I've just had the car MOT'd and got the following results:
Fast idle test:
CO: 0% vol
HC: 0 ppm vol
lamda: 1.003
Natural idle test:
CO: 0% vol
How is this possible?
Surely there must be some products of combustion.
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Yes there should be! I think you must have the most environmentally clean car on the road either that or they forgot to turn the engine on.
--
\"Nothing less than 8 cylinders will do\"
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The main products of combustion are CO2 and H2O. These are not measured for the MOT. Levels of CO and HC will be very low if all is well and I am not surprised that the meters read zero.
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The CO (carbon monoxide) and HC (hydrocarbon) measurements show whether the cat-converter is working correctly. If it has reached running temperature, both CO and HC should be fully oxidised to CO² and water, so both should read zero. Lambda should be 1.00 if 'carburation' is correct, i.e. fuel and air (oxygen) are exactly in balance as controlled by the ECU.
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Neither will actually be at zero but the accuracy of the relatively low-tech analysers does not register at that low level.I worked on exhaust emissions for more than 30 years and current levels are getting so low that more and more hi-tech equipment is required nowadays.For example,our analysers would be calibrated(not just chcked)before and after every test(about every hour)not just once or twice a year.
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So are you saying that before every test, the equipment is recalibrated.
If so, how is it done?
Reggie
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Doc, what car do you have ? Thought my figures were low too, almost went back to ask if their m/c was calibrated properly!
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Doc, what car do you have ?
Nissan Micra 1.4 (1991)
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I'm talking full legal testing for certification testing not for MoT.On a certification test each analyser would be checked against a standard gas supplied by a gas manufacturer(British Oxygen Co. for example).This would be in the range that would be expected to be used for the test.At a MoT station the analyser would occasionally be checked with a multi-gas sample of quite a high concentration.
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