Fuel Pressure reg

SpidersWeb · Post by **SpidersWeb** » Thu Apr 22, 2004 8:25 pm

StarionChef wrote:whats the standard JB fuel pressure?

Pump was rated at '47' and I can't remember the units, think it may of been L/min which is flow not pressure, so no idea if that even helped at all.

Cookiemonster · Post by **Cookiemonster** » Thu Apr 22, 2004 8:32 pm

Injector flow rates are measured usually at 3 bar (45psi). This is enough pressure to atomize the fuel.

Didn't I read somewhere that the starion runs 38psi fuel pressure with an additional 1psi of pressure for each pound of boost?

NXTIME · Post by **NXTIME** » Fri Apr 23, 2004 2:47 am

StarionChef wrote:
NXTIME wrote:What pumps are you planning on using?
What we discussed awhile ago

I am getting too old to remember.

Retail or retro parts? ;)

Barney · Post by **Barney** » Fri Apr 23, 2004 11:07 am

I run a Malpassi rising rate twin diaphram regulator. I have seen this on many 600hp Skylines. It is available from most EFI suppliers, should cost you arround $250.00

ASHLY

Camotec · Post by **Camotec** » Fri Apr 23, 2004 1:19 pm

Fuel Pressure was measured on my car at 250psi without the FPR which is due to a crapped out standard item. Standard JB Fuel Pressure should be between 245psi - 325psi

I have connected my Webber Fuel Pressure Regulater to sustain 350psi.
for higher boost.

(Fuel Pressure was measured as it entered the Throttle Body).

StarionChef · Post by **StarionChef** » Fri Apr 23, 2004 4:34 pm

Thanks guys, bit of a difference though. 45psi to 350psi??

nxtime, you might be old, but not as old as kelfie :D

I'm going to try twin starion pumps, mounted in the spare wheel well.

ProZac · Post by **ProZac** » Fri Apr 23, 2004 5:32 pm

Camotec wrote:Fuel Pressure was measured on my car at 250psi without the FPR which is due to a crapped out standard item. Standard JB Fuel Pressure should be between 245psi - 325psi

I have connected my Webber Fuel Pressure Regulater to sustain 350psi.
for higher boost.

(Fuel Pressure was measured as it entered the Throttle Body).

W.T.F?

Fuel rail pressure in a starion should be about 3bar (~45psi), and increases 1psi per psi of boost... with the factory regulator.

StarionChef · Post by **StarionChef** » Fri Apr 23, 2004 5:45 pm

--------------> Ben :)

Cookiemonster · Post by **Cookiemonster** » Fri Apr 23, 2004 7:04 pm

Camotec wrote:Fuel Pressure was measured on my car at 250psi without the FPR which is due to a crapped out standard item. Standard JB Fuel Pressure should be between 245psi - 325psi

I have connected my Webber Fuel Pressure Regulater to sustain 350psi.
for higher boost.

(Fuel Pressure was measured as it entered the Throttle Body).

Must be an awesome fuel pump to be able to run these pressures. Sure your not mixing up KPA with PSI?

StarionChef · Post by **StarionChef** » Fri Apr 23, 2004 7:12 pm

He's getting all muddled up, must have something on his mind, a big day perhaps?

Camotec · Post by **Camotec** » Sat Apr 24, 2004 1:15 am

Stop feeding me those hash cookies man!! jeepers!

:drool:

Must be KPA man but I swear i must be going stupid, when i get back from this wedding stuff and settle back into the groove i will confirm the bullshit in my head :)

SpidersWeb · Post by **SpidersWeb** » Sat Apr 24, 2004 8:27 am

This would explain the 50% duty cycle cut on the factory ECU.

Pump Rating: 47psi
Stock Pressure: 38psi
Increased Pressure at 9psi of boost: 47psi

So anything over 9psi is not getting the intended fuel pressure, which may be why the ECU dies at ~12psi - think it was designed this way, not an error.

Also in order of flow rate: GTO/EVO/VR4 fuel pumps may be best if you can get a hold of some.

jakobsladderz · Post by **jakobsladderz** » Sat Apr 24, 2004 2:17 pm

On the Starion, as with almost all factory EFI setups, the fuel pressure regulator has a reference connection to the volume of air that the fuel is injected into. For the Starion, this reference point is in the upper part of the throttle body (it's the little right angle rubber hose from the regulator to the TB). In port injection (MPI..) the fuel pressure is referenced to the manifold pressure.
Because of the reference connection, the fuel pressure regulator maintains a constant pressure through the fuel injector(s), regardless of boost and vacuum. If you connect a pressure gauge to the fuel rail you will observe a change in pressure with boost on a starion, and with vacuum and boost on an MPI setup, relative to atmospheric, but the injectors would see the same pressure difference end-to-end no matter what. The only time this falls apart is if the fuel pump cannot keep up with the fuel flow and the pressure across the injectors will drop.
There is no point going overboard with fuel pumps however. Use a big enough fuel pump for the job. Too big a fuel pump wastes battery power and serves mainly to heat up the fuel, causing it to evaporate. A race car may use more fuel pumps for reliability but on the road, one usually suffices.

To work out the flow rate of an injector at a different pressure, use
New Flow Rate = Old Flow Rate * square root of(new pressure / old pressure). This means that doubling your fuel pressure will only increase fuel flow by 1.41 times (root 2). The increase in pressure may cause other problems such as longer opening/closing time etc that may make this increase less. The best way to get more injector flow is to put bigger injectors in...

ProZac · Post by **ProZac** » Sat Apr 24, 2004 3:42 pm

Im just gonna sum that up a bit... The factory regulator does not increase the fuel pressure to add more fuel, it increases the pressure to keep the pressure difference between the manifold and fuel the same. You have 9psi of pressure in the manifold when boosting, so you need another 9psi of fuel pressure to keep the difference between them at around 3bar, or whatever the factory rating is.

SpidersWeb · Post by **SpidersWeb** » Sat Apr 24, 2004 5:29 pm

Cheers ProZac for summing it up.

I get it now, ehehe well nevermind then, just a thought :D

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Fuel Pressure reg

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