OK, from what I understand the FPR has two settings, normal and WOT. It recognizes the difference based on boost pressure from the intake plenum. (I am assuming this because of the little tube that runs to it.) So what happens when you have a boost controller?

This spring I plan on going to the stage III setup, and I'd like to be able to run 8 or so psi for normal driving, and then have the 15psi setting for those little mustang run-ins.

So how do I setup the FPR for this situation? Just set the WOT Fuel Pressure to where it needs to be at 15psi? It seems to me that in this case I'd be getting too much fuel when running 8psi...?

I'm sure this isn't the case because all kinds of people run this setup. Can someone explain this to me?

Thanks

Old School 2GNTer
Now rockin an 05 SRT-4

Please read all of the fuel related stuff on these pages. I think that will give you a good understanding of what is going on. Then you can worry about Stage III stuff.
http://www.geocities.com/vttalon/tech.html


Corbin

'95 ESI-T
HRC+FMIC+ETC...

Corbin
'97 GSX dressed like a '95 ESi

The FPR gets the signal from your manifold. at vacuum, it does nothing other than let the fuel flow through. However, it is set internally to raise your fuel pressure some amount for every pound of boost. I don't know what the Hahn disk is set to. The star kit has a 12:1 ratio (meaning the fuel pressure raises 12psi for every pound of boost).
Example...assuming idle FP of 55, at 1psi, my FP is 67, at 2 it's 79 and so on. It theoretically will vary linearly and continue on up. As it's set, my fuel pressure won't go above about 98 psi even when running about 6 or 7psi. That's why many star owners have to change the fuel system to reach 10+psi of boost. Since the hahn stage II kits are set to run at 10, I would assume their ratio is lower b/c 173psi (53+12*10) would be unrealistic.

Hope that helps,
Matt

Star Stage III

99GS MT | Star Stage 2 | GC coilovers | HurriganeGS tie bars | Tokico Illuminas | 17x7 Enkei RS5 | Baer track brakes |+

OK Matt, thanks that'd helped alot...I get it now. I was just wondering what that ratio was.

When Passen installed my turbo they had no trouble getting plenty of fuel pressure...actually, they had a little problem getting it low enough. I have the 5psi wasgate, and the fuel system wanted to push like 125psi at WOT (talk about killing the injectors)

Anyway, they got it to work out...I hit about 106psi of fuel pressure at 5psi of boost. Things is gravy.

Thanks again Corbin and Matt...

Peas

Old School 2GNTer
Now rockin an 05 SRT-4

>Anyway, they got it to work out...I hit about 106psi of fuel
>pressure at 5psi of boost. Things is gravy.

But 106 psi is way too much for 5 psi boost. You should see 80-90 psi at 6 psi boost. At 5 boost, I would expect to see 77-87 psi. I'm assumming that you have stock injectors and comp ratio.

Corbin

'95 ESI-T
HRC+FMIC+ETC...

Corbin
'97 GSX dressed like a '95 ESi

Hey Corbin, I must've made a mistake then, it's been a while ago and I might be thinking of something else. Seems like I remember them saying 105psi for 5 pound of boost in the install manual, but who knows...all I know is my A/F numbers are right on...and my EGTs are in a decent range... about 700-750*C (1300-1380*F) at WOT

Old School 2GNTer
Now rockin an 05 SRT-4