Exhaust question.

[Tekkigizmo]

I have a slight problem with joining my back box to the rest of my system, namely the 430mm cat section.
The back box and the cat currently on my car is one piece with no flange, the new exhaust has a 3 inch flange where the cat-decat section would fit.
The down pipe flexi section looks to be about a 2.5 inch flange, but someone has told me the standard size is 2 inches??? (should find out for sure later this week).

I would like to keep a cat on it but the car is a n/a rev 1 1991 on a j plate so I could decat it if I had too.

My question is where can I get either a cat or decat section to fit?

[Torero]

Cat or decat can be bought from eBay or some of the MR2 traders on the forums.

The diameter is easy, just take a tape measure and measure the circumference most wall thicknesses are .049 or .065 so 2.5" (65mm) is roughly 8.2" and 3" is roughly 9.75".

If it is 2.5" you'll need a change piece to make it up to 3" so why don't you get one fabricated and use it in place of the cat. You then just have the issue of adding a flange to the downpipe.

John.

[Tekkigizmo]

Hi John,
Had a look online and found Fast Lane Styling in Romford, they are going to custom build a sports cat for me for about £140.
Thanks for the info but that would mean me going underneath the car and doing some work for a change, made me break out in a cold sweat just thinking about it lol

[Torero]

Lol Yes I know what you mean about getting off your butt in this weather.


That's not a bad price btw Cliff.

[SonicSW20]

I would like to keep a cat on it but the car is a n/a rev 1 1991 on a j plate so I could decat it if I had too.

Bear in mind that it will still fail an MOT Cat test as it was fitted with a cat as standard.

[Tekkigizmo]

Well the exhaust is on and thanks Kaboota it sounds great, it now has a sports cat that is more free flowing than a standard cat and the car feels better for it.

[Gazza_DJ]
Bear in mind that it will still fail an MOT Cat test as it was fitted with a cat as standard.[/quote]

Not strictly true there is not a cat test in the mot as such, it is an emissions test, on my car it needs to be under 3.5% co and 1200 hc, an easy target if the car is well maintained and as long as the test figures are below that it is a pass, cat or no cat. You could just as easily fit a resonator box in place of the cat and who's to know.

My mot tester bought the subject up about the cat on my car and told me that he would still have to pass it as long as the figures were within limits and he is not the kind of mot inspector to let things go, (if it ain't right he won't pass it).

All the cat does is convert some of the more harmful gases into less harmful ones, but the presence of these gases is not tested in the mot.