View Full Version : timing and mixture - do they relate

08-30-2006, 07:43 AM
I have what may be a silly question, but here it goes.

If one leaves the carb mixture setting alone and then changes the timing, does this effect the mixture. In other words, if you were to put a colortune plug in the car and then start to change the timing would the color you see in the colortune change? If so which way.

This is more of an academic question but I am trying to wrap my mind around the interaction of the two with each other.

08-30-2006, 08:12 AM
Are you talking about big changes; I don't think you will see much diff with less than 10 degrees.

08-30-2006, 08:27 AM
yes I am talking about big changes.

Simon TR4a
08-30-2006, 08:54 AM
I am just guessing here, but I imagine the colourtune actually measures combustion temperature rather than mixture.
If this is correct then lean mixture or early timing should show a hotter combustion temperature, and a rich incoming mixture or late spark should give a lower temperature reading.
It is notoriously difficult to tell if symptoms of poor running are due to spark or carb problems, so I would say they are closely related.

08-30-2006, 12:47 PM
Hello Adrio,

I would say no to that, mixture is purely how much air the engine takes in and the amount fuel that is drawn or pushed in (fuel injection).

The colourtune device does not actually measure anything, you are visually assessing the combustion.

Correct timing, on the other hand is affected by mixture, a weak mixture requires more advance than a richer one.


08-30-2006, 01:48 PM

Thanks for that. i am starting to get a feel for the answer here. I am afraid that by introducing the colortune I may have thrown in a red hearing. I only used it to try and demonstrate what I was asking about. I was trying not to get into the specifics of my 'problem' but rather trying to learn the theory. I have an other question but will put it as a separate post so as not to confuse the issue here.