jza800 Posted March 23, 2015 Share Posted March 23, 2015 I am gonna remove my 2nd cat, with the decat downpipe, but what size should i go for 2.5" or 3", or dosent that really matter??? Link to comment Share on other sites More sharing options...
listy Posted March 23, 2015 Share Posted March 23, 2015 3" is what people recommend. Just make sure you fit a restrictor ring to stop overboosting. Link to comment Share on other sites More sharing options...
jza800 Posted March 23, 2015 Author Share Posted March 23, 2015 i have drived with the 1st cat and 2.5" catback with no overboosting.. on my last supra with no problem Link to comment Share on other sites More sharing options...
jza800 Posted March 24, 2015 Author Share Posted March 24, 2015 no one else have something to add???? Link to comment Share on other sites More sharing options...
Chris Bailey Posted March 24, 2015 Share Posted March 24, 2015 2.5" would be okay, but 3" would be better as it would be less restrictive. As suggested fit a restrictor ring just to be on the safe side. Are you making the car BPU or just fitting a 2nd decat? Link to comment Share on other sites More sharing options...
tony tt Posted March 24, 2015 Share Posted March 24, 2015 Click on the BPU highlighted in blue. It will tell you all you need to know regarding decatting and over boost issues. Link to comment Share on other sites More sharing options...
Mk4Gaz Posted March 24, 2015 Share Posted March 24, 2015 If you're fitting a 2" restrictor ring, it makes no difference what size decat pipe you fit. You're still restricting the flow of exhaust gas Link to comment Share on other sites More sharing options...
jza800 Posted March 24, 2015 Author Share Posted March 24, 2015 i am gonna raise the boost to 1.2 bar, and keep the 1st cat, and remove the 2nd cat with the decat pipe, with the time i gonna remove the 1st cat.. so if i fit a 2" restrictor ring, can i still hit the target boost?? Link to comment Share on other sites More sharing options...
tony tt Posted March 24, 2015 Share Posted March 24, 2015 1.2 bar with the 1st cat in place will generate A LOT of heat!! Rule of thumb for bpu is double de cat with a 1bar restrictor ring and raise boost if required to 1.2bar. I wouldn't run 1.2bar with a 1st cat in place. http://www.mkivsupra.net/vbb/showthread.php?94705-BPU-(Basic-Performance-Upgrade) Link to comment Share on other sites More sharing options...
jza800 Posted March 24, 2015 Author Share Posted March 24, 2015 the cat is only to my mot to keep my emmision Down.. Link to comment Share on other sites More sharing options...
Benjy Posted March 24, 2015 Share Posted March 24, 2015 Don't run 1.2bar with a cat in place. Mine occasionally hit 1bar with the 1st cat in place, but only very cold weather when the air was dense. Remove both cats, fit a restrictor ring, if you need to fit a cat for MOT purposes, switch the boost controller off if you intend to hit full boost. Link to comment Share on other sites More sharing options...
MadMax2042 Posted March 24, 2015 Share Posted March 24, 2015 So do you need a restrictor ring with a boost controller if you have both cats removed and want to run at a switchable 1 bar and 1.2 bar Link to comment Share on other sites More sharing options...
listy Posted March 24, 2015 Share Posted March 24, 2015 So do you need a restrictor ring with a boost controller if you have both cats removed and want to run at a switchable 1 bar and 1.2 bar It's advisable. A boost controller can only raise boost, not lower it. With no restrictor ring you would have no lower limit, so it could easily overboost. Link to comment Share on other sites More sharing options...
MadMax2042 Posted March 24, 2015 Share Posted March 24, 2015 It's advisable. A boost controller can only raise boost, not lower it. With no restrictor ring you would have no lower limit, so it could easily overboost. Over boostcand detonation would not be fun. Cheers for the advice and sorry for hijacking the thread. Link to comment Share on other sites More sharing options...
Swampy442 Posted March 24, 2015 Share Posted March 24, 2015 You should still pass an MOT with no cats fitted. Link to comment Share on other sites More sharing options...
tony tt Posted March 24, 2015 Share Posted March 24, 2015 You should still pass an MOT with no cats fitted. Or depending on the garage they plug the probe into a nice Audi diesel or something for the emissions test Link to comment Share on other sites More sharing options...
Mad Hatter Posted March 26, 2015 Share Posted March 26, 2015 You should still pass an MOT with no cats fitted. No you won't, it's an instant failure. The rules changed last year to include a visual inspection as well as the emissions test. If you have removed the cat(s) = fail. Mine failed for this reason so I had to buy an old cat... Search for MOT rules, I posted a link sometime back to the official bumf' - - - Updated - - - Or depending on the garage they plug the probe into a nice Audi diesel or something for the emissions test Looks like we'll all follow you to your garage then Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now