Jim_1979 Posted November 9, 2006 Share Posted November 9, 2006 Just double decatted the car and fitted a cat back exhaust. Curious as to what one of the cats you need to put back on for the MOT? The larger one (underneath the car), or the smaller one? (closer to the engine) Thanks in advance! Link to comment Share on other sites More sharing options...
dilocruzy Posted November 9, 2006 Share Posted November 9, 2006 Just double decatted the car and fitted a cat back exhaust. Curious as to what one of the cats you need to put back on for the MOT? The larger one (underneath the car), or the smaller one? (closer to the engine) Thanks in advance! I kept the smaller one in the car and it passed, think it is also easier to remove the longer one. Link to comment Share on other sites More sharing options...
Jim_1979 Posted November 9, 2006 Author Share Posted November 9, 2006 Yeah.. it would be easier to re-fit the longer one as it's miles easier to get to the bolts on it. But if you re-fit either should it pass emissions testing? Link to comment Share on other sites More sharing options...
dilocruzy Posted November 9, 2006 Share Posted November 9, 2006 Yeah.. it would be easier to re-fit the longer one as it's miles easier to get to the bolts on it. But if you re-fit either should it pass emissions testing? Couldnt tell you mate, i failed full decated and scraped a pass with the front one in so think it would be a close call. Link to comment Share on other sites More sharing options...
Jim_1979 Posted November 9, 2006 Author Share Posted November 9, 2006 Cheers mate.... anyone else? Link to comment Share on other sites More sharing options...
Ian W Posted November 9, 2006 Share Posted November 9, 2006 unfortunately i'd suggest keeping the second (longer) one mate. this is mainly for ease of refitting of course. Link to comment Share on other sites More sharing options...
Kranz Posted November 9, 2006 Share Posted November 9, 2006 Catalysts increase the exhust temperature by an exothermic reaction inside them. There is a specific exhaust gas temperature where the catalyst starts to 'light off' and begin converting the nasty gasses, and also creating more heat. The front cat is a close coupled cat, called the 'starter' cat, that gets the exaust gas heated up quickly for the second cat during cold starts (i.e. its there to get the main second cat working faster). Doing an MOT emissions test won't need this starter cat as the exhaust gas will already be up to temperature. So...... to cut a long story short, just refit the main second cat, and make sure the car has been for a good blast prior to the emissions test to get the exhaust nice and hot!! Link to comment Share on other sites More sharing options...
ardasaliah Posted November 9, 2006 Share Posted November 9, 2006 Which one is more restrictive? Link to comment Share on other sites More sharing options...
Ian W Posted November 9, 2006 Share Posted November 9, 2006 first is the more restrictive iirc. Link to comment Share on other sites More sharing options...
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