Pre cat emsissions

[antonyj]

Just a quick one, Griff passed the MOT this morning.
The only thing that was mentioned was the emissions(CO2?)was a bit high.
What should it be for a April '92 car?
And what might make it too high?


The car has stood for a while whilst other issues were sorted , could this effect it?
In other words , does it need a good run?

Thanks

[Trooper2]

Co2 coming out of the tail pipe should be at a rate of 14-15 % ,this indicates that your engine is having efficient combustion (stoichiometry). If it climbs higher than this it's starting to be considered bad as Co2 is a green house gas.

It depends on whether you believe in global warming how bad Co2 actually is.

[barreti]

I've heard stories of cars just failing their CO2 emissions and the garage advising the owner to take the car out for a good thrash and bring it back for retest. When they subsequently did this the car passed the test.

>> Edited by barreti on Sunday 17th April 17:31

[pantani201]

The Emissions tested in a none Cat test, ie a vehicle first used between August 1 1986 and July 31 1992 is

CO <=3.5%
Hydrocarbons <= 1200ppm
For a vehicle first used between August 1 1992 and
July 31st 2002 a Cat test is carried out providing and exact match is found in the Analyser Database or in Service Emissions book. If no exact match is found then a none cat test is carried out.
Source:www.vosa.gov.uk/...gnition%20-%20non%20cat%20test.pdf

and www.vosa.gov.uk/...20passenger%20cars%201992-2002.pdf



>> Edited by pantani201 on Sunday 17th April 17:53

[antonyj]

pantani201 said:

The Emissions tested in a none Cat test, ie a vehicle first used between August 1 1986 and July 31 1992 is CO <=3.5% Hydrocarbons <= 1200ppm For a vehicle first used between August 1 1992 and July 31st 2002 a Cat test is carried out providing and exact match is found in the Analyser Database or in Service Emissions book. If no exact match is found then a none cat test is carried out. Source:<a href="http://www.vosa.gov.uk/...gnition%20-%20non%20cat%20test.pdf"><a href="http://www.vosa.gov.uk/...gnition%20-%20non%20cat%20test.pdf">www.vosa.gov.uk/...gnition%20-%20non%20cat%20test.pdf</a></a> and <a href="http://www.vosa.gov.uk/...20passenger%20cars%201992-2002.pdf"><a href="http://www.vosa.gov.uk/...20passenger%20cars%201992-2002.pdf">www.vosa.gov.uk/...20passenger%20cars%201992-2002.pdf</a></a> >> Edited by pantani201 on Sunday 17th April 17:53

Thanks for that, whats the difference between CO and CO2?
What might cause the reading to be around 4.2%????

>> Edited by antonyj on Sunday 17th April 18:26

[pantani201]

The level of 4.2% CO is due to the fact that the fuel/ air ratio is not at the Stoichiometric ratio. This is usually in the ratio of 14.7:1. At this ratio or slightly higher there is enough oxygen in the air entering the engine to completely burn all the petrol to carbon dioxide and water. There is therefore very little carbon monoxide in the exhaust and no free oxygen. Where the mixture is richer than the Stoichiometric ratio (ie more fuel or less air) there is insufficient oxygen in the air to burn all the carbon in the fuel completely to carbon dioxide. The only info I can find as to the manufacturers recommended level for a Rover V8 3.9 engine giveds levels of CO 0.5 - 1 % and Hydrocarbons of 300ppm.
To achieve this adjustment of the Idle Mixture (CO) must be made on the MAFM on the air intake. In order to get the correct readings a gas analyser is needed to monitor the emissions during adjustment.

[steve-v8s]

CO is Carbon Monoxide, CO2 is Carbon Dioxide. In my experience the problem is high CO at idle, which as I understand is because the mixture is too rich. Normally this is adjusted with the twiddle pot on the Air Flow Meter. Despite many attempts at fixing it, (different ECU, sensors, fuel pressure regulator, AFM) my 92 V8s (same engine as a pre cat Griff) always struggled with this. For MOT I removed the bypass pipe at the rear of the plenum chamber and replaced it with one fitted with a radiator drain valve. Opening the valve a little let un metered air in and leaned up the mixture.