Knock sensors for M20 turbo/megasquirt

[fergie]

Ive been contemplating the idea of knock sensors for my m20 turbo, as I would like megasquirt to control knock if it were to happen.

Ive searched and searched, and have not found anything for if someone has ever done this before. So Im asking to see if anyone here has ever done this?

My biggest concern is there doesnt seem to be a threaded location on the block of an m20 to install 2 knock sensors, thats my biggest issue.

My tuner who I will be going back to for an ignition table adjustment said they can tune and listen for knock on the dyno, but for safe measures as Im running pump gas it is highly recommended for me to install knock sensors, since megasquirt can operate them.

[nomansland92]

I use knock control on my m20 theres a threaded boss under the intake that works great.

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[fergie]

Care to elaborate? Does that mean you're only using 1 knock sensor in the middle of the block?

Also are you using a generic knock sensor, and did you have to calibrate the sensor to the engines bore diameter etc?

[nomansland92]

Ya just one sensor, I calibrated the frequency with the bore diameter then used knock ears to find the center of the frequency. Im not using megasquirt but its the same prinsible.

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[downforce22]

what sensor are you using and what settings?

[nomansland92]

what sensor are you using and what settings?

Just a bosch 3 wire, can't remember the frequency off hand but I'm a 2.8l anyway.

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[e30davie]

The frequency of the knock is dependent on piston diameter,

http://www.phormula.com/KnockCalculator.aspx

Years ago i made some DIY "knock ears", which was a nissan 2 wire knock sensor (ie a microphone), connected to an amplifier with a headphone jack.

How good is the signal conditioning of the megasquirt? A quick google suggest you have to add a signal conditioning board, like so

https://www.diyautotune.com/product/ms3-knock-module-kit/

reckons the bandpass is prorgammable, so you can program in the knock frequency from above. but not sure exactly how you program that board :S

[fergie]

So Im going forward with knock sensor install on my M20. Since that threaded boss on the m20 black is m10x1.5 I was able to install a HeliCoil to bring it down to an M8x1.5 to install a N63 2 pin knock sensor.

Ill be wiring it in possibly tonight or tomorrow and hopefully have it working before the e30 picnic.

[downforce22]

please keep this updated, I would love to install a knock sensor on my turbo.

[fergie]

So the knock sensor is installed and wired into megasquirt. I can plug in my headphones to the mspnp2 and listen for knock although there is alot of feedback from the valvetrain, so i suspect i will have to adjust the gain sensitivity.

I know the knock sensor works as i can tap on the block and pick up the audible sound of the knocking through the headphones.

[e30davie]

Did you set the knock frequency into the ecu somehow?

[DesertBMW]

Ive been contemplating the idea of knock sensors for my m20 turbo.

1986-1991 Saab 900 turbo, uses a stand alone boost regulating system that listens to the knock sensor and regulates boost according to the knock. It is called APC(automatic power control). You can install the system in your E30. APC brain box has potentiometers where you can adjust the sensitivity of the knock. There is also an LED light output where it will flash if it senses a knock. Very reliable and simple system, that you can buy for cheap. But I can only imagine this would be a hassle for you

[fergie]

anybody have any info on how to setup the knock sensor? Im still trying to figure it out.
It appears to be getting 5 volts all the time, as when the engine running the knock frequency is at 100%, even tho the engine is just idling and confirmed to not be knocking.

[mr2peak]

http://www.viatrack.ca

By far the easiest way to get a knock sensor running with MS.

http://www.megamanual.com/ms2/knock.htm

[ForcedFirebird]

I have found the m20 will knock far after MBT.