This may be crude science, but---a few years ago, out of curiousity I clamped a Volvo knock sensor into a vise and proceeded to tap the vice with a hammer with the knock sensor hooked up to a digital multi-meter--the knock sensor was producing from a half to a full volt under those circumstances. There are a few sometimes unused threaded bolt holes in the B20 block/head where a knock sensor could be attached--might be worth a try. -- Dave