fuel psi

brettdodds88 · Post by **brettdodds88** » Fri Nov 30, 2012 4:50 pm

Just woundering.if any one knows what psi should be running from my fuel pressure regulator to the injectors on a standed 84model ja starion sohc turbo. Well what should my fuel pressure regulator be set at/reading...thanks people

Starion VR4 · Post by **Starion VR4** » Sat Dec 01, 2012 9:42 am

43PSI with no vacuum supplied to it. 37PSI with it. :beer

ProZac · Post by **ProZac** » Sat Dec 01, 2012 3:00 pm

Depends on the vacuum in your intake manifold. It maintains a 43psi difference across the injectors and the intake manifold.

John196701 · Post by **John196701** » Sat Dec 01, 2012 4:33 pm

the fuel pressure on a standard throttle body injection is around the 43psi mark, the pressure dose not change till you are on boost, the line from the regulator goes to the fitting just above the throttle body

brettdodds88 · Post by **brettdodds88** » Sat Dec 01, 2012 5:38 pm

Hi guys thanks for that. I for got my motor now has 60thou over sized pistons and im running a eci setup but fully rebuilt so from my fuel pump to my fuel pressure regulator to the injectors the regulator gauge should be saying at idle around 37 to 43psi and yer its got the vac line to

ProZac · Post by **ProZac** » Sun Dec 02, 2012 6:17 am

John196701 wrote:the fuel pressure on a standard throttle body injection is around the 43psi mark, the pressure dose not change till you are on boost, the line from the regulator goes to the fitting just above the throttle body

Yeah, Nah.

The fuel pressure above the injectors, with respect to the atmosphere, will be lower when there is vacuum in the manifold, as the manifold pressure is now negative with respect to the atmosphere.

The regulators job is to keep the difference in pressure above and below the injectors constant at all times. Thus it adds 1 psi of fuel pressure for each psi of positive pressure in the manifold, but it also goes the other way when the engine is idling or at cruise. Other wise, fir the same injector duty cycle, you'll get differing amounts of fuel delivered at different times.

coop1er · Post by **coop1er** » Sun Dec 02, 2012 8:35 am

The spec for fuel pressure is 245 kPa which is roughly 36psi. (Incidently the pump should flow 110 litres per hour at this pressure)

As the injectors are above the throttle plate and so is the fuel pressure regulator reference, they never really operate in a real vacuum, so fuel pressure will not go under 36psi.

ProZac · Post by **ProZac** » Sun Dec 02, 2012 8:06 pm

crikey, you're completely correct! I was thinking in MPI terms, hah :-).

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fuel psi

fuel psi

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