What pulley size runs out the stock injectors?

[97AutoXVette]

Title pretty much says it. What is the smallest pulley that can be safely run with the stock injectors? If anyone knows, what pulley size causes the injector duty cycle to go above 85%??

[16MustangVet]

Forget the injector cycle many many other things matter more.

KNOCK!?
TUNE?
FUEL TYPE?
CAM?
HEADS?
Stock Fuel Pump?
Fuel Pump rewire?
Gen5?
Gen3?

[97AutoXVette]

Yepp, understood that all those are important. Just wondering what would run the injectors out on an otherwise stock motor seeing no knock (I know this isn't really a feasible situation)

[Bio248]

you'll run out of fuel sometime around 3.2-3.0, but that's not really your concern as of right now. you can't just start dropping pulleys without having everything else under control...which you may have, but you haven't told us what's done to the car.

[16MustangVet]

injectors are impacted by X number of mods and the efficiency of the engine not XXX hp or X.X pulley size.

[97AutoXVette]

Good points. Guess I should have given some more background:

I have have 3" DP, PLOG, intake, plugs/wires, and that's about it. I am using HP TUners to tune and data log. Right now, with my stock 3.8" pulley, I am seeing up to 77% injector duty cycle around 5,500 - 5,700 RPM. Just seems surprising to me that a lot of people are able to drop to 3.4" pulleys without running the stock injectors out. I remember throwing a 3.5" pulley on my other 99GTP last year and was already seeing every bit of 85+% duty cycle on my injectors around stock shift points/RPMs.

I am trying to decide if I want to go with a 3.4" pulley if it will mean running outside of what my stock fuel system can safely handle.

[Bio248]

watch the IDC in pulse width. they can go fairly well beyond 100%. once the pulse width is something like 20-22ms then you're getting close to static.

[97AutoXVette]

watch the IDC in pulse width. they can go fairly well beyond 100%. once the pulse width is something like 20-22ms then you're getting close to static.

hmm, interesting... I am not sure off hand how I view/monitor the pulse width but I will look in the software this evening when I have a chance to open up HP Tuners. Thanks for the info guys!

[Iceman6669]

watch the IDC in pulse width. they can go fairly well beyond 100%. once the pulse width is something like 20-22ms then you're getting close to static.

I was told it was 18+ ms is where you start pushing your injectors.

[Fivefingerdeathpunch]

I run 18-19ms but only 80-85% duty cycle on my 3.6. But I also run it heavy on fuel, 10.9 to 11 AFR.

[97AutoXVette]

I run 18-19ms but only 80-85% duty cycle on my 3.6. But I also run it heavy on fuel, 10.9 to 11 AFR.

How much advance do you run? Do you see much knock with that setup?

[Fivefingerdeathpunch]

13-14º of timing. Minimal knock if any, might see 1-1.5 at times but that doesnt bother me at all.

[Iceman6669]

Hmm that's odd... Your setup is similar to mine, and I run 16~ms IPW and 75% duty cycle. Granted I'm a touch leaner and a touch more timing.

[97AutoXVette]

Hmm that's odd... Your setup is similar to mine, and I run 16~ms IPW and 75% duty cycle. Granted I'm a touch leaner and a touch more timing.

Stock timing I am assuming? I already see up to 17 ms and 80+% duty cycle with stock timing on my stock pulley (some KR in there as well. up to 2-3 deg)

[Iceman6669]

No I run 14.5-15* wot. And I will see up to 2* kr at the shift if I'm pretty heat soaked.

[Fivefingerdeathpunch]

Make an account on HP Tuners forums if you want, I'm on there.

You can also ask questions there and post logs and the tunes itself aswell as any configs you are running, so that way people can see what you are seeing and better advise you.