Tachometer With Aftermarket Ecu #2

[petert 550]

Some time ago I posted a circuit from Haltech on how to add multiple coils to fire a tacho. This circuit does not unfortunately work with a 205 tacho (it does with a 405 tacho however). Around the same time I purchased a tacho adpator from MSD. As it turns out, the tacho adaptor is just one side of a transformer. So this got me thinking. All one has to do is use the Haltech circuit to fire a standard 205 ignition module, which in turn connects to the secondary side of a small 240/12V transformer. You'd cut the primary wires off and tape them up so you didn't zap yourself accidently. The standard 205 tacho attaches to the output of the ignition module as normal.

[James_R 3]

Sounds interesting, as I'm about to move to a coil pack set up, and was hoping to just take a feed off each coil add some resistance and rectifiers, but you're saying this doesn't work.

 

Can you do a rough diagram of what you've just mentioned?

 

James

[petert 550]

See attached. The transformer could be replaced with the MSD 8910 tach adaptor. They're approx. $60.

 

http://www.msdignition.com/pdf/8910_tach_adapter.pdf

[B1ack_Mi16 67]

Anyone know if the Haltec method works on the BX 16v clocks?

I have those to go in my 205 with Emerald management.

 

Couln't really understand that last drawing of yours there petert.

You need to get the ignition module into busienss too?

 

Emerald has built in ignition module, so my wires are supposed to go directly to the wasted spark coil...

[pug_ham 240 3 Cars]

Kristian, doesn't the Emerald send the rpm from the ecu?

 

If it does I'm hoping a rev counter mod like I've done here for the Motronic & 8P systems will work on that. I've yet to test this but will post once I have done. (might be a while).

 

Graham.

[petert 550]

Couln't really understand that last drawing of yours there petert.

You need to get the ignition module into busienss too?

 

Yes, there's an extra Bosch ignitor (ignition module) used just to fire the dummy coil (transformer).