hi

i have a PFC and its tuned on the dyno to 15 psi. i had an AFR of about 11:1 to redline. now the question is, if i run only say 10 psi does that mean that the car will be running at an AFR less than 11:1 because i have less air going into the motor?

is the PFC "smart" enogh to know that i'm running less than 15 psi and tune the fuel to 11:1 so i can make max power?

thanks

the pfc (and every other ecu), has basically a 3d map of fuel vs load(1) vs rpm. so yours is set to 15psi, 11:1 afr in a given rpm range. if you change the load its looking at a different part of the map. hmm example; when the ecu sees 7000rpms, and 15 psi it looks at the fuel number there and outputs that injector time. at 7000rpms and 10psi it might have a different fuel number, and a different output and a different (or the same) afr. the exception to this is like a t2 with a fuel cut defencer, the stock ecu has a fuel cut at 8psi, and to go over that you put this little box on so the ecu cant see any more than like 7.8psi, so to the ecu 7.8psi and 15psi look the same.



sorry that got so long

mike



1. load is defined as; the input(s) the ecu uses to determine airflow. some cars use a tps, some use an air flow meter, some a map sensor, or some like the fc use all three

thank you very much. it makes sense now.

so to make the max performance out of 10 psi , 15 psi and 17 psi , i'll have to tune it at each pressure.

one more question please: if the car is running rich/safe at 15 psi is it always safe to assume that its going to be safe at 10 psi?

i know that you have already gone over it.

the reason i'm asking is because a 3D map looks like a mountain/building from the side and the peak is 15 psi so 10 psi can't be alot lower in height. right??

you could map it out so that its safe at 15 psi and super lean at 10, but since you are starting with a pfc which already has a good map it prolly is safe



mike

Think of a 20x20 map (PFC) with location lower right being 20x20 being 8000rpm and 24 psi, x-axis pressure and y is rpm.



Most cars running (PFC at least) base maps have rich spot when in high boost but lean from 7-10psi from 4200rpm to 5600rpm. Lean-ness depends on the mods, I am sure.



Most people tune "horizontally" where they tune for a boost setting through the RPM band. Now if you can tune on a Mustang type non-interia dyno you can get "vertical" tuning where you can tune an exact cell....say 14psi at 5000rpm...and get a reading for that cell.



Tony

Think of a 20x20 map (PFC) with location lower right being 20x20 being 8000rpm and 24 psi, x-axis pressure and y is rpm.



Most cars running (PFC at least) base maps have rich spot when in high boost but lean from 7-10psi from 4200rpm to 5600rpm. Lean-ness depends on the mods, I am sure.



Most people tune "horizontally" where they tune for a boost setting through the RPM band. Now if you can tune on a Mustang type non-interia dyno you can get "vertical" tuning where you can tune an exact cell....say 14psi at 5000rpm...and get a reading for that cell.



Tony [/quote]

yeah, i'm gonan take my car to shivs dyno and tune each bar/cell that way



mike