shaft Posted January 24, 2008 Share Posted January 24, 2008 on a j spec tt what decat option is recomended for those on a budget? the restrictor ring is that needed with 1 decat or 2? and is it only needed if your car hits the boost cut? how much can i expect to pay for the decat(s?) and restrictor ring? Link to comment Share on other sites More sharing options...
bodilx6 Posted January 24, 2008 Share Posted January 24, 2008 on a j spec tt what decat option is recomended for those on a budget? Do you have a cat back exhaust? In that case I just had a metal skilled mechanic to weld some 3" pipe in in stead of the cats. Cost close to nothing. the restrictor ring is that needed with 1 decat or 2? and is it only needed if your car hits the boost cut? If you keep the first cat in you will hit a max of 0.8 - 0.9 bar and you wont get fuel cut before you run over 1 bar for 3 seconds. If your car is standard J-spec, you are not running the stock muffler and remove both cats, your car will definately hit fuel cut. You can get a FCD very cheaply made if you can find a guy that know about making them for the MKIV. I payed something like 20£. Otherwise I think they are something like 130£ from well know brands like HKS i guess. But before doing this, make sure to get an upgraded fuel pump like the walbro and make sure your air/fuel mix is measured as well as fit an RR or do as I suggest below. If not you will easily go to 1.5 or more without restriction and this will not make more bhps, it'll just smash the tubbies how much can i expect to pay for the decat(s?) and restrictor ring? Again, depending on if you know someone who can just weld some pipe and make the Restrictor Ring them selves or you purchase from a dealer. I solved the RR issue with keeping the 1st cat and getting my mechanic to knock a 50mm hole through it thereby keeping the cat should the police take a look for it at some point (cats are required by law in Denmark). I'm hitting 1.2 bar max which is good for me. The "safest" way is to hit a max of 1 bar to save the tubbies and then use a boost controller to push to 1.2 bar if needed. This will be a bit more expensive though. Link to comment Share on other sites More sharing options...
shaft Posted January 25, 2008 Author Share Posted January 25, 2008 i'll do as you say and leave the first cat in, 1abr will be fine. how much should i pay for an air/fuel meter? and how are they fitted? i know a guy who can make up the decat, would your guy make me up one of his fcd's for me please? even if he could explain it i mite have a go myself, i dont know whats involved tho Link to comment Share on other sites More sharing options...
jamesmark Posted January 25, 2008 Share Posted January 25, 2008 i'll do as you say and leave the first cat in, 1abr will be fine. how much should i pay for an air/fuel meter? and how are they fitted? i know a guy who can make up the decat, would your guy make me up one of his fcd's for me please? even if he could explain it i mite have a go myself, i dont know whats involved tho I would not leave the first cat in as this is the most restrictive and you will not see 1 bar with it still in place, infact you will probably remain at stock boost. The best route to take is go double decat with a decent cat back exhaust and fit a 1 bar restrictor ring. Doing it this way leave you with plenty scope for extra gains when money becomes available. When more money does come available fit a boost controller to then raise the boost to either 1.1 bar or 1.2 bar. To go BPU you are looking at appx £1000 ish (depending what you already have). FCD's do not cost £130 they are only about £70 for a Greddy one, do not go for the HKS FCD. Link to comment Share on other sites More sharing options...
jamesmark Posted January 25, 2008 Share Posted January 25, 2008 To go BPU you will need the following: - Cat Back exhaust New smic or fmic (you really need to replace yours if it has seen better days, to test if it has run your fingers accross the fins and if the crumble get it changed. Colder plugs Double Decat 1 bar restrictor ring Uprated fuel pump. Boost guage. FCD (Thor is the best or Greddy) Optional for BPU Boost controllor (to raise boost over 1bar) Cams 550cc injectors Hybrids Standalone ECU The list goes on. The above is for even better gains but can be exspensive, if you plan to go single anytime in the furture do not consider hybrids. Link to comment Share on other sites More sharing options...
bodilx6 Posted January 28, 2008 Share Posted January 28, 2008 Keeping the 1st cat in, removing the second and having a more free flowing muffler gave me 353bhp, so it did make a difference. My boost went to a max of about 0,9 bar. It should be said that removing the 1st cat changes the car to more of a beast than the roughly 40bhp it gains suggests. The way the torque is delivered when the 2nd turbo kicks in is very agressive as well as the 1st turbo will spool quicked due to the lower restriction. But again if you put in a 1 bar RR then you will probably end up with something being not very far from how it feels with the 1st cat in. So you have to decide if you want to push 1.2 bar and put more of a load on the tubbies if you drive like a maniac most of the time or just leave them at 1 and keep them more safe. Statistacally speaking at least. would your guy make me up one of his fcd's for me please? I'm in Denmark and the guy who makes these FCDs has been very hard to get a hold of and to get it done, so I wouldn't reccomend it. You can try to drop him a mail at [email protected] but I can't guarantee you anything, and don't know if he writes English But just mention that you have a j-spec MKIV supra and it'll hopefully work out. Mine workes fine Link to comment Share on other sites More sharing options...
jamesmark Posted January 28, 2008 Share Posted January 28, 2008 Keeping the 1st cat in, removing the second and having a more free flowing muffler gave me 353bhp, so it did make a difference. My boost went to a max of about 0,9 bar. That dyno must have been over reading a lot. 353bhp from just the 2nd cat removed? Removing the 2nd decat offers very little gains if you still have the 1st (and most restrictive cat) still in place. Link to comment Share on other sites More sharing options...
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