trigeek37

running 15 lbs of boost my injector usage peaks at bout 89% at 7000 rpm under wot
running 13 lbs of boost my injector usage peaks at bout 83% at 7000 rpm under wot

if I upgrade my fuel pump, is that enough, or do I need to do injectors at the same time? I REALLY don't want to do any more serious engine work atm... very tired of that, but if it is necessary, I will replace my injectors too....

maxcooper

The ECU doesn't know anything about your fuel pressure or fuel pump, and (rightfully) ignores the O2 sensor under boost, so adding a fuel pump will have exactly zero effect on your injector duty cycle. It might deliver more fuel to your engine, though, if your current pump is inadequate and the fuel pressure is dropping at high boost & RPM, though.

Since you are running 15 psi, it is probably a good idea to upgrade the fuel pump. Just don't expect your duty cycle to change.

Installing bigger injectors won't change the duty cycle unless you get the car tuned differently or change the injector size setting in the computer (necessary when you upgrade the injectors). If you don't have a programmable fuel computer, you can't use larger injectors.

-Max

trigeek37

maxcooper - thanks, that makes sence....

my next question is: is peaking at >90% injector fuel duty a problem?
or is this ok, as long as it dosen't happen regularly?

jspecracer7

I've heard that taking above 85% injector duty is too much. I would just boost 13 PSI if I was you.

...AND save up for a stand-alone/injectors/fuel pump