providing the AFRs are in the safe zone or there is something else to look for?
2) Do I have to worry about that ping in the transition from vacuum to boost?

The car is a ?87 740T, squirter block, getrag, 3 in. downpipe and 2.5 cat back, V cam

Thanks for the input.
while not favorable, ping during spoolup isn't all that uncommon. I assume you're running premium fuel and all that, correct?
you'd probably have to re-map the ecu or something like that to get it to lean out.. or switch to something other than LH.
you could back up the base timing a bit more, set it at about 6 degrees to start and see what happens. LH 2.2 is not really adaptive and the timing curve is fairly aggresive. you don't have resistors in your AMM line or anything do you? i don't recommend that anymore as it's more trouble than it does good.
i'll be honest with you, it's going to be faster with a 2.5 bar fpr but your piston breaking threshold will be lowered. i ran a 2.5 bar on lh2.2 with 9.8:1 and i'll tell you it ran like a bat out of hell but it liked to kick a piston every once in a while when i beat on it.