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Thread: What RPM do you turn off knock sensors?

  1. #1
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    What RPM do you turn off knock sensors?

    At what RPM do you guys turn off the knock sensors to avoid the normal engine interference?
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  2. #2
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    never turn them off
    1998 Turbo M3 Nick G tuned setting 5 934Whp 849Wtq @27.88 Psi. ignite E90 setting 6=

  3. #3
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    Quote Originally Posted by SM3 View Post
    never turn them off
    I thought that too.

    However, from 4000-6000 rpm I can watch my knock sensor voltage move from .0-5.0v with no actual knock registering on the datalog. This is on e85 and 15psi with 17 degrees timing.

    At 6000 rpm when the sensor is at 5v the EMU pulls timing and shuts down the car.

    I read this tuning guide and it's got me thinking.
    KNOCK SENSORS.PNG
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  4. #4
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    Welcome to our primitive knock sensors

    If you intend to use knock sensing up high our blocks are just not good for it. There is a lot of filtering considerations and more modern ECUs are aware of cylinder timing and such or use DSP.

  5. #5
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    Quote Originally Posted by 5mall5nail5 View Post
    Welcome to our primitive knock sensors

    If you intend to use knock sensing up high our blocks are just not good for it. There is a lot of filtering considerations and more modern ECUs are aware of cylinder timing and such or use DSP.
    Understood.

    What is DSP?
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  6. #6
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    Quote Originally Posted by trthrrt489 View Post
    Understood.

    What is DSP?
    Digital sound processing - some standalones will filter the signal more liberally than others. Factory DMEs know exactly the freq to target and with modern processing can target the time window to look at - per cylinder knock. They know when the detonation could occur vs. ordinary detonation so no use just objectively "listening".

    The best solution is ion sensing. Very fascinating if you haven't researched it. Unfortunately, I can't say I have ever come across a perfect solution - even factory my car will pull some timing based on false knock.

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    Quote Originally Posted by trthrrt489 View Post
    I thought that too.

    However, from 4000-6000 rpm I can watch my knock sensor voltage move from .0-5.0v with no actual knock
    I'd say something is wrong somewhere as that isn't normal - if you have a TEC3R like it says in your sig. then the first step would be to toss that door stop of an ECU in the trash and move to something from this past century along with checking/replacing the knock sensors and wiring, and making sure the knock sensors are torqued to spec.

  8. #8
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    Quote Originally Posted by 5mall5nail5 View Post
    Digital sound processing - some standalones will filter the signal more liberally than others. Factory DMEs know exactly the freq to target and with modern processing can target the time window to look at - per cylinder knock. They know when the detonation could occur vs. ordinary detonation so no use just objectively "listening".

    The best solution is ion sensing. Very fascinating if you haven't researched it. Unfortunately, I can't say I have ever come across a perfect solution - even factory my car will pull some timing based on false knock.
    In your experience which units are more user friendly that have the DSP?

    - - - Updated - - -

    Quote Originally Posted by NOTORIOUS VR View Post
    I'd say something is wrong somewhere as that isn't normal - if you have a TEC3R like it says in your sig. then the first step would be to toss that door stop of an ECU in the trash and move to something from this past century along with checking/replacing the knock sensors and wiring, and making sure the knock sensors are torqued to spec.

    LOL, I actually just got another one on Ebay for $250 as a backup.....

    I hear you though.
    Last edited by trthrrt489; 09-08-2022 at 03:10 PM.
    TEC-3R, T4 GT40, WISECO, EAGLE, SUPERTECH, O-RING'D "FRANKENSTEIN" STROKER.

  9. #9
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    Quote Originally Posted by 5mall5nail5 View Post
    The best solution is ion sensing. Very fascinating if you haven't researched it. Unfortunately, I can't say I have ever come across a perfect solution - even factory my car will pull some timing based on false knock.
    SAAB did this with their Trionic EMS. They could tell AFR, knock, burn rate, misfire, and all by applying a high V across the plug gap, post ignition. The ignition coil cartridge was a nice bit of tech with self-contained CDI, but the 'in joke' amongst SAAB owners was how we all kept a spare cartridge in the trunk!
    1989 E30 - M50B28 Turbo - ZF 8 Speed

  10. #10
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    BMW used ionic knock sensing on the S65 in the E90 M3 and the S85 in the E60 M5, but I don’t think they used it in any other motors. If it is so good, why doesn’t BMW still use it?

  11. #11
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    Quote Originally Posted by pbonsalb View Post
    If it is so good, why doesn’t BMW still use it?
    Likely the normal reasons - Complicated and Expensive.

    Either way the point of this thread is that the normal Bosch Wideband knock sensors work perfectly fine when the sensors are good, and TQ'd properly as well as attached to a capable ECU.

  12. #12
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    Quote Originally Posted by NOTORIOUS VR View Post
    Likely the normal reasons - Complicated and Expensive.

    Either way the point of this thread is that the normal Bosch Wideband knock sensors work perfectly fine when the sensors are good, and TQ'd properly as well as attached to a capable ECU.
    Yes, the key being expensive. High strung NA engines that will see 91 octane can definitely benefit from ionic sensing. However, temperamental, expensive, complex, etc., all come in to play, also.

  13. #13
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    Don't bother with knock sensors unless you are going to spend the time to daily in the frequency. You will have to induce knock to know what you knock threshold/window is.

    Sent from my SM-S908U using Tapatalk

  14. #14
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    The Bosch wideband knock sensors work great just be sure to use them with a good coax shielded harness to ensure the ecu is getting a nice clean signal. I always recommend the VE wideband knock kit for cars I’m tuning as it comes with a coax harness you just pin straight to the ecu.
    IMO Motec M1 ecu’s have the most elegant closed loop knock strategies.
    Last edited by tunermt; 09-25-2022 at 07:52 AM.

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