Y2K2LS1

Looking for people who have run 28lb injectors hard. Like 500rwhp hard. And I'm not talking about boosted applications since you'll max out alot earlier, just NA or n2o combos. I have heard up to 140% duty cycle without problems.

GuitsBoy

iTrader: (4)

Im certain that you can run them over 100% duty cycle. I guess you dont really run out of injector till they go completely static. However As you pass 100, fueling accuracy must take a serious nosedive since the injectors are squirting before and staying open longer than optimum.

dynocar

100% duty cycle, by definition, means that the injector's pintle, disc or ball is 100% open 100% of the time. Can someone explain how we can get more fuel at more then 100% DC without increasing fuel pressure, excluding incorrect DC computations. Maybe my physics book is outdated. In theory a 28 Lb injector is good for up to approx 400 net SAE RW (Dynojet) HP in an NA, manual trans, LS1 application for proper cyl to cyl fuel distribution, unless we can defy the laws of physics with this DC thing.

GuitsBoy

iTrader: (4)

Who's definition is this? I was under the impression that 100% duty cycle was having the pintle open 100% of the intake valve open event. Thats why you can open it a little before hand and run over 100%. Atleast thats what ive read. Please correct me if im wrong here.

Moparnos (The SLP Guy)

iTrader: (55)

you shouldn't use them if they are over 80%. i know some complete stock cars that are at 100%DC plus. you should cough up the cash and get some new injectors. this is exactly what i was talking about in a previous post. people lack in having the proper fuel setups in their built motors.

dynocar

Every formal definition of injector duty cycle I've come across goes something like this, quoted out of Accel's Performance Products Catalog 2005, Pg 211, "duty cycle. This is the percent of time that the injector is actually open (which is also referred to as pulse width) vs. total time between firing events. When an injector is open 100% of that time, the injector is in what is called a static condition."

GuitsBoy

iTrader: (4)

Then the question really is; why dosnt the car go lean when the injectors extend past 100% duty cycle?

Doing some quick calculations, @ 6600 rpm, there's only 18.2 ms between firings (2 revolutions). My injectors were staying open for greater than 19.5 ms. I take it that in reality it is like you say, and that theyre static. However according to my logs, they injectors were hitting 100% duty cycle by 6100 rpm, however the air fuel ratio did not lean out at all as the motor climbed those last 500 rpms. I was running an LC-1 wideband at the time, as well as the dynojet wideband. both show a rock solid 13:1 all the way to the end of the pull.

dynocar

Because we are usually past the peak tq RPM when this happens. This means that the VE (air % per induction stroke) is less and less as RPM increases but the proportional fuel is not changing as much. Did you ever notice that a properly tuned car's injector pulse width actually decreases as the RPM increases past the peak tq RPM.

GuitsBoy

iTrader: (4)

Im looking at it right now, the duty cycle continues to increase, but the pulse width does decrease. This makes sense as the engine passes its peak efficiency. Good info, thanks for curbing the misconception.

Y2K2LS1

How can you spray 175-200 dry on a 98 or 01+ injector and still be safe (yes you can do it on a stock internal motor) That would be over 400 HP easily. I think there has to be some safety factor built in to that % somehow somewhere. Otherwise people would be blowing up all over the place.

Y2K2LS1

I found the post I was thinking of-

I cannot find the original post in reference to the guy who runs real high DC, because the search feature will not look back far enough.

GuitsBoy

iTrader: (4)

Holy crap he's got ***** to try that on his motor. How is this even possible?!?

SSDude

Back to the origional question, what is the maximum hp that can be run of the stock 28.8# injectors

white2001s10

iTrader: (4)

I set up the vette to do that. It was a stock 1998 LS1 with a 200hp dry shot and trapped 127 MPH, so I'd say around 500hp.

The DC was way up there past 100%, but the wideband showed way down in the 10's for AFR, so leads one to believe there was more left in it.

I plan on doing an experiment very soon to see what exactly happens over 100% DC on the same car. I will post up the info when that happens.

oh by the way, the DC is 90% just on motor runs, and staying in the low 13's AFR.

BriancWS6

iTrader: (18)

How do you find out what duty cycle the injectors are running at? I had my car on the dyno this past weekend and couldn't figure out where to look to find this out.

white2001s10

iTrader: (4)

The EFI-live scan-tool or other good scan tools will report DC% for each bank. You can also report the pulse-widths in milliseconds so you can then check against the RPM to verify the DC was correct, which I did. This of course assumes that the pulsewidths are reported correctly.

Moparnos (The SLP Guy)

iTrader: (55)

oh well blow it up

KrisR

iTrader: (2)

The injectors in my '02 Z06 were at 98% duty cycle at ~405-410rwhp, with a 13.0-ish AFR. I could have left them but upgraded to be safe (and because I figured I'd make more power with more upgrades in the future anyway), plus they had a slightly-used set for $175, so it wasn't a big investment. Now I'm at 68% duty cycle with 414rwhp.

BriancWS6

iTrader: (18)

This was on a GM TECH II. And he couldn't find it. Does the TECH II have it???

flyin red TA

I honestly wouldn't try to run more than 480 rwhp on 28# injectors.

I did it for about 6 months with around 530rwhp...it never went lean, but then I also got smart. This was on a stock 98 fuel system with a walbro 255lph inline.

Edit: I did it with a NOS 5177...the car was making 375rwhp on motor.