oem tacho incorrect
 

i have tried using the standard connection from the secondary coils and the tacho only works above 5000 rpm, below this the tacho hovers around 0.
i have now hooked up the tacho to the primary coil via the microtech and it works properly but near 1000 rpm out, can anyone help? is this common?

Anyone else get hungry after reading this thread? What car are you working on then we could help some more. All the tachs ive seen are based off the Trailing coil FYI.

yeah sorry its a 1991 rx7 t2 with a lt8 microtech.
the laptop shows that the microtech rpm is ok but my car tacho is wrong. ive tried a new tacho,
i have now got the tacho feed inlined with microtech wire that goes to the primary coil

THE TACH WIRE DOES NOT COME FROM THE COIL PACK

on a TII you must get it from the trailing ignitor.

the YELLOW WIRE coming from the ignitor is your tacho feed.

get back to us tell me how you go

yes at first i hooked the tacho to the yellow wire from the trailing coil pack but the tacho will not move till about 5000 rpm, then it becomes accurate,
on hooked up to the primary's the tacho is sort of accurate but around 1000rpm out