attyjeff

I think it is 12.1 does that sound right, too lean is very bad but good hp, to rich good but less hp.

dime1622

By stoichiometry, it's 14.7. However, you'll see most ECUs run closer to 12, especially in higher RPM ranges, where running lean, obviously should be avoided at all costs.

dime1622

I should add that some additives, like ethanol, can reduce the stoichiometric ratio to about 14.1.

rberry951

If your systems uses the stock O2 sensor then closed loop mode will maintain stoic (or close to it) any time you're aren't accelerating. But if you lift completely of course it'll go very lean and that's normal.

Different chips seem to have different target goals. If someone is running 15-18psi boost I like to see it 11.5-11.8 under full boost and up to 12.1 in the higher RPMs as boost bleeds off. Prior to boost it can go as high as 12.5, this helps spool-up. So ideally it should not be a single AFR across all ranges. Just driving around 14ish is nice, passes emissions, good fuel economy, good temps. In very high boost conditions it can be a bit richer on the top end and under full boost, this helps keep EGTs down and protects against detonation to some degree. Again, I map mine pretty specific to the car's power curve, but any generic chip that keeps you in the 11.5-12.2 range should be safe unless you're running insane boost, in which case 12+ could be dangerous.

Regards,
Russell

attyjeff

Russel I am running your chips from L/R, 951max

attyjeff

and I keep my boost set at 16-17

lart951

I run 11:3-11:7 @ 21 psi

Perry 951

I run 12:5 @ 16PSI, 1550 EGT.

reno808

I am confused the higher the number the leaner it is or the other way around?

hp18racer

Higer a/f ratio number is leaner.

special tool

Higher number the leaner, yes.