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  1. #1

    Running out of injectors

    Here is what a classic case of what running out of injectors looks like in a data log. The motor starts out a little lean at the beginning of the WOT pull and continues to get leaner as the motor pulls up thru he power band. There is nothing the tuner can do with the ECU tuning to fix this. My bet is the injectors are at 100% Duty Cycle early in the pull and things just get worse thru the pull.

    http://www.nbs-stl.com/RxpxTuning/In...allLogView.png

    and in the scatter plots view...

    http://www.nbs-stl.com/RxpxTuning/In...allScatter.png

    You can really see where the motor zings to nearly 10000 RPM when it grabs air. I hope the owner has done flywheel bolts and a valve train in these sorts of conditions.

    Have fun tuning

    Andy


  2. #2
    Notice that all looks good at 8000 RPM and 184 KPA (where the circle is) and then things start get ugly, and continue to get worse.

    Andy

  3. #3
    NateRXP's Avatar
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    My ski likes 157% DC. Pulls hard.

  4. #4
    Is PW or DC in that log to confirm?

  5. #5

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    Quote Originally Posted by whittlebeast View Post
    Here is what a classic case of what running out of injectors looks like in a data log. The motor starts out a little lean at the beginning of the WOT pull and continues to get leaner as the motor pulls up thru he power band. There is nothing the tuner can do with the ECU tuning to fix this. My bet is the injectors are at 100% Duty Cycle early in the pull and things just get worse thru the pull.

    http://www.nbs-stl.com/RxpxTuning/In...allLogView.png

    and in the scatter plots view...

    http://www.nbs-stl.com/RxpxTuning/In...allScatter.png

    You can really see where the motor zings to nearly 10000 RPM when it grabs air. I hope the owner has done flywheel bolts and a valve train in these sorts of conditions.

    Have fun tuning

    Andy
    I'm curious how do you know your at 100% cycle duty? I see no data on the graphs actually showing cycle duty. Am I missing something?

  6. #6
    Quote Originally Posted by lt401vette View Post
    Is PW or DC in that log to confirm?
    Not in a vtech log. You need a power commander set up to see that.

  7. #7
    Quote Originally Posted by Askin View Post
    Quote Originally Posted by whittlebeast View Post
    Here is what a classic case of what running out of injectors looks like in a data log. The motor starts out a little lean at the beginning of the WOT pull and continues to get leaner as the motor pulls up thru he power band. There is nothing the tuner can do with the ECU tuning to fix this. My bet is the injectors are at 100% Duty Cycle early in the pull and things just get worse thru the pull.

    http://www.nbs-stl.com/RxpxTuning/In...allLogView.png

    and in the scatter plots view...

    http://www.nbs-stl.com/RxpxTuning/In...allScatter.png

    You can really see where the motor zings to nearly 10000 RPM when it grabs air. I hope the owner has done flywheel bolts and a valve train in these sorts of conditions.

    Have fun tuning

    Andy
    I'm curious how do you know your at 100% cycle duty? I see no data on the graphs actually showing cycle duty. Am I missing something?
    Experience mostly.

  8. #8
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by Askin View Post
    Quote Originally Posted by whittlebeast View Post
    Here is what a classic case of what running out of injectors looks like in a data log. The motor starts out a little lean at the beginning of the WOT pull and continues to get leaner as the motor pulls up thru he power band. There is nothing the tuner can do with the ECU tuning to fix this. My bet is the injectors are at 100% Duty Cycle early in the pull and things just get worse thru the pull.

    http://www.nbs-stl.com/RxpxTuning/In...allLogView.png

    and in the scatter plots view...

    http://www.nbs-stl.com/RxpxTuning/In...allScatter.png

    You can really see where the motor zings to nearly 10000 RPM when it grabs air. I hope the owner has done flywheel bolts and a valve train in these sorts of conditions.

    Have fun tuning

    Andy
    I'm curious how do you know your at 100% cycle duty? I see no data on the graphs actually showing cycle duty. Am I missing something?
    When your shit blows up from ignoring this info you will know you went beyond 100% duty cycle. Just SAYIN, ASKIN!

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  10. #9
    Sanfish's Avatar
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    I've done many changes along the way but the moment I did a mod (can't remember which one) that made my motor spin in the 8600rpm range I lost complete control of my AFR. It was literally like a cliff where just prior I could control my AFR to the tenth decimal point. I put a Walbro 255 and VT1100 3 days later and all went back to normal - had to completely re-tune but thats expected.

    ps. Don't forget, we have thicker/warmer air here and can get away with a little more compared to you northern guys.

  11. #10

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    Quote Originally Posted by whittlebeast View Post
    Quote Originally Posted by Askin View Post
    Quote Originally Posted by whittlebeast View Post
    Here is what a classic case of what running out of injectors looks like in a data log. The motor starts out a little lean at the beginning of the WOT pull and continues to get leaner as the motor pulls up thru he power band. There is nothing the tuner can do with the ECU tuning to fix this. My bet is the injectors are at 100% Duty Cycle early in the pull and things just get worse thru the pull.

    http://www.nbs-stl.com/RxpxTuning/In...allLogView.png

    and in the scatter plots view...

    http://www.nbs-stl.com/RxpxTuning/In...allScatter.png

    You can really see where the motor zings to nearly 10000 RPM when it grabs air. I hope the owner has done flywheel bolts and a valve train in these sorts of conditions.

    Have fun tuning

    Andy
    I'm curious how do you know your at 100% cycle duty? I see no data on the graphs actually showing cycle duty. Am I missing something?
    Experience mostly.


    Ok. Well with the CDM I can add fuel at max rpm's and bring the afr down to 10.0 that's telling me I still have room in my injectors. This is real data if I could not lower my afr then I would suspect the fuel pump/ Injectors...

    To get accurate cycle duty from the injectors via ecu/piggyback module don't you need to monitor voltage from injectors and crank position? The only systems that I have used is Motec & Vi-Pec that can actually do that. With Vi-Pec you can even change pulse time on the injector.

    What I'm trying to say these graphs really don't help with true injector cycle duty. You will need a better ecu/software and a few more sensors to give accurate data. And another note it's impossible for a injector to go over 100% cycle duty if your seeing higher then 100% the formula is wrong... Possibly why some think they are close to maxing out three 1000 cc injectors?

    If your looking to size and injector there are easy formula's from injector manufactures that will get you in the ball park.

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