..I've swapped my engine to a smallport GZE with DLI running an aftermarket Omex ECU, it's supposed to be turboed but the less said about that the better for the time being!
I noticed today that the tacho is being somewhat erratic.
It kind of works, with the car idling it'll sit at 1000rpm, when I rev it it seems to behave up until about 2-3000 rpm then it develops a mind of its own and either stutters, drops to zero or occasionally tracks engine speed properly. I've noticed that pressing the brake pedal makes it more likely to behave (guessing that the load from the brakelights is doing something to help). The ECU software only has one option for configuring the tacho output which relates to the number of cylinders, this is set correctly. I also have a racelogic datalogger that takes an rpm signal from the same wire that goes to the dash, this reads correctly at all times.Electronics aren't my strong point
(I can follow simple electrical stuff but struggle to visualise what's going on in a more dynamic electronic circuit.) however reading around it seems that the mk1 tacho is expecting a high voltage 'spike' signal and the ECU is likely to be feeding it a low voltage square wave. So first question is, do my symptoms appear consistent with this diagnosis or is there likely to be something else going on?Assuming that's the problem, it seems there are a variety of fixes including various signal boosters etc either bought off the shelf or assembled from parts however I've also seen suggestions that you can modify the stock tacho by changing one or more resistors on the tacho board.
As I've got a spare set of clocks here I can butcher I figured that modding is the way forward however every mention I find of this links somewhere else for the details and they're all dead links. So has anyone got the details on what modifications I need to make?
