Have you failed MOT due to secondary cat delete?

[stereophoney]

After reading loads of threads on the subject it seems clear that a secondary cat delete should mean a fail, but is that the experience of those who have had it done?

 

[brucemillar]

No.

Leave the cats in place. Gut the innards of you are really concerned. My 55 passes every time. Never been questioned.

Sent from my iPhone using MBClub UK

 

[lisa110rry]

Cats, primary or secondary, wouldn't stand a chance in my house due to the terrier...

 

[RattlerRattler]

I've had the secondary cats removed with the X pipe installed and the SL55 passed the MOT last week. No issues from my side.

 

[John]

Although it is technically a fail, it relies on MOT testers knowing that, say in my case, my car had 4 CATs from the factory.

In my case, when they saw the two primaries, they passed it assuming it had CATs. I never asked whether they knew it had 4 from the factory as that would be counter-productive!

 

[m2287]

I'd like to know who has failed an MOT because of removing the secondary cats?!

 

[BlackC55]

We have done hundreds. Not one has failed.

 

[andy27168]

My 202 C43 M113 V8 passed many times without the secondary CATs both with the 43 and the 55 engine, though the last time I MOTed it it had been in a body shop for two months having a complete respray and had only done 3 miles to the test station and it failed. I took it back a week later having covered some 300 miles 50-60 miles a day, and it passed easily.

 

[automaniaman]

Having spoken with a local area VOSA inspector on this subject, he confessed to being unaware of its significance in regard to MOT ruling...

 

[nb_racing]

Had de cat on my old C43 with 55 engine same as andy above. Passed legit MOT no problem. The primary cats are plenty for uk emissions.

 

[gasman2]

its the emmisions that are important not the no of cats

 

[John]

its the emmisions that are important not the no of cats

Incorrect.

The situation changed and it is indeed a fail not to have CATs the car left the factory with - and has been like this for a while.

Technically, a 1990 car which left the factory with a CAT, which now does not have one, could fail albeit unlikely.

 

[GeeJayW]

Had de cat on my old C43 with 55 engine same as andy above. Passed legit MOT no problem. The primary cats are plenty for uk emissions.

If by primary cat you mean the small catalyst nearest to the engine; this may be sufficient to pass the MOT 'emissions check', but it is woefully inadequate to meet the UK emissions regulations. It's only there because it's small, close to the engine and warms up more quickly than the main (secondary) catalyst, so becoming active sooner. Often it is only an oxidation catalyst to take out initial cold start HC and CO. Does nothing for NOx emissions.

Without the main catalyst, the tailpipe emissions out on the road will effectively be at the same level as engine-out, i.e. NOx will be more than 10x higher than the regulated limit.

There is a lot of discussion about the effects of vehicle exhaust emissions on local air quality. Removing the secondary cats should be illegal IMHO.

 

[AMGeed]

Removing the secondary cats should be illegal IMHO.

It is illegal. Fortunately, my MOT tester is only interested in the emissions of the car and has passed it 3 years running without secondary cats.:bannana:

 

[markjay]

Regardless of the MOT Certificate status, I would be concerned about any modification that cannot be officially declared to the insurer on account of it being illegal.

99.99% of the time it will not be an issue, but in the rare event that it does become an issue... well, it's risk. Some might be happy with the odds, but even so it's worth being aware of it rather than ignoring it.

 

[Cymruambyth]

Just to clarity for an ignoramus like me what are the secondary cats replaced with? X pipe? I just can`t get used to the quietness

 

[b1g1an]

It is illegal. Fortunately, my MOT tester is only interested in the emissions of the car and has passed it 3 years running without secondary cats.:bannana:

Out of interest, what readings do you get?

I think the CLS has the same bits up front and with everything as per the factory I got these a couple of weeks ago...

 

[renault12ts]

If by primary cat you mean the small catalyst nearest to the engine; this may be sufficient to pass the MOT 'emissions check', but it is woefully inadequate to meet the UK emissions regulations. It's only there because it's small, close to the engine and warms up more quickly than the main (secondary) catalyst, so becoming active sooner. Often it is only an oxidation catalyst to take out initial cold start HC and CO. Does nothing for NOx emissions.

Without the main catalyst, the tailpipe emissions out on the road will effectively be at the same level as engine-out, i.e. NOx will be more than 10x higher than the regulated limit.

There is a lot of discussion about the effects of vehicle exhaust emissions on local air quality. Removing the secondary cats should be illegal IMHO.

When science and medicine solves all the things that kill us...what will we die of?

Serious question....the biggest problem facing the world is exponential population growth...yet everyone wants fewer people to die.

 

[grober]

Its important to distinguish between what's illegal and the likelyhood of getting caught. Experience of past MOT test practice would indicate you may well get away with it. However------an increasing focus on vehicle tailpipe emissions accompanied by a possible tightening up of MOT testing with a number of urban borough councils also designating ‘Air Quality Management Areas meaning the council can test vehicles at the roadside and issue fixed penalties to drivers whose vehicles fail, may mean things may change in the near future.

 

[AMGeed]

Out of interest, what readings do you get?

I think the CLS has the same bits up front and with everything as per the factory I got these a couple of weeks ago...

Looks like my reading are a bit higher than yours but passed anyway. MOT this morning.