Capri tacho

Abarth · Post by **Abarth** » Tue Jan 24, 2012 10:21 pm

Hi all

I have a Megajolt instalation in a Mk3 Capri fully working, with the exception of the tachometer, I tried to connect to the edis module, but don't work. How can i wire it? A drawing would more apreciated, because my english is horrible.

Best regards

David

Post by **brentp** » Wed Jan 25, 2012 4:06 pm

Hi David,

Tachometers vary quite a bit - some can be driven from the IDM output of the EDIS module, or the TACH_OUT of the Megajolt unit. Many require seeing that high-voltage pulse from (-) connection of the original ignition coil - in these cases you can build an adapter circuit that joins the signal from multiple coil packs. Information here:

http://www.autosportlabs.net/MJLJ_V4_ve ... back_pulse

We offer a pre-made adapter board as well: http://www.autosportlabs.com/tach-adapter-p-65.html

Please let us know what you end up working out!

Abarth · Post by **Abarth** » Thu Jan 26, 2012 7:41 am

Hi, Brent

I brought a module to Trigger Wheels and i connected according Chris instructions. The tacho works at idle, but whe the rpm are increased, the tacho goes to zero. Any advice?

Best regards

Post by **brentp** » Thu Jan 26, 2012 9:04 pm

Hi Abarth,

Unfortunately, I'm not familiar with the design of the Trigger Wheels adapter. Sometimes a tachometer needs to see a small current bypass the blocking diode, as we have in our adapters (see schematic here: http://www.autosportlabs.net/File:Tach_adapter_sch.png ).

When we were adapting an older Porsche 914 tachometer we saw the exact same problem - it worked a bit at idle, then died. Adding at least one 100K bypass resistor across one of the diodes solved the problem.

You might be able to modify the adapter you have to add this diode - it could be a simple operation.

Let us know what you find out!

Abarth · Post by **Abarth** » Sat Jan 28, 2012 6:38 pm

Brent

Can you draw an scheme with this modification? I,m not sure wich wire must to do the modification...

cng1 · Post by **cng1** » Sat Jan 28, 2012 8:12 pm

If you click on the link that Brent included that has a diagram for his circuit. For your case you would just add a 100K Ohm resistor onto each of the two wires going into the tacho adaptor and join them to the wire going into the tacho.

Post by **brentp** » Sun Jan 29, 2012 1:19 am

Thanks, Chris!

Abarth, keep us posted on how that works out.

Abarth · Post by **Abarth** » Sat Feb 04, 2012 9:37 pm

Hi all. I added one resistor in each cable from the adaptor and still the same problem. Any advice?

Post by **brentp** » Sun Feb 05, 2012 9:04 pm

Not sure how you added the resistor. could you post a picture of what you did?

Abarth · Post by **Abarth** » Mon Feb 06, 2012 11:46 am

I done like sheme attached.

Regads

cng1 · Post by **cng1** » Mon Feb 06, 2012 11:57 am

That isn't actually what the schematic that Brent shared showed. His schematic had the resistors bypassing the tacho board in effect. You may find that trying it that way may work better.

Abarth · Post by **Abarth** » Mon Feb 06, 2012 12:01 pm

Hello

My english is horrible. Can you modify my drawing showing how must install the resistors?

Regards

cng1 · Post by **cng1** » Mon Feb 06, 2012 12:16 pm

OK, here you go.

Abarth · Post by **Abarth** » Thu Feb 23, 2012 6:30 pm

It works¡¡¡ Thanks a lot Chris and Brent.

Regards from Spain.