De-tuned hybrids in a PMR

[F-127]

Well I don't like making another thread, but I think that it may get enough discussion to get its own seperate from my other 'project' thread. With larger injectors going in one truck, the current 238/100 hybrids are going in another.

Just so happens to be a 02 SuperDuty with a PMR engine. Now with all the past talk of more HP or larger nozzles and the resultant window to wave "hi Mr. Crankshaft" on a PMR engine, it's got me a little worried, but I'm pretty confident I'll have it working. I have my single shot timing(fairly conservative) related maps copied/grafted in the SD file. Then grafted in the pulsewidth map I had working on the OBS. The PW map for the hybrids I started with has flow detuned to basically match output of an AA injector across the entire map.(that was because I was initially seeking a like-stock file when I started tuning the injectors for the OBS).

Now is where I started looking a little closer, and perhaps I should have done this when tuning for these injectors the first time. Being a little more cautious for the PMRs got me looking closer though. For the most part, my PW map for the 238/100 is fairly close to stock. Hybrids needing a little more PW here, little less there, but the big changer is up top, the PW map for AA stock and the hybrids starts deviate a lot more for me for MFDs >70. The hybrids can flow equally to stock AAs about .5ms quicker. I suppose I should pull some timing, unsure of how much. Took me a while to figure it out, but after staring at the ICP desired, SOI, and PW(namely the change in PW), I pulled some timing from all RPMs down to about a MFD of 70 using the rotational time calc that Bill has made for excel. At 3000 RPM and high MFD, with a shortened PW of .5ms, to have injection 'end' at the same time, 9* of timing would be pulled. When at 1000 RPMs that drops to 3*. (just so happens that PW difference was equal at that MFD over varying RPMs, it was not always like that so it wasn't always 1/3 less timing to pull at 1000RPMs).

Now I thought I found something that could likely have caused issues, and it was the biggest difference I could find when going with larger nozzles. If you raised the PW map in those areas MFD>70 and they match more like stock PW length, timing wouldn't really need to be pulled. For most, PW probably wouldn't be decreased to limit HP like I have, unless you were to say make an economy tune. My guesses are either what I seemed to have found or just too aggressive low RPMed fuelling, lotsa torque.

Anywho, thats my thoughts for the night, if anything else talking(writing) about it helped. Just thought I'd post it to get some additional opinions, hoping to avoid a windowed block myself, and if it helps others avoid one too even better!