hrubago

I have 2,5 USDM STI engine, 550 blitz injectors, TD05/TD06 20G, standard fuel pump, Haltech engine management.
On the datalog i see 90-95% injector duty.
Standard pressure regulator works 3 bar at iddle and 3,5 under load.
Standard fuel pump is good enough for the 440 injectors at 3,5bar.

1) But the question is if std fuel pump is good enough for the 550 (could deliver more fuel than injectors could inject).
2) If I will raise fuel pressure to 4 bar: what is assumed injector flow gain and if the standard pump could do the job.
3) is good idea to install 2nd paralel fuel pump?

john banks

You are way out of the league of the standard fuel pump already.

3.5 bar is very low - are you only running 0.5 bar of boost?

Increasing fuel pressure from 3 to 4 bar results with a good pump in a 15% increase in fuel flow.

hrubago

Fuel pressure = 3 bar + turbo pressure?

tweenierob

That reads as you have set it to 3 bar at idle and when the car is under load (ie on boost) it is at 3.5, so as john says 3bar + .5bar boost..??

hrubago

I have fuel pressure meter next to fuel pressure valve. I have no possibility to read it from the cockpit. :-(

R19KET

Your max fuel pressure should total your fuel pressure at atmospheric (0 boost) + your max boost.

So, if you're running 3.5bar at atmospheric, and 1.3bar of boost, your max fuel pressure SHOULD be 4.8bar.

See if you can extend the reg' into the car, just to see what pressure it hold when on full boost.

Mark.

hrubago

How to measure 0 bar? (at iddle i have 0,3+bar vacuum).
Then the iddle setup should be 2,7 bar fuel pressure?
If only the IDC is more than 85% then its the time to rise the fuel pressure. Are you agree?
But question is still the same. Could std. subaru fuel pump deliver enough fuel at 4,3 bar for the 550 injectors?
Is there a way to buy second std. pump for paralel lining or one uprated pump? Which pump? Walbro? Which specs?

R19KET

IMHO, I wouldn't be pushing a standard pum that hard. They are notorious for not being up to the job.

A Walbro 255lt high pressure pump will be more than enough on it's own. You don't need twin pumps, or the hassle of fitting them.

Mark.