Injector duty cycle measured by speed pro

[Dave King]

Does anyone know if this is an actual accurate measurement?
I've been told that the duty cycle is a calculated measurement
of what it would take the injector to be open to obtain the desired
a/f ratio set in the a/f target table?

My car is non intercooled and I'm throwing lots of fuel at it up top.
I'm seeing about 29 psi, so I need to throw as much fuel at it as I can.
My readings for duty cycle read at 100% or even higher as I go
toward 8000 rpms.

I'm using 83 pounders with a base fuel pressure of 58 psi without
vacuum, 53 psi with vacuum. I"m thinking 83 pounders should be enough
to support 1250-1300 hp. I'm only making about 825 engine hp.
The car runs 9.3's at 147 mph at 3000 pounds.

 

[Lance]

It's not really a measurement. It's a calculated representation of the electrical signal controlling the injector. It is calculated from RPM and injector pulsewidth. Because it's a calculation, it can overflow to beyond 100% but in reality, 150% is the same as 100%. In other words, If you are at or over 100%, you are out of injector.

If you are supercharged, don't forget about the loss of power (which still needs to be fueled) from the supercharger drive. If it is not intercooled, you will need plenty of extra fuel just to keep high manifold air temps from melting down your engine. I've seen many cases with non-intercooled, supercharged engines where the air temp was maxed out (>250 deg.) for most of a 1/4 mile pass.


Lance

 

[Nashty]

Is that 83# actual or stated flow rate? Might want to have the injectors flowed as well. I would imagine your fuel system is pretty good but are you positive there is no cavitation in there at those very high pressures?