Rev Counter Wiring Edis

[Guest whiz]

I was trying to wire up my rev counter today from what I found out before hand was that It had to be connected to pin No.11 on the edis4 this was done. Started the engine the rev counter did move but true to the amount of revs I was giving it. In fact it never rose above 2000 rpm.

Does anyone have any solutions.

Andy

[Guest whiz]

Can one of the mods please delete one of my double posts

Thank you

Andy

[Snapperpaul]

There are 3 ways to get a Tach signal,

EDIS Tach feed out

ECU Tach out

3 Zenner diodes 2 from each coil pack initiation feed joining to 1Zenner that then feeds to the Tacho.

Diagrams on the Megajolt website on how to wire it.

 

What Tacho are you using?

What ECU?

Have you used the correct pin from EDIS?

[Guest whiz]

Hi Paul I'm using no.11 pin out on the edis green wire. I don't have an ecu bit I'm considering getting a mega jolt I believe it's the right way to go I can't remember the tachometer name it worked fine when it was run from the dizzy when I had my pinto in

Andy

[Snapperpaul]

The EDIS alone only runs 10 degrees advance, needs a PIP and SAW signal from an ecu to advance the ignition, you would also need a crank position sensor

I would think the signal out of the EDIS is not compatible with your Tacho

 

Please clarify

Engine?

Distributor removed?

 

Your running EDIS- yes

ECU-No so what changes ignition advance?

Does the EDIS have a vac connection could be an ECC1V looks similar to EDIS

If using EDIS you must have a coil pack so the Zenner diode fix should work depending on your Tacho.

[Guest whiz]

I'm running the red edis unit which has a vacuum pipe connected to the inlet manifold. I am considering buying a mega jolt unit. Trying to find the best place to buy one.

Andy

[Guest old_timbo]

I struggled getting a tacho output from EDIS when I converted to megasquirt. I used the diagrams on the Extra EFI forum and built the simple diodes circuit to drive my standard Smiths tacho from a Truimph Dolomite. This drove the tacho fine up to 3000 rpm after which the needle dropped back to zero. Dropping the revs below 3000 again and it would come back to life.

Apparently the rev counter needs a good voltage spike to trigger and this is normally provided by the primary coil in the ignition coil when the points open. As the first circuit didn't work, the suggestion was that this spike could be replicated by building another circuit (also on the forum) with a relay coil in it instead. I never got round to trying this as I twigged that the PIP signal from the 4 cylinder EDIS to megasquirt is a nice +12vdc square wave at 4 pulses per rev. like that from the coil. So thought it worth a try, connected the tacho up to this and everything worked fine and has been ever since.

Not sure whether this would work with other makes/types of tacho. The Smiths one is powered by a separate 12vdc supply so only needs a trigger signal from the PIP. I think some tachos are powered off the 'signal' so these types might pull the PIP voltage down and cause problems. Still, worth a try.

[Guest Matt Thorne]

The real problem is most of you guys may be converting from a single coil over to EDIS. Standard tachos rely on the feedback from the coil collapsing to drive the dash, wheres the EDIS IDM line is a nice saetady 12v line, at around 512uS pulsewidth. (IIRC)

 

This means your standard dash analogue dial will never get the current needed to move the needle very far, hence the 2k limit.

 

The best way is as the chap said above, 3 zeners and away you go.

 

The other option which I have seen work is wire the IDM line from the EDIS unit through a relay coil (dont use the contacts of the relay, just the coil) and the collapse can make the dash work properly. I know it works on Smiths gauages as I have seen it with my own eyes, but as for others (and this may of just been a lucky one) I am unsure!

 

If you need Zeners they are pence, and I cam bring a back of them to Newark...

 

Matt

 

PS the chap above has hit the nail on the head, should of read all the way through!

Edited June 14, 2012 by Matt Thorne

[Guest whiz]

Ive got mine sorted now, it's now wired through my megajolt

Andy