what should normal fuel pressure read?

 

I believe mine was 38 psi at idle and about 42 when I give it gas.

 

Part numbers of these parts would make this thread more awesome, Chris.

My KA fuel pressure was 43psi @ idle and went up when I gave it gas. I do not know about sr20s, though.

 

alright, thanks! and +1 for parts numbers!

 

good gah.

READ THE FSM.

43.5 psi, or 3 bar referenced to intake manifold pressure.

that means that if intake manifold pressure is -15inHg (-7.5psig), then you should see 36psig. conversely, if boost pressure is +7.5psig, then you should see 51psig on the gauge.

it is references to intake manifold pressure because injector flowrate is dependent on the difference in pressure between the two sides of the injector (fuel rail on one side, intake manifold pressure on the other). in order to maintain constant flowrate for a given pulse width, the fuel rail press must increase with manifold press

also, read up on psig/psia.

 

that's high, and probably a product of aftermarket fuel pump on stock regulator.

assuming that you're talking 43psi referenced to atmospheric, as most gauges are. DEFIs have an option to reference to manifold pressure, which is realllly nice for making sure your FPR's rising rate is good

 

That's one thing I liked about my last Defi gauge system. I always ran in base fuel pressure mode. I could actually watch it drop .2 to .3 bar of pressure at redline!

Every car I've ever seen with any aftermarket pump and stock regulator has had a consistent 3.5bar (50psi) base fuel pressure. That's including my setup above. Personally, I've run Walbro, Tomei, and Supra pumps with the same outcome in base pressure.

The correct way to measure base pressure is to unhook the vac reference line on the top of the fpr, then read the gauge. Alternately, you can just key the car to "ON" without starting it. That will prime the system, and the vac hose will of course have no vac. It may take a little running around because the system only primes for 5 secs.

About the simple gauge setup, the part numbers are as follows:
Marshall pressure gauge for injection: PN: hello Mr AE employee, I need a Marshall pressure guage for injection with 1/8" NPT connection.

Brass fittings = 1/4 NPT "T", 1/4" to 1/8" reducer for gauge, and 2x 5/16" bung/hose to 1/4" NPT fittings. Screw together with teflon tape, enjoy.

 

Yeah, disappointing actually. In industry, a pressure regulator only good for 7-10% accuracy is garbage.

 

It was repeatable, so I tuned around it. The problem was actually at the pump. I don't think the Tomei pump could keep up with the flow required at 70psi plus the pressure drop of the stock 8mm hardlines.

 

True. My SARD regulator will drop .1 bar just from idle to atmospheric (not boosting) Easy enough to tune around, and actually flowrate is proportional to sqrt of pressure so small variations do very little