Cat Removal /MoT Question

[iain1067]

I am toying with the idea of getting hold of a couple used cats, cutting the top open and removing the insides, then welding in a pipe and then welding a plate or the original metal back on so they look from the outside like they haven't been touched. My question is has anyone done this before and also how will it affect the mot, how will the mot tester know it hasn't got cat converters?? Obviously i could swap the cats back in once a year but that's just a pain.


Thanks


Iain

[phil2.016v]

They won't know unless your emissions are sky high, then they might recommend new cats!! I've done this on a few cars and got away with it.

What year is your car?

[iain1067]

it's a 96 urS6 so it does need cats.

Iain

[Jamo]

I am toying with the idea of getting hold of a couple used cats, cutting the top open and removing the insides, then welding in a pipe and then welding a plate or the original metal back on so they look from the outside like they haven't been touched. My question is has anyone done this before and also how will it affect the mot, how will the mot tester know it hasn't got cat converters?? Obviously i could swap the cats back in once a year but that's just a pain.


Thanks


Iain

No cats post 1992 no pass the MOT on emissions, as simple as that

[iain1067]

Thanks i will bin that idea then


iain

[Crawford_S2]

Just done a decat on mine, not happy with it yet though it makes the exhaust sit too low, going to have another go at it on monday. the plan is to keep the cats for mot, fire them on for the test then take em off and put em away til next year. Don't know if i can be arsed though!

[pastures16]

why not have gutted cats all you do i break the insides to bits they look like cats but are straight through also there are two tests for emissons mine has just passed again 2nd time with them and thats at a council mot stations

[Crawford_S2]

why not have gutted cats all you do i break the insides to bits they look like cats but are straight through also there are two tests for emissons mine has just passed again 2nd time with them and thats at a council mot stations

I always thought 92 on cars would not pass the emmisions part of the test without cats, its not the fact that they are there its the emmisions are too high without them.Like Jamo said

[blown_vr6]

Cars after August 92 do not need catalytic converters to pass the Emissions test.
They do however need to pass the emissions test and manufaturers fitted cats to help cars pass this test - some cars will pass the test without a cat fitted due to good lambda control,sophisticated management,condition of plugs,air filter etc - some will not....
Gutting a pair of cats just to make it look like the cats are still in place is silly imho (just buy a decat) - they are not interested if the cats are/arent there just whether or not it passes the emissions test.....

[Crawford_S2]

Cars after August 92 do not need catalytic converters to pass the Emissions test.
They do however need to pass the emissions test and manufaturers fitted cats to help cars pass this test - some cars will pass the test without a cat fitted due to good lambda control,sophisticated management,condition of plugs,air filter etc - some will not....
Gutting a pair of cats just to make it look like the cats are still in place is silly imho (just buy a decat) - they are not interested if the cats are/arent there just whether or not it passes the emissions test.....

Yeah, thats what i meant too. Ministry couldn't give a feek if you have cats its the emmisions they get all chin rubbing and sharp intakes of breath over.

[Crawford_S2]

Right, decided to get my homefry in, redo the decat, its just had a service so seems like the ideal time to go to a friendly MOT centre and see how far away the emmisions are without the cats!

[s2driveruk]

Guys, this is the answer i got when i tried to do this....from the MOT forum - all testers with access to the new d/base:

In general (there may be variations depending on vehicle type):

Spark ignition vehicles first used on or after 1st August 1992 will require a BET test (a quick CAT test) limits: CO<=0.2%, HC<=200ppm, Lambda 0.97 to 1.03.

If it fails to meet these limits, a full test is required that has various limits depending on the vehicle tested.

1/Aug/1992 to 31/Jul/1995: if an exact match is found in the analyser data / emissions book then those limits must be used.
If no exact match, then a non-CAT test is done to limits CO<=0.5%, HC<=1200ppm

1/Aug/1995 to 31/Aug/2002: either a vehicle specific cat test is done, or a default cat test CO<=0.3%, HC<=200, Lambda 0.97 to 1.03, idle co<0.5%. This depends on whether vehicle is in analyser data / emissions book.

[s2driveruk]

Interestingly I just had my MOT done (at Audi..) and i thought i would go check the paperwork and seems last year (again at Audi) they did a non-cat test and this year a cat test. Anyone know how they measure a non cat test emission? as the car passed easily on the non and was well inside the 'with' test. I'll post up a couple of pics of the values later.

Cheers

David

[Dan_s2_coupe]

the non cat test is done with the car at idle
where as the cat test they hold the revs at 2500-3000 rpm

[blown_vr6]

the non cat test is done with the car at idle
where as the cat test they hold the revs at 2500-3000 rpm

Proper cat test involves idle and fast idle