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knock sensor on an L series


spdcrazy

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specifically, an L20b. Is there a way to simply add a knock sensor to a dummy light on the dash to help identify detonation?

 

I understand the basic workings of a knock sensor, so I don't believe one can just buy a knock sensor and randomly place it. any thoughts on this?

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It's not something I would ever consider doing, but why not?

 

The sensor has to be in the block, but I don't think it should be exposed to water. You could use one of the extra motor mount bolt holes and drill/tap it to fit the knock sensor.

Too low on the block. It won't sense detonation.

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Years ago in what seemed like a previous life (about 18 years ago), I used a detonation sensing system when tuning race jet ski engines. These were three cylinder 2-strokes with individually tuned chambers. At around 1150cc, these made about 220 horsepower on pump fuel. Since there was no transmission, they had to make power throughout the powerband. However, to make them reliable, I used a detonation sensing system that uses piezo sensors mounted underneath the spark plugs, replacing the washer. Spark plug torque was extremely critical. The control unit uses the piezo sensor to "listen" to frequencies (pressure changes) associated with detonation. The detonation threshold was adjustable and would activate a light (or give me voltage values when on a dyno) to indicate the detonation met the threshold. I learned that a certain amount of detonation was actually desirable, yet still not be destructive.

 

I  have not worked with these systems in some years, but here's something I found doing a quick google search that shows what the sensor looks like.  http://www.gtrlife.com/forums/topic/46194-spark-plug-combustion-pressure-sensors-for-tuning/

 

Though this article was written for the jet ski crowd, Kevin Cameron is a semi-famous technical writer in the automotive and motorcycle world. Detonation principles are still pretty much the same.

http://factorypipe.com/t_deto.php 

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I once picked up a '85 Toyota 4x4. that needed an engine. for cheap. I found an engine from a '84 and proceeded to intall it. Come to find out the '85 had a knock sensor and the '84 did not. I just picked up a brass union with the correct threads and JB welded it to the block in pretty much the same spot as the original. It didn't even notice at all. 

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