GtoRx7

iTrader: (5)

Okay, I have 99% of all the bugs worked out of my car finely. But the other day I bought a fuel pressure gauge, because I suspected a bad Fuel pressure regulator (hooked it up backwards when motor was first installed, fuel on return, return on fuel...DUH) I'm running a walbro external inline pump, and its wired direct to 12v, with no resistors. But anyway, the fuel pressure is 80psi when I start it up, and usually is at 70 psi once warmed up!! If I turn everything electrical on in the car I can get it down to 60psi, but this still seems EXTREME. I want to know what I should do, because this much psi will ruin my injectors wont it?

Option 1) Get a resistor wired to the pump to lower the pump voltage
Option 2) buy a new factory mazda regulator ($230)
Option 3) buy a aftermarket rising rate regulator and replace the factory one
Option 4) Buy a normal EFi regulator and run it before the injectors , turn it to 40 psi, and keep the factory FPR.

I want to go with option 3, but Im not sure if I can do that without a special rail for the secondaries, or if I can just unscrew the factory one, and put on a Aftermarket one. Option 4 is the easiest, but would it also restrict flow on the top end?
Look in sig. for the mods done to motor. Still have 4x 550cc.
Thanks for any help

89t295k

don't know too much but thought our cars have multi stage pressure (high/low) voltage for when sec injectors kick in....sounds like u have bypassed that??
someone correct me or clarify.

scathcart

The fuel pump ups its voltage (and thus flow) based on load. Fuel pressure should remain relatively constant.
The rewiring of the pump is causing the pump to flow too much at idle, and thus over-running the stock FPR.




It sounds like you are just beyond the capabilities of the stock FPR.
Option 4 will not work correctly, BTW.

I choose option 5:
Buy a aftermarket FPR and replace the factory one.

Why bother with a RRFPR (like a malpassi/cartech unit)? I find them to be a pain in the ***, especially when the S-AFc is so reasonably priced and gives you much better results.

It is not all that hard to adapt. You will need some fuel inection hose, a tap for the fuel rail, and two barbed fittings to fit into your FPR and fuel rail tap. Shouldn't take much more than an hour to set-up.

You're not confusing a RRFPR with one that increases rail pressure, are you? All FPR's do that. you set a base pressure, and then for each ~2 inches of vacuum, the fuel pressure drops by 1 psi, and increases by 1 psi for every 1 psi of boost. So, for example, set a base pressure of 39 psi. Start the engine, get 16 inches of vacuum, fuel pressure drops to around 31-32 psi. At 10 psi, the fuel pressure is 49 psi.
A Rising rate FPR does the same thing, but has a light difference: it allows you to increase boost reference. It should be adjustable, so you can increase how much the fuel pressure increases in accordance to a boost increase. For example, if you set it to 1.3:1, the fuel pressure would increase 1.3psi for each 1 psi of boost.
so at 10 psi, your fuel pressure would now be 52 psi.
RRFPR's are for fuel enrichment under boost only. RRFPR's are called the "poor man's EMS", since they are not tailorable to RPM or load points.

RRFPR's are too much of a compromise for most people to work with.