Decat exhausts - do I have to have one?

[tigers6]

I have searched through here, and pretty much every thread has contrasting results!! hehe
If a car can pass the cat test without a cat on it... does it still have to have one??
I cannot see anything on net that indicates you must do?
Cheers

[tigers6]

have just re-read my title.... I mean do I have to have a cat... not a decat exhaust!

[sultanbrown]

As long as you pass the emissions, you DO NOT need a Cat.

[streaky]

sultanbrown said:

As long as you pass the emissions, you DO NOT need a Cat.

I've been passing emissions for years (the more so as age takes it's toll) and I've never had a cat (I'm a dog person). Does this meaan I'm OK? - Streaky

[tigers6]

Right, thats what I thought
but I have just been given this answer from another forum

elsewhere said:

For a MOT test it just needs to pass the emissions test, if it can do it without a Cat thats fine... it can pass... But the car must have a cat fitted if it was built after a certain date (which i cant remember till i get my MOT manual at work tomorrow) to meet the CONSTRUCTION AND USE section of the governments motor vehicle legislation.

All bikes including 2 stroke mopeds have to have Cats fitted to be legal, but they are not subject to a emission test at Mot time...

Mot test is a vehicle health check... not a legality check Theres lot of items that will pass a MOT test but be illegal as soon as its on the public highway when the Police rules come into play.

For example...

Tinted Windows... we all know tinting the fronts is illegal... but its not a MOT failure...

Speedos... Speedos must work and be withing a % to be road legal... but its not a MOT failure even if missing...

Wheels protruding the arches... is illegal... but as long as they dont foul the arch or have a rough edge they are not a MOT failure...

Number plate FONTS/COLOUR.... not a MOT failure if CLEARLY READABLE but anything other than BLACK and STD FONT is illegal for road use...

Theres tons of things that differ between the two... so just remember if the CONSTRUCTION AND USE legislation says it must be fitted... it must be fitted

Does this sounds feasible?

[combemarshal]

Take it off, remove the insides and put it back on!

[deeps]

It's an emissions test not a CAT test, so if it passes the relevent CAT emissions test it doesn't matter whether the CAT is on the car or not. Unlikely that the emissions will be low enough to pass a CAT test without it though.

I can't imagine con & use regs applying to exhaust pipes or types of silencer, as long as they are fit for purpose. They are interchangeable service parts of no fixed description or make. I may be wrong though.

[combemarshal]

I asked the guy who did my last Mot if it would fail and he said it would if there was not cat as it's the done thing on my car, but why not get a bypass pipe made up, leave it in the boot and ask the guy to swap it over for the test for a tenner, I bet it will go through and he won't touch it!

[SpidermanUK]

Why not downgrade your insurance to 3rd party at the same time?

Because you'll be paying a premium for a policy that won't pay out if your Insurance Company discovers the mod.

[kenp]

SpidermanUK said:

Why not downgrade your insurance to 3rd party at the same time?

Because you'll be paying a premium for a policy that won't pay out if your Insurance Company discovers the mod.

Urban myth and should not be perpetuated.

[SpidermanUK]

kenp said:

SpidermanUK said:

Why not downgrade your insurance to 3rd party at the same time?

Because you'll be paying a premium for a policy that won't pay out if your Insurance Company discovers the mod.

Urban myth and should not be perpetuated.

Please elaborate?

Are you suggesting that modifying your car so that it no longer complies with Construction And Use Regulations doesn't invalidate your insurance?

Are you aware that all modifications are notifiable to your insurer so that they can reassess risk?

[chrispy porker]

pardon my ignorance but, apart from the expense, why would someone not want a cat, if the car was designed to operate with one. Does it make it go faster?

[catso]

elsewhere said:

All bikes including 2 stroke mopeds have to have Cats fitted to be legal, but they are not subject to a emission test at Mot time...

Since when? the latest bikes may have Cats but I'm not sure it's a requirement yet.

And if a car passed without a cat, I very much doubt an MOT tester would look to see if one was present or not.

[deeps]

SpidermanUK said:

kenp said:

SpidermanUK said:

Why not downgrade your insurance to 3rd party at the same time?

Because you'll be paying a premium for a policy that won't pay out if your Insurance Company discovers the mod.

Urban myth and should not be perpetuated.

Please elaborate?

Are you suggesting that modifying your car so that it no longer complies with Construction And Use Regulations doesn't invalidate your insurance?

Are you aware that all modifications are notifiable to your insurer so that they can reassess risk?

If the insurer is notified and accepts the CAT has been replaced with a different type of exhaust component there will be no problem.
But they should be notified yes.

[deeps]

chrispy porker said:

pardon my ignorance but, apart from the expense, why would someone not want a cat, if the car was designed to operate with one. Does it make it go faster?

A CAT creates power sapping back pressure, the loss in power is very noticable especially if the car has a turbo. Removing it allows exhaust gas to escape far quicker and allows the engine to rev with less effort, no longer having to push the exhaust gass through the CAT. More exhaust gas is released from the combustion chamber allowing room for more air to be inducted into it (less overlap), hence more power. Also, the heat from a CAT is like a furnace under your car, not good!
Simply removing a CAT on a turbo'd car can gain in the region of 50 BHP.