Autosport Labs

This would be no different than a properly made home-made diode circuit.

Could you describe your problems? Does it always read low RPMs? If not, does it read exactly 1/2 RPMs when it's exhibiting the problem?

hello Brent,

Tach was efficient for a few weeks but the problem became more consistent over time. but yes..reading is consistently low now.

below is how I did my circuit.

is it possible the diode is shot? anyone?

We're not familiar with that circuit design- it's different than what we have, but it seems that it could work. You might want to check connections on the diodes - if all connections are good it's possible one of the diodes might need replacing. Replace both just to be sure.

Make sure you're using diodes rated for at least 400V - like a 1N4004 or equivalent.

found a short in the wiring which subsequently affected the tach to be lazy. All is well now. Thanks Brent.

Good morning, before attacking my wiring loom, wanted to check where to place the circuitboard i just recieved. Im running a v6 with wasted spark and an after market ecu - Vi-PEC (the same as link). My tacho is a standard Ford one and expecting the 400v, but the aftermarket ecu only puts out 12v.

Understanding the circuit board needs the 3 pulses, but does it need the 3 pulses from the ecu (low voltage) or the 3 pulses after the ignition amplifier that go direct to the coils?

Many thanks

Hello,

The board is designed to tap off of the drive lines for the coil packs - after the ignition amplifier you have.

Worked a treat thanks

That's great to hear! Thanks for the feedback.