The V8 Owners Forum -

Im getting close to firing up the 5.3 (JE X over with ITBs) Just waiting for the oil to arrive from Opie oils
with the ignition on the reading on the gauge shoots right round then settles at 40psi? does that seem about right? i just used Today as a excuse to check for fuel leaks etc, all seems ok there.

mine does that but once engine is running it sits at 36psi,
im using an adjustable rising rate reg on my 044.

Depends what you're regulator is set at. But yes when the pump is operating you should of course have fuel pressure crated by the regulator.

That sounds fine. As Stevie said it depends what your regulator is set to. Obviously that is the fuel pressure at no vacuum, when you start the engine it will be lower.

im using an adjustable rising rate reg on my 044.

Personally I don't like the idea of using a rising rate fuel reg with mapable engine management. They are used as a bodge to increase fuel pressure with a standard ecu but a mapable ecu is 'mapped' so you tell it the base fuel pressure and the fuel flow at that pressure and it calculates the injector pulse width. If your using a rising rate fuel reg this could confuse things! Yes it probabbly can be tunned arround it, but the standard fuel reg works perfect and is usually free!

Tom.

People often confuse rising rate with a normal FPR.

The only "rising rate" ones commonly found are the FSE power boost valves.

Although any FPR with a vac/boost reference will alter fuel pressure in relation to manifold pressure.

Either way, neither should pose any problem to tuning as long as they are consistent

stevieturbo wrote:People often confuse rising rate with a normal FPR.

The only "rising rate" ones commonly found are the FSE power boost valves.

Although any FPR with a vac/boost reference will alter fuel pressure in relation to manifold pressure.

Either way, neither should pose any problem to tuning as long as they are consistent

IIRC, most of the adjustable ones I've seen are rising rate. I wanted an adjustable non rising rate and did eventually find one - at a price. Those are usually marked as being for forced induction use.

DaveEFI wrote:

stevieturbo wrote:People often confuse rising rate with a normal FPR.

The only "rising rate" ones commonly found are the FSE power boost valves.

Although any FPR with a vac/boost reference will alter fuel pressure in relation to manifold pressure.

Either way, neither should pose any problem to tuning as long as they are consistent

IIRC, most of the adjustable ones I've seen are rising rate. I wanted an adjustable non rising rate and did eventually find one - at a price. Those are usually marked as being for forced induction use.

Ive never seen any for sale other than the PBV that suggests they rise at a rate anything other than 1:1 with manifold pressure.

Again, it depends what you interpret as rising rate. If it's simple 1:1 or anything close I wouldnt call that rising rate.

There are some extreme versions that offer huge increases, although they are typically called FMU's, Fuel management units, weird name for an awful tuning device. They can be around 6:1 or more

I would inclined to set the static (engine off, no vac) pressure to 43psi/3 bar - as thats a standard pressure.

What fuel injectors are you using? What flow?
There is a simple calculation you can do (google, fuel injector calculator) to ensure you have enough fuel flow for your target HP.
You can then check that 40psi with your injectors will flow enough (plus a bit!) for your HP target.

Tom.

SuperV8 wrote:What fuel injectors are you using? What flow?
There is a simple calculation you can do (google, fuel injector calculator) to ensure you have enough fuel flow for your target HP.
You can then check that 40psi with your injectors will flow enough (plus a bit!) for your HP target.

Tom.

350cc injectors x 8, 50 psi fuel pressure. Hopfully off for mapping in the next couple of weeks if it decides to stop raining

Thats gonna sound the nuts on TB's. you lucky fella.

I run 8x 315cc@3bar injectors with my +380hp 5.2litre RV8.. Fuel pressure is 3.8bar and i think injectors will flow approx 350cc now? I have got similar fuel pump like yours, slightly smaller Bosch..

ps:hope we can see your dyno chart in future..