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wiring tacho
luke2152 - 17/6/14 at 11:26 PM

Have a small 'universal' cheap tach from ebay. It is 4 wired (-,+,lamp, signal). Comes with no instructions. mk1 MX5 engine. Where should I run signal to. I'm guessing not straight to HT leads. One of the coil wires maybe? Or perhaps off the cam angle sensor?

snapper - 18/6/14 at 04:50 AM

luke2152 - 18/6/14 at 11:02 AM

Thanks. But do I need to take the signal off both coils? I take it the diodes are to stop the needle jumping around?

r1_pete - 18/6/14 at 11:56 AM

quote:
Originally posted by luke2152
Thanks. But do I need to take the signal off both coils? I take it the diodes are to stop the needle jumping around?


Yes, you need to take a feed from each coil pair, in a 4 cyl setup you need two ignition events per revolution.

The diodes are to prevent cross firing the coils.

Smoking Frog - 18/6/14 at 12:31 PM

If using MX5 ECU it has a signal wire for the tachometer.

Edit
Hang on, I think it comes from the igniter not ECU. Pin D yel/blu wire.

[Edited on 18/6/14 by Smoking Frog]

luke2152 - 18/6/14 at 12:47 PM

Could just set tach to 2cyl and use one coil and just the zener diode? Im using megasquirt but didn't make the internal links for tach if i remember right so ill just go off coils

[Edited on 18/6/14 by luke2152]