MiniTorque.com banner
1 - 6 of 6 Posts

·
Premium Member
Joined
·
653 Posts
Discussion Starter · #1 ·
Hi all, I have a manic stage 2 remap that was listed as requiring either a decat or fitting a sports cat. If I was to refit the standard cat, would it have a negative impact anywhere other than performance?

It's a cooper S but I have a JCW turbo and backbox fitted.

Not linked to my MOT emission issues by the way which I scraped through on the retest!
 

·
Premium Member
2005 R53, 2005 R53 lightweight, 2008 R55S, 2012 R58FJCW, 2014 R60SD All4, 1996 Mini Cooper 35SE.
Joined
·
6,637 Posts
just more fuel harming the full cat as above I'd expect, flow might be stifled a bit,

same cat on a JCW as an S isn't it. A stage 1 on an S might be around 215 if that and a 2 around 240 odd from what I've seen iirc, a stage 1 on an FJCW goes to around 240 anyway I think, so I doubt it'd actually be an issue for the small difference in play, the same requirement for a cat change doesn't appear to be specified for stage 1, not clearly anyway that I've seen, maybe a recommendation here or there along with IC change.

might be wrong, the cheap sport cat's appear to be the problem ones from what I've read, I have one here with one fwiw that also wouldn't pass, I've read people saying Scorpion and Akrapovic seem to go through alright?
 

·
Registered
Joined
·
289 Posts
just more fuel harming the full cat as above I'd expect, flow might be stifled a bit,

same cat on a JCW as an S isn't it. A stage 1 on an S might be around 215 if that and a 2 around 240 odd from what I've seen iirc, a stage 1 on an FJCW goes to around 240 anyway I think, so I doubt it'd actually be an issue for the small difference in play, the same requirement for a cat change doesn't appear to be specified for stage 1, not clearly anyway that I've seen, maybe a recommendation here or there along with IC change.

might be wrong, the cheap sport cat's appear to be the problem ones from what I've read, I have one here with one fwiw that also wouldn't pass, I've read people saying Scorpion and Akrapovic seem to go through alright?
I can confirm above with a Akrapovic sports cat fitted to mine and has always passed the MOT with no problems.
 

·
Registered
Joined
·
29 Posts
hi yes definitely a bit less power as more air in restricted and you might be sending to much fuel and start Burning up the cat and destroying it and a sport cat should pass an MOT
The amount of fuel is regulated by the Lambda sensor - you will not be stuffing a lot more fuel into the cat unless your tuner requests silly low AFR.
The cat will act as a restrictor - so there will be more pressure on the turbine wheels in the turbo, which means the turbo will have to work harder to reach the target boostpressure on the turbine side of the turbo. That increases the EGT - which is a stress factor on the engine. Removing the cat (or replacing it ith a high flow version) will make the turbo struggle a bit less, and in return give you better EGT.

The challenge with a sports cat @ MOT is that it takes quite some more time to get it properly hot - you need to make sure that it is thoroughly hot before going to the MOT. A cold cat is really not very effective.
 
1 - 6 of 6 Posts
Top