Is a cat needed on a diesel engine?

tsb

Is a catalytic converter needed on a diesel engine in order to pass a mot?

The vehicle in question is a ten year old 1.9 litre non-turbo small van and I can get a stainless steel made-to-measure full exhaust system without the cat (with life-time guarantee) for half the price of the replacement standard exhaust.

bengalknights

It would be as you would usually fail the emissions test unless you can keep the exhaust emission within the tolerance limit.

Notmyrealname

bengalknights wrote: »

It would be as you would usually fail the emissions test unless you can keep the exhaust emission within the tolerance limit.

It is a 10 year old DIESEL . It does not need to have a CAT.

pulliptears

Decatted our old 2.2 CRD PT Cruiser some years ago, always flew through emissions tests

forgotmyname

Diesels are not tested for emissions only a smoke test.

No issues so far, Next years MOT i going to be strict on decats but, The wording says it applies to all
vehicles where the CAT is part of teh emission test and on a diesel it doesnt.

So your safe even with the new 2012 rules.

Unless they bring in emission tests for CAT equipped diesels. Had mine removed a while back, I got
slightly better fuel consumption after, And slightly more more.

Not the 25BHP they claimed but i knew that from other peoples experiences, Expect upto 5 BHP extra and
you should be happy.

sarahjayne1977

My Hubby got a decat on his 2005 Mondeo ST diesel and never failed MOT for it.

citykid5

have recently mot'd my 2001 seat arosa 1.4 tdi,which i had decated in april.mot test showed permisable levels are 2.5ppm and my car read at 0.35ppm without the cat.better fuel economy upto 80mpg and a lot more responsive.i wont be fitting a cat to my car if i can avoid it in the future

paulday

My company still runs alot of Cirtroen Dispatch 1.9D's, all around 5/6 years old. None of them will have Cats anymore and they all go through MOT's without any issues so all should be fine with yours.

Paul

tsb

Thanks to all who replied. That'll save me some money!

cepheus

The MOT and roadside tests are not nearly as stringent as the type approval tests when new. This requires testing on a rolling road dynamometer for a wider range of emission types such as particulate (PM10) and Oxides of Nitrogen (NOx) which are probably the two most important pollutants.

In an MOT test these emissions are not measured which explains why tampered vehicles manage to pass the test, since it is easy to reduce the others after a bit of fiddling with the engine management system at the cost of increasing NOx.

If people are fiddling, tampering and taking off particulate Traps and catalysts, no wonder cities are having to introduce low emission zones! Type approval legislation will also get stricter, and vehicles become more complex and expensive if air quality remains poor in a desperate attempt to solve the problem at the design stage, wereas it is partly an in-service problem by the sound of things!

No doubt when the penny drops at VOSA they may introduce a requirement to check after-treatment devices if this fiddling is widespread.

Traps and catalysts should only increase fuel consumption by a few percent.