injectors are too small

[shawnxj]

kinda weird 24# injectors are too small for my motor. i'm running 90-100% duty cycle at cruising speeds.....can't believe it took me so long to figure that out but it makes sense now why the motor was bucking so much. what uses something in the 30# or bigger with an ev1 connector on a stock motor? not even sure 30# will be big enough

[SilverXJ]

90 to 100% with just cruising? I can't see how that is possible, even with stock injectors. The engine doesn't need that much fuel when cruising.

What is the part number on the injectors? Maybe they really aren't 24#.

What is your fuel pressure?

Do you have a wideband? If so, what is it showing under WOT?

[shawnxj]

ya i double checked it like 4 times when i bought them. i have 4 sets of injectors floating around here and i double checked them again before i installed them. fuel pressure is 39#'s which is what those injectors are rated for and the wideband starts going lean the longer i drive it then flat lines when the motor starts bucking so that tells me 1 or several injectors are shutting down from too high a duty cycle, and according to my ecu it shows that i'm running 80% to 100% for most of my driving and if i try to cruise at 70-75 my duty cycle is 95 to 100%. wot pulls stay pretty much 100% the whole time

[wjtom]

Make sure the wideband o2 is actually good.I just went throught this with mine.The o2 will flatline at a really lean reading that doesnt make any senese.If its a innovative wideband they dont last very long.I just got a bosch one to replace mine as ive had good luck using the bosch in the past.I think the part number is 17014 i can check to be sure if you need me to.I know it fits a vw.lol

[wjtom]

One more thought.Do you have enough fuel volume?You can have pressure and not enough volume.Not enough fuel would cause the injectors to stay open longer trying to compensate.

[SilverXJ]

One more thought.Do you have enough fuel volume?You can have pressure and not enough volume.Not enough fuel would cause the injectors to stay open longer trying to compensate.

Good point.

Also, check the fuel pressure while driving. At idle isn't good enough.

[shawnxj]

i need to get a new fuel pressure gauge so i'll do that next week

i'm using an aem wideband and haven't heard any bad things from this 1

[Muad'Dib]

Is this in the 88? Did you buy used injectors? Refurbished Injectors? New Injectors?

[shawnxj]

ya it's in the 88 and i bought used injectors off a running motor. buddy put a turbo on his 5.0 and swapped in 60#ers i think

[Muad'Dib]

Its possible that your injectors just are not good. I would try to get my hands on a MT2500 and check what your STFT is.

Interestingly, I had funky lean issues with my RENIX stroker and root cause was my injectors were too large. Even a wideband didn't help with this until I was able to check STFT. My 4.7L RENIX stroker likes 19ish#hr (at our fuel pressure) injectors.

If you cant get your hands on something that can show you STFT (DRBII, MT2500 or possibly arduino interface), then start with either quality refurbished injectors, or new injectors and check your fuel pressure while driving. Its also possible that your injectors may be 24lbhr, but they are that flow rating at a lower pressure than normal (3bar). A part number would really help here to verify.

[shawnxj]

i'm running megasquirt 3 instead of the stock electronics and it shows what the injector pulse width and duty cycle are

part # is F1TE-D5A

[Muad'Dib]

Is this a turbo / supercharged scenario? If not why the MS3?

Could the programming of the MS3 be off? Those injectors should be plenty for the engine if its just a normal 4.x stroker. 24# @ 3bar.

Do you have an AFPR? OR Different injectors you can swap in for shits and giggles?

[shawnxj]

according to the ms people everything looks good on the program side. i'm running ms3 because i want to go to sequential injection and cop plus i think the renix system is a joke and is untuneable. i have $4000 in this motor i want it to run right so this was the best option i could afford in my opinion. yes i have a wideband on it and as the injectors heat up the leaner the wideband shows. i drove it around sunday and as long as i kept the duty cycle under 75% they didn't give me any issues but soon as i went over it for any length of time i had nothing but issues. think i'm going to pick up a set of 30# injectors and go from there. i'll test them before i install them

oh and i'm also considering running cng for fuel in the future and even toying with the idea of a turbo

[Muad'Dib]

I was asking about a AFPR (Adjustable Fuel Pressure Regulator) not AFR Meter. Since your planning on turbo later etc makes sense to go with MS. I personally like the RENIX system, although the fairly limited lack of tunability does suck.

With an AFPR you could bump up the pressure and see if it helps. From what you describe though it seems to get worse with heat which to me points to bad injectors.

[shawnxj]

ya i have an afpr but i need to get another fuel pressure gauge to change it.

tested the injectors and all work just fine, have a nice spray pattern, don't leak and measured out to half a gram from highest to lowest. i pulled the rail and stuck each injector in a gatorade bottle and sprayed alot. then measured all the bottles. all came with in a .5 gram and all the bottles were within .1 gram empty

so it's not an injector problem except for being too small