Ignitech TCIP4 as a replacement for Marelli Digiplex

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I alluded to this on Facebook, but figured I should put up a bit more info as there's not a lot out there.  It's also a continuation on from this post - Dellorto carb tuning on a Moto Guzzi Sport 1100, with some gearing and ignition rambling - as one of the theories I had on the poor low speed running was it being related to ignition timing.

Many years ago (back in the Moto One days, so 9+) I had a fellow with a Sport 1100 contact me as he was trying to replace his Digiplex with an Ignitech.  The had said it would work, but he failed and gave up from memory.  I asked Ignitech the question again last year, and they assured me it would work.  Like a lot of things, sometimes the only way to prove (or disprove) a theory is to do it.  So I ordered a TCIP4 to suit, which is just a normal TCIP4, not a Ducati / Kokusan specific unit.  It is supplied with a generic connector under the expectation of cutting the original out, but I don't like the point of no return if I can avoid it.

To make sure I wasn't wasting my time I put some terminals on the Ignitech wiring and plugged it in for a test.  Hit the button and it fired straight up, which was a great relief.  I went for a ride and that was good too, so moved on to the making it right bit.

Before I pulled the Digiplex I did some tests to check the ignition timing as was.  I had marked the flywheel with some paint marks, using the teeth on the ring gear.  I had counted them and got 97, which gives about 3.5 degrees per tooth.  I then put a degree wheel on the alternator to be a bit more accurate and that gave the idle at 6 degrees and the full advance at 33 degrees BTDC.

With the Digiplex it appeared with the vacuum hose disconnected (mimicing WOT) to not have a lot of advance under 2,500 rpm, and not a great deal more with the vacuum hose connected.  With the Ignitech you can make up the map as you wish, and a linear increase in spark advance generally gives you a nice feel - no holes or bumps, etc.  Much like good suspension, good ignition timing is often not noticeable in any way.  It just works.

The table below shows what I set the Ignitech map to.  The base advance setting of 12 degrees appeared to correspond with full advance set to 35 degrees, and that gives an idle setting of 12 degrees where it does certainly happier than with the Digiplex.

RPM	1400	2000	3000	4000	5000	6000	7000	8000
Advance	12	18	28	33	35	35	36	36

To connect the Ignitech I didn't want to cut off the original Digiplex connector on the wiring loom, just for retro-ability.  I had no idea where to start looking for the correct connector, as I doubt it would exist outside of oem, so made one from a block of plastic.  It was actually pretty easy.  I measured the terminal spacing and drilled holes as required.  The hole from the back (wire side) was large enough to fit the wire through only, with a countersink on the terminal side to hold the terminals in the loom connector while not allowing them to move back out.  I drilled then filed a slot into the front edge to allow the original loom connector to slot in.  A couple of zip ties seemed like the most appropriate way to keep it all together.

To mount the TCIP4 I bent up a piece of aluminium sheet and fitted it using the original Digiplex mounting holes and rubber bushes.

And that was done.  At this point I gave it back to the owner and he was very happy with the result.  While there's still some low speed jerkiness, it's much less than it was.  Quite amazing, really, how much difference some more spark advance can make.

Personally I think fitting a rear wheel with a cush drive (realistically a 17" from Sport 1100i and V11) would cure that and shorten the gearing a little as well for a nice side benefit.

If you wanted to go further, you could fit a MAP sensor as the version 88 of the TCIP4 has the ability to take a MAP sensor input to allow for a 3D ignition map.  A 3D map allows you to add ignition timing on part throttle, which makes a difference to response and fuel economy.