regulating fuel pressure

[PWRD_BY_HKS]

Ok let's start this one off with a question.

What is the stock fuel persure on stock set up.

Reason for question.

Doing some resarch I found that fuel pressure should be turned up 7% per pound of boost.

So does this mean at 4 psi the regulator should be reading at 28 psi. Or how should this be done. Am I supposed to turn it up 7% plus what ever its supposed to put out stock. Little help here! Thanks guys.

[mr1in6billion]

Doing some resarch I found that fuel pressure should be turned up 7% per pound of boost. So does this mean at 4 psi the regulator should be reading at 28 psi.

4 times 7% is 28%, not 28psi. That would only be true if stock fuel pressure was 100psi. The 7% comes from the idea that at 14.7 psi you are pushing twice as much air into your engine (so you need 100% more fuel). 100%/14.7psi is roughly 7% per psi. Whether that holds up in the real world though, I don't know.

[hgallegos915]

Thats where the windeband sensor and gauge comes in my friend....

[PATDIESEL]

I'm no turbo guy, but I would think it would be better to get larger injectors and modulate the fuel with injector pulse width. Fuel injected cars run a high PSI to start with, so adding that much more fuel pressure would seem like a fuel problem waiting to happen without upgrades to the lines and attention to any old line or joint. I've also heard it said that if you get a adjustable FPR that you want a raising rate one to keep up with the extra fule demands as the boost climbs. However, I think you would just add a second unecessary thing to tune since you should have some sort of piggyback fuel management for best results of power, safety, fuel economy and emisions. From what I understand a rising rate FPR is used in place of a fuel management, but is less accurate and thus more dangerous to the motor than running proper injector size and pulse width.
All that said, it would be best to get a "real" answer from one of the more turbo knowledgable guys on the board.
my .02 for what it is worth

[mr1in6billion]

I'm no turbo guy, but I would think it would be better to get larger injectors and modulate the fuel with injector pulse width.

Considering the pansy boost he wants I definitely agree that this would be the cheaper and better option. The right injectors tuned correctly can handle quite a bit of boost.

Fuel injected cars run a high PSI to start with, so adding that much more fuel pressure would seem like a fuel problem waiting to happen

Fuel pressure isn't that high in our cars and a 28% increase won't be anywhere near dangerous. A new pump would be needed, but thats about it.

From what I understand a rising rate FPR is used in place of a fuel management, but is less accurate and thus more dangerous to the motor than running proper injector size and pulse width.

Yes, it is inaccurate. No, you don't need to use it alone. In high hp race cars the change in fuel needed over the course of the rev range is so great that injector pulse is stretched further that can handle. If kept like that either high output or low output (or both) suffer. The correct thing to do then is either add injectors in sequence, which is expensive since you need much more hardware, special software, and lots of tuning. Or you can add a rrfpr. The rrfpr keeps the flow rate of the injectors in their best performing range by controlling fuel pressure. The injectors can then be tuned for best performance.