How Much Should I Increase Fuel Pressure Per PSI Of Boost?
 

Hey everyone my question is what is the formula for fuel pressure to turbo boost for example 1 lb of boost pressure to 10 lb of fuel pressure can someone tell me that formula

i only know that the stock FPR is a 1:1 rising rate type...

so i THINK that when you run 12lb boost your fuel pressure is rised by 12lb

There is no formula relating boost pressure to manifold pressure.

Stock FPR's maintain a constant pressure differential across the injector, so fuel pressure is increased by the same amount as manifold pressure changes.

What exactly is it you want to figure out?

Just wanted to figure out how much fuel pressure i would need to put for 15 to 22 lbs of boost

Yeah, I've been wondering something like this. Will my Walbro 255 fuel pump and the stock setup for a TII be enough to run 9 lbs of boost? Something says yes, but just want ot make sure

Sorry to hijack thread, I'll be done soon! :P

i believe you can get more then 9 lbs but i'm not sure

actually if you dont have a FCD you wont get more than 8.9 PSI.

and with out stand alone computer i would never go over 12psi. IMO 12psi is pushing the stock computer, casue it doenst have any real maps set up for timing above 8psi.

so to get 15-22 lbs of boost you would need a lot more than just a FPR.

It doesn't quite work that way. As I said above, the FPR increase fuel pressure as manifold pressure increases. So if you increase your max boost, your max fuel pressure will also increase by the same amount, as long as your pump can actually keep up.

In terms of how much is required, there's is no relationship between fuel pressure and boost. You need to provide enough fuel flow for the power you're trying to make.

You won't be making 15-22psi with a stock turbo and pump, not for long anyway...

Nz I was wondering if you know what the exact diffrence is between the flow output of a Stock 300ZX Twin Turbo Fuel Pump, compared to an stock FD fuel pump? Or even a Walboro 255? The reason I ask is because, my S5 has a 300ZX TT Fuel Pump, and I am getting terrible MPG. I had a stock Fuel Pump on another Turbo-II I had running the same setup and my MPG was a hell of a lot better. Im debating wheter to swap out the 300ZX pump and install an FD Pump? Would I get better MPG or is the stock 300ZX and FD fuel pump about the same as far as the flow output is concerned? Sorry for hijacking the thread fellas.

Tell you what. PUt a source of Pressure to the vacuum nipple on the FPR and tap in the fuel lines with a fuel pressure gauge.

Jumper the fuel pump check connector so the pump will run when the key is put to ON. Now apply as much pressure to the FPR nipple as you like. I can almost guarantee you'll never see over fifty psi in the fuel rail. You can do that with a turbo or a non turbo FPR. Results are the same.

Stock fuel pump. Either n/a or turbo fuel pump

ok cool thanks for the info

Hailers how are you buddy? Was the above post in regards to my question?
Are you saying I can use the stock Turbo-II pump or FD Fuel Pump?
Please clarify. Thanks for your input.

I need to be careful. I don't run above 10psi and don't KNOW what is needed above that.

On the whole I know that the fuel pressure rises about 1psi more for each psi of boost. Like at zero psi the fuel pressure will read about 39psi. At 10psi of boost the fuel pressure will get up to around 49-50psi.

I've played with putting pressure on the vac nipple of the FPR and watched the fuel rail pressure (fuel pump check connector jumpered and the key to just ON), and the most pressure I see in the rail is approx 50psi no matter how much pressure I input to the FPR vacuum nipple.

I'm just saying that the fuel rail pressure will rise as you boost, but once you get above 10psi boost, then the fuel in the rail will not rise anymore.

I'm talking a stock turboII fuel pump and stock turboII FPR.

I was just guessing that the fuel in the rail won't be high enough for real high boost pressures i.e. over 10psi boost.

Let it be known.........I know little about high boost and don't plan to learn. Going to forget about these cars and go back to sailing/wingsurfing/sculling and maybe kitesurfing.

Exact difference? No idea. :)

That's no surprise. Even if you don't know the pumps' specs, it's safe to assume that if you put the fuel pump from a 300hp car into a 200hp car, and make no changes to compensate, you'll use more fuel. FPR's can't compensate for increases in upstream pressure, so any time you install a bigger pump, rail pressure and hence injector flow will increase. Unless you use an adjustable FPR to lower fuel pressure to stock levels or a fuel controller to electronically dial back how much fuel is injected, your mixtures will be richer.

Undoubtedly.

That's probably because the FPR has reached its mechanical limit. It raises fuel pressure by closing down to restrict flow, so I guess it's as closed as far as it can go.

22PSI of boost?


i smell a blown motor thread in the near future.