Monday, January 31, 2011


Back in December I wrote about the new "123Tune" distributor I had just ordered from the Netherlands. It arrived a couple of weeks ago, and I fitted it last weekend, naturally on one of the hottest days of the year.

123Tune in shiny packaging

This was a bit of an experiment, since I hadn't been able to find anyone who had installed this particular distributor on a twin cam Alfa engine. All the dimensions seemed to be correct, but you never know for sure until you put it all together...

I needn't have worried - it went in quite smoothly. First item of business was to rotate the engine round to top dead centre on cylinder 1. Reasonably straight forward, but I pulled the plugs to make turning the crank easier. #2 was looking a bit sooty, but otherwise the plugs were a reasonable colour. The 123Tune manual suggests setting the timing from the engine's static timing mark (from memory about 4-6 degrees on the Alfa), but it made more sense to me to use TDC, since then the numbers on the curves I load into the distributor will be the absolute advance, rather than relative to the static setting.

Next it was time to remove the old dizzie. Here are a couple of pics of the two side by side....

As you can see, there is a bunch of wires attached to the 123Tune, which does make it look a little intimidating. However, it's all fairly straightforward - one wire to each terminal of the coil, one to earth, and a fourth can be wired to a dashboard switch to change between two stored ignition curves.

Before I took the collar off the old distributor, I marked the advance point with some liquid paper, just in case it had to go back in. Then it was off with the collar, and with a bit of work I was able to ease it onto the 123Tune. The Alfa engine uses an o-ring between the collar and the block to seal the distributor shaft, but the 123Tune has its own o-ring further along the shaft (you can see it in the photo above). I decided to put the Alfa o-ring back in anyway, figuring it couldn't hurt to have two!

Because of the o-ring, the 123Tune is a firm fit in the shaft, and required a bit of a push to get in place. All seemed good, but... I couldn't get the drive to mesh. Out it came while I measured everything again. All looked ok, so I took the original Alfa o-ring off and tried again. This time I was able to get the drive to engage, although there is a little play in the mechanism - presumably between the distributor shaft dogs and the slots in the drive.

From there it was just a matter of finding a convenient orientation of the distributor body so that the wires didn't clash with anything and so that the USB port was accessible. The distributor can do both vacuum and mechanical advance - the 1750 engine only has mechanical, so I didn't need to worry about hooking up the vacuum intake on the distributor.

After tightening the collar, it was time to hook up the wiring. The 123Tune comes with nice, long, unterminated wires, so you need to have some terminals to hand. The instructions say to connect all but the negative coil terminal wire and then adjust the static timing.

The 123Tune has a neat feature to help with the static adjustment - there's a green LED that shines through a slot in the body when the rotor is pointing to a firing point. It's functionally equivalent to the old trick of wiring a test lamp across the points, and makes the whole job pretty easy - make sure the timing marks are where you want them, and then turn the distributor body counter clock wise until the LED just lights.

123Tune in place - the LED shines through one of the slots either side of the rotor

All good, so I connected the last wire, popped the cap on, put the plugs back in, connected up the the spark plug wires (checking firing order carefully - the Alfa uses the standard 1342 sequence), and then connected my laptop. I had pre-installed and loaded the 123Tune software, and after the usual "device connected" beep, the software announced that it was connected to a 123Tune distributor.

I had already set up several standard Alfa distributor curves, so I loaded one up. The software is reasonably easy to use, although with a few idiosyncrasies, and it has a nice visual representation of the ignition curve. You can edit points either by selecting one and dragging it (although only up and down, which means you can only change advance, and not revs, with the mouse), or by editing a text box for each point (which allows you to change the revs and the advance). Points on the curve can be deleted, or new ones added, up to a maximum of ten. After playing with it for a while I'm fairly confident that pretty much any valid curve can be represented with ten points - the most I've used so far is nine, and I could probably remove several points from that one without losing the shape.

Then I tried to start the car... No dice. Turned over all right, but not even a cough. Resigned to checking everything from scratch, I started with the wiring, and found the problem straight away. I'd got the coil wires the wrong way around... No excuse, since I installed the coil only a few weeks ago, but somehow misremembered which terminal was which, and didn't bother to check. A good reminder to always check everything, even when I'm sure...

With the wires connected correctly, the engine fired first go, and the "gauges" on the 123Tune software all seemed good - showing a live picture of the revs, advance, coil current, etc.

The only problem I have now is the temptation to constantly fiddle with the timing. I spent a happy hour earlier this evening just trying out different amounts of advance with a single curve. There was something slightly surreal about driving around, occasionally stopping and jumping out to connect a laptop to the engine and fiddle around for a minute before roaring off again...

I think the 123Tune is mainly aimed at engines that 123Ignition don't have a specific distributor for, but it should also be useful for modified engines, or for optimising a particular engine for the fuel supply and driving conditions. It can also act as a rev limiter, which is handy. I plan to find a curve that suits this engine and then leave it alone, but I can envisage altering it slightly for the season, or for any changes to engine tune.

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