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Thread: Any Actual Need For Pilot Injections Other Than Cold Weather Cold Starts?

  1. #1
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    Any Actual Need For Pilot Injections Other Than Cold Weather Cold Starts?

    I can totally see the need for the pilot injections for cold weather cold starts, to pre-warm the combustion chamber for the main injection event, but after warmup, it seems to me that there is no use for the pilot injections other than noise management, and emissions (limiting NoX). Anyone know if this is true?

    My inclination is to get rid of pilot injections after the warmup cycle, and see what that does to my efficiency.

  2. #2
    Tuner in Training dhoagland's Avatar
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    https://forum.hptuners.com/showthrea...nabled-warm-up

    There are some discussions in the Cummins section of the forum on single event tuning, might get you headed in the right direction
    2011 Camaro 2SS Convertible L99 Bone Stock for now
    2003 Dodge 2500 5.9 Cummins QC 4x4. Airaid, 2nd Gen Intake, Grid Heater Delete, D-Tech 62/65/12, Magnaflow. Bully Dog: Propane Injection, Triple Dog W/Outlook Crazy Larry. Edge EZ, BD Flow-Max, 48RE: Sonnax Sure Cure/Transgo combination, Derale turbulator, billet input, Triple Disc, Super servo, 4 ring Accumulator. :beer

  3. #3
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    Thank you sir, I will check that out!!

  4. #4
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    Keep us posted with your test and results please. I'm certainly interested.

    Thanks,
    Jason
    1996 Camaro SS M6 - 24X conversion - stock bottom end - heads - shorty headers - 58mm TB
    Ultradyne 230/238 .565/.565 112+4 - 30 LB red top SVO injectors - LOTS of suspension...

    2002 GMC 2500 HD Duramax M6 - Just starting the tune on a stock motor now that I have a good clutch on order...

  5. #5
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    Thanks, I will! The weather has been such a wild card that I'm not sure how much I can really draw from the anecdotal observations of driving around, but the truck is really nice to drive at this point. I will probably make a couple of medium length trips in it soon, and see where the fuel economy stands with the maps all closer to stock than they were when I bought it. There were a couple of spots that made no sense to me, where the pilot pulse was actually bumped up by the tuner.

    On a separate, but somewhat related note, I almost have my play car completed to a point where I wouldn't mind getting it on a dyno to verify the N/A timing curve before adding boost. I was thinking maybe I would use that as an opportunity to check out the dyno place that I'm thinking about taking the truck eventually. That will allow me to find out if I feel like that place will suit my needs for my diesel tuning foray.

    My biggest hurdle other than the weather currently is that I need to figure out some sort of a logical testing process of what to adjust between pulls when I finally buy some dyno time. I feel like it requires a bit more planning ahead to make efficient use of the dyno time than it would if it was a tune-on-the-fly style ECU setup. The need to shut down, make a change, and reflash is a bit of a hassle to me, but I know it's pretty normal for a lot of people. Combine it together with the mysteries of diesel tuning though (speaking as a lifelong gasoline tuner), and it's just a little daunting. Lol

    One observation I can comment on so far is that the very first tune I made for the duramax had the pilot pulses turned completely off, and very little was changed other than that. Predictably, the engine was louder and more rattley (diesel sounding) all around, and it had a bit of a drivability problem/stumble right off idle. However, it did seem like it might have been willing to run in a slightly lower fuel demand area at lowish highway speeds than it did with the pilot pulse turned on. But I didn't really care for the overall feel of the engine like that, and the sound was definitely a bit intrusive.

    Add to that the fact that HP Academy had a webinar up where they showed a massive increase in torque production from including properly timed pilot injection with a given total amount of fuel injected, and I said to hell with the pilot-less tune for a while and went back to trying to figure out how to make best use of pilot pulse before I really get back to eliminating it. There's a tremendous amount of tuning to be done to really nail it all down.

    I think it would be good to make some attempt to optimize a tune WITH pilot pulse, and then optimize a non-pilot pulse tune in the MPGs area. At this point I do not intend to run without pilot pulse at and around idle, and definitely in warmup modes I will keep it. That's all of the useless rambling I have for now. Haha

  6. #6
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    Thanks for sharing. Yeah, I was looking at eliminating or reducing it in the fwy cruise / MPG areas. Good data on the tune without it completely.

    Jason
    1996 Camaro SS M6 - 24X conversion - stock bottom end - heads - shorty headers - 58mm TB
    Ultradyne 230/238 .565/.565 112+4 - 30 LB red top SVO injectors - LOTS of suspension...

    2002 GMC 2500 HD Duramax M6 - Just starting the tune on a stock motor now that I have a good clutch on order...

  7. #7
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    Quote Originally Posted by JasonS5555 View Post
    Thanks for sharing. Yeah, I was looking at eliminating or reducing it in the fwy cruise / MPG areas. Good data on the tune without it completely.

    Jason
    If you have already spent the credits to open your ECU, it would be great to compare notes with your impressions of stuff like this! It's super easy to wipe out the pilot injections in an LLY tune, and looks only slightly different in LBZ. If yours is an LB7, I haven't looked yet, but I'm guessing those are pretty similar to the LLY.

  8. #8
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    Yeah, I think those tables aren't too different. And yes, mine is an LB7. My stock tune is in another post in the forum.
    1996 Camaro SS M6 - 24X conversion - stock bottom end - heads - shorty headers - 58mm TB
    Ultradyne 230/238 .565/.565 112+4 - 30 LB red top SVO injectors - LOTS of suspension...

    2002 GMC 2500 HD Duramax M6 - Just starting the tune on a stock motor now that I have a good clutch on order...

  9. #9
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    I've been hunkering down, hiding from the cold weather (Michigan), but I just now downloaded your tune from your other thread. Have you messed with the pilot injections yet?

  10. #10
    pilot injection is a wonderful thing for efficiency and a clean burn, post injection, can help with turbo spooling.. I bet you will actually drop mpg by disabling it, under light cruising, the pilot starts the fire for the main event, then the main event has the ability to burn more completely since the combustion chamber is already pre warmed, this also helps with noise, and noise is directly related to how "smooth" your engine spins, the only real gain to dropping pilot injection is when trying to maintain rail pressure and injector fill when running high rpm and high pulse width, but also if you can maintain and fill the injectors, you will make more( and cleaner) power with a small pilot to get the fire going, but up over 2900 or so rpm, the time of pilot would be so short that quite a few stock calibrations already have the injector events cut to 1 which is the main event only

  11. #11
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    crash01, have you tested the results of changing pilot parameters at all? HPA has some conflicting information about it that they have developed on their dyno. I'm not sure what differences they have documented are attributable to pilot pulse timing relative to main injection, or whether it actually boils down to the fact that pilot pulse is really just wasted fuel as some of their earlier testing/instruction seemed to be saying.

    FWIW, my seat of the pants impression has matched your description of things, and I ran pilot pulse all winter (a single pilot pulse in my situation IIRC), but I do want to do some more testing with pilot pulse timing at the very least this spring. HPA documented massive light throttle torque changes just by adjusting the pilot pulse timing. But that could have had a lot to do with their main pulse timing too...

  12. #12
    yes, any time injector nozzle size is changed,its very important to adjust pilot injection, and the torque changes you are feeling are correct, you are adding more fuel to an early event, which in a sense would be the same as having a single event with lots of timing, hope this helps what your thinking

  13. #13
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    I 100% understand what you're saying in terms of theory. I'm just hoping that you have actually done some testing of some of the specifics involved, and preferably, with a duramax. There seems to be a shortage of people who have, and as of yet, I haven't either.

    In terms of the generalities you mentioned about pilot injection, HPA recorded massive changes in light throttle torque production just by moving pilot injection from 10 degrees before main injection, to 15 degrees, and then to 20 degrees. IIRC, 15 degrees before main injection was their sweet spot, but since the pilot injection references main injection timing, obviously there is a lot to play with. It's quite possible that our main injection isn't necessarily at the optimal point for torque production, due to concerns about NOx, smoke, and whatever else.

  14. #14
    yes ive done alot on the duramax platform in testing on the road and on my dyno, just make sure you are using a timing calculator when adjusting pulse width and timing on the main injection,

  15. #15
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    Can you share any specifics you've found on this topic?

  16. #16
    i hate to repeat myself on the topic but its mostly all explained in my previous posts, if you want to pm me ill gladly share my phone number and we can chat about it more if you wish or if you want to try it for yourself on my dyno c'mon down, but let me see if i can sum it up quickly for you---- no pilot injection = 12v cummins, put in big injectors and they are smokey as hell but can make decent power, ---now take a 2005 dmax, with very similar fuel rates, they can make gobs more power and at times are firing the injector 5 times per cycle, ---pilot and post injection are more for efficiency and power than they are for emissions(but they go hand in hand), if you want a dmax with no pilot injection, go ahead and turn it off, u will have to adjust your main pulse width to make it run even close to the same power level, and it will sound like a pre '99 ford 7.3 cackling away, and just because of design of the motor, you risk longetivity of the bottom end,to say it in short, for stock and mild injectors, there is better ways to make power and adjust things, kory willis has the name for it, but 600hp is achievable on all stock parts(other than lift pump) on a dmax and pilot injection is hardly touched in these files.

  17. #17
    set up a good 20/20 tow tune, dont forget to use the timing calculators, set timing at 50/50 for cruising speeds and enjoy the best mix of power and mpg... fussing over the pilot so much is just not worth it for the very minuscule gains...

    we have had a few "streetable" 1000-1400hp ish dmaxs with very very minor adjustments to these injections, they run clean, hard and fast. IMO playing with pilot and post injection on stock injectors is just tinkering, and not worth any good hard gains be it power or mpg. I'm open to debate this topic, but i feel it has been beat to death on multiple forums,

  18. #18
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    Ok, thanks!! And where are you located?
    Last edited by tjabo; 4 Days Ago at 03:08 PM.