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Thread: Knock threshold

  1. #1
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    Knock threshold

    I'm trying to re-calibrate knock threshold on a 2.4 swap and I'm going crazy trying to figure this out.
    Seems as though the cal isn't reading the knock threshold table.

    I'm running a 2.4 with a 88 SMEC, dizzy adapter, etc. Using the 88 knock sensor in the stock 2.4 location with teflon tape around the threads and using the 2005 knock sensor as a listening device to determine actual knock.
    Cal is the base 2.4 with only some minor fuel and knock threshold tweaks. Engine is a 2005 2.4 with Arias dish style forged pistons.

    Just got back from a logging run and have noticed the following:
    RPM: 4629
    Boost: 9.3
    Engine temp: 161
    Charge temp: 83
    AFR: 10.15
    knock voltage: 0.7
    ADV: shows -40.5

    #4 shows knock retard of between .5 and 2*

    The crazy thing is that at that RPM in the the knock threshold table, the knock voltage is 2.84v

    What am I missing?
    Last edited by player1up; 03-18-2019 at 09:48 PM.

  2. #2
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    Re: Knock threshold

    I also verified that the knock threshold is being set correctly in the cal by actually logging knock threshold in MPScan and when it "sees" knock, the knkv is WAY below the threshold.

  3. #3
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Knock threshold

    id get rid of the teflon. the sensor body grounds the sensor.

    then log knock volts and rpm at your lowest boost setting. ride the brakes in 2nd gear to increase load and slow down the rev rise so you get more samples. put in super conservative timing values. put in race gas or torco accelerator to prevent actual knock. then you can reshape the knock threshold curve to your actual combo.

    Brian.

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  4. #4
    Supporting Member Turbo Mopar Contributor A.J.'s Avatar
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    Re: Knock threshold

    When I was running my 2.4 with a SMEC I drilled and tapped a spot in my intake manifold for the knock sensor between cylinders 2 and 3 like Chrysler intended on the 2.2/2.5 and I didn't have any problems. When I went Megasquirt I put a factory 2.4 know sensor in the block in the factory location and tuned my own knock table with a listening device I built.

  5. #5
    Supporting Member II Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Knock threshold

    Quote Originally Posted by A.J. View Post
    When I was running my 2.4 with a SMEC I drilled and tapped a spot in my intake manifold for the knock sensor between cylinders 2 and 3 like Chrysler intended on the 2.2/2.5 and I didn't have any problems. When I went Megasquirt I put a factory 2.4 know sensor in the block in the factory location and tuned my own knock table with a listening device I built.
    You mean you mounted it right into the intake manifold flange?
    Jon J.

    1989 Daytona ES 2.4L DOHC
    2003 Neon SXT - gone but never forgotten

    Can't polish a turd? Sure you can! Just don't reuse the rag afterwards, dummy!

  6. #6
    Supporting Member Turbo Mopar Contributor A.J.'s Avatar
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    Re: Knock threshold

    Quote Originally Posted by jonnymopar View Post
    You mean you mounted it right into the intake manifold flange?
    Yes. If you go to this thread: http://www.turbo-mopar.com/forums/sh...ler&highlight= post #8 has pictures.

  7. #7
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    Re: Knock threshold

    Thanks guys, I will be moving it to the intake.

    What still doesn't sit right with me is that the knock threshold in the cal isn't being read correctly.

  8. #8
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Knock threshold

    Quote Originally Posted by player1up View Post
    Thanks guys, I will be moving it to the intake.

    What still doesn't sit right with me is that the knock threshold in the cal isn't being read correctly.
    it could be that the knock volt spike that triggers knock retard is so fast that it blips up, triggers retard, and goes back down fast enough that it doesnt log the actual voltage value.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  9. #9
    Supporting Member Turbo Mopar Contributor A.J.'s Avatar
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    Re: Knock threshold

    Quote Originally Posted by player1up View Post
    Thanks guys, I will be moving it to the intake.

    What still doesn't sit right with me is that the knock threshold in the cal isn't being read correctly.
    I'm a professional mechanic and I've been burned many times overlooking the obvious. Chrysler wrote the knock table to be read through and intake manifold and through a gasket. You streamlined the signal by moving the knock sensor to the block. If you move it to the intake like I did and your problem is solved, great. If not, at least you have more information to work with than you had before.

  10. #10
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    Re: Knock threshold

    Quote Originally Posted by A.J. View Post
    I'm a professional mechanic and I've been burned many times overlooking the obvious. Chrysler wrote the knock table to be read through and intake manifold and through a gasket. You streamlined the signal by moving the knock sensor to the block. If you move it to the intake like I did and your problem is solved, great. If not, at least you have more information to work with than you had before.
    Thanks AJ, I'm beginning to think there is some other factor that contributes to the reading, like possibly a knock counter or a knock voltage delta. The assembly file has some odd comments about knock code being tied to some other code and references a knkcnt value that's only in the file once....I'll have to wait as the engine is back apart due to ARIAS shipping the wrong rings for the pistons and me not catching it...so mad at myself for that. ( oil ring pack was the wrong thickness )

  11. #11
    Supporting Member Turbo Mopar Contributor A.J.'s Avatar
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    Re: Knock threshold

    Quote Originally Posted by player1up View Post
    I'll have to wait as the engine is back apart due to ARIAS shipping the wrong rings for the pistons and me not catching it...so mad at myself for that. ( oil ring pack was the wrong thickness )
    I just went through the same thing to get rings for my 2.4. It took two parts stores and three tries to get the correct ones.

  12. #12
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    Re: Knock threshold

    Quote Originally Posted by A.J. View Post
    I just went through the same thing to get rings for my 2.4. It took two parts stores and three tries to get the correct ones.
    I was so worried about bolt torque and ring gap placement that I just overlooked it...stupid and costly mistake for sure.
    I don't want to say that's funny, but I found out that the Arias 3120000 pistons for the 2.4 use the same ring pack as the 2.2..
    1.5mm compression rings and a 4mm oil ring pack.
    Some manufacturers use the stock ring sizes ( 1.2mm, 1.5mm compression rings and 2.5mm oil ring packs ) and there's at least one that uses stock compression rings with a 2.8mm oil ring pack

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