Fitting a temporary cat for MoT

[Frimley111R]

My Megane R26 is decatted and was like that when I bought it. I have the cat but apparently it is the devil’s own job to fit/remove (driveshaft out!). I’ve seen someone who had cut the straight pipe (under the car, between the front seats - see pic below) and fitted a cheap cat there that can be unbolted/bolted for MoTs. Just before I do this I want to be sure that pretty much any cat will do (bear in mind my car is only a 4 cylinder turbo).

In the other example I saw the guy welded in two slightly larger sections so the cat/straight pipe could just be slotted in/out. Seems quite a good solution?

Or is there an alternative?

[Bdevo3]

I went to the local scrappy and bought the biggest converter (evo 7) I could fit under my evo 3. Cut out a section of pipe the same length. I got a local engineer to cut 4 flanges to match the cat and welded up a decat pipe. 4 bolts to swap it every year and always passes

[Tyre Smoke]

Or find a friendly garage?

[Frimley111R]

Tyre Smoke said:

Or find a friendly garage?

Is there such a thing or it this some mystical place that always gets brought up when these type of questions are posed?

[stevieturbo]

What you propose is quite easy to do.

You can even get flush fitting exhaust clamps that would allow you to simply cut the existing and then insert a cat of same dimensions very easily

eg this type of thing.

Just joins 2 pipes together that are butted together. No flanges etc needed

https://www.ebay.co.uk/itm/Vibrant-STAINLESS-STEEL...

Or you could use flanges, v-bands, whatever you want really.

[E-bmw]

Just be aware of the fact that cats need some warming up, which is why they are at the front.

You shouldn't have a problem if you give it a good run of at least 10/15 minutes before getting it tested.

[Frimley111R]

Thanks, I quite favour the 4 bolt system even if it requires a bit more work initially but I may try this too.

[paintman]

What stevieturbo says ^^^^
Friend of mine bought a used supercharged RRS & wanted the autobox fluid & filter changed even though it's supposedly filled for life.
Exhaust is in the way & apparently needs a lot of other dismantling to remove it.
The solution was to cut out a section & then refit using the type of clamps shown in the link.
I'm told the fluid that came out of the box was pretty grim & so was the filter.

Edited by paintman on Friday 9th February 12:45

[Bennachie]

'Course, you could just make it legal............................

[E-bmw]

That'll never catch on.

[Frimley111R]

Bennachie said:

'Course, you could just make it legal............................

Its only my track car and hoon car. If it was my daily it'd be different.

[Frimley111R]

paintman said:

What stevieturbo says ^^^^
Friend of mine bought a used supercharged RRS & wanted the autobox fluid & filter changed even though it's supposedly filled for life.
Exhaust is in the way & apparently needs a lot of other dismantling to remove it.
The solution was to cut out a section & then refit using the type of clamps shown in the link.
I'm told the fluid that came out of the box was pretty grim & so was the filter.

Edited by paintman on Friday 9th February 12:45

Yep. I found this http://bit.ly/2H1Ac1h so all I need to do is cut it and the exhaust..

[stevieturbo]

I wouldnt have high hopes for a £30 cat performing well....even more so when it's the secondary cat of a system that normally uses a couple.

And the front flange on those will usually required a tapered mate as opposed to a flat flange if you wish to make use of the flanges.

Really the best cat you could use...is an OEM one.

[Tyre Smoke]

Frimley111R said:

Tyre Smoke said:

Or find a friendly garage?

Is there such a thing or it this some mystical place that always gets brought up when these type of questions are posed?

I know of three within 10 miles of me. I think it's a case of getting to know the garage well. Not just rock up expecting to wink and touch the side of your nose whilst handing over your key wrapped in a £20 note.

[Frimley111R]

stevieturbo said:

I wouldnt have high hopes for a £30 cat performing well....even more so when it's the secondary cat of a system that normally uses a couple.

And the front flange on those will usually required a tapered mate as opposed to a flat flange if you wish to make use of the flanges.

Really the best cat you could use...is an OEM one.

An R26 only has one cat. i think I'll try the flange option second and go with the cut and connect option first

[E-bmw]

He knows that, he was meaning you are fitting a cat that is designed as a secondary cat & assuming it can fulfil the duties of a sole cat.

[Frimley111R]

E-bmw said:

He knows that, he was meaning you are fitting a cat that is designed as a secondary cat & assuming it can fulfil the duties of a sole cat.

Ah I see. That's a good point, thanks.

PS: Would it for the purposes of and MoT?

[paintman]

Only one way you're going to find out.

I do know from personal experience that the pattern cats will get through an MoT straight after fitting but may not the following year.
One of our Pug 306's was overdue its MoT & the cat fitted had holes in the pipes. Time was of the essence so I fitted a pattern cat - of the correct type for that car - & it passed without problem. Following year it failed on emissions.
I still had the old - genuine - cat so a bit of welding later fitted it & resubmitted. Emissions now virtually zero.
The pattern was about half the size of the genuine.
Chat with the tester, who I've known for years, was that he sees this all the time with pattern ones.

Edited by paintman on Saturday 10th February 11:37

[E-bmw]

Hence why they are cheaper, the "expensive" bit is smaller.

[Frimley111R]

Ok thanks, swapped the cat for another one. TBH at £40 its not too much to buy one each year