whitneyd

I've seen it said that for a certain amount of bosst you need to a certain A/F ratio. For example 20psi = 12.1 a/f, 30psi = 11.1 a/f

Can anyone give some good info on this or is it engine set up dependant only? Thanks, David

Garage19

It is usually a case of what your engine is happy to run without detonation and with reeasonable EGTs. Expect on boost AFRs to be between 12.5:1 and 11:1 in most boosted applications.

AlexF

boost is only linked to AFR is the same was a N/A engine is...

ie you need to run the engine with in a certain range of AFRs.

Alex

JohnnyB

all to do with engine design mate, there is no set figure.

whitneyd

That what I thought. But was having a conversation the other day with some local gearheads and one of them said that with running 32psi that they should be running around 11:1 afr. I asked how he could just come up with that figure. He couldn't really give me an anwser. So I figured I'd ask if there was a formula or something.

AlexF

Its about that figure for most engines... it does vary but not by much!

Peak power is around 12.5:1 but you normal run a bit richer than that to be on the safe side.

Alex

Rick

more load and more heat, then we use a little more fuel to keep things cool. At 10psi im around 12.8:1, with low 11's on full boost.