I need more fuel pressure. Is there any difference between the stock GSL-SE FPR and the stock S5 Turbo FPR?

 

The T2 FPR won't help you out at all. The T2 fuel pressure is listed as 28 psi at idle, just like the SE. The only difference is that since the FPR reference will see boost in the T2 application, the fuel pressure will be higher under that condition. The T2 pump can put out high pressure to account for this: SE pump (50-70 psi), T2 pump (70-90 psi).

Are you just looking for more fuel? What do you have know (SE intake, stock injectors?)? You could go with bigger injectors to get the flow, or you could go with an FC intake so that you can run 4 injectors. You could these use a 2nd gen ECU, standalone, or SE ECU + AIC to control the additional injectors.

 

I'm actually running an S4 TII engine and manifolds, with my -SE's old 680's and a pair of 1680's. I'm running a Walbro 255lph pump through otherwise stock (-SE) diameter lines. The rails are both stock s4 TII with the PD replaced with a banjo bolt. My Haltech is showing very high duty-cycles on even the 1680s and I was thinking it must be the -SE FPR that I used. I picked up an S5 Turbo fuel rail with the built-in FPR. I had hoped it might help, but didn't want to go through all the work if I'm not going to see any lower load on the injectors.

 

Wow, that is a lot of fuel. Do you have the FPR connected to the manifold (should see both vacuum and boost)? Have you tried to check the fuel pressure just to see what it is (maybe the FPR is stuck open a bit, reducing fuel pressure)? The SE FPR should be fine with boost (even though the SE isn't designed to see boost). Check the fuel pressure first, then if it is out of spec, thow on the S5 one.

The fuel pressure should be:

about 28 psi at idle
about 37 psi if you disconnect the FPR reference line (same as WOT on a NA)

The fuel pressure should increase from 37 psi by 1 psi for each psi of boost (13psi boost = 50 psi fuel pressure).

As you probably already know, increasing fuel pressure increases fuel flow as the sqareroot of the increased pressure, i.e. double fuel pressue increases flow by a factor of sqrt(2)=1.4. To double the fuel flow rate, the pressure would have to increase by a factor of 4.

What kind of duty cycles are you seeing? 80%? Higher? Good luck.

Kent

 

This FPR wasn't too bad on price and works great.

 

Yea, I can't believe I need more!

Affirmative, to the only source on the manifold that isn't blocked-off. One of the former-OMP vaccum sources. I thought about connecting it right behind the throttle-plates, but figured the closer source might be better.

That's the next step. I don't have a gauge, but I think I can borrow one.

I'm hitting 100% duty-cycle at WOT, 17psi. Even then, It holds a steady 11-to-1 A/F right up until 6800 or so. It'll creep up to 12-to-1 at redline, but it's still on the safe side. It's bad for the injectors, I know.

I was looking to up the boost to 20lbs on race gas but am worried about not having enough fuel or screwing up my gear. I was hoping the S5 would have some advantage over the S3. I guess I'll get a gauge and check the fuel pressure tommorow. Thanks for your help!

 

Ok, got a fuel pressure gauge today and installed the fuel line tap between the two rails. I saw 43 psi at idle, and over 60 psi fuel pressure at 17 psi of boost. So I'm well within specs. I also noticed I could tune out that rise in A/F at redline.

I think the Haltech may simply be reading the duty-cycle incorrectly.

Also, wewt... who knew S3 fuel-pressure regulators could handle boost?