Knock detection and control

[BigBlueIron]

Anybody have any experiences good or bad with this product http://www.jandssafeguard.com/safeguard.html Or anything for knock detection? Or am I overthinking it.

[jayb]

I tried one, couldn't get it to work right on any dyno engine.  I was pretty disappointed with it.

[RustyCrankshaft]

I have not tried that particular product. But I have done a few swaps of OEM injected engines that have knock sensors. Most "performance" engines has configurations that cause harmonics that the knock sensor sees as a combustion event and gets confused. If it's a mild case you can sometimes tune around it, but in most cases I've just tuned the knock sensors out all together.

[WConley]

+1 on the above comment.  At Ford, we had to tune the knock sensor for each engine.  Even if you moved the sensor on the engine more than a little bit, no more workie!  Sometimes we had to search hard to find a spot on the engine with a clean signal.

A knock sensor is basically a tuned resonator with a coil attached.  Electronics guys would call it a "band pass filter".  You're looking for a particular telltale frequency in a sea of noise.

I'd be very skeptical of a one-size-fits-all product.

[RustyCrankshaft]

It's amazing what the signal looks like just moving the sensor a few inches one way or the other! It was on one of those other engines (SBC) that I was using a lot of OEM EFI stuff on but it was a solid roller engine and just changing valve lash tighter or looser would make a difference. I think making a knock sensor work on a typical street/strip build is possible, but I don't think the reliability and the gains are worth the hassle. You could spend the afternoon on a chassis dyno or at the track with a laptop and get better results for preventing "unwanted combustion events" I think.