Question, as in the title. I've previously overlooked this simple device but it would appear to privide a very accurate way to get the carburettor set up properly.

fiat500 said:

Question, as in the title. I've previously overlooked this simple device but it would appear to privide a very accurate way to get the carburettor set up properly.

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Hi Peter, Yep done that, I used the 'G4074' kit for 14mm plugs. I will say that I only used the Colourtune to trim the mixture of my Weber 30DGF and I can admit that it did a good job too. I only used the device in the number one cylinder, but as the Weber only dumps fuel mixture into a Siamese port I don't believe it would make any difference which plug hole you use. My old engine builder would probably not agree though, as he is big on airflow through the induction tract and it's differing movement into the cylinders You could compare both results if you wanted ???? All in all the differing plug colour was remarkable after the fact showing a good clean burn. Hope this helps.
All the best for Christmas.
Ian.

Aye that brings back memories. Never forget that blue is the colour

I have had a couple, found them quite useful, not to mention interesting. I thought it was amazing seeing the combustion taking place

I know they say bunsen blue but in real life i have found bunsen blue almost starting to see a little yellow is best. Many times if it's just bunsen blue it tends to be a little lean and the Car can hesitate a little.
Alan

plasticpig1972 said:

I know they say bunsen blue but in real life i have found bunsen blue almost starting to see a little yellow is best. Many times if it's just bunsen blue it tends to be a little lean and the Car can hesitate a little.

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Reading up on the instructions, I think you're spot-on there.

I've read before that the 500 should be run slightly rich in any case, as the surplus of petrol has slight cooling effect on the valves and head. Sounds a bit odd to think of petrol having a cooling effect, but obviously it uses a temperature difference to enable vaporisation.

Lean fuel air mixture causes some fuel to condense on the metal parts forming the combustion chamber. When the condensed fuel burns the metal parts in contact with it can reach higher temperatures than designed for.

That is strange---I had always been taught that air-cooled engines should be run slightly rich, but never had it explained as to why---onelives and learns!

the hobbler said:

That is strange---I had always been taught that air-cooled engines should be run slightly rich, but never had it explained as to why---onelives and learns!

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Hi Hobbler,

I was puzzled for years as why weak mixture could cause overheating . Had equated overheating to coolant overheating for a long time . Then thanks to the internet eventually found the fuel condensation and burning in contact with metal explanation ....localised overheating.

Glad you found this interesting too, makes posting worth while

From memory weak mixture can promote detonation and preignition- I don't know exactly why perhaps due to hot spots in combustion chamber.

Cheers

Jack

On the internet, there are a lot of explanations for the reasons why a lean mixture causes overheating. I have seen contradictory explanations in consecutive posts within the same conversation within a given forum.

It seems that at times when you need the maximum power output from an engine, you need a surplus of fuel to be provided in order that in the turbulent and highly pressurised environment of an operational, engine cylinder, each fuel molecule has a good chance of "meeting" an oxygen molecule. In that way, every "ounce" of power is guaranteed to be liberated. With full power output comes maximum heat liberation. The fuel which is surplus and cannot be burned on that stroke is either partially burned or evaporated, and that provides the cooling.

If a surplus of oxygen is provided (lean mixture) you're more likely to be guaranteed that all of the fuel will be burned very quickly and release all of its heat; but the buffering effect of surplus fuel is not available, so excessive heat may transfer to the cylinder-head and valves.

If all of the above is somewhere near the truth, it's obvious that a blue flame with a slight transition to yellow, will be the thing to aim for. Yellow is an indication of incompletely burned carbon molecules....ie. there is slight surplus of fuel.

It looks fairly straightforward for us numpties who may struggle to adjust the mixture correctly.

My biggest concern, given that I always have my heart in my mouth when removing the plugs, would dropping the thing into the fan housing!

I may give it a go though (not too expensive I guess).

To reduce the risk of dropping the plugs (especially the front plug!) may I suggest that you get a proper 'spark-plug' socket which has a rubber 'plug-holding'-holding' insert in it. When REMOVING the plug push the socket fully on to the plug--when RE-FITTING the plug, only push the socket on just enough to hold the plug---sometimes the insert can hold the plug (when fully pushed on) to the point that the socket is difficult to remove.

I had already jumped and bought one of these and it provided a relatively expensive but interesting five minutes of fun.

After one, short test-run I decided that nothing needed changing and that my previous setting by ear and eye was fine.:bang:

In the images you can see a lovely blue colour at idle. With a rapid throttle opening you get a proper, orange fire as the carburettor dumps excess fuel into the engine to give the instant power. With a more gradual throttle opening, the flame loses its pure blueness slightly, indicating that there is a slight excess of fuel to provide acceleration. When the engine is allowed to settle at a constant load at higher revs, the pure, blue flame returns.

As far as I can see, the carb is set up properly and I'll be leaving it alone for now.

https://youtu.be/Cg6nFxgIHnU

Hi fiat500,
for me the cost to buy the "Colourtune" is a cheap price to pay to know the Mixture is correct. It's not even 1 hour for a garage to check and you always have the Tool.
Now you know the Mixture and are not guessing.
Have you got a Strobe Light for the Timing also a good tool to have.
Alan

plasticpig1972 said:

Hi fiat500,
for me the cost to buy the "Colourtune" is a cheap price to pay to know the Mixture is correct. It's not even 1 hour for a garage to check and you always have the Tool.
Now you know the Mixture and are not guessing.
Have you got a Strobe Light for the Timing also a good tool to have.
Alan

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Thanks Alan. It wasn't my intention to sound cynical or dismissive of the device. On this occasion, to my delight, it confirmed that I had been on the right track and had sorted out a minor problem. But just a few weeks ago, it would have helped to shortcut to the solution. So I heartily recommend it and will be using it again.

I do have a cheapo timing light and it has also made a big difference to the performance of the engine and my security of mind in knowing I'm properly set up.

The only negative about the Colortune, with regard to the Fiat engine, is that the special sparking-plug is very difficult to fit and to extract. It is very compact in comparison with a normal plug and has a loose sealing washer; it's like the problem when normally changing plugs, but 150% harder.[emoji3061]
Regards, Peter

Good luck Pete,
just look on the Colour Tune as a nice Christmas present.
cheers
Alan

There are lot of things out there that i want to buy but don't know they exist Just a question, isn't the engine supposed to be hot when adjusting? I guess this process takes place with a cold engine isn't it?
Thomas

gordinir8 said:

There are lot of things out there that i want to buy but don't know they exist Just a question, isn't the engine supposed to be hot when adjusting? I guess this process takes place with a cold engine isn't it?
Thomas

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Engine at normal operating temperature or you can't adjust mixture correctly.

gordinir8 said:

There are lot of things out there that i want to buy but don't know they exist Just a question, isn't the engine supposed to be hot when adjusting? I guess this process takes place with a cold engine isn't it?
Thomas

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You have to be well organised and quickly change to the Colortune after a run in the car. In my standard engine I found the mixture was right without needing any adjustment.