Fabio421

I haven't ordered the knock sensors yet so I don't have one to use as a reference. My question is this. How many knock sensors can be fitted to an early engine block? There are two locations in the early blocks just like the later ones, but the rearward one appears to be covered by the "U" going into the throttle body. Is it possible to fit two or will I only be able to use one? FYI, this is for my Megasquirt build.

Thanks

123quattro

One should work just fine. You don't have the processor/signal conditioning power to make use of the benefit of a second one.

davek9

On the 85/86 32v, one in the front hole.
You will need to replace the block plug with a threaded one for the sensor bolt or you can remove, drill&tap the one that's there.
Like John said one is all that's needed to detect knock, I followed PorKens install.

Fabio421

On what are you basing this assumption? The way I read my literature, it shows that I can use two sensors with the MS3x. I'm not asking because i'm trying to challenge you. I'm asking so that I can learn if I'm wrong.

Thanks

123quattro

Knock sensors are piezo electric devices. When a cylinder knocks there is a huge pressure wave in that cylinder bouncing around. That wave in turn rings the block like a bell. For knock sensors to work well you want to be sampling the sensor only when you are around a firing event in a single cylinder. You also want to be filtering the sensor to only look at signal generated around the frequency that a knock event has output. I doubt a MS controller can really do any of that, but maybe? Someone could easily implement some code to do that, but then you need real engine knock data vs sensor output.

Having two sensors lets you either do better bank to bank or front to rear depending on where they are located. You probably can't do any signal conditioning to optimize the knock sensor output vs which cylinder is knocking so having a second sensor won't gain you any resolution.

RCinXS

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