Adjusting carb mixtures with "Colourtunes"...

Some will know of my extensive work I've been doing to the car recently, in preparation for this long drive down to Concorso. My first real big trip with the car. Only set-back so far was one of the oil-cooler hoses decided to blow today... Fixed it by putting in the old, original hose... Hope that holds!

Anyways, to finish it off, I wanted to get it tuned so that it would run as efficient as possible. That's the point when the car runs best anyways. Up till now, I've just been adjusting the mixtures based on the rise and fall of RPM's. That works, but wanted to know the exact results. With the Colourtunes, you get that.

In the following set of pictures, is the kit of four Colourtunes (14mm Motorcycle kit), how the viewerscope attaches to the 'Tunes and the view of light from my living-room window through the 'Tune.

After that, is how its installed in the car for the front bank of cylinders on my 308. Its a good thing I put 90 degree boots on the plug wires, as with the 'Tune extension installed, makes the whole set-up close to the firewall. It also took a long time to install just because it is an awkward location. A key "tool" to help is the Borescope laying on the blanket, which helps to look down the plug well to see if the scope is attached correctly and to pick up the copper washer of the 'Tune if it falls off (putting grease on helps to keep them on and it worked, only one fell off down into the well). The borescope is not included with the Colourtune kit, I bought that a while ago... It has saved my butt many times already, I recommend it. Naturally, installing the 'Tunes in the rear bank only took a few minutes...

The engine is warm (the window fan blowing at the radiator keeps things from getting too hot) and tuning begins. Obviously one needs to make sure the timing is correct and the airflow of the carbs are enough to get it running at the right idle speed (about 4 kg/h on my STE Synchrometer).

I was amazed at how at an instant, when the screw is turned too much to rich, that the combustion flame turned orange instantly. Also leaning it out too much produced a white-ish flame. I went for the middle, which resulted in a nice sky-blue flame - which turned out to be not far off from the usual settings I had before, this time an average of 3 1/2 turns out of the mixture screws.

I'll take the car out tomorrow out on the highway to see how well it runs, but my initial runs around the block were great. Nothing does beat running one of these cars with the air-box off to hear the carbs, even though that's not a good thing to do!
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1. Damn that engine is clean.
2. You got a set with 8 colortunes?
3. Want to rent them?
4. Damn that engine is clean.

I may make it to Monterey this year, for a day. See you there perhaps.

 

This is really cool.
Love to know much and where do you get the boroscope to go on the front bank?
Excellent post and pictures!
thanks
rt

 

Hi Mitch,

The set I have is only 4. That is the largest kit that they produce. I just worked on one bank of cylinders at a time. I did the front bank first as I knew it would be the hardest to get to/work with. Then when done, pulled them out, put the plugs back in and then worked on the rear bank.

I've already had an offer from another F'Chatter to use them, but I'm not too keen on lending out my stuff... Bad experiences in the past... This kit of four Colourtunes was 80 UK Pounds, which is a reasonable amount considering you get all of the accessories with it in the kit (if you buy the Colourtunes individually, they are 21 UK Pounds with nothing else - no viewerscope, no extension, etc). How much do you figure it costs to have a carb tune done at an F shop?

I'm always wiping up when working on this engine. Any and all oil weeps/leaks, grime, etc, I wipe up before it builds up and gets worse. I had plenty of opportunities to clean up after this pre-trip service!

Keep your eyes and ears open for a black-boxer GT4 running around Monterey...

 

I got it from a local industrial/automotive tool supply store, KMS Tools. It was around $400Cdn. It really is a cool tool, not just for this job, but anytime you drop something deep down into the engine, for peering down into pipes, the underside of the car, into the ventilation system, you name it.

 

That engine is amazingly clean!

So... How would one use the Colortune with a V-12?

 

Maybe this method is interesting for comparison...

I bought a Gunson CO analyser for about £65, (they make the colortune as well) on the basis that the 308 has a sniffer plug fitted to each exhaust port and I thought this should be the real bee's-knees.

No complaints about the CO analyser. It drifts a bit but it is very easy and quick to set the correct mixture, (if memory serves the target was 2.5% CO for my 77 308).

The problem was that the sniffer plugs on the rear bank were thoroughly corroded and the one I tried broke off and I had to drill it out and replace it with a bolt. Didn't touch the others! The front bank looked a lot easier since the sniffer pipes are permanently fitted. However of the 4 pipes, 2 were blocked and no amount of compressed air or bike brake cable shoved down them was going to un-block them.

By adjusting the ones I could get to and doing the rest at the tail pipes, the tail pipe values went from an original left/right of 2%/6% to a final 2.2%/2.9%. So the end result was acceptable, just not as easy as I expected. But then come to think of it, what is on these cars..