Tach out signal

bossie · Post by **bossie** » Sun Nov 28, 2010 9:30 pm

What are the specifications of the Tach Out signal of the MegaJolt? We are trying to get the original tachometer to work and a friends has built a converter, but it is not working, althoug his converter is working on a Citroen AX with DIS ignition.

One of the thoughts is that the signal is not dropping to 0v between ignitions.

So if someone can help us to get the specs of the signal, we might be able to get the original tachometer working.

volksnut · Post by **volksnut** » Fri Dec 10, 2010 2:44 am

I picked the tach out from the EDIS module # 11 wire ....if I remember correctly

Post by **brentp** » Fri Dec 10, 2010 4:23 am

For V4 it's a 12V square wave, in the form of an open-collector output with a pull-up resistor to 12v.

Broke4speed · Post by **Broke4speed** » Fri Dec 10, 2010 10:42 pm

I miss my tach

.

NITROPIXIE · Post by **NITROPIXIE** » Sat Dec 11, 2010 5:00 pm

Broke4speed - you not got your tach working?? I have a spare in my room at work which I'm sure can be modded to work and I can send you a 'How to'. I have done it on a 205gti before.

Broke4speed · Post by **Broke4speed** » Sat Dec 11, 2010 8:53 pm

That would be fabulous. I've tried the diodes/flyback circuit thing, but just can't get it to go

. I've been relying on my hard-cut limiter to tell me when I've hit the redline, and it isn't always convenient, lol.

I've still got access to the Pin 11 on my EDIS unit, as well as the coils and tach out on my MJLJr, so if there was any option I'd gladly take it!

NITROPIXIE · Post by **NITROPIXIE** » Mon Dec 13, 2010 1:29 pm

Bossie - What tach is the car out of or what type of Tacho is it??? Have you had any luck recently getting it to work yet?? I believe the spec's of the tach out signal on the megajolt is 0V - 12V square wave.

Broke4speed - I had a look at the tach I have in my cabin and I believe that it is achieveable just as I have done on a friends 205gti as I have said. Give me a bit of time and I will post a "how to" on how to make a modification for it. I may need your help initially, but I will start a new topic and notify you when I have. Hopefully we should get this done this side of crimbo

Ryan

Broke4speed · Post by **Broke4speed** » Mon Dec 13, 2010 1:52 pm

I'll help in any way I can, I've got a spare cluster sitting around, and a running MJLJr car for testing

.
HUGE thanks for the help, even though I know it must be busy 'round there what with the new arrival

.

bossie · Post by **bossie** » Mon Dec 13, 2010 7:41 pm

It's not yet working, but we are working on it. When I told my electronic guy that it is an open-collector signal he just said: Aha, that's the reason. His converter was build for an open-drain. But with a little modiication his converter will work with MegaJolt he told me. So I'm just waiting at the moment. The tachometer is the original one that's fitted in my Citroën AX with distributor ignition.

I will keep you all updated when there is some news.

NITROPIXIE · Post by **NITROPIXIE** » Mon Dec 13, 2010 8:59 pm

broke4speed check out http://www.autosportlabs.org/viewtopic.php?t=3046