Cthulu

I have a set of injectors that have a static flow rate of 320GM/min n-Heptane at 300kPA (43.5 PSI)

does the flow rate scale evenly with fuel injectors as PSI goes up?

If so I would run them at 58PSI then the static flow rate would go to 426.666 GM/min. That sound about right?

Old Geezer

iTrader: (3)

369 is what I get.

ZL1Killa

iTrader: (17)

to scale from 43.5 to 58psi rating take your flow and multiply by the square root of (58/43.5psi). Read fuel injector sticky here

joecar

+1 +1

the squareroot of pressure ratio gives you 369 g/min...

and then you have to scale for octane (multiply by the ratio of the densities of octane to heptane).

Cthulu

That's good data, thanks man.

Cthulu

Crap. so my advertised Racetronix (Lucas) "42#" injectors are ACTUALLY 48.49 lb/369 gm/min injectors at 58 PSI which is too much injector for me. That puts my duty cycle around 55%.


Is there any reason I wouldn't be able to run them at a lower PSI?

I have a fuel pressure regulator and could trim it down to 43.5 so they act like the size injector I was looking for.


***EDIT*** yes I tried search "lower PSI with larger injectors" and many other combinations to no avail.

Cthulu

Looks like running a lighter duty cycle is ok and the racetronix pump isn't meant to supply pressure under 58PSI, something about "jet pump" which fills the fuel bucket.

joecar

The problem may be that the injectors spray too much at idle...

there is a calibration parameter called "Small Pulse Adjust" which may help with this.

Edit: I meant "Transient Minimum Pulsewidth"

ZL1Killa

iTrader: (17)

you can run them at their rated pressure of 43.5psi. just setup your FPR with the manifold reference removed and set the pressure to 43.5psi. Don't forget to also tune the car for this (change the ifr).

Racetronix

iTrader: (2)

If you turn the FP down to 43.5PSI the jet-pump in your fuel system will shut down.

ZL1Killa

iTrader: (17)

I take it racetronix has spoken to you over the phone or something? Please consult them further as they seem to know your fuel setup more than what you are telling us.