De-Catting The Beast

Dear All
I have heard that it is possible to de-cat my 4.6 v8 petrol RR (97).
Is this true, if so what is the procedure, what does it cost and who would do it?? Not KwickFit I suppose!!!!
Will it still past the MOT and will it be fit for the road?
Cheers
Happy New Year to you all!!!!

you could fit a stainless sports exhaust if you are after a better sound but you cant remove the cats as it will not pass a mot.. the emissions would be way to high.

What you hear is true, it is possible. But it is also illegal to drive on the road without them.

4x4 jake said:

you could fit a stainless sports exhaust if you are after a better sound but you cant remove the cats as it will not pass a mot.. the emissions would be way to high.

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unless you run on lpg

If you run on LPG you don't need the cats
Due to it's low emissions.

tonybirch said:

If you run on LPG you don't need the cats
Due to it's low emissions.

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Actually it's because the CO limits for vehicles running on 'alternative fuels' are higher than petrol only cars!
Mind you, mine runs 0.6% CO on petrol at idle (no CATs) and I'd expect the LPG reading to be even less.

Wrong, It does not matter what fuel you run off from time to time. Any internal combustion engined vehicle using public roads in the UK MUST have a catalytic converter fitted if manufactured in or after 1993. That is the law.

Basic facts are, as an MOT tester my self

If your vehicle is petrol and is post August 1992 it would be subject to a Basic Emissions test, this is a cut down form of the Cat test, designed to save some time! 90% of vehicles pass the BET, the rest will undergo a full CAT test if they fail the BET.
Now, having a Catalyst removed, is in its self NOT a reason to fail, there is nothing in the manual that even metions that you must have a cat fitted.
So yes you can remove your cat, as long as your vehicle can pass the emissions without a cat fitted then you will have no problems whatsoever!
But..... you may fall foul of construction and use regulations, but when do they get checked?
So essentially, as I see it, it is technically illegal to remove your cat (under C&U regs) but not 'illegal' for the MOT test

Alternatively, run your car on LPG remove the cat, and then you have no worries at all, as LPG car do not require the BET or cat test, just the old 2 gas test!
Just something I found on the net.

There are low restriction sports cats avialable from various suppliers/specialist, but probably not cheap !

Or take the cat's off,then knock the insides out of them to make them straight through.Then re fit.
That way if anyone (plod) takes a peak underneath they will still see the cat fitted.

If you do take them off, dont forget to sell them to a scrappy for £20-£30 each. Well thats what they were worth a while back !

Mines been without CATs for probably 7 years now. As above, there is NO legal requirement to phsically have a catalytic convertor fitted under your vehicle, regardless of whether it left the factory with one or not.
What you must comply with, is the emissions test which is easily achievable when running a fuel such as LPG.
I don't go along with the old 'construction and use regulations' thing- if it were that strict, no (even slightly) modified vehicle would comply in the slightest eg a change from a cast to a tubular exhaust manifold!

David_Cooper said:

Mines been without CATs for probably 7 years now. As above, there is NO legal requirement to phsically have a catalytic convertor fitted under your vehicle, regardless of whether it left the factory with one or not.
What you must comply with, is the emissions test which is easily achievable when running a fuel such as LPG.
I don't go along with the old 'construction and use regulations' thing- if it were that strict, no (even slightly) modified vehicle would comply in the slightest eg a change from a cast to a tubular exhaust manifold!

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So the government go to the trouble of generating construction and use regulations making them law for no reason. Try taking your seatbelts out or running a radial tyre on the same axle as a cross ply. Then explain that you don't go along with the old construction and use regulations to the MOT tester or the nice man from VOSA when you get spot checked. There is a legal requirement to have a cat fitted to ANY vehicle used on the public roads made in or after 1993 whether YOU like it or not. Is your vehicle capable of running off petrol, does it still have a tank, do you start on petrol and change to gas, can you run it off petrol between gas fills? If you can you need a cat. Construction and use regulations don't cover exhaust manifolds, don't talk daft.

what a great discussion!!!
thanks for all your imput
so let me see - I can take the Cats out but its illegal but not for the MOT, so I could but I can't!!!!
I think I'll leave them in, afterall what would I have to listen to if I didn't have the Cat Rattle????
thanks again for all your imput

I'm in the same boat - still can't decide what to do with mine.

I think I'll probably end up with a pair of sports cats from double s as they're supposed to be fairly free flow and metallic so hopefully won't disintegrate like the original ceramic ones do when they get wet and muddy...

I did investigate the decat route, but quite frankly a decat pipe seems to cost as much as the cats.

Guy

rrmonty said:

what a great discussion!!!
thanks for all your imput
so let me see - I can take the Cats out but its illegal but not for the MOT, so I could but I can't!!!!
I think I'll leave them in, afterall what would I have to listen to if I didn't have the Cat Rattle????
thanks again for all your imput

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Well i suppose you could always fit an old 3.5 V8 with carbs in it. And get round the emissions that way.

wammers said:

Well i suppose you could always fit an old 3.5 V8 with carbs in it. And get round the emissions that way.

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Still would not be legal as in it would not pass the stricter emmisions test (assuming it was registered after Aug 92) for the later plated car.

alfaitalia said:

Still would not be legal as in it would not pass the stricter emmisions test (assuming it was registered after Aug 92) for the later plated car.

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Oh yes it would. Emissions test applied to year of engine manufacture not to year of vehicle manufacture. You have to be able to prove it with documentation of course word of mouth is not acceptable.

wammers said:

Oh yes it would. Emissions test applied to year of engine manufacture not to year of vehicle manufacture. You have to be able to prove it with documentation of course word of mouth is not acceptable.

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Hmmm. Interesting. Just off to get the tape measure to see if the big block HEMI (7.2l) chevy lump from 1976 ive got in the garage will fit under the bonnet of my 2001 alfa!

alfaitalia said:

Hmmm. Interesting. Just off to get the tape measure to see if the big block HEMI (7.2l) chevy lump from 1976 ive got in the garage will fit under the bonnet of my 2001 alfa!

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Way to go. For confirmation see MOT testers manual section 7.3 Exhaust emissions - Spark ignition. General information. You see us old opinionated farts do have a use.

Hi all

just a thoght on the cats you could all move to the channel islands where we dont have MOT's and once the cars on Jersey plates no body gives a stuff.

So bring your cars over to jersey get then on J plates take the cats of and then go back to the UK, My duaghter been in the uk for 4 years now in her Jersey car and still nobody gives a stuff over there.

funny old world.

Tony