Exhaust Emissions

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Tue 2 Nov 2004 20:47
Exhaust Emissions - Doc
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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Tue 2 Nov 2004 21:05
Exhaust Emissions - v8man
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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Tue 2 Nov 2004 21:21
Exhaust Emissions - Pete F
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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Tue 2 Nov 2004 22:37
Exhaust Emissions - Andrew-T
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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Wed 3 Nov 2004 07:51
Exhaust Emissions - jc
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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Wed 3 Nov 2004 10:17
Exhaust Emissions - Reggie
So are you saying that before every test, the equipment is recalibrated.

If so, how is it done?

Reggie
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Wed 3 Nov 2004 10:37
Exhaust Emissions - SP
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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Wed 3 Nov 2004 20:29
Exhaust Emissions - Doc
Doc, what car do you have ?



Nissan Micra 1.4 (1991)


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Wed 3 Nov 2004 19:19
Exhaust Emissions - jc
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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