11 replies to this topic

[littlebluemonster2]

Hi guys,

I know this is a lot of text but please reply if you can... running out of time.

...... in the past 12 months i have had to take my exhaust apart and re-seal it 3 times as it keeps blowing at the joint of the cat to the stainless pipe attached to my back box.

When i rebuilt my mini i took off the standard exhaust back box etc just leaving the standard down pipes and cat. i then cleaned off all the rust that formed on the joint flange and then smeared exhaust assembly paste on it and bolted it together to my new stainless link pipe which was sealed and clamped to my twin DTM back box etc.

Question is..... the back box is secure, all the rubber hanger brackets are secure but the joint in question keeps blowing, the mot is due again next monday so i need to strip it and seal it again. i have noticed that there are gaskets available for cat joint.... do i need one of these or have i done it right already?

If i need a gasket do i need to use the paste as well as the gasket or just pinch the gasket between the two flanges? the gasket on minispares looks thiner than the gap and looks like steel? i have heard of thicker copper gaskets that squash and seal before but not sure.

Any help would be great....... was also thinking of replacing my cat with a link pipe, is this worth doing as i'm led to believe the mot guy has a bigger tolerance to play with regards emissions and it is better on performance? any input?

Regards,

Chris

[bobs]

I use the metal CAT gaskets and paste and don't have a problem.

I put the CAT on for MOT, and then link pipe afterwards, the only difference I've noticed is the sound, CATs don't really restrict power to a noticeable level.

All injection models need a CAT. I think cars after '93 need to have a CAT for the MOT (but this is not a legal requirement for the road), mine greatly reduces the CO2 output when installed and coupled with the standard carb needle and a leaner tune (as I run with a stage 1 the rest of the time) is the only way I can pass the MOT emmissions test.

Never taken it to a MOT without the CAT on to test if this is the case, always assumed that when they see the link pipe they'd assume that parts were missing from the exhaust system, and I can't get it to run right with the required CO2 without it.

It's four bolts and I have ramps so it take 5 mins to change each year...

[littlebluemonster2]

cheers for the reply mate,
mine is a 93 sprite, which is non injection but a carb model.....one which is on a model change.... so has a cat although doesnt require one...

chris

[coopermpi]

i have a genuine rover gasket for cat brand new lying about, still in the packet if its any use to you. its the metal type, minispares part number GEX 7761. Rover number CRC9328SLP. im just by the merry hill centre if youn need it quick?

[bobs]

Snap! '93 Sprite

I think it does require a CAT if it's after 93, this always bothered me hence why I only put it on for the MOT, also save it getting damaged as it only stays on the car one day a year, they're expensive to replace.

I asked a MOT inspector at VOSA and he checked the database and said something like "all cars after (92 or 93 can't remember) must have a CAT fitted" I didn't want to risk it as others have said to just get rid of the CAT but in my experience you'll have a hard job getting the emmisions down without one.

The Haynes Manual states 0.3% CO2 and 0.5% (don't have it at hand so this is from memory) for that year of car. MOT man just punches it into a PC and goes by the specs for that year/model, it goes on the year not if it's SPI or Carb... before that date (which is in the Haynes manual) it's 3.5% CO2, and the old ones (pre '74?) are immune from testing, only visual test (lucky b'stards).

Mine runs and sounds nice at about 15% with no CAT and richer Carb needle.

I think Rover had to overcome this on the cheaper sprites by just chucking a CAT on, before the change to SPI in '94.

[littlebluemonster2]

i was told if a cat fitted its low but if non cat then its 3.5 Co2, even on our year.....

might just leave it on but need to get the thing to stop cracking the seal so it stops blowing... more than anything its anoying. lol

thats why i asked about the gasket. (Thanks for the offer Coopermpi, for the gasket, as there cheap enough i ordered one anyway just in case. thanks anyway)

cheers

chris

[bobs]

i was told if a cat fitted its low but if non cat then its 3.5 Co2, even on our year.....

I was told both... but VOSA seem to know, and it's in the haynes manual. So the risk is yours, do let me know if you do remove it and pass a MOT.

I doubt many MOT testers know, but I wasn't prepared to take the risk and have to buy another exhaust system after I'd bought one to remove it each year.

[littlebluemonster2]

bobs,
just thought you might like to know. asked my MOT guy this morning when i took mine in, and he said the date for cat is 1st august 93. anything after that date of registration must have cat fitted. As mine is Aug 24th good job i decided to leave it on....... lol
Regards

Chris

[bobs]

Cheers mate, that's good to know!
So that's "L" reg mini's onwards, regardless of Carb or SPI.

Good luck with the MOT!

[littlebluemonster2]

cheers mate.... it passed. had to turn down the mixture while hooked up to the machine. was at 3.95 even with cat on. MOT guy is very understanding though as he does a lot of classics, he let me adjust it till it was 0.1.

[bobs]

cheers mate.... it passed. had to turn down the mixture while hooked up to the machine. was at 3.95 even with cat on. MOT guy is very understanding though as he does a lot of classics, he let me adjust it till it was 0.1.

Good to hear mate, congrats, guess you can't go back and use his gas tester to tune it back up eh?
Mine ran best at about 4-5% with the cat on, I'm lucky having access to a gas tester I guess...

[littlebluemonster2]

bobs,
I do have a gas tester that i bought from halfords, although i didnt think much of it. i could not get it to move on the readout...... wouldnt mind but it cost me £90... lol.

will probably leave it at 0.1

chris