Basic fuel setup

more on ait to fuel ratio & fuel pressure

Ya, I found through the years that setting up air to fuel ratios with nozzle & jet size numerical control took all the guess work out of tuning. Numerical control of fuel pressure was also vital.

FUEL PRESSURE: Our engine with only hat nozzles ran the best with 140-150 psi fuel pressure. At that pressure, plug color was consistent even with a front delta opening blower. I saw several FI systems from more than one flow bench service routinely set up fuel injection below 100 psi. That pressure was too low for our hat setup with a delta blower.

HIGH SPEED: I used the calculator to determine high speed poppet blow off for an opening pressure at an RPM target.

PORT NOZZLE POPPET PRESSURE: For port nozzles with a pressure poppet, I used the calculator to determine pressures at various launch rpms. Some tuners want the ports closed at launch for even heating; others want them open at launch for response. The fuel pressure info from the calculator made it easy to determine port nozzle poppet settings for either goal. As well as launch rpms to stay below or above.

Bob Szabo
www.racecarbook.com
www.airdensityonline.com

 

Is there any "easy" way to calculate the fuel pressure at any given RPM from the pump flowtag and the total nozzle, jet area?

I can not calculate at what RPM the port and highspeed will open. There is no datalogger on the car so I can not check after the run if it opened the way I want.

 

During idle the EGT is very low in the front and high in the back. I would like to have them more in the same range at launch. I know it is the blower but what can I do about it? A test with bigger nozzles in the back of the hat has been tested but no difference.