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Old 01-05-2003, 03:34 PM
Vronsky's Avatar
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Join Date: Jul 2002
Location: Amsterdam, Old Europe
Posts: 839
CO emission

Hi All,
Does anyone know of a way to measure the CO emission DIY?

'01 DT41 - M54 - A5S 325Z - 482
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Old 01-05-2003, 03:40 PM
sunil190e-1.8's Avatar
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Join Date: Jun 2002
Location: uk
Posts: 236
i used to use an exhaust co analyser on cars without a catalytic converter.

i would also like to know how to check the co emissions on a diy basis on my 190e-1.8 litre ,1993,w201 engine with a catalytic converter.
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Old 01-05-2003, 11:06 PM
Mark Herzig's Avatar
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Join Date: Apr 1999
Location: Austin, Texas
Posts: 380
I'd also like to know the answer. IF you measure the exhaust at the tail pipe with a catalytic convertor, I'm wondering if there is some basic adjustment you can make to guess-ti-mate the Co level...
Mark Herzig
1995 E300D 153K
1985 300D 142K (sold)
1979 450SL 122 miles (sold)
1992 500E 127K (sold)
1987 300SDL 132K (sold)
1986 300E 161K (sold)
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Old 01-06-2003, 10:49 AM
Posts: n/a
co emissions


There is a way to set CO without an analyzer but I do not have my manual handy, so perhaps I can look that up tonight.

With an analyzer, on vehicles with a cat one must keep in mind that cats do not effect the amount of CO2 and O2 in the exhaust stream, therefore by measuring these gasses along with HC and CO we can see what an engine is doing. If your engines have an air pump or air injection system it must be disconnected or plugged before testing the exhaust.

The exhaust of a normal engine will be about 13.8 to 15% CO2 and 1-2% O2 if an engine is running rich the O2 will be lower than this and CO will be high, if lean, O2 will be higher and CO low. Since CO2 is a by product of combustion, the % CO2 is dependant on combustion efficiency including the air/fuel ratios. The % CO2 decreases as as the air/fuel mixture becomes rich or lean.

measuring the exhaust quantity of a vehicle with a cat does not accurately descibe the conditions of the engine. If the cat is working properly it will be reducing the amount of HC and CO in the exhaust stream before it exits the tailpipe So to use an analyzer one should test exhasut gasses that have not been treated. One way to do this is to insert the test probe into a hole drilled in front of the cat or, on some models techs are to insert the test probe into the exhasut opening of the ERG valve.

A properly tuned vehicle with computer controls will emit approximately 50ppm HC or less.Less than .5% CO, 1-2% O2 and 13.8-15% CO2.

Good Luck
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Old 01-06-2003, 12:56 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
CO is the gas used for mixture analysis. It should be about zero after the cat. Not much use.

It is represented by O2 sensor voltage for electronic calculations. Within the CO range of 0.0 to 1.0 the o2 sensor will give voltages of 0.0v to 1.0v and can be used for mixture correction and analysis. Mixtures above 1.0%CO will all look like 1.0v on an O2 sensor, so some correction is needed to find the range.

The DIY article: evaluating engine controls shows a couple ways to use the KE engine management system for adjusting/reading mixture.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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