Anybody here use Colortune?

[Neil Bardsley]

I have a 56a, with a pellow big bore engine, It came back from the shop running very nicely but in my mind was still getting too hot then running at 4k rpm for extended periods on the motorway. I have 40 IDF webber with F11 emission tube, 115 main jets and 200 air correction jets and a freshly rebuild dizzy by Bruce Smith. I decided to have play! First I decided that the car must be running lean at the top end so I upped the main jeb to 117.5 then I decided that they timing was wrong. On no real factual basis.

I set the timing to 34 degrees max / adv (it was pretty close to there already) and tuned the carbs by ear. My method for tuning by ear is to open the idle mix screw until the rpm slows down. Then I screw in until the rpm slows then I open a bit until I find the best rpm spot. I repeat this on all 4 screws and it normally produces an engine that is idling about 200/400rpm higher and sounding smoother/more stable. Then I looked at number 4 using the colourtune. Blue at idle (blue is the ideal mix), then yellow onwards (yellow means rich). This made me think that I should go back to the 115 main jet. Which I did and it helped. I readjusted the carbs again for the new main jet. Now I got blue at idle, then yellow between 1500-2500ish then blue again. I believe this means that I'm running a little rich in the transition zone between idle and main? The color tune is suggesting that I need increase the size of my air correction jet? However, the plug number 4 didn't look fouled when I took it out? Anybody on here use the colortune Does timing have any affect on the air/fuel mix could it be a size of too advantaged or retarded?

I took the car out again and it run better. Much smoother maybe 97% of how it came from the shop. I occasionally got some coughing/backfiring under hard deacceleration as I took my foot off the gas while braking into corner. Maybe it's time to stop playing.

[Martin Benade]

The hard part will be looking at the combustion color while under load, driving. That is when it would give more useful information.

[Neil Bardsley]

Might be a problem

[Dennis ODonnell]

"Maybe it's time to stop playing."

Careful. Read Brian Adams' posts re coughing on deceleration with Webers.

[Dave Wildrick]

"Maybe it's time to stop playing."

Careful. Read Brian Adams' posts re coughing on deceleration with Webers.

And make sure your fire extinguisher is handy and in good shape.

[Neil Bardsley]

The hard part will be looking at the combustion color while under load, driving. That is when it would give more useful information.

What happens to the fuel/air mix when a car is underload? Trying to think it through if I'm driving along at a constant rpm/speed and I come to a hill then I have put my foot down a little more to keep the speed constant. Which opens the throttle. Which mean more air/fuel into the head which is still turning at the same speed? It's not clear to me out the mixture changes?

[Emil Wojcik]

Can't comment on how Colortune works on a 356 or with Webers, but I've been using one for over 20 years to adjust the duel SUs on my MG. For me, the Colortune gets them balanced better that any other device I've tried. I've always just followed the instruction supplied, including adjusting at various RPMs. I think if you're having problems adjust them it's not a Colortune issue, it's a carb issue.

[Steven Clarke]

Neil:
I have been using a colortune since buying a '66 911 back in 1977. It made adjusting those six Solexs easy. Since then I have used it on various Webbers, Solexs, and Zeniths on my 356s and 911s. I really think it is a great tool for getting the idle mixture right.

However, like Martin said, I don't really think it is a valid tool for determining the mixture with the engine under load. I also doubt that you are really seeing the transition to the main jet when reving the engine to 2500 rpm there in your driveway. The rich mixture (yellow flame) that you are seeing is probably the result of the accelerator pumps adding fuel when you open the throttle.

If you could put the car on a dyno and put the engine under a real load, then you could see the mixture at various rpm and loads with the colortune, but then you would also have an oxygen analyzer there which would tell you the same thing, but even more accurately.
Steve
#2311

[Dave Erickson]

Disclaimer: I've never used a colortune, but it sounds interesting. I read online that the kit comes with a tube that has an angled mirror. So maybe a good solution for viewing while driving would be a USB camera mounted in the tube, connected to an Ipad, along with someone else to watch the Ipad while you drive .

[David Jones]

I used a colourtune many years ago to tune BMC engines in the UK before I got wise and switched to a Porsche. I got lazy and instead of writing what I remember I did at the time I stole from the internet. Thhis is pretty much how I did it all those years ago. Paraphrasing the words of the Mythbusters. "Don't try this at home, we are what you call experts". I would add to the write up that it is probably pointless to do this on each cylinder unless you have a lot of jets and want to end up with different jetting for each cylinder.

The Colortune, then, is indicating at the colour transition
points the mixture strength of the ingoing charge. Maximum
power occurs when the fuel/air ratio is between about 12,5 and
13,5:1. The exact point varies from engine to engine, but
most cast iron tuned production engines seem to be best around
12,8:1. The best economy is achieved on weaker mixtures than
that giving maximum power, and fuel/air ratios between 14 and
16:1 seem to be the easiest on the pocket.

To set up the mixture in the manner about to be described you
will need an accomplice. The first and essential step is to
part the car in some place which is poorly lit, so that you
can see the combustion colours. Jack up the driving wheels of
the car until they are just clear of the ground and in the
interest of safety, securly blockthe car so that it cannot
move under any circumstances.

At this point, warm up the engine, then remove a spark plug and
replace it with a Colortune. Set up the mixture so that you
have a fuel/air ratio of about 12 to 12,5:1 (orange/blue) at
normal tickover revs. If you have multiple carbs you will
have to do this for each cylinder or set of cylinders having a
carb.

Next, get your accomplice to put the car into gear, usually
third gear is best, and increase the throttle opening but at
the same time put on the brake. (Continue opening the
throttle and increasing breaking pressure until your
accomplice ends up with the throttle wide open and the revs
pulled down by braking to 2000 rpm). You can now look ath the
Colourtune and at this point it will reveal what the fuel/air
ratio is under the prevailing conditions.

It can then be noted, preferebly by colour rather than
reference to its fuel/air ratio. After this, let the brakes
cool for a few minutes, then repeat the procedure at 3000 rpm
then at 4000 rpm and finally at 5000 rpm, stopping to let the
brakes cool between each run.

As far as brake overheating is concerned, it should not take
more than fifteen seconds to ascertain the mixture ratio at
each rpm interval, so they will be well within their capacity.

Once you have an indication of the state of affairs of the
fuel/air ratio up the rev range to 5000 (5000 rpm is the limit
on the Colortune) the necessary corrections can be made to get
it right. Not only can the full throttle conditions be
catered for in this manner, but so can part throttle and
transient conditions. For instance, a hesitant pickup when
going from part throttle to full throttle could indicate that
the mixture is too weak during the transition from one state
to the other. During the transition period and for a short
while after the Colortune should show a rich mixture
condition. If it doesn't, then you can bet your life that on
a fixed jet type carb, the accelerator jets or pump stroke are
inadequate.

[Brian R Adams]

"Maybe it's time to stop playing."

Careful. Read Brian Adams' posts re coughing on deceleration with Webers.

My posts were really critical of K&N filters, but since they are ubiquitous on Webers, the association is valid. Anyone running Solexes w/ K&Ns would also be at risk , as it were, for obvious reasons.

Brian

[Brian R Adams]

Maximum power occurs when the fuel/air ratio is between about 12,5 and 13,5:1.

Not trying to be pedantic, but don't you mean "air/fuel" ratio (not "fuel/air") is 12,5:1 etc?

Brian

[David Jones]

You are being pedantic. I did not write it I stole it off the internet to save time. We Brits learn to interpret cockups and correct them.

[Brian R Adams]

We Brits learn to interpret cockups and correct them.

Sorry, I missed the plagiarism part, I thought you'd written it all. As for the pedantry, it's saved me from some little grief in technical work over the decades.

BTW where can I find any articles you've written on tuning for Ethanol mixtures?

[David Jones]

Brian, Do a search under "ethanol" and also send me your E-mail address and I will send you a PDF of an article I wrote for the magazine some years ago. Unfortunately there is no link for your E-mail or your location in your posts.