Fuel Injector Question

[Jeff Teuton]

We get two different messages on injector duty cycle. Some say no more than 80% and some say go to 99% and the management system should adjust in the pulswidth. I know there has to be some real knowledge out here. What do yall think?

[Chad Rhodes]

if you're consistently over 80% you probably should step up one size in injectors.

[Jim Craig]

I'm not an injector guy, but I'm a fuel pump guy and I hear mid 70's to mid 80's is good....90's are bad as you're getting close to locking the injector. Another item that can occur is your injectors go high due to lack of fuel volume in the system, this is normally seen in boosted applications although I believe can occur in N/A apps as well.

There are some pretty good "injector" guys out there.......Precision, Injector Dynamics, Kinsler and some pretty good tuners as well (who also know injectors....Hyperaktive, PTP, Shane T, Travis Quillen, Young's Performance out of Alabama, Jeff Taylor......good luck

[boostedf22c]

I wouldn't go past 80-85% duty cycle. You run the risk of the injector not being able to open and close quickly enough which can cause an injector to "hang". This could lean out the mixture.

You can compensate this with more fuel pressure, and even run past 100%, however that is a bandaid. If you are in the 80-85% range, I would get bigger injectors.

Injector Dynamics are some really nice injectors that are high impedance.

[art leong]

I got a question about "duty cycle".
This is in the lower rpm ranges just after launch. 2 different tracks duty cycle is the same for a given rpm IE 3500, 3700, 4000, etc. Ambient temp is 20 degrees (Celsius) different
O2 sensor readings are way different? On the cooler day the O2 shows it is much richer.
Should that be the be the other way around?

[Adger Smith]

Art,
Read your PM and call me!

[GUMP]

Originally Posted by Jeff Teuton

We get two different messages on injector duty cycle. Some say no more than 80% and some say go to 99% and the management system should adjust in the pulswidth. I know there has to be some real knowledge out here. What do yall think?

For drag racing a N/A combination the 80% rule seems to be a bit of a myth. I think that 99% is extreme too. (You do need a little room to work!) I would much rather run a smaller injector at high pressure than what the manufacturers call the "correct" injector at the recommended pressure. We can talk about this over a beer one night.

[Chad Rhodes]

There is possibly something in running a smaller injector at a higher pressure, I would think.

[Ed Wright]

There absolutely is.

[boostedf22c]

I run over 100psi of fuel pressure with 2 sets of 200lb injectors per cylinder.