Air/fuel ratios - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

SVO XR6 · 03-17-2004, 19:13

Hi, im in the process of tuning a EMS 8860 ecu.

I was wondering if anyone konws of the best air/fuel ratios to run?
Has anyone tried or tested this?

TIKFD6 · 03-17-2004, 19:20

Rollin is probably the best one to speak to about this mate, he has done some little experiments lately.

Xeron · 03-17-2004, 22:33

I would imagine 12:1 or as close as would be the best as that's what most tuners seem to aim for isn't it?

TVS · 03-17-2004, 22:52

Well you want to keep it under 13:1 at full throttle, forced induction cars should be around 12:1 at full throttle.

Rollin · 03-17-2004, 23:57

as TVS said - around about 13:1 is good, as a general rule of thumb.

i was speaking to the dyno operator about what kind of AF ratios we should be aiming for, and he said

Quote:

keep taking fuel out till it blows, then put a little bit more fuel in

he told me pretty much every production car on the planet runs too fat through the rev range, my guess for the reasoning behind this is to make sure the engine doesnt ping - people hate it when their car pings.

i scored about 13 hp by putting a stock falc fuel pressure reg in my car (instead of the XR6 one that came with it, as, of course, it is a EB XR6)

it had been running very rich since putting the cam in (i wish i had access to a digital camera - i would post my dyno graphs!) it was around 10:1, the stock reg leaned it out to about 12.5:1 or thereabouts, i would gain a few more hp from taking even more fuel out, but without an adjustable reg i cant, i need a new computer (thats coming soon :s6:)

TIKFD6 · 03-18-2004, 00:18

I did the mod yesterday Daniel, very happy with it.
Thanks.

not ford · 03-18-2004, 01:06

Some cars like richer and some like leaner you have to suck and see. A good start point is 12.5:1. On high boost engines some tuners run about 11.5-12:1 to add a little tolerance.