3.6 conversion tach question
 

Progress on my conversion is moving ahead slowly I should have most of the cooling done this weekend. I seem to have a problem with the tach though. When the car is running at idle the tach works fine and if I apply steady pressure to the throttle the tach needle won't go past 4200 rpm althought the engine continues to rev. If I blip the throttle hard the tach stops at about 4200, goes to zero, then shoots past 4200 to where it is supposed to be and then goes back to idle. Do I need to go to a later model tach. The engine is a 95 993 non VRAM and the tach is original from a 1981 SC.
Thanks,
Manny

I assume you are not using a conversion harness. In the conversion harness, from Patrick Motorsport, it has a voltage amplifier because the earlier tachs require more voltage then the 5 volts the 993 DME puts out for the tach signal.

Maybe try taking the old tach wire and extend it to one of the coil + leads. I tought about doing this also but have not tried it yet. I dont see why it would not work.

I had the EXACT problem. Ended up switching to a turbo tach (unknown year) from a parts bin and it works fine. Maybe requires lower voltage?

yes, the later tachs require less voltage. Just try running a wire to the coil like the original tach was connected. Let us know of it works.

My '81 Tach works perfect and I made my own conversion harness w/o an amplifier.

Okay, let me make sure I understand this. Connect the old tach lead back to the tach and run the other end to the positive on one of the coils? I find that the problem is intermittant. Sometimes there is no problem and other times it sticks.

Slightly OT, but close: I have a Eurovario 3.6 (1996 I believe) in my '88. The stock tach works fine. However, I am not sure what the redline for the new motor is. If it is higher than the 3.2 it replaced, I might have my tach redone with a new redline. Does anyone know the redline of that motor?

Thanks

yes, it could be a voltage issue.

Got it, thanks.