VTC_CiViC

I'm trying to find out exactly how the relationship between injector size and pressure works, and how to determine what size injectors to use and what pressure to keep them at. For example... as I understand, the ideal fuel pressure for a stock fuel rail on a Civic with 240cc injectors is something like 80-90psi and no higher under boost. Now let's say hypotheticaly that I went with 500cc injectors, do you need more pressure in the rail with larger injectors? Or is the target pressure the same as with the smaller injectors? See my thing is, I wanna know if I need to increase pressure with bigger injectors or is the pressure rate at the rail always supposed to be a set amount regardless of injector size. If not though, how much do you increase rail pressure to compensate for injector size? BTW this is for my Civic which will be running 290cc Prelude injectors. I want to boost 7-8psi daily, for which I planed on usuing an 8:1 FMU so that at max boost, pressure would be something like 100psi (35psi idle, 64psi added by 8:1 FMU @8psi = 99psi), now if this is too high I could go lower with a 6:1 FMU rate and push about 80-85psi at the rail, but is this too low for the injectors?

VTC_CiViC

I know SOMEBODY has to know this...

Giuseppe

yeah come on guys there has to be a
standard, i'm trying to understand this
fuel pressure topic too..!!!!!!

Holden

The simple answer is the bigger the injectors, the lower the fuel pressure, leaving everything else alone.

Go here for the real math: http://www.rceng.com/technical.htm#WORKSHEET

All you wanted to know and more is there.

VTC_CiViC

Excellent, thank you Holden. I'm going for some 350cc injectors (perfect turbo DSM auto-tranny injectors)