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  1. #1
    WannaM
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    How does the (anti) knock sensor work?

    How does it avoid knocking? Obviously it can't do anything about the fuel mixture pre-detonating because of reaching its kindling point early, so it must control the ignition timing. Is that what it does?? And how does it calculate the load/cylinder to determine the timing retard?


  2. #2
    Zajo
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    Re: How does the (anti) knock sensor work?

    I am no expert but I think that the sensor simply detects if the mixture detonates early. Then the computer can adjust ignition timing, valve timing, and fuel mixture. These are the parameters that CAN be adjusted, but I have no idea which are the ones actually tweaked. I hope someone has more info on this topic...

    One thing is for sure: this engine is happy with whatever octane you throw at it. :)

    --Zajo

  3. #3
    Karl Seeger
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    Re: How does the (anti) knock sensor work?

    It is a simple transducer that detects a knock. When it does your timing is backed off until it does not detect it again.

    If you tap on the engine with a screwdriver and monitor the timing you can "see" it happen. Pretty simple.

    -Karl

  4. #4
    WannaM
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    Really? Then under high boost, should I install

    one of those "bobbing birds" on the valve cover to retard my timing? Heh

  5. #5
    Karl Seeger
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    "knock" yourself out!


  6. #6
    Pinecone
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    Re: How does the (anti) knock sensor work?

    Pre - ignition and detonation are different things.

    Pre-ignition comes from the fuel air mixture igniting too early. There is little thengine management can do to stop this.

    Detonation occurs after ignition occurs. It can be stopped by retarding ignition, lowering boost on forced induction engines, also richening feul air mixture. With adjustable cam timing it could be controlled with cam timing changes.

    The sensor is a microphone that "listens" for detonation (knock) and then makes changes in the engine parameters to reduce it to an acceptable level (actuallly highest performance is with a small amount of detonation). Most engine management only retards timing. My old Dodge Daytona Turbo Z also reduced boost.

    For adding forced induction, unless you have electronic control of boost, you need to do nothing. The engien will retard timing to reduce detonation.

  7. #7
    Karl Seeger
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    Pre-Ignition = Detonation

    You are correct that Pre-Ignition is the mixture igniting before the engine wants it to. Detonation is the same thing, just a different word to discribe it.

    If the mixture ignites AFTER ignition that is call "working like normal"!

    The transducer (microphone) detects the knock and will back the timing off to counter the pre-ignition. It can not detect it before it happens but it can correct it once it IS happening (and for as long as it is happening).

    If you over boost your engine or run too low of an octane you can STILL destroy your engine since this feature will only work when the engine initaly knocks and backs the timing off until it stops, too much will take too long to correct and will result in destruction.

    -Karl

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