Fuel Pressure calculation

Can someone tell me what my approximate fuel pressure should be with a .900 gear lil bertha with a total area for nozzles at .040345 and a total pill area (loops, main, etc) of .022291.

The reason was that I put these .900 gears into my pump thinking it would be around 19gpm at 100psi at 4000 rpm and adjusted the nozzles and pills to get a baseline. However, on the first test pass the fuel pressure at 8000 engine rpm was only 55lbs. I was thinking it would be around 150psi. Trying to figure if my math is wrong or the pump gears are shot.

Thanks

 

You should be somewhere between 150 and 200psi.

Brandon Booher
NHRA TAD #34

 

pump pressure

Were did you take the pressure from? It needs to be right at the pump. Is that from you racepack download? Don

 

I took the reading off the racepak. The sensor is in the hat dist block. I understand there would be some pressure drop from the pump to the fuel blok, but should not be that much.

 

You'll lose about 50-70# of pressure measuring it there.

Brandon Booher
NHRA TAD #34

 

Why would there be a pressure drop of that magnitude (50%)?

 

That is what I show on my graphs and those numbers are consistent (relative to one-another) throughout the recording process. I use a .900 Waterman, the nozzle area is different...but I imported it into Jetsize and the psi. didn't change that much. The only true way to get a # is to measure it at the pump. You can't take engine RPM based off the driveshaft....

Brandon Booher
NHRA TAD #34

 

Interesting. On the Pump psi vs the Psi after the K valve. But since your tune ups are based on what the NOZZLE itself see's wouldnt it be a better place to put it after the K Valve???

 

I run a Gorr BV for informations sake.

Brandon Booher
NHRA TAD #34