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I have a gastester and sofar it was brilliant. Today I did a check before my MOT on Monday and I did not believe the values. My set up is too good with a CO values from 2.5% this value is very near to the initial calibration value. Is there any easy way to confirm that the tester is working properly? Or at least that it is measuring the exhaust gas. I know I can do a test with another tester and compair the values. When one is doing the check in the middle of nowhere (away from people and houses) it is just a pain in the neck. I could just turn the carb screw a half a turn in and look if anything changes. Then turn it back but with my carbs, it is very time consuming to get them correctly back in balance.

Edited by Peter Douglas Winn
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Yes I also believe in them. I wanted to know if somebody had a brilliant idea to make sure id the Gunsons was reacting.

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9 hours ago, Rodbr said:

Hi Peter,

I use four Gunsen colour tunes and match the colours, in my view a more reliable state of tune throughout the Rev range.

Rod

Why do you need four?  Or do you have more than two carbs?

Rgds Ian 

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I also use 4, it gives you a better view of whats going on.

You sometimes have to compromise the carb settings to get an acceptable flame colour on adjacent pots.

Bob.

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Waldi

I was in the middle of the sticks. I could go to a testing station/garage and compare the values but I was trying to set it up for Monday's MoT.

I only use 2 Colourtunes because I only own 2, no other reason. The garage that did my engine, have put 2 openings in the manifold so that lambda sensors can be used. This is far too high tech for me. I was bought up on a piece of wood and a short hose pipe and a vacuum guage to get the carbs right . That was how the garages up to the early 60s did it.

I admit one does not have to do it in such a primative way. The Gunsons are nice and easy.

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Hi Peter, ok, got it. Here the allowable percentage for CO on cars first registered before Sep 30 1986 is 4.5%. 
Waldi

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Just taken the car out for a long run to check everything. From the consumtion, Gunson's is correct. The consumption matches under 3%. I have had for 4 years troubles with the carbs going rich. Absolutely nobody could find out what was wrong and now for 2 years the values are constant. :P:):D

Waldi aren't you lucky here in Germany it is 3.5% max. Normally they turn a blind eye so long as it is reasonable. i.e. 12% is a no go.

TR Enterprises did some work for me and the carbs afterwards were setup for over 10%. When I found out, I rang them. The answer was good "Peter the car goes like hell and you don't come back and complain the cylinders have burnt out. If you want to change the value then just do it." Afterthought "naturaly at your risk." A fair logic. You can't complain about that.

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Just come back from the MoT the CO value was 2.34 % how about that. Gunson is measuring very accurately. Thank god.

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Very good Peter.

And thumbs up for the Gunson, are they always that reliable?

Cheers,

Waldi

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Hi

By breathing across the probe does it measure your own co2 which should be about 3.5 to 4% , you would know if it's in the basic ballpark I've used an old patient monitor before to get a basic reading.

Richard

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Lebro

I have an California car and there is a label on  the wing stating the allowed CO values. If you look in the Moss catalogue you can see these labels and none are above 3%. I did about 150,000 miles on the old engine and had no problem what so ever. with about 2.5%. I had top speed,  acceleration and no valve burning. Also the man behind me did not complain of stinking exhaust. I take the attitude everyone can do as he wants with his own property. So long as it does not disturb others. If somebody wants to have a consumption of 20 mpg then why not. I don't think the greens like me.

Edited by Peter Douglas Winn
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On 16 May 2020 at 11:45 PM, Peter Douglas Winn said:

Yes I also believe in them. I wanted to know if somebody had a brilliant idea to make sure id the Gunsons was reacting.

Try it in a modern car, it should be almost zero if it's working ok.

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Used the digital and before that the analogue CO test meter for 25 years. The Gunson is an excellent piece of kit for home mechanic. Most classics 1950/60's weren't designed to run at a mixture CO of 2.5. more like 3.5 to 5. That was why we saw a reduction in engine power in the 1970's, the changes were to reduce the emission level and hence CO. Having set-up many engines, from my own long term experience the older type can have problems running at a CO of 2.5. But it up to you what you do.

The Gunson does drift off cal with temperature, and you have to allow for this by rechecking the cal now and again. Which takes time. Un-like the much more expressive professional kit which allows for this. 

 I like the idea of the colour tune, but find it difficult to use reliably. I set-up the carbs using the old standard methods, plus a flow meter, then trim in the mixture on the CO meter. The final check I do is to use the car, and then check the two outer plugs, 1 and 4 or 1 and 6, for colour and adjust accordingly.

Dave 

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I agree with what you have said. Years ago (young, no money and rallying) I used a vacuum gauge and firstly set up the dissy for max Vacuum then backed it off 1 " Hg. Igniton solved. (Still applicable with modern petrol. The manufacturers values are not valid anymore).

After that I played around with the carbs mixture balance etc. The problem was always at what revs should they be balanced. The was where my colour tunes came in. Took it for a drive and listened for pinking and god knows what else. Got home and did it all over again. Something had always changed.

By the way did you know that the temperature compensation thing under the Yellow cover on the Strombergs is very important. To set them up use a small container of water. Put a thermometer in and drop the compensator in the water. The add hot water untill they open. This should be about 140°F. then put in cold water and see when they close.  It does not matter which temp +/- a brick but they MUST open and close together. There is and ajusting screw. If you don't get it right you will have Kangeroo petrol when the car is luke warm. 1 carb rich and one carb lean.

By the way they make about 1 to 2 mpg more when completely closed all the time.

I still have all the gubbings from those days.

Who knows when I will need them again.

Edited by Peter Douglas Winn
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Thank goodness I don't have the temp compensation, Stromberg CD150S, on the Vitesse. These came later when the Vitesse had finished production. I have set-up GT6's with them and agree with your findings. Take you time setting them up.

The later Waxstates on the TR7 don't generally, apart from age, give any problems because it's a cross flow engine and there isn't a hot exhaust sitting just below them. The opposite on a Spitfire or 2000, the best thing to do is to fit standard jets.

I bet you had a favourite test route, can't beat the road test. 

Dave

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Yes. I bet it is now a housing estate or a delivery depot for Amazon or the like.

Get out on the road Boot it, nobody to complain, no 40 Tonner blocking the little road and lots of parking bays to do checks. I wasn't all bad in those days. No money but fun.

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On 5/22/2020 at 11:08 PM, DRD said:

Try it in a modern car, it should be almost zero if it's working ok.

That may be related to running on efi with a cat!

Unless you have a standard car where idle CO levels were stated by the manufacturer then idle readings are of limited value unless you have done a “calibration” exercise on a rolling road to see what/how a tickover CO level of x% relates to at running speeds.

Many cars can be set to give negligible CO levels by weakening the mixture which is why current MOT tests on modern cars also specify the lambda readings too to prevent people tricking the system by leaning way off just to meet the CO levels.

Many of our cars were not built with emissions in mind and trying to get the, to fit modern levels at a single point in the Rev/load curve may be damaging to the engine or result in worse pollution at other revs and loads.

It doesn’t mean our cars can’t match the modern emissions but realistically that requires Efi and a cat along with computer and rolling road time.

 

 

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1 hour ago, Andy Moltu said:

That may be related to running on efi with a cat!

That is exactly my point!

The whole issue of whether setting the CO at idle is going to give the correct mixture at other engine speeds is another matter entirely. 

The OP just wanted an easy way to check whether his meter was working or not.

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My garage who did the engine, have put 2 entry points in the exhaust for Lambda sensors. They have a rolling road and they set their cars up this way. The are looking for a sensible system when the car is on the road and not on a test bed. So far no luck. I think it is a question of the price.

What should I do with my underground garage no electricy or lighting? I get my Gunson out and connect it to the battery and do my best. The colour tunes are a very primative approach to solve the higher revs problem. My 6 had the complete emmision gubbins. Interestingly my consumption was about 5% to 10% better than my friend who had removed all that stuff. Our production numbers are only about 20 apart.

Question:- if you have an old Steam Engine do you fit it out with fuel cells or try and keep it running with minimum of changes? Or perhaps rebuild it to take E10 fuel.

I thought we are in a Classic car club not a formula one development team?

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