20 replies to this topic

[MinipixMatthew]

As GW and Sprocket mentioned, there are different types of test depending on the age / model of car. Before going anywhere near taking the manifold off and replacing the lambda sensor I would go back to the garage and ask them what sort of test they were doing! If your Mini originally had a cat then it probably means it should be tested as fitted with one (not in every case, I'm sure GW's done a huge post on this elsewhere). If the results were really really way out, then it may be that they were testing against the cat figures rather than the non-cat ones. As your Mini is on the cut-off point, it's essential to make sure they do the right test - it's less about age and more about the actual model. If the MOT tester starts quoting tests based on the registration letter then shout at them!

-M-

[Sprocket]

Wouldnt worry about removing the cat, it wont make much difference other than just making it louder. I still run a cat at 100bhp and the supercharged Vmax boys at 140bhp do too. A decat pipe is lining the pocket of the person who has made them.

[minimat]

Thats what i thought thats why ive left it on,just means that if it ever have a prob with it ie rust or it gets blocked i can replace it with a de cat for £20 instead of a new cat for £150.

[taffy1967]

Wouldnt worry about removing the cat, it wont make much difference other than just making it louder. I still run a cat at 100bhp and the supercharged Vmax boys at 140bhp do too. A decat pipe is lining the pocket of the person who has made them.

Good point, but it does affect carburettor Minis though. Still I've heard that NO carb Mini needs to have a cat (regardless of age) for the MOT test and there's even a special note on this at the back of the MOT testers manual.

So if he tries giving you a hard time and saying you're carb Mini should have a cat, just ask him to look it up in his little book.

Edited by taffy1967, 24 May 2007 - 11:25 AM.

[AlexM]

Wouldnt worry about removing the cat, it wont make much difference other than just making it louder. I still run a cat at 100bhp and the supercharged Vmax boys at 140bhp do too. A decat pipe is lining the pocket of the person who has made them.

I think people leave them on because its not worth the hassle of legislation for the small power gain. Plenty of aftermarket exhaust systems have catalysts of different designs to improve flow, unless this is just marketing babble. I noticed the exhaust note was definately deeper after removing the cat. I can't say anything for power gains but from what ive heard its a few bhp.

[Sprocket]

Wouldnt worry about removing the cat, it wont make much difference other than just making it louder. I still run a cat at 100bhp and the supercharged Vmax boys at 140bhp do too. A decat pipe is lining the pocket of the person who has made them.

I think people leave them on because its not worth the hassle of legislation for the small power gain. Plenty of aftermarket exhaust systems have catalysts of different designs to improve flow, unless this is just marketing babble. I noticed the exhaust note was definately deeper after removing the cat. I can't say anything for power gains but from what ive heard its a few bhp.

Well the aftermarket cats may well flow more but are less efficient, but the bonus is they are more robust and can take real good abuse. Modern OBD cats require a certain performance for the OBD to work correctly, that requires more CPI and as such restrics the flow. Free flow cats = less efficient at doing its job. The only way out is to make it bigger.

A few bhp?? like how much is a few?

2 to 3 hp has been noted before maybe five at the higher hp end. Where do you stop, the fan costs hp, as does the water pump, alternator and helical cut gears

Is it worth worrying about on a road car?? certainly not worth the hassle, you wouldnt noticebly notice a noticeble difference worth noting

Horse power is nonsensical anyway

Bottom line is the cat is meant to be there for a purpose an that is yours, mine and everyone elses health. Do we really want to go back to days of smog and choking on the fumes of the car in front when every man and his dog are removing the cat because they think it makes the car faster.