Whenever I give at least 30% throttle and approach around 4-5k in my gs-r w/SC61 I notice my fuel press. drops from mid 40 to mid 30 psi. I'm running an AEM EMS, Walbro 255 lph, MSD 754cc's, and a Dynamic Autosports FPR (chop the stock top style). Could the vaccum line be snagging?

 

Sounds like the piggy back regulator is not allowing a proportional increase in fuel pressure when under boost. The stock (un modified) regulator will give you about 1Psig of fuel pressure for each lb of boost.

Get yourself a new un modified stock regulator, or some other brand, and set the fuel pressure to stock, and tune away.....

The other possibility is the the fuel pump is starting to wear out, but that would be dependent on how many hours you have on it, that's how they are rated.

Go with your instinct though and check the vac line going to the regulator.

 

I'd say it's a reg problem, because that fuel pump should be able to handle 754cc injectors no problem.

 

apply pressure to the reg. w/ the engine off and pump running, if the pressure increase is normal, check your pump. It is not flowing enough. this could be mechanical or electrical, so check your voltage at the pump under load (raise fuel pressure as high as you can w/o closing it off completely).

 

I'd say along the lines of everyone else you should definatley check out the regulator but a clogged fuel filter could also be to blame.

Matt

 

Where is the fuel pressure reading coming from? The end of the rail? Technically your fuel pressure always drops in boost, but if the probe is far enough away from the injectors you won't see it.

 

I would say that it's the pump. Check your fuel filter also....and make sure the vaccums are all hooked up. Remember that the filter on the pump could be clogged also.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Freemantle &raquo;</TD></TR><TR><TD CLASS="quote">Where is the fuel pressure reading coming from? The end of the rail? Technically your fuel pressure always drops in boost, but if the probe is far enough away from the injectors you won't see it.</TD></TR></TABLE>

The sender is on top of the banjo on the fuel filter.

 

-The pump is fairly new, over a year old.
-I was suspecting the FPR is taking a ****. I don't mind swapping it out for a stock one.

Any more feedback?