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Thread: confused about how to scale inj and other things that are "missing" - jeep 4.0L JTEC

  1. #1
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    confused about how to scale inj and other things that are "missing" - jeep 4.0L JTEC

    Screenshot_HP_tune_file.png

    Sooooo where and how do I scale for larger fuel injectors? I read and watch YT vids on how others do this and even right here in the dodge tuning section and I just dont seem to have the option? What am I missing?
    This isnt the only thing I cant seem to find that others are doing to tune. What I mean is, how are you guys setting up Lambda in HP tuners when you have a Jeep JTEC PCM that your Scanner is linked to? I dont see any Lambda or AFR error channels to add..? The only option I can figure is to do a narrow band LTFT part throttle tune. Yes I do have a WB O2 but I can only log the AFR. What am I missing here? I see lots of vid on You Tube explaining how to set up a AFR error Histogram but again, its not coming up when I search the channels list in my VCM scanner...whilst my scanner is connected to my 2000 Jeep 4.0L PCM anyways.
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

  2. #2
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    Just replied to your other post, After thinking about it if your fuel tables were dialed in before changing fuel injectors it does make sense to set up a fuel error histogram and change the injector which should remap the fuel tables automatically versus readjusting the maps, one number versus the entire table. Again I am new to Dodge but hope this helps

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    Hey Kev,
    Thanks for your reply, I really appreciate it. You are right in what I am asking/trying to learn. I am going to reply here from your other post too because I kind of hijacked that thread, well sorta anyways.
    In reply to your comment above. No, I dont already have the fuel tables dialed in. I am starting from scratch with a newly installed 4.6L stroker engine. I have started "tuning" but have realized that my 24# fuel injectors as recommended and supplied by the stroker kit company just arent enough.(yes I have upgraded my fuel pump and pressure is stock at 49 psi, so fuel supply is good). Inj duty cycle is at like 105% up near 5000 RPM redline. So i am still waiting for some 30# injectors in the mail. However I can still at least begin to tune and wrap my head around tuning these Jeep 4.0L JTEC PCM's. for cruise and part throttle. I know Ill have to pull more fuel out once I get the 30#inj.
    So again, how do I go about scaling for larger injectors? I dont see where even if I had the injector flow data I could input it to re-scale..?
    DO you have a 4.0L Jeep? can you also see the different maps & tabs in the VCM editor?
    Thanks
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

  4. #4
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    This is a dumb system - not like the newer systems that you can find commonly explained on Youtube where there is a VE table and fuel mass vs pulse width is known by the ECM.

    There is no VE table or injector flow vs pulse width table. You directly input the injector pulse width. To "scale" you start by doing a bit of math to figure the percent change in injector flow and then modify the table by that amount of change. Then dial it in.
    Make sure that when you calculate your change in flow, you take rated fuel pressure into account. Most injectors are not rated at the stock fuel pressure.
    If in doubt, multiply everything by 1.1.

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    Hi Rudy,
    I have a 99 Durango JTEC with a 5.9 that is stroked to a 410. My tables are similar. I would go ahead and dial in the fuel tables with the 24 lb injectors. Once you get your 30's it should be as easy as changing the injector parameters to change the flow rates and the PCM should automatically adjust pulse width to accommodate. Unfortunately I dont know enough about the tables to tell you how to enter the injector specifics. I have the same tables you have but like you very new in the Dodge tuning. I think and alternative would be to multiply your fuel table by the % difference in injector flow rates once you get the new injectors ( injector mfg should be able to give you inj data. Would not seem like the best way but should work. If the injectors are significantly different in their flow rate versus duty cycle my method would be off but not much and would only require slight modifications. Hope this helps, let me know if you need help in dialing in your fuel maps, are you logging with a wideband O2? Understand your frustration, I have a surging idle I can't seem to correct and it is frustrating because a lot of the tables don't have units and it is difficult to determine how they work. I have just been doing a lot of changing numbers and documenting the affect. I have learned a lot but have a long way to go. I plan on posting what I determine once I figure out some of the tables. Maybe we can learn from each other :-). Hope this helps, it kind of seems like we are on our own on these platforms. I get little to no response to any questions I post. I have one question how are you getting injector duty cycle? I cant seem to find where HP tuners supports injector parameters on my platform which seems crazy? Injector pulse width on mine does not appear to be supported. It is not a highlighted channel ??
    Last edited by kevhill47@aol.com; 05-15-2021 at 07:12 AM.

  6. #6
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    Quote Originally Posted by spoolboy View Post
    This is a dumb system - not like the newer systems that you can find commonly explained on Youtube where there is a VE table and fuel mass vs pulse width is known by the ECM.

    There is no VE table or injector flow vs pulse width table. You directly input the injector pulse width. To "scale" you start by doing a bit of math to figure the percent change in injector flow and then modify the table by that amount of change. Then dial it in.
    Make sure that when you calculate your change in flow, you take rated fuel pressure into account. Most injectors are not rated at the stock fuel pressure.
    So just to be very certain I understand please reference this post: https://forum.hptuners.com/showthrea...fset-parameter
    Taking note of my initial reply. Are you saying to enter the percent difference in inj flow into the "injector offset" table like discussed in that post or enter my the percent difference like you explained above into my "Fuel Base - EGR off" table like shown here in my screen shot. Which BTW this is after me trying to pull fuel out at idle & part throttle cruise using LTFT's.
    fuel map snip.png
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

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    Kev,
    Thanks and sorry for the delayed responses, ive got a mechanical issue right now with my engine and am beating my head against the wall trying to figure out why my header glows bright orange after only a few minutes of running(like before engine reaches operating temp). meanwhile we have a big offroad trip planned next Saturday May 22nd. I dont think its a tuning issue as I have swapped the stock throttle body, fuel injectors, sensors, even the stock tune file back in and its still glows at 2000 rpm's while in park.
    Anywho, back to this threads topic... I do have a WB but as you suggested earlier I have tried to setup a histogram to use it as a lambda/error but for reason its not working. I followed the Goat Rope garage guys explanation but must have messed up somewhere..? I just havent had time to take a second look at it because like I mentioned am still diagnosing a glower header issue.
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

  8. #8
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    Heres the screen shot of my AFR histogram math parameters. Does it look right?
    AFR error snip.png

    Afr error setup snip.png
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

  9. #9
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    [QUOTE=b.rudy;650475]Heres the screen shot of my AFR histogram math parameters. Does it look right?
    AFR error snip.png

    [ATTACH=CONFIG]109886[/ATTACH

    let us know if you get the for formula to work , i know the jtec ecm doesn't support those channels like gm stuff does.

  10. #10
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    Quote Originally Posted by kevhill47@aol.com View Post
    Hi Rudy,
    I have a 99 Durango JTEC with a 5.9 that is stroked to a 410. My tables are similar. I would go ahead and dial in the fuel tables with the 24 lb injectors. Once you get your 30's it should be as easy as changing the injector parameters to change the flow rates and the PCM should automatically adjust pulse width to accommodate. Unfortunately I dont know enough about the tables to tell you how to enter the injector specifics. I have the same tables you have but like you very new in the Dodge tuning. I think and alternative would be to multiply your fuel table by the % difference in injector flow rates once you get the new injectors ( injector mfg should be able to give you inj data. Would not seem like the best way but should work. If the injectors are significantly different in their flow rate versus duty cycle my method would be off but not much and would only require slight modifications. Hope this helps, let me know if you need help in dialing in your fuel maps, are you logging with a wideband O2? Understand your frustration, I have a surging idle I can't seem to correct and it is frustrating because a lot of the tables don't have units and it is difficult to determine how they work. I have just been doing a lot of changing numbers and documenting the affect. I have learned a lot but have a long way to go. I plan on posting what I determine once I figure out some of the tables. Maybe we can learn from each other :-). Hope this helps, it kind of seems like we are on our own on these platforms. I get little to no response to any questions I post. I have one question how are you getting injector duty cycle? I cant seem to find where HP tuners supports injector parameters on my platform which seems crazy? Injector pulse width on mine does not appear to be supported. It is not a highlighted channel ??
    i just did a GC 5.9 with big cam bored 0.30 ford blue top injectors, I had to remove over 30%on the first 3 rows, and around 10 % at WOT

  11. #11
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    Quote Originally Posted by b.rudy View Post
    So just to be very certain I understand please reference this post: https://forum.hptuners.com/showthrea...fset-parameter
    Taking note of my initial reply. Are you saying to enter the percent difference in inj flow into the "injector offset" table like discussed in that post or enter my the percent difference like you explained above into my "Fuel Base - EGR off" table like shown here in my screen shot. Which BTW this is after me trying to pull fuel out at idle & part throttle cruise using LTFT's.
    fuel map snip.png
    Reduce the fuel base egr off table by the percent of flow in crease from the new injectors. If you had 24lb and now have 36lb, multipy by .66 for example. This won't be perfect by any stretch, but it should get you in the ballpark. Then it's basic tuning. You may hit limits for minimum pulse width on the bottom and could have latency issues.
    If in doubt, multiply everything by 1.1.

  12. #12
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    Thanks for the clarification, that helps get me started 👍

  13. #13
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    sorry for the slow reply, the channel selected is in lambda so you don't need to divide by 14.7. You just need to get it in a % that you can multiply the fuel table by., below is the formula I useCapture.PNG

  14. #14
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    fuel error histogram

    sorry forgot to add how I have the histogram set up. Let me know if this does not help or have questions?cap1.JPG

  15. #15
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    Excellent thanks man, i?ll take a look at it. However it may be a few days before I can sit down and play with it.

  16. #16
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    Quote Originally Posted by kevhill47@aol.com View Post
    sorry forgot to add how I have the histogram set up. Let me know if this does not help or have questions?cap1.JPG
    Ok so I copied yours and my histogram still doesnt work?

    When you right click - graphs layout, do you select something under "new variable" ??
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944

  17. #17
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    Sorry for slow reply. send me a scan file. Is your wideband showing up when you scan? If it is showing up what are your numbers? Is it in lambda 1.0 or afr 14.7?

  18. #18
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    Quote Originally Posted by kevhill47@aol.com View Post
    Sorry for slow reply. send me a scan file. Is your wideband showing up when you scan? If it is showing up what are your numbers? Is it in lambda 1.0 or afr 14.7?
    ok sorry it took me so long to reply.
    Heres a scan file. I hope I attached it correctly..?
    As you can see, Yes my WB does log, but only as AFR, I cant seem to figure out how to make it log Lambda..?

    Thanks for your help man I really appreciate it.

    quick WOT.hpl
    current build: 2000 Jeep Cherokee XJ, 4.6L stroker w/mild cam, competition ported Newcomer Racing head, Hardland Sharp rockers, full 3" exhaust, 62mm TB. 24# injectors etc..

    LS6 swapped Porsche 944