I'm hoping this might help somebody eventually. I started my ABZ 4.2 project with a small 60-2 wheel mounted to the front pulley using the original Audi 90 (v6) flywheel sensor. It worked well with wasted spark for some years. Later, I decided to replace the sensor with one from a 1993 BMW 325i because I had a new one in a box of random parts acquired. After this and a bunch of other modifications, the car was very difficult to start, would backfire and my trigger recordings showed many errors. Due to other factors I elected to get a TTV racing 60-2 flywheel for the engine. Well, when assembling the new crank trigger setup, I discovered something I NEVER would have without the flywheel switch. The original Audi sensor magnet is a small diameter cylinder (inside the larger casing). This worked well with the small teeth on the 60-2 disc. However, the BMW sensor magnet is oblong and, in fact, the magnet was the same width as the 60-2 disc teeth and I had it oriented so that the magnet was bridging the gaps between the teeth longways. DOH! The engine would never have had a good signal. Even with the much larger teeth in my new flywheel, I was still careful to orient the magnet crosswise to the teeth. The result is a very large difference between the missing tooth and background and no errors at all. So, if you are using a 60-2 wheel, pay attention to the shape and orientation of the CPS magnet.
