fuel pressure????

[RB25sean]

i have a nismo adj pressure regulator. i have a fuel pressure gauge, but i dont have any emissions equipment, or a dyno to figure out a good pressure to set it to. supposedly it is a must for the rb25 swap with the walbro pump cause it runs very rich?. i want to know if anyone has done any dyno tuning, just with changing the fuel pressure , and has a rec. pressure to set it to. my setup is pretty much all stock. thanks

[Project240]

I tuned my RB20 to 35 psi at idle, I'm not sure about the 25.

[JonPowell]

RB25, and most Nissan cars, the stock fuel pressure is 43 with the vacuum line disconnected and 35 at idle with it connected. I prefer to set it at 43 disconnected and let the regulator do the rest. If your idle is a little high or a little low, it will affect whether 35 is the correct pressure for idle.

[NISMO_RB25]

my fpr will be in next week, but I haven't gotten a gauge yet. Any recommendations?

[JonPowell]

any regulator designed for 25-75PSI at least.

Nismo is nice.

[NISMO_RB25]

I ordered the Nismo regulator, it is the gauge that I need. Any recommendations on the gauge?

[Project240]

Jon: so when you set your FPR, you took the vacuum hose off, set it to 43 psi, then put the hose back on and left it as it was?

[Wulfgang]

I have a VDO gauge (from Jegs, $20). It goes to 100 psi and is small enough to put just about anywhere in your engine bay. No matter what gauge you buy, you'll need to get an adapter for it. The gauges have an NPT fitting.... your hoses need barb connections.

[JonPowell]

Yeah, thats it....Make sure you do it while the engine is running because the alternator puts a little more power out than the battery and that will change your base fuel pressure.

Battery is like 12VAlternator is like 14V

That can change your fuel pressure alot.

Take off the vacuum line, set for 43, then connect the vacuum line and see what happens.

[NISMO_RB25]

Thanks guys

[Joe]

my nismo FPR was pre-set to factory levels because all nissans use the same pressures (as far as im aware. every one i know of does)

and i thought it was 37 psi @ idle with vac. the 43 without is correct IIRC.

[JonPowell]

As long as the base pressure is 43, the rest is variable. depends on the amount of vacuum in the intake manifold. All Nissans have a base pressure of 43PSI.

[NISMO_RB25]

Then I have a question. Is the need to replace the stock fpr, because the walbro is simply overpowering it?

My nismo FPR came in yesterday so hopefully I can get a gauge and install it this weekend.

[JonPowell]

The Walbro pumps more fuel than the stock regulator can flow, which results in a higher pressure.

Change the regulator, reset it to 43PSI with no vacuum line hooked up and it will run alot better.

[RB25sean]

thanks for all the info. i did as suggested, set to 43 no vac. car runs way better. i think if i remember right, i measured pressure with the stock reg. on and walbro it was like at 45 with vac or something, so turning it down made a huge difference.

[JonPowell]

That is everyones problem with the Walbro, that unit aint no joke.....