injectors are too small

[Muad'Dib]

Its still possible that your injectors are no good considering your problem exists as they get hotter. Its unlikely that during your tests you were able to apply heat (unless your on fire right now lol).

Anything is possible... just seems unlikely that your Stroker would be that much different than everyone else's. Crazier things have happened. I guess try some 26 or 30 pounders and see what happens.

[shawnxj]

went through my desktop dyno again and redid the calculations and it came up as 286 hp 370 ft lb of torque. then plugged that into an injector calculator and it came out as 29.8#.....now i know the desktop dyno isn't very reliable but it gives me something to go off of. think i'm going to try and find some 32#'s just incase

[SilverXJ]

If your are cruising and the duty cycle is 90-100% I really doubt its the injectors.

[wjtom]

My 4.7 10.3 -1 compression 218-228 on110 with 525 lift is only using 24lb injectors.Something else is going on.

[Muad'Dib]

went through my desktop dyno again and redid the calculations and it came up as 286 hp 370 ft lb of torque. then plugged that into an injector calculator and it came out as 29.8#.....now i know the desktop dyno isn't very reliable but it gives me something to go off of. think i'm going to try and find some 32#'s just incase

Keep in mind injector calculators are never accurate for our I6 Jeep engines. They usually call for injectors that are way WAY to large.

[SilverXJ]

Keep in mind injector calculators are never accurate for our I6 Jeep engines. They usually call for injectors that are way WAY to large.

x2, which I believe to be a function of the PCM programming.

As well as the fact that desktop dyno tends to be optimistic.

Another thought is if you are using the correct injectors for the megasquirt. There are low impedance peak and hold injector and high impedance saturated injectors. Stock injector are the later, but I don't know what the MS' injector drivers call for.

You also never stated the part number on your injectors.

[shawnxj]

scroll up silver i did post it and the ms i'm running wants the high impedance injectors which is what i'm running

[CobraMarty]

286 hp 370 ft lb of torque

That is way overly estimated.

[SilverXJ]

scroll up silver i did post it and the ms i'm running wants the high impedance injectors which is what i'm running

Don't know how I missed that. They should be fine.

[Cheromaniac]

went through my desktop dyno again and redid the calculations and it came up as 286 hp 370 ft lb of torque. then plugged that into an injector calculator and it came out as 29.8#.....now i know the desktop dyno isn't very reliable but it gives me something to go off of. think i'm going to try and find some 32#'s just incase

Hold on a minute before you go buying another set of injectors.
What are your engine specs and do you have any other external performance bolt-ons?
What year is your Jeep?
Your desktop dyno calculations seem to be overoptimistic for a N/A stroker.
Running at close to 100% injector duty cycle during highway cruising seems highly questionable to me, and I'd say there's something wrong with your MS3 programming. What do your plugs look like?

[shawnxj]

last time i check my plugs they looked lean. i'll check again this weekend

fuel pump is pushing 43lbs no problem but now i have to replace the starter and i already found a set of injectors that if i don't use i'll make money selling

258 crank
4.0l rods
kb 945's .020 over
lunati 63501 cam
lots of port and polish work
67mm throttle body
0630 head
.044 quench
somewhere around a 9.5 compression if i remember right
ls truck coil
2.25" cat then 2.5" out the back

jeeps an 88 cherokee

the only thing i can think of that could be effecting this is i do have a cracked header

[Cheromaniac]

the only thing i can think of that could be effecting this is i do have a cracked header

That'll definitely affect your A/F ratios so it's a good time to upgrade to an aftermarket header with a 2.5" downpipe and 2.5" cat. Depending on the quality of your head porting job, outputs could be anywhere between 255-275hp and 315-320lbft so your engine shouldn't run lean with 26lb injectors.

[SilverXJ]

While a cracked header could effect the air fuel ratio, I don't think it would be that much.

[Muad'Dib]

Any update on this?

[shawnxj]

waiting to get my header back from my machinist buddy. he's resurfacing it since it's warped and and filling in a hole where all the pipes come together in the collecter