You are the exception, not the rule. There are countless people running 28-30psi on a single fuel pump setup on stock frame turbos. As fast as these things spool, the fuel pressure will jump to 71-73psi almost immediately. Same difference as the double pumper really.

I agree that keeping the low voltage circuit intact is the wisest choice. People sell rewire kits, plus there are a lot of DSM owners that now own Evo's and will ASSUME that a rewire kit is a logical 'upgrade'.

This isn't true. The double pumper has enough flow capability to apply the same load on the FPR even with a large injector at a decent duty cycle. It has been tested to do the exact same PSI spike on cars while boosting in real-world conditions.

-Jamie

 

I know this is an old thread, but I concur.
My second pump kicks in at 15 lbs of boost and I have no issues with fuel pressure.
the extra flow through the injectors is what this test is lacking and proves nothing without that part of the equation.

 

So Do I need a bigger FPR with my larger than 255 fuel pump or not?

 

Nope. Main thing is to drill out the siphon slightly.

 

Drill what now? on the pump? on the FPR?

 

On the fuel return on the fuel pump assembly, you're supposed to drill out the siphon with a 9/64 bit.

MrFred can correct me if my recollection is incorrect

 

Which nosal is the correct one on top of the fuel pump housing? And a verified answer on size of bit would be excellent.

Thanks in advance.

 

Mine is drilled to 9/64's, works great. The part you drill is on the housing in the tank. Its a little y looking thing.


In picture #2, the guy is holding it. You run the bit through the part that says "DENSO" on it.
https://www.evolutionm.net/forums/ev...evo-8-9-a.html

 

I still dont understand what purpose dose it do by drilling a hole? how much is 9/64? like 3,5mm?

is this where to drill?

upload photos

 

9/64 is 3.571875mm

It means the stock return won't get over run with a hard wired bigger pump or pumps.

Someone can correct me if I'm wrong.

 

OK, let me get this straight, when hardwired aeromotive 340lph intank pump and aftermarket FPR I should drill there a hole for better fuel return ?

 

No.
You remove it, then drill it through tube sticking out from either side, like so, enlarging the existing hole on the inside.

There is a hole in there that is small. Fuel coming through the return line hits it, creating a siphon and pulling fuel over from the other side of the tank. When using a higher flow pump, you need to enlarge that hole.

 

aaaaaaaaa O.K. I get it now. Enlarge the hole from inside through
Thanks for the clear up.
now, letsgetthisdone

 

Hardwiring a high flow pump for full-time full voltage can still lead to fuel pressure control issues even if the siphon is drilled out. I have a thread that shows how to do a simple rewire that maintains the the factory low/full voltage capability but still provides for better voltage when needed.

 

Yes, I was about to mention that...lol. The walbro 450 will overrun the stock FPR if run on full voltage for idle and cruise. Also, pumps live longer with a dual voltage setup since they aren't constantly running full kill.