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Technical => Spud Miller's Cave => Topic started by: Rat on April 15, 2019, 06:08:49 AM

Title: Idle Fuel Pressure
Post by: Rat on April 15, 2019, 06:08:49 AM
Hi Spud, I know there are many variable but what approximate fuel pressure should we expect to see at idle.
392 Hemi, 6.5 GPM Hilborn pump, .034 nozzles, .125 Main with 22% leak down
Calculator shows around 110 psi at 8000 rpm.
Title: Re: Idle Fuel Pressure
Post by: Spud Miller on May 23, 2019, 02:49:53 PM

 If you're measuring on the nozzle side of the metering valve, you'll see "0" at idle on a gauge.

 On the pump side, it'll be in the 10-15 PSI at idle depending on how many PSI your main check valve is set at and typically, a main would be 1-2 PSI on a naturally aspirated setup.

If you run a 5-10 PSI main check valve, not only will your leakdown percentage be artificially low, but the idle fuel pressure on the pump side will be more like 15-25 PSI.

 Also, a secondary check valve (off your metering valve) could affect indicated idle fuel pressure. I typically set those about 18-20 PSI and that will limit things in the idle position.