Knock sensor placement

Just received a very interesting knock sensor/controller kit from SafeGuard. They are “semi-custom” in that the kits all share the same basic hardware, but the owner and software developer (same person, an electrical engineer) customizes each kit for a specific car. Actually found it on a bimmer forum, and apparently it’s been in successful use for over 20 years. Virtually the only complaints about it were about the price.

When the sensor detects knock it knows which cylinder just fired, and will pull timing in either 1 or 2 degree increments (user sets this) on that cylinder next time it fires. It can do this for multiple cylinders with up to 10/20 degrees retard depending on user settings. Then it adds timing back in at 1 or 2 degrees and keeps it below the knock threshold for a single cylinder or all of them. I still haven’t installed it because the car just had the fuel cell installed, and there are a few other mods I want to make that need access to the firewall before the engine goes back in.

Anyway, the company owner insists that one knock sensor is sufficient for both banks, and the BMW guys confirm this, even those few with V-8 or V-12 engines.

So I am wondering where to install the sensor. It’s a regular Bosch donut style. The ideal place is on the block just below the head, and it uses an 8mm bolt (although can use a 10mm if necessary). To adequately cover both banks I’d prefer to install it on the inside of the V.

Has anyone else installed an aftermarket knock sensor? If so, what is the ideal location? I’m a bit worried that with such a wide angle V on this engine sounds may not transmit well from every cylinder. The other option is to buy a second kit and install one sensor on each bank, but that is a PITA.

So if anyone has gone to an aftermarket system (Motec, Link, Megasquirt, etc.) kindly let me know how many knock sensors you used and where you put them. Many thanks and I hope you are all well. Stay safe.

Have you asked the manufacturer, themselves?

Found this.

Thanks Paul. Yes, of course I asked the developer/manufacturer. But like 99.999% of the world, he has never seen an XJ 220 motor, so that was the best advice he could give me. Also looked at the Plex unit, but it’s CAN BUS which obviously isn’t in the XJ220. The Safeguard Vampire unit can be hooked up to coil negative and ground to get cylinder firing signal, and to the sensor. Very simple layout.

I remember reading somewhere, that a knock is a knock is a knock, almost irrespective of the engine that makes it.

That’s what I was heading for: sorry for not making that clearer. Were it me, I’d mount it in one one of those places, and see if it picks up any detonation. On a rolling road, one could sneak up on it.

Well, we’ll have to see what happens when we finally get it to the tuner and can run it up slowly. At this point I have no idea when that will be. But the car may as well spend the winter at the shop’s storage facility, as I have no room in my garage anyway. Stay safe.

Steven Solomon

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