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soldave

Using a Colortune with a Carbtune

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Thinking about the future and when my carbs need balancing once again (or mixture needs changing due to me modifying the intake), I have a question.
 
I've read in guides about balancing carbs that it talks about adjusting the idle mixture for the strongest manifold vacuum for each barrel.  However, if I have the Colortune in one cylinder, would I be adjusting for the right mixture according to the flame colour instead?  And is that the case even if that doesn't give me the lowest vacuum?
 
Thanks for anyone who can clear up what is probably a very simple question :)
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No. The carbtune will sychronize the butterflys of the two bodies and the colourtune sets the idle and transition mixture.

 

They are easy to use and do a good job. If you can get a second colourtune adjusting time is shorter and even easier to do.

 

Vivid blue to slight yellowing gets the low speed tune and smoothness pretty well correct on most carbs.

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Thanks for that.  I read about the vacuum thing here: http://www.mlmparts.com/media/pdf/carbtune/using-carbtune-ii.pdf

 

So I'm understanding that I'd balance the carbs, setting the mixture screw for the strongest vacuum.  Then I use the Colortune to tune each barrel of the cylinder for the vivid blue to slight yellowing, right?

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Not necessarily but quite likely the highest vacuum. Without a vacuum gauge you won't know.

 

Use the carbtune to get the same airflow through each barrel. Try to get the idle smooth and of low rpm. You'll find that adjusting the idle mixture screw may or may not upset things and further fine tuning is required on the carbtune is necessary. The weight of the miniscule amount of emusified fuel drawn in may effect the airflow balance.

 

If the idle is too high the idle jets may be no longer working and fuel is being pulled from the main jet which isn't adjustable while the engine is running.

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Thought about making a new thread but will just update this one.

 

Used the Colortune across all cylinders and found that all of them needed richening up a bit (in fact, in cylinder 2 you could only see the spark from the plug and no combustion).  Mixture screws were unscrewed by the following amounts:
Cylinder 1: 2 full turns
Cylinder 2: 3.5 full turns
Cylinder 3: 2 full turns
Cylinder 4: 2.75 turns
 
So things were richened up until the flame was blue with the odd yellow fleck.  It's running fine now when the engine is warm but when the choke is pulled on cold starts, the engine starts and idles at around 800rpm but the idle slowly drops and becomes rougher.  If left to idle on its own, the revs will drop and eventually die.
 
Would richening the mixture have caused this, maybe causing it to be too rich now when the choke is pulled?  If so, how would I remedy it without just increasing the idle (which would also raise the idle above where I want it when the engine's warm)?

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Also, am sure I'm being really dumb with this, but if I'm using the mixture screws to get the same airflow through all the carbs (and likely the strongest vacuum), then when I adjust the mixture screws to get the right fuel mixture according to the Colortune, won't it always knock things out of sync?

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Idle and choke are different circuits and not related. The colourtune is applicable only after the engine has reached normal running temperature. Often the choke is superfluous and not necessary. At least that's the case in our climate, a couple of pumps with the throttle to prime the carbs, hit ignition, play with the revs for several seconds and everything's up and running.

 

Those idle settings are out. They should be virtually the same. Something else is seriously wrong. Did you check the butterfly syncro, float levels, that all the emulsion tubes and jets are the same, undamaged and not blocked? Stripping, checking and rebuilding the carbs is worthwhile especially if the car hasn't been run for a long time.

 

What carbs are you tuning, Webers, Dellortos or Solex?

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Twin Dellorto DHLA 45, and I'm pretty sure they were rebuilt fairly recently.  Car has been run fairly regularly in the past.  Will try putting my mixture screws back to where they were and see how that goes.

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Dave when balancing the carbs you dont do it with the idle screw. You adjust the each carb by reducing the flow of the highest by opening the air bleed until both chokes flow the same on each carb, Then you can use the linkage to get both carbs to flow the same amount as each other. 

 

Once the carbs are all flowing the same you can then do the coloutune. I would reset the idle screws again by winding them all in then out 3 1/2 turns and see where you are. Once the colour tune is good go back and check the balance then the colourtune then the balanceuntil everything looks good.

 

Thats what I would try.

 

Buddsy

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Dave when balancing the carbs you dont do it with the idle screw. You adjust the each carb by reducing the flow of the highest by opening the air bleed until both chokes flow the same on each carb, Then you can use the linkage to get both carbs to flow the same amount as each other. 

 

Once the carbs are all flowing the same you can then do the coloutune. I would reset the idle screws again by winding them all in then out 3 1/2 turns and see where you are. Once the colour tune is good go back and check the balance then the colourtune then the balanceuntil everything looks good.

 

Thats what I would try.

 

Buddsy

Think that dim light bulb over my head has finally switched on.  Not sure how you've done it but I think I follow now.  Many thanks :)

 

Will get on it in the morning.

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If you havent got it there is the book called "How to build & powertune wbber & dellorto DCOE, DCo/SP & DHLA Carburettors by  Des Hammill" I think it is a must have if you have carbs. There was a downloadable copy going around but the book is readily available for about £12 or £15.00 Worth every penny if you ask me.

 

Good luck with it all.

 

Buddsy

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If you havent got it there is the book called "How to build & powertune wbber & dellorto DCOE, DCo/SP & DHLA Carburettors by  Des Hammill" I think it is a must have if you have carbs. There was a downloadable copy going around but the book is readily available for about £12 or £15.00 Worth every penny if you ask me.

 

Good luck with it all.

 

Buddsy

Got it on my birthday list and should be getting it in a couple of weeks :)

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Just to add as a result of this thread I thought I would check my car last night. Ive never got on very well with the colortune as our plugs are down the hole at an angle. I thought last night I would be ok as it was dark outside and I now have my much quieter exhaust I can start the car at night times. Firstly I connected my Carbtune. Its the balancer with four columns which connect directly to the carbs. For turbo owners this is great as you dont have to remove the whole plenum assy to check the flow. Once up to temp I was able to see one set of carbs was flowing a tiny bit more than the other and was able to adjust to get right. 

 

I tried with the colortune but again I just cant see well enough down and round the corner. I think it looked ok? (chaps with a front engine maybe easier than on the Esprits?) 

 

I have been setting my idle mixture by the colour of the plugs. It has taken me a long while to keep adjusting and they all look spot on except No.1 which was a tiny bit rich. The DHLA have very fine adjusting screws but still I am adjusting maybe under 1/8th of a turn to get right. When I leaned that one off a bit the engine RPM increased slightly and I then had to readjust the flow of that bank of carbs again.

 

All looks and sounds pretty good.

 

Keep us upto date how you get on. Sometimes these things like the colortune seen easier than in reality!

 

Buddsy

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Buddsy, you need to steal the wife's make up mirror & then you'll be able to get an excellent view of the business end of your ColourTune plug.

 

I suggest you persevere, the results will be worth it.  :thumbup:

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I suggest you persevere, the results will be worth it.  :thumbup:

 

Ok so connected up the carbtune and spent a bit more time with the colortune. Not sure if its the colortune or the combination of that with the carbtune and my new exhaust but she is now driving really nice! Feel so much smoother. It used to be a bit like driving a lorry but now feels so much lighter on her toes!

 

Thanks for making me persevere with the colortune. Still not too sure where the correct blue comes after the yellow but think Im somewhere near!

 

Buddsy

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:thumbsup:

 

Yeah, I only ever saw yellow, blue or just the spark but it always passed the MOT when set to blue. :o

Edited by jonwat
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The carbtube is a must if you have a turbo...and carbs.

 

Buddsy

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I never used a carbtube, always got on better with a carbalancer. :lol:

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Doh!

 

Buddsy

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My Carbtune came yesterday so this morning I finally got to balancing the carbs (using http://www.espritfactfile.com/carbbalancing.html ) Cylinder 2 (which you might remember was initially only sparking and not igniting when I used the Colortune) was pulling much more vacuum than any of the others.  Once I got them both carbs pulling the same vacuum the idle increased and engine sounded much stronger.

 

The guide I used was just using the Carbtune (adjusting mixture screws until I was pulling the most vacuum), but I might use the Colortune to set the initial mixture, and then balance with the Carbtune.

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Not got around to doing this yet, but do you think I'm better tuning by highest vacuum at idle, or for the ideal flame colour (starting to go amber)?

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Two different things. You need to balance the carbs with each other. Set the idle with the colourtune.

 

Buddsy

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OK, so you're saying balance carbs using Carbtune, then use Colortune to get an ideal flame colour, followed by Carbtune to make sure that changing the mixture hasn't knocked anything out of sync?

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Yep I would balance the carbs. Find lowest flow on each and use the bypass to reduce the flow of the other to match. Then use the adjustment on the linkage to get the flow of both carbs the same. 

 

Use the colourtune to set the idle.

 

Check the flow again

Check the colour tune

Check the flow again.....bored yet? hahaha No just keep on until you are happy with it.

 

Buddsy

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