Guest Carsten Posted March 22, 2011 Share Posted March 22, 2011 Hey guys, i now read all topics regarding downpipes and couldnt figure out which diameter to choose. I currently run a "near" BPU jspec TT. Now i want to take it a bit further by installing a downpipe and a BC. Only limitation i´ve got: Maximum 1.1 Bar. Nothing more! So my question is: Would it be enough to install a BC and bolt a 1st Decat pipe in. Or do i need to replace both cats? If the first decat is enough and i install a restrictor ring for about 1.1 bar, would it be wiser to choose a 2.5" decat pipe or a 3"? Thanks in advance Carsten Link to comment Share on other sites More sharing options...
Bailey. Posted March 22, 2011 Share Posted March 22, 2011 Have you got 1.1 with both cats in mate? Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 22, 2011 Share Posted March 22, 2011 Currently i´m running between 0,6 and 0,75 Bar with Both cats in (and a third small cat which is empty). Link to comment Share on other sites More sharing options...
Mistermann Posted March 22, 2011 Share Posted March 22, 2011 Sorry to hijack but can you use a 3" 2nd decat with a 2.5" 1st decat? or do both need to have the same diameter. Link to comment Share on other sites More sharing options...
Wez Posted March 22, 2011 Share Posted March 22, 2011 3" all the way through and use a restrictor ring to pull boost back down to about 1.2bar if you have an FCD fitted. Link to comment Share on other sites More sharing options...
Wez Posted March 22, 2011 Share Posted March 22, 2011 Sorry to hijack but can you use a 3" 2nd decat with a 2.5" 1st decat? or do both need to have the same diameter. I would personally keep it the same all the way through. Link to comment Share on other sites More sharing options...
Mistermann Posted March 22, 2011 Share Posted March 22, 2011 If the restrictor ring has a smaller diameter than the decat pipes would it make too much of a difference though? Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 22, 2011 Share Posted March 22, 2011 3" all the way through and use a restrictor ring to pull boost back down to about 1.2bar if you have an FCD fitted. Thanks for your advice Wez, but would it be possible to run a full 3" with the stock second cat? Just for legal issues here in germany (the smell of a full decat is very obvious ) Link to comment Share on other sites More sharing options...
Wez Posted March 22, 2011 Share Posted March 22, 2011 Thanks for your advice Wez, but would it be possible to run a full 3" with the stock second cat? Just for legal issues here in germany (the smell of a full decat is very obvious ) If you need to leave a cat in the 2nd one would be my preference but I would monitor EGT closely if you intend to run higher than stock boost. Link to comment Share on other sites More sharing options...
Wez Posted March 22, 2011 Share Posted March 22, 2011 If the restrictor ring has a smaller diameter than the decat pipes would it make too much of a difference though? Prob not, just my personal preference would be to keep the diameters the same Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 22, 2011 Share Posted March 22, 2011 Awesome thank you. Link to comment Share on other sites More sharing options...
Mistermann Posted March 22, 2011 Share Posted March 22, 2011 Awesome thank you lol Link to comment Share on other sites More sharing options...
Nic Posted March 22, 2011 Share Posted March 22, 2011 Thanks for your advice Wez, but would it be possible to run a full 3" with the stock second cat? Just for legal issues here in germany (the smell of a full decat is very obvious ) You could cut open the cat, remove the insides and then weld it back together. If you do leave one cat fitted you might need a boost controller to raise the boost, as Wes says I'd make sure you have an EGT gauge fitted. Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 23, 2011 Share Posted March 23, 2011 Nic somewhere i read that you could support me with a first decat pipe? Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 23, 2011 Share Posted March 23, 2011 http://www.jperformance.co.uk/toyota-supra-turbo-jza80-2jzgte-exhaust-downpipe-1st-decat-p-643.html This looks promising Link to comment Share on other sites More sharing options...
Wez Posted March 23, 2011 Share Posted March 23, 2011 http://www.jperformance.co.uk/toyota-supra-turbo-jza80-2jzgte-exhaust-downpipe-1st-decat-p-643.html This looks promising Have you tried all the registered traders on here, most of them stock Cat replacement pipes, ie Chris Wilson, Whifbitz, Garage 786 and AFR Tuning etc Link to comment Share on other sites More sharing options...
Guest Carsten Posted March 23, 2011 Share Posted March 23, 2011 Tried them yes. But the price of the jperformance downpipe is just unbeatable. Know traders on here charge about 130 gbp for the downpipe + shipping to germany. Link to comment Share on other sites More sharing options...
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