for those that have never heard of one, a gunsons colortune is a device that replaces one of the spark plugs in your motor, it has a glass window that you can see through, actually seeing the colour of the air-fuel mixture as it burns.....
I've read about these in Vizard for years, but always been a bit of a sceptic - how can a spark plug that's not a real spark plug work the same as the plugs we buy specifically for our cars. I found the best results with a champion N11YC, but another motor might go better on an N9YC - I know why now - the different plugs only really make a difference when the engine is under load - so the colortune does work for tuning when the car is in the workshop....
anyhow, a few weeks ago I was sorting the mixture on my mate Ivan's exhaust analyser computer, I got it to a nice mixture and the car runs great, but while I was doing it, Ivan came over and said "hey Simon, why don't you try doing this at home, with this" and pulled out a colortune, in it's original packaging - I laughed myself silly, I'd only ever read about them in Vizard, and that's not exactly a recent publication... it still has a UK price tag on it... him or his dad bought it in england on a trip back there - he keeps it in the engine analyser trolley, with the original BMC mirror on a bracket for setting the timing, and the ancient suction dealie for balancing twins.... great stuff, anyway, I digress...
I took the colortune and it's been sitting on my shelf for a couple of weeks, the cooper hasn't been behaving, and I've been busy, but this afternoon I gave it a go
check this out!
the packet:
here's what the 'plug' looks like, it has an electrode deep inside it, you can see my finger through the glass bit
installed and ready to start the motor - the long skinny thing is a screw in extension you need to use
and at idle... the perfect mixture is this colour blue, you can see the actual spark in this photo
Under sudden acceleration, the pump jet action of an SU carb (as the piston jumps up it draws fuel out) causes the mixture to go slightly rich, which turns the burn to a bright yellow, if the burn is a light blue to white, then it's lean. If I ran the revs up slowly, the colour stayed blue, and got a little whiter at high revs, so I richened the mixture a tiny bit, but it was very close to where I wanted it to be
and here's a short 4mb video - you'll notice as I give sudden revs the colour changes, then when I drop the revs the colour goes back to blue, after almost dying away
http://members.iinet.net.au/~kerrsim/minipics/colortune.mpg (right click, save as)
this was about 6 months ago.