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Thread: Injector Timing? Reference Periods? refereencing what?

  1. #1
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    Injector Timing? Reference Periods? refereencing what?

    so I'm starting to look at Injector timing for my new cam.
    I've been told the design of the design of the LS1 was to spray the back side of the intake valve.
    but with overlap that could allow it to suck all the fuel out before it can get combustion.

    so I'd like some insight in how to work out injector timing on an LS1.

    on LS1's its in Reference Periods?
    but what are the reference periods in crank degree's?
    what is it referencing?

    it would be nice to be able to have an understanding rather than a blind guess and hoping it helps.

    I'm planning on going to a dyno to play, but what amount should I move it, and how much should I move it each time?

    going in blind could be the difference between $100 or $300 in dyno time.


    and how much more power can be had from just playing with injector timing?

    also which tables do I mess with. Boundary? Normal? Makeup?

  2. #2
    I'm interested in this as well

  3. #3
    Senior Tuner Google's Avatar
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    Quote Originally Posted by skippy View Post
    so I'm starting to look at Injector timing for my new cam.
    I've been told the design of the design of the LS1 was to spray the back side of the intake valve.
    but with overlap that could allow it to suck all the fuel out before it can get combustion.

    so I'd like some insight in how to work out injector timing on an LS1.

    on LS1's its in Reference Periods?
    but what are the reference periods in crank degree's?
    what is it referencing?

    it would be nice to be able to have an understanding rather than a blind guess and hoping it helps.

    I'm planning on going to a dyno to play, but what amount should I move it, and how much should I move it each time?

    going in blind could be the difference between $100 or $300 in dyno time.


    and how much more power can be had from just playing with injector timing?

    also which tables do I mess with. Boundary? Normal? Makeup?

    keeping it simple for everyone...

    normal and makeup tables is what you would adjust.. if the valve event happens sooner as in more duration or advancing the icl or any cam changes.. then the tables would require adjusting and after ve would need tuning as now you will have a better spray pattern and less cyl wash.. this also helps with the rich idle smell everyone complains about.. bigger numbers mean the injecton will finish sooner and there by start sooner..

    best way to adjust it for most is on a dyno.. but then again most don't even think about adjusting the timing of the injectors.. why would they.. but it makes a very big difference in low end power and torque! you can adjust it by afr and feel in the pants but it would require more exp. then most have..

    hope this helps you out..
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    http://www.hptuners.com/forum/showth...797#post238797

    This thread is about this as well. Hopefully he is still working on this. With the simulator it may help in determining the correct offset for the camshaft change.

    Dennis

  5. #5
    Senior Tuner LSxpwrdZ's Avatar
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    Actually the bigger the numbers the later it will finish and the later it will start.

    According to Bluecat's findings it's this formula to find end of injection in reference to crank degrees after TDC compression stroke:

    -784 + ((Boundary + Normal) * 90)
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    Based on this info if the formula is indeed valid with the cam card you could adjust the normal or bountry values to adjust for the difference in degrees of the intake valve opening from that of a stock cam.

    What about makeup, what's it function?

  7. #7
    Senior Tuner Google's Avatar
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    Quote Originally Posted by LSxpwrdZ View Post
    Actually the bigger the numbers the later it will finish and the later it will start.

    correct.. I had a brain fart.. smells good huh?..

    here is a link to Chris and Greg talking about it in more depth.. but as Greg has pointed out and I have used it for in some applications.. increasing the inj timing will help with raw fuel going streight into the exhaust and causing the raw fuel smell.. this still helps in low end torque as well..


    http://www.hptuners.com/forum/showthread.php?t=18549



    ..
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    Quote Originally Posted by LSxpwrdZ View Post
    -784 + ((Boundary + Normal) * 90)
    I come up with 300.5 when I use my numbers: Normal 5.55 (@ 176° F), boundary 6.50.

    Here is how I did it, tell me what I did wrong, I flunked high school algebra:
    6.5 + 5.55 = 12.05.
    12.05 x 90 = 1084.5
    1084.5 + negative 784 = 300.5.
    2000 GMC 2500 2-bar SD
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    I believe your math is correct. "According to Bluecat's findings it's this formula to find end of injection in reference to crank degrees after TDC compression stroke:"

    Which would make sense.

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    Quote Originally Posted by MikeGyver View Post
    I come up with 300.5 when I use my numbers: Normal 5.55 (@ 176° F), boundary 6.50.

    Here is how I did it, tell me what I did wrong, I flunked high school algebra:
    6.5 + 5.55 = 12.05.
    12.05 x 90 = 1084.5
    1084.5 + negative 784 = 300.5.
    That's just using the stock values right? What does the 300.5 represent? Degrees atdc?

    I understand the need to change the injector timing based on new cam specs but how do we convert the duration/lift/lsa into new injector timing? Maybe I took a dumbie pill today...

  11. #11
    Senior Tuner LSxpwrdZ's Avatar
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    There is no end all be all value for x valve events at least not yet. There needs to be things taken into consideration like air column load as the piston reaches BDC and starts coming back up. Ideally it would make sense to have the end of injection pulse right around or after peak velocity of the intake port to better atomize fuel but that is where different setups need tweaking to find the sweet spot.
    Last edited by LSxpwrdZ; 05-30-2011 at 07:43 PM.
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    Quote Originally Posted by LSxpwrdZ View Post
    There is no end all be all value for x valve events at least not yet. There needs to be things taken into consideration like air column load as the piston reaches BDC and starts coming back up. Ideally it would make sence to have the end of injection pulse right around or after peak velocity of the intake port to better atomize fuel but that is where different setups need tweaking to find the sweet spot.
    So would the best approach for now be incremental adjustments to the "normal" table on a dyno and log the results and changes from that?

    Sweet spot in this instance being tq/hp increases?

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    By the way did you buy Silvers Z06?

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    Quote Originally Posted by LS1Vette View Post
    That's just using the stock values right?
    Yes, nobody has changed them.
    Quote Originally Posted by LS1Vette View Post
    What does the 300.5 represent? Degrees atdc?
    Yes.
    Quote Originally Posted by LS1Vette View Post
    I understand the need to change the injector timing based on new cam specs but how do we convert the duration/lift/lsa into new injector timing? Maybe I took a dumbie pill today...
    I just figured out my seat-to-seat valve timing (actually @.006), my exhaust valve closes at 387.5° ATDC, or 361° @ .050 lift.
    Quote Originally Posted by DrLoch
    I believe your math is correct. "According to Bluecat's findings it's this formula to find end of injection in reference to crank degrees after TDC compression stroke:"

    Which would make sense.
    300.5° would make a lot more sense to me if it were the starting point of injection.
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    Quote Originally Posted by MikeGyver View Post
    Y
    I just figured out my seat-to-seat valve timing (actually @.006), my exhaust valve closes at 387.5° ATDC, or 361° @ .050 lift.
    How did you determine your seat to seat?

    Can't you determine seat to seat using the cam card data?
    Last edited by SargeZ06; 01-03-2011 at 07:31 PM.

  16. #16
    Senior Tuner LSxpwrdZ's Avatar
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    Quote Originally Posted by LS1Vette View Post
    By the way did you buy Silvers Z06?
    No I didn't... I don't know who bought it. Was a stout running car for sure though.
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  17. #17
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    Quote Originally Posted by LS1Vette View Post
    How did you determine your seat to seat?

    Can't you determine seat to seat using the cam card data?
    What I should have said was "I put my advertised duration into the cam manager in my DynoSim5 program, so that I could see where the valve timing events happened".
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  18. #18
    Advanced Tuner MikeGyver's Avatar
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    Quote Originally Posted by MikeGyver View Post
    300.5° would make a lot more sense to me if it were the starting point of injection.
    Also especially it would make more sense since my intake valve begins opening at 332° ATDC.
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  19. #19
    Senior Tuner S2H's Avatar
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    so would it be safe to say that you could just do some backwards math and move injectors back that far?

    like old cam/new cam Intake valve opening difference...
    lets say stock ls1 = opens at [email protected]
    my current cam = opens at [email protected]
    Difference of 26* (26/90=0.29 rounded)
    move back the injector timing using the "Normal" table by 0.29
    so it makes it 5.26 instead of 5.55
    move the Makeup table by the same amount?

    safe starting place to guess at still spraying the back of the valve like GM does from the factory?
    -Scott -

  20. #20
    Advanced Tuner MikeGyver's Avatar
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    I don't get it. It is desirable to spray the injector only when the valve is closed? ...(?)!
    2000 GMC 2500 2-bar SD
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