Tacho Problem with Apexi Power FC on an EVO

[Sean1933]

My friend has just bought an Apexi Power FC for his EVO 3. We plugged it in last night and took it for a drive on the base map to see how it was, obviously monitoring AFR, etc.

 

The problem that seemed to arise was that the Tacho decided to not work until running at over 4000rpm, when it registered. As soon as you let off and/or fell below 4000rpm the Tacho stopped registering. I have checked on the FC Commander and it is showing the revs on there correctly, and obviously it would not know where to look on the maps if it did not know the rpm so it would not run right. There are no faults showing on the ECU (engine warning light).

 

What weired is that as soon as you plug the standard ECU in it runs fine. This makes me think that its the ECU Wiring harness that is wrong, but my friend says its def the right one. If it was the harness then the ECU would not know the rpm, and why would the Tach only register over 4000rpm??? Any ideas cause its driving us nuts and we cant progress until this is sorted as we can datalog with the LM1 either as that is tapped into the Tach wire (i have tried it without this connect but makes no difference) so it reads the same as the Tach...wrong!

 

HELP!!!

[Tricky-Ricky]

OK i'll have a go, it would be worth a check on the EVO forums if you haven't already, as i know on the 200SX PFC when using on the S14a two or three wires need to be changed so its a possibility that its picking up then wrong wire for taco, but the strange thing is the commander is showing full RPM?

Try putting a meter on the taco output wire, although it should be a pulsed signal it will read as a steadily rising voltage.