Tach signal

[Christ]

What signal does the OE tach expect to see?

I'm wondering if it takes a single pulse per revolution so I can hook it up to my Briggs engine [provided I use that engine] and still get a tach signal.

[FestYboy]

it looks at the ground signal from the coil and cuts it in half (2 spark events per revolution of the crank) via a filter.

[FestYboy]

ok i was half right: the tach is a glorified volt meter, and the signal from the coil is a variable DC voltage once sent through a low-pass filter. as the RPMs increase, the DC voltage also increases (post filter).

the trick is finding a volt meter that will read a single cyl engine (1/4 that of a 4 cyl voltage output) so either find a smaller scale to work with or one that is more sensative

[Christ]

Yep, I'll just get an aftermarket tach designed for my engine I think.

Thanks for the input.