installing a tach

[Jon Davis]

Enoch Chow wrote:

> the archives say the pin coming out of the ecu to the stock tach is
> different than for an aftermarket. why is that? and how come i can't hook
> them up together? would i still get interference if i tap into the pin
going
> into the ecu from the distributor? thanx!

The output at the pin may be different, I've never looked at it. I'll try to
look at it tomorrow. Most tach signals are just a pulse train that varies
its frequency vs. rpm. For noise considerations, it would be better to tap
into the wire at the ECU... under the hood is a pretty noisy place. If you
can't use the tach output from the ECU, use a shielded cable if you can find
one, keep the wire short and keep it away from other wires, especially the
stuff for the ECU or any CB radios. If you use a shielded cable, ground the
sheild only on one end, preferably the same place the shield for the angle
sensor is grounded (looks like pin 48, black wire on my diagram).

Jon Davis