High Fuel Pressure

[T-rev]

I am running a Walbro 255 L/hr pump and stock fpr. My fuel pressure at idle is ~43 psi, and at wot under boost it hits a max of 60psi. That seems awfully high, especially with stock injectors. http://www.pdm-racing.com/products/power.html mensions stock fuel pressure is 36psi.

Im having fuel problems as it is, running rich, bogging and studdering under boost, back firing, etc... Is this fuel pressure excessively high? Would this cause me to run rich? Should I get an adjustable FPR and tone it down a bit?

[Hijacker]

Idle pressure should be right around 43 PSI. However, the jump to 60 sounds high udner load. I would consider just getting a replacement for stock.

[otterman]

The hipress pump and stock fuel regulator will make you have really high fuel pressure.

[homeslicej2]

....I would consider just getting a replacement for stock.

stock fuel pump or stock regulator?

[otterman]

stock fuel pump or stock regulator?

I'm pretty sure he means regulator. OP doesn't have a stock pump and you shouldn't run a stock pump on a SR very long, or so I hear.

[homeslicej2]

I figured that's what he meant. Makes sense. yeah, stock SR pump on completely stock SR maybe okay (probably not after all these years), stock KA pump bad idea. I have a Walbro and stock reg too.

[Hijacker]

I did mean stock FPR, but you can run an SR on a stock pump. Just don't turn the boost up on it.

One thing a lot of people forget is that the stock pumps in silvias are the same for the US cars. The problem a lot of people just assume is a low flow pump issue is that these pumps are going on 18 years old in the oldest cars. They're past their prime and are just plain tired.

[homeslicej2]

I did mean stock FPR, but you can run an SR on a stock pump. Just don't turn the boost up on it.

Yeah, i've been getting confused a lot today. I guess having a lot on my plate at work did it that and sleep deprivation

Quote »One thing a lot of people forget is that the stock pumps in silvias are the same for the US cars. [/quote]I did not know that. I thought the KA had a different pump.

[Hijacker]

I did not know that. I thought the KA had a different pump.

As far as I know, they should be the same. But at the age that the cars are getting, it doesn't really matter. They should be changed out regardless just due to wear

[T-rev]

Should I get a stock regulator or an adjustable one? Is the nismo one a good bet?

Would high fuel pressure contribute to running rich problems?

[Seishuku]

90LPH pump is good for 4 375CC injectors190LPH pump is good for 4 790CC injectors255LPH pump is good for 4 1000CC+ injectors

[T-rev]

well I just have the stock 370cc injectors, but theres no way I'd trust only a 90 L/hr pump

The way I see it the injectors are an open loop system. They dont know what theyre doing they just open and close acording to the ecu, which thinks it has some 40 odd psi at the rail. Now if Im spiking to 60psi, the injectors are shooting 150% what they should, or they just max the flow out, whichever happens first, probably maximum flow. So Im drowning in fuel, running rich, running like crap. If I drive at partial throttle, it runs great, floor it and it studders.

What is everyone with a walbro pump running for a fpr? Adjustable?

[homeslicej2]

Should I get a stock regulator or an adjustable one? Is the nismo one a good bet?

Would high fuel pressure contribute to running rich problems?

adjustable if you're having issues (like you wrote below), NISMO is better than none. I know some people prefer an AEM or aeromotive, but for the price the nismo is a good bet. high pressure can cause you to run rich, and if it's too high well, you already know for you last post.

As far as I know, they should be the same. But at the age that the cars are getting, it doesn't really matter. They should be changed out regardless just due to wear

I had a Walbro installed with the SR swap. No way I was trusting the stock pump. T-rev, I still have a stock FPR, but I'm not experiencing any problems (yet). If I start to (or after I take care of a few more things) I'll get a Nismo unit.

[whiplash willy]

Idle pressure should be right around 43 PSI. However, the jump to 60 sounds high udner load. I would consider just getting a replacement for stock.

Idle pressure should be 36psi with the vacuum hose attached to the FPR. Disconnected, idle pressure should be 43psi. Pickup a nismo adjustable FPR to turn it down.