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Chris and Alana
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Will a j-spec soop boost to 1.0 bar with the second cat left in (with a perfermance exhaust aswel)? I know the first cat is alot more restrictive so if I keep the second will I still be able to reach 1.0bar?

 

I know alot of you will recomend a full decat but I dont want to boost 1.2 bar just 1.0 bar and if it will do this with the second cat left in, it should also pass MOT and keep the noise of the exhaust down a bit. Iv heard they are really loud fully decatted.

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I'm curious on this one too, although i think i read somewhere that this set up would punish the 2nd cat.

 

I dont think leaving the second cat in does any harm. I think if you leave the first cat in and up the boost with a EBC for example the restriction of the cat will cause very high EGT's and put alot of stres on the turbos. But as far as I know the second cat is less restrictive and further away from the turbos so at 1.0bar EGT's should be fine but I dont know if the restriction will be little enough to allow the turbos to create a natural 1.0 bar boost, thats why I'v started this thread. (I hope Im right with everything there)

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If your car doesn't run 1.0bar with that setup then you can easily stick an EBC/MBC in to up it to that. :)

 

Thats abit expensive to do it that way. Im going to try it at the end of the month (first decat that is) and see what happens. If it doesnt reach 1.0bar I think Il take the second cat out aswel and put a 1.0bar rr in. that should sort it. It would just be nice if I could keep the second cat in and reach that boost level as it keeps it legal and keeps the exhaust noise down a bit aswell as give me more power:eyebrows:

 

If anyone has this set up it would be nice to know what boost you are making

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Hi,

 

I've got the first cat replaced and second cat still fitted. I get 1.0Bar nicely. EGTs (manifold) usually around 850, but have hit 900 on extended blast at WOT. In the summer only saw about 0.9-0.95Bar. :)

 

J

 

Thanks very much, just what I was looking for:) Did you find a difference in performance at 1.0 bar with the second cat left in (over stock)?

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Definately more pull when 2nd turbo comes online - much more kick. Also spools up quicker and easier. Not as punchy as 1.2Bar, but easier for MOT time and not so much strain on turbos etc. I've also got a Greddy 2-row FMIC, which I think helps keep temps more down, which means power too :)

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I didnt notice much of a noise increase when I decatted, however, the NurSpec-R is a noisy beast anyway.

 

You only ever have a problem at MOT time, and a quick pint for the hard working garage owner soon sorts that little problem out.

 

Boost is a funny game, im decatted, with a 1bar RR, but still manage to hit 1.2 bar on the cold days.

 

Jaymdee - the FMIC cools the inbound air charge, not the EGTS so although the FMIC helps maintain the power you have it's not really relevent to the EGTvs Cat issue.

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Jaymdee - the FMIC cools the inbound air charge, not the EGTS so although the FMIC helps maintain the power you have it's not really relevent to the EGTvs Cat issue.

 

I know mate, hence the comment on increasing power. I mentioned it as I really noticed the difference vs stock and wanted to make it clear that the effect could be down to 1st Cat AND FMIC. :)

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well Im not the best at this either but from what Ive read the first cat is the more restrictive than the second. restrictive enough to allow the wastegate to do its proper job (keep boost down) I think from other threads you 'may' get a slight increase of a couple PSI or 0.1 bar with the first cat left in.

Buy a boost gauge, that will answer your question straight away. I bought a cheap autogauge one of ebay for £18 and it works fine, easy to install, just take the clock out (for a 52mm gauge and it fits perfect. or the air vent for a 60mm. its worth the small amount of notes just so you know what your boosting.

Anyway thats the limit of my knowledge, hope it helps

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