Fixed-rate FPR at 4 bar?

[Jonny 290]

240sx stock FPR = 43.5 psi? anyways, it's a 3 bar above reference FPR. I'm curious what everybody's thoughts are on:

Walbro 255 pump370cc injectors300zx fuel filterNew soft lines from fuel filter forward4 bar above reference 1:1 FPR

Giving an effective injector size of 493 cc/min. This setup would be running at 58 PSI above the reference port - not too bad, in my opinion, and would be tuned with an E-manage (orig inj size 270, new inj size 490).

Opinions? will the Walbro be unhappy at 58, or even worse 65 psi (assuming 7 psi boost)?

EDIT: Specs on the Walbro say it's good to 90 PSI. Anybody have a ballpark on the pressure drop of the stock fuel system?

[d240t2]

Yes, the stock regulator is a 3 bar. Setting one at 4 bar would work, but you wouldn't have 493cc/min injectors, you would have 427cc/min injectors. The reason is, fluid flow through an orifice is proportional to square root of pressure drop (Bernoulli equation). So at 3bar, you have 370cc, at 4 bar, you have 370*sqrt(4/3) = 427cc/min.

At auto performance engineering, http://www.autoperformanceengineering.com , they have a chart that lists the fuel flow vs. pressure curves. You'd need to use that to determine if you could get enough fuel at the pressure you want...it isn't like the pump just goes kaput at some pressure...the flow decreases with increased pressure so you need to make sure that at the pressure you'll use, you have enough flow.

Suffice it to say, you'll be fine on a Walbro 255lph high pressure pump to do what you are asking.

[Jonny 290]

Nice info, thanks!

Anybody else have any input on the matter?

[D-UNIT]

where do I acquire a four bar FPR for my car?