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Thread: AMC 401, How do I pick a knock sensor?

  1. #1
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    AMC 401, How do I pick a knock sensor?

    Configuration: AMC 401 (.030 over), slight cam, port matched heads, edelbroke intake, 454 TB, 16197427, $OE, BIN=BMHK, using TunerPro RT, and a Burn2

    Right now my system has a standard 4Kohm knock sensor I bought at McParts (I don't remember the application but I have the part number on the receipt so I could find out) mounted to a grounded bracket behind my dash. I would like to hook up a knock sensor to my block so I can tune my timing a bit better. I have read that a knock sensor is "Tuned" to the block. What does that mean? Can I use any GM 4kOhm Knock sensor that will screw into my block? There is a coolant passage on the side of the block that I think will work. How do I pick the "correct'est" one?

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    The knock sensor is tuned based on the bore diameter of the engine. Thus, pick the engine with the bore diameter closest to yours.

    Untuned knock sensors are also out there, and will require a knock filter tuned to the bore diameter of your engine. Basically, knock is identical to a musical note, and as such has a specific pitch. Pitch is based on the diameter of the cylinder, so we can cut out a LOT of false knock signals by only listening for the pitch that would be generated by a detonation event that causes the cylinder to ring.

    The location on the block, high/low/left side/right side/front/rear is mostly to avoid sounds that make it through the filter or are in the same range as the desired signal, or just loud sources that overwhelm the filter totally.

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    That makes sense. My bore is 4.195. 454 is 4.250, 350 and 4.3 are 4.00, so probably the 454 would be best?

    I assume the advantage of the untuned knock sensor is that it can be tuned for my bore, right? Are they "alot" more money? I think I paid $25 for my knock sensor so if a better untuned senor and knock filter is $50, that's worth it to me. but if an untuned knock sensor and knock filter are $200, I will run a 454 sensor....

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    NAPA lists only 2 stock knock sensors... 1 for auto.. and 1 for manual..

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    Interesting read when deciding which ks... http://www.gearhead-efi.com/Fuel-Inj...5-all-the-time

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    I'm using a single KS on my 454 BBC because I can't find anyplace on driver's side for the second one - don't know if you have this issue or not. Since these are the single wire type and the 0411 PCM is looking for two of them can I fool the PCM by running both leads from the PCM to the same sensor or can I turn off one sensor in the tune? Engine not running yet so can't just try something and see if it works. -Bob

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    I'm running with a single knock sensor, it's just not in the block yet. My computer seems happy with the one input. I asked about knock sensors in the past (here: Link Jeep-401-16197427-OE-what-do-I-do-about-a-knock-sensor-Getting-code-43 ) when I was troubleshooting.

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    Quote Originally Posted by BBPanel View Post
    I'm using a single KS on my 454 BBC because I can't find anyplace on driver's side for the second one - don't know if you have this issue or not. Since these are the single wire type and the 0411 PCM is looking for two of them can I fool the PCM by running both leads from the PCM to the same sensor or can I turn off one sensor in the tune? Engine not running yet so can't just try something and see if it works. -Bob
    For an 0411 you can select 1 or 2 knock sensors and which type in the programming.
    1995 GMC K2500 SUBURBAN 2001 LB7 DURAMAX/ALLISON swap, mostly stock, tuned by me with EFILive

    1999 Tahoe 2 door 2X4, 5.7l with 0411 swap, and marine intake

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    Quote Originally Posted by THEFERMANATOR View Post
    For an 0411 you can select 1 or 2 knock sensors and which type in the programming.
    I knew I could pick type but don't recall being able to specify 1 or 2 - I'll have to look again. I started to use the 2-wire flat response KS but wasn't sure how to wire/pin it on a single-wire harness. I thought I might be able to use the two 1-wire leads on the 2-wire KS and re-pin one of them to ground but not sure it would work so I got the 1-wire p/n 10456232 (Std KS50) for 7.4L L21/L29 blocks. I have mounted it on a brass 45-deg fitting so maybe its impact on timing will be minimal. Interesting comment(s) on the 4kohm - I'll have to see what mine reads.

  10. #10
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    The 4k ohm knock sensor is for the 7427 ecm. The 0411 uses a 100k ohm knock sensor. You have to match the knock sebsor to which engine, single/dual knock sensors, separate knock module or integrated, and so on.
    1995 GMC K2500 SUBURBAN 2001 LB7 DURAMAX/ALLISON swap, mostly stock, tuned by me with EFILive

    1999 Tahoe 2 door 2X4, 5.7l with 0411 swap, and marine intake

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