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 Post subject: Exhaust Emissions
PostPosted: Wed Aug 10, 2022 2:31 pm 
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Clubman

Joined: Sat May 18, 2019 9:39 pm
Posts: 58
Location: Herefordshire
Car Model: ST185 CS/RC
I took the RC for it's MOT recently and tester came to me and said the emissions were just outside the pass levels and suggested I took the car for a run at high revs then recheck. This surprised me because it's always been OK on previous tests but I did what he asked then he rechecked. He came to me again to tell me it was still just outside and at this point I followed him through to the test area where he showed me the readings which included the fast idle test which isn't required for a car of this age but was just above the 0.2% CO limit. It transpired that he was testing the car based on it's import date of 2005 which had come up as "first used" and not the manufactured date of 1991. When I pointed this out he retested correctly and all was well.
The results at idle were: CO 0.17% (pass up to 3.5%) HC 83ppm (pass up to 1200ppm)
It was interesting that the car nearly passed the test for modern cars even with the cat removed. I was pleased that everything was well within the limits showing an efficient fuel injection system and good condition engine but then began to wonder if it might be running a bit lean so would be pleased to hear what other owners are finding and what are typical test results.


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 Post subject: Re: Exhaust Emissions
PostPosted: Sun Aug 14, 2022 11:14 am 
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Group B
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3679
Location: Bournemouth
Car Model: None
If it was running lean, the lambda figure would be out.

I'm surprised the CO readings are that low without a CAT, but I have heard of decatted cars passing the cat test. I think this is why the MOT includes the clause that if a car is meant to have a CAT (i.e. pass the cat test) then it must be fitted.
Are you sure it doesn't have a sports cat disguised as a small extra silencer ?

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 Post subject: Re: Exhaust Emissions
PostPosted: Fri Aug 19, 2022 4:48 pm 
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Clubman

Joined: Sat May 18, 2019 9:39 pm
Posts: 58
Location: Herefordshire
Car Model: ST185 CS/RC
When he was resting the car to 2005 spec the CO and lambda were both going in an out of the pass level but not both at the same time so I suppose the mixture must be about right. Would the MIL come on if lambda was out or is the ECU not that clever?
The car is fitted with a Berk decat downpipe with two O2 sensors close to each other at the top and a two box custom s/s system. Being a pre 1992 car it can pass with the cat removed.


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