efi EDIS TACH HELP

[fiftytakedowns]

Okay, I dont understand the Diagram, I dont know what Diodes are, or how they hook up to any of the wires, which wires they go to, or how they go to the tach wire that connects to the tach itself.....

Sorry for being so Naive, but I searched for a half hour, and had trouble coming up with a Basic walk through for people stupid like me.

Thanks.

[2002john]

Print that and go to

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Now that I had the ignition working on the bench, the next step was to get the '02's tach to work with the new ignition. I tried the circuit at the bottom of this page. It seemed to be fine at first, but then when I disconnected my test equipment it no longer worked. The fix was to put a 100k ohm resistor across one of the coil diodes (either D1 or D2), and the tach stayed happy

That is from Tim-Megasquirt || web page. circuit he'

s talking about is same yours.

http://www.hbci.com/~tskwiot/2002_MSII.html

[JHG762002]

The bottom two are diodes

http://en.wikipedia.org/wiki/Diode

The top one is a zener diode

http://en.wikipedia.org/wiki/Zener_diode

[Grover]

I struggled with this too when doing my install. Attached is a photo that JohnC sent to me that helped clear things up. Basically, each of the two wires coming from the coil pack toward the tach needs to be spliced and you put a diode into it. Secondly, one of the diodes has a resistor (if I remember correctly) also added on top of the diode. Once all that is in place, you put shrink tube over the various sections to protect the pieces and make it look nice and tidy. In the photo below, the black wire on top has both the diode and the resistor there shown before shrink tubing. The brown wire below has the diode in place but it has already been covered in tubing. Make sense? Drop me an email if you need more guidance. trichardson AT clifbar DOT com

[fiftytakedowns]

Okay, so I solder those diodes onto the wires that is spliced into the coilpack?

Which Wires do I splice into?

It's starting to make sense now, once I have the two separate wires with diodes in them, then I connect them together, and that connects to the wire that goes to the tach.

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[themoose]

you splice 1 & 3 on the EDIS coil plug. I'll be doing this this weekend!

[FunkyLaneO]

Think of a diode as a check valve, it only flows electricity in one direction. Make sure any diodes you install are pointed the correct direction or they are guaranteed not to work for you. There is a little triangle printed on the side of most diodes that indicate the direction of current flow. If it only has a stripe on one end that is the cathode end, think of that line as the tip of the arrow, current will flow out that side but not into it.

[JHG762002]

I added some text to the photo attached above. This might clarify it a little. The resistor is added next to one of the diodes, and I tried to point out that they are soldered at the same points. The 'arrows' show the orientation of the diodes, the zener diode points the opposite way of the others.

[fiftytakedowns]

Ive been having some troubles with the wiring still. I made that adapter, it was not letting the coil spark, so I donno what is going on.

[fiftytakedowns]

I got the tach workin for a bit, until the zer diode decided to explode.... Why would it do that?

It also wouldnt rev past 4k

[Sett]

I just got my tach working this weekend, I used the two diodes and the 100K resistor with no Zener diode, works good. If you want I could meet you and show you my set up.

Steve T.

[fiftytakedowns]

That would be great, I could use an excuse to go for a little datalogging. you available today?

[Sett]

Sent E-mail, Wednesday would be better.

Steve T.

[Sett]

Did you get it working, let me know if you want to met up.

Steve T

[TJF]

I tried initially the two diodes and a zener and that didn't work at all. I added a 100k resistor in parallel with one of the diodes and that got it so that the tach worked up to about 2k rpm then it read zero.

I tried a 100k resistor to ground. Could get a reading up to almost 2500 rpm then zero reading above that. Assumed that the issue was that the signal was a larger amplitude and that the signal off the EDIS coilpack had to be similar to the original signal from the (-) side of the coil. I tried adding another smaller zener diode in series with the first thinking it would drop the voltage seen at the tach. No difference noted.

I disconnected it all and drove around without a tach at all for a week. Today if tried just the two diodes to combine the two sides of the coil and two 100k resistors in series to ground. The tach connection is taken off between the two resistors - I figured if the problem is a too large of a signal why not cut it in half and see what happens. Works like a charm. I didn't yet do the math to figure out how much current draw this works out to be and I assume that the tach has a relatively high input impedance.

Just another way to make the factory tach work with an EDIS setup. I'm running megajolt V4, but the same thing may work for those running megasquirt as well.