Hearing Spark Knock

[RAVC1]

Many are concerned about the presence of spark knock under boost so I thought I would provide the forum with a useful means of hearing spark knock before it becomes a problem.

Soft copper tubing (meaning the kind you can bend with your hands) works as an excellent transmitter of audible spark knock to the passenger cabin. 3/8" diameter tubing should be sufficient for these purposes. Here's what you'll need to do:

1. Squeeze one end of the copper tube in a vice or an arbor press.

2. You'll need to experiment to determine your best engine mounting location. This is often a bolt boss on the block or similar location on the cylinder head. Secure the flat tubing section to its mounting location well. A loose bolt will not transmit a good signal.

3. Route the copper tube from the engine bay into the passenger cabin WITHOUT CONTACTING ANYTHING; particularly the unibody. Grounding the copper tube in this manner will degrade the level of the spark knock you here via the tubing. If you decide to drill a hole in the firewall or floor board in order to get the tubing into the cabin be sure to use a rubber grommet to surround the tubing.

4. If you have the sqeezed end of the tubing mounted to a good location on the engine it will not matter where the open end of the tubing is located in the cabin; you will here audible knock! However, if you're working in the vehicle by yourself make the location convenient so you can concentrate on driving not on listening to the tube.

5. You'll need to learn the sound spectrum of your engine to determine knock from valvetrain noise, etc. Maybe a recording is useful? Perhaps using the laptop because then you can see the sound spectrum the engine generates.

You should find this method inexpensive yet useful.

Rick

[Yellow2]

Very cool. I used this same method to locate which of my valves was tapping by placing the tubing around the valve cover bolts and using a piece of copper tubing. It was very aparrent that the #1 Cyl Ex. valve was tapping and needed to be fixed.

Do you have any pictures of you doing this on your car? It might be alittle confusing for some people.

[RAVC1]

Yellow2,

Sorry, I've never instrumented an M30 in this manner. I just know the technique.

Rick

[Shawn D.]

1. Squeeze one end of the copper tube in a vice...

What vice? Liquor, drugs, or wanton women, maybe. Using a vise might be more effective!

[RAVC1]

Okay Shawn,

I stand corrected. However, for the record I'll take the wanton women. I've always admired the kept man thing!

Rick