Colour Tune

[sean sherry]

How accurate is Colour Tune ? How Blue should the Blue be ? ( Weak ) Blue with yellow traces ( Richer ) in mid range ? All from final setting on twin SUs, a '50s 140 Jag. Had white plugs , now light brown and clean through the rev range.
I've always set my 107 280 SL K - Jetronic by ear , not hard to do. How accurate ?

What should I expect from Colour Tune on my Jetronic Merc. ?
Like the Pilot said, instruments don't lie. Do they ?

 

[Styria]

Well Sean, where can I start ? Our late JohnS., the gentleman that he was, actually handed over to me his colour tune equipment some years ago - BTW, for those that are unaware, poor John passed away in March of last year. John was quite a lair from way back when, and he used to tune an MG"B" that he owned with that Colour Tune instrument. Well, so he reckoned. I personally could never get the hang of it - too much work doing one plug hole at a time, and on the Rover V8s it was quite an exercise without any really accurate benefit. I never knew really what I was looking at and looking for.

In the end, I settled for a vacuum plunger type gauge which at least told me precisely how much work each carburettor was doing - and you know the mixture drill on the SUs - lift the pin and if the engine falters ever so slightly, you've just about got the mixture right. With K-Jet the adjustment is extremely fine and quite accurate. It probably pays to observe a rev counter whilst you are adjusting the 3mm Allen headed grub screw. Additionally, the engine soon tells you how rich or lean the mixture is - at does not take long for the engine to start responding to an inaccurate adjustment. I'd be very interested to see if you can make the Colour Tune work on your Benz - I just realized, of course, that you have the twin cam six in your car - would the Coulor Tune unit not bee too far down in the "valley" ? It is pretty deep and a little awkward to get to. Regarding beloved Jaguars ? Another chapter altogether. Regards Styria

 

[sean sherry]

Well Styria,
The colour tune result was a mixed bag, showed me the changes going on at different revs. most important to me was that the mixture was getting richer at the higher revs. Idle was not as easily read but a vacuum gauge allowed me to fine tune idle mixture from there. a slight tweak and 17 inches instead of 15.5. Steady and clean at all revs. I like to see a rich mixture at the top end and also the correct max mechanical advance , per the book. 36% for a 280 107. Plugs were a nice mid brown at the electrodes and centre insulator. Black on the body ....unleaded residue.
Sean