Emissions way off, no lights ... Cat?

T

tertius

Active member
Just got the car MoTd, it passed but the emissions are well off what they should be.

There are no warning lights on the dash, so presumably not a sensor, what's the likely culprit? Cat failing? I have a Supersprint sports cat, so I guess not that long lived. And of course stupidly expensive.
 
my MOT is due in the next couple of weeks, i always hate the emissions test as the car barely passes..... :o :o :o :o :o :o :o :o :o

im guessing those 100 cell cats just needed to be properly warm to do their thing.... cold they'd be useless.... wouldn't worry about it tbh....
 
Good point I hadn't thought about the temperature of the exhaust/cat. It would probably have been stone cold, given where it was tested.
 
tertius said:
Good point I hadn't thought about the temperature of the exhaust/cat. It would probably have been stone cold, given where it was tested.
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deinfitely !! those HJS cats last a very very long time!!!


on a completely different subject but as your here and run track tyres....

fitted my road legal slicks (ad08R) and i was kinda shocked to see how wide they were (more so than pilot cups) when your using 888 are you ordering one size smaller to compensate?? what size rim / offset are you using currently and whats your rub situation like under track use.... this was never a worry with cups but with these newer brands they seem wide, the 265 I've just put on looks very close to a 275 section tyre to me.....
i run pretty aggressive offsets but I'm pretty certain it'll be fine but I'm also running a pretty aggressive rim and width too so i may need to raise the car slightly.... i doubt it however.
 
Take your car for an Italian tune-up before the MOT and also on the way to the MOT test and have it nice and hot for the emissions test and it should be fine. :thumbsup:
 
tertius, had the exact same thing but with my stock cats and it turns out they were destroyed... The car was at around 40k miles if i remember correctly. I believe it must have been the combination of fuel quality and possibly/maybe the fact that it had been running very rich at some point for a couple of months (bad O2 sensors)... Bought a set of used ones from UK and the car's been OK with emissions since, now at 65k and had my MOT last week.
 
Beedub said:
on a completely different subject but as your here and run track tyres....

fitted my road legal slicks (ad08R) and i was kinda shocked to see how wide they were (more so than pilot cups) when your using 888 are you ordering one size smaller to compensate?? what size rim / offset are you using currently and whats your rub situation like under track use.... this was never a worry with cups but with these newer brands they seem wide, the 265 I've just put on looks very close to a 275 section tyre to me.....
i run pretty aggressive offsets but I'm pretty certain it'll be fine but I'm also running a pretty aggressive rim and width too so i may need to raise the car slightly.... i doubt it however.
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I suspect that is more to do with the way a given manufacturer make and size their tyres than it is to do with track tyres per se.

I haven't used R888s on the M so can't comment on those. The Avon ZZ-Rs I currently have are 265 at the rear and not noticeably different from the 265 PSS I use as road tyres.
 
Mine is standard and even I was nervousness watching the emissions readout on the computer screen come down to an acceptable figure. Encouraging the young mot tester to give it a few more rpm helped ignite the cats as from cold they were not doing much ;). After about 30s holding at moderate revs things were warm enough. Am I right in thinking that euro Z4Ms run 200 cell cats as standard?


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What effect would a dirty air filter have on the mot? My mot test is this evening? I do have a new filter in house, but if it has no effect can't really be arsed to change it now as I'd rather do it during oil change.
 
Vanne said:
What effect would a dirty air filter have on the mot? My mot test is this evening? I do have a new filter in house, but if it has no effect can't really be arsed to change it now as I'd rather do it during oil change.
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No effect on MOT.


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Beedub said:
What's your rear rim width and offset ??


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10J re. offset the Apex wheels are ET25, not sure exactly for the Forgestars but very similar.
 
Beedub said:
Vanne said:
What effect would a dirty air filter have on the mot? My mot test is this evening? I do have a new filter in house, but if it has no effect can't really be arsed to change it now as I'd rather do it during oil change.
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No effect on MOT.


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Couldn't a dirty air filter cause higher emissions & risk failing the MOT emission test?
Regards
 
Smartbear said:
Couldn't a dirty air filter cause higher emissions & risk failing the MOT emission test?
Regards
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A dirty filter will restrict the airflow (i.e. reduce volume of air entering the cylinders). The MAF will simply monitor the flow of air and the ECU will adjust fuelling accordingly in conjunction with the O2 sensors. This won't change the emissions.
 
Yup no dramas, my car passed without a hick up. And with my race cans on.. Lol gotta love it.
 
I'm a bit confused by this mention of cold cats, I always thought it was part of the test to ensure the cat was up to operating temperature. Again it's all well and good taking in a warm car but only if the test follows very soon afterwards.
 
BRC said:
I'm a bit confused by this mention of cold cats, I always thought it was part of the test to ensure the cat was up to operating temperature. Again it's all well and good taking in a warm car but only if the test follows very soon afterwards.
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do you think the cat gets warmer by idling away on the ramp or when your cruising along???? trust me they aren't getting to proper temp by idling.
 
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