Explain how my stock fpr is at 78psi then at 18psi boost :-) My friends is 92psi high boost,he gained 200hp more fuel by putting it down to 50psi using a adjustable fpr .Ive been kitesurfing all weekend so i can't explain im to nackerd sorry head hurts lol

 

When I swapped in the replacement pump the hose was very tight. I wonder if we, the OP and I, should use fuel line screw clamps instead of the OE spring clamps?

For the OP it's likely the pumps ability to draw the required current so a relay direct wire with 12GA wire should do the trick.

 

You're measuring pressure on your fuel rail? If so that's not related to pressure at the pump inside the tank.

 

The way most all FPR's work in a turbocharged application is on a 1:1 rising rate. So what that means is for every 1 pound of positive pressure (MAP/boost) applied to the diaphragm, the regulator increases fuel pressure by 1 psi. This is needed because the fuel system is now trying to spray fuel into a positive pressure environment inside the intake manifold. Base fuel pressure on a Honda is roughly 43.5 - 45psi, so if you were running 10 psi,the fuel pressure would now be 53.5psi under load/boost.


This is entirely related to the fuel pump pressure. The pressure the pump is pumping is directly related to the condition inside the fuel rail. The fuel pressure is caused by the restriction on the fuel return line (ie Fuel Pressure Regulator) As the FPR opens and closes as the manifold pressure changes the fuel pump can pump more/less or maintain a constant head pressure inside the fuel system. As pressure increases, flow decreases, and walbros are terrible in hi pressure applications as they cannot maintain proper flow rates under higher pressures (boost pressure)

 

I did some more reading on the subject and it makes more sense now. Good link I found below if anyone is interested.

http://www.injectordynamics.com/Stec...reArticle.html

 

In my case pressure was dropping above 8K RPM (a little over 10psi of boost).

 

Thanks for the responses

I'm running the oem fpr on the oem rail so base pressure I'm guessing is around 45.

I don't see much point in trying to rewire the pump, seems like a waisted effect. It looks like people are getting to my 400hp goal without the rewire. I will probably do this down the road but my main focus is to fix the issue.

I'm going to pull the hanger this week when I find some time and check all the connections.

No one thinks its a fpr issue?

 

I doubt you could tell by inspection if the OE spring clamp is coming loose under pressure. It's simple enough to swap them out with screw type fuel hose clamps.

 

I went through the same issue on the dyno a while back (same setup also...Walbro 255, ID1000's, stock fpr and rail). We were running 12psi and I was going lean after 7k rpm or so.

Tuner suggested I add a fuel pressure gauge so we could see what was happening. I bought an AEM fuel rail, AEM fpr and a fuel pressure gauge. I rewired my pump with a relay off the battery also. Went back to the tuner and same thing happened on the dyno. We could watch the fuel pressure drop on the gauge after 7000-7500rpm.

What I did to fix the situation:

Brand new OEM fuel pump hanger
Brand new OEM fuel pump "sock" filter
Fuel line specific clamps on the small hose from the pump to the hanger

Went back to the dyno (again)...fuel pressure held (increased) all the way to redline.


I would still suggest hardwiring the pump with a relay right off the battery.

Hope that helps!
Scott-

 

Yes I had a rewired walbro and was able to make 610 hp at 95% duty cycle on 1000cc injectors, that should solve your problems.