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Discussion Starter · #1 ·
My back box needs replaced on the 9k Aero and I have a speedparts stage 1 already done. I can't afford to get the full JT system so I reckon it's sensible to get the cat back just now ...
Is there a decent 'real' performance improvement? The spec. quotes 5bhp, but is it more responsive too?
Any experience welcome!
 

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I would think the extra response would be hardly noticable with cat-back, the really noticable response is after fitting the down pipe and sport cat. But if the exhaust is in need of replacemnet then fitting the JT from cat back is certainley worthwhile doing now, then easy to upgrade to downpipe+sport cat at a later date when finances allow.
 

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Speaking from my own experience on this issue, I can advise that the fitting of a Hirsch cat-back exhaust system gave me a bhp gain of 10bhp.

Car felt "livlier" but not significantly so. The power gain was only 5% given that the car started from 200bhp.

Fitting a 3" downpipe and sport cat at a later date gave a significant improvement of around 15-16bhp and the car defininitely felt quicker.

This is my own experience using rolling road readings on a 200bhp Saab 9-3 with a standard Saab ECU. I suggest that you may get a percentage gain, rather than an absolute bhp gain, based on original bhp.
 

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On the dyno, I registered a 7 hp increase when I fitted a Saab Sport Stainless Steel catback exhaust. There wasn't much of an extra gain by the feel of it though. But as /john mentions, it is a pretty small percentage. Mine was 185 hp stock.
 

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There is a potential problem for future upgrading- because it is a sleeve fit range than flange joint system, the JT will be supplied with an adaptor. I had one for my downpipe. The problem is that you will then need to cut some length off the system in order to accommodate the adaptor, meaning that if you go for a full system in the future, you will need to replace the section you have shortened (the mid box).
 

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Discussion Starter · #8 ·
oh - having not looked at the connection, can I cut material from the front section instead of the new rear part?

thanks for all other comments - pretty much what I expected, but at least is does give a measurable increase ...
 

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Discussion Starter · #10 ·
I'm still keen to do the downpipe mod. but don't have enought cash for the £530 sport system. I do have enough for the £300 full non-cat system though.
My car is 1996 with the integrated downpipe/cat so I can't see a way of running without cat (track days..for example) unless I change the downpipe everytime which could be a pain. i.e. I can't use my existing cat without the downpipe as the two are integrated.

Has anyone else got round this or am I tied to the sport-cat downpipe route?
I had thoughts on liberating my cat and connecting it in a removable manner to the pre '94 system somehow?

Cheers!
 

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I'm pretty certain that although they are different configurations, the sections of the CS exhaust system are the same length whether it is front or mid cat. This being the case, I don't see any reason why you shouldn't get the downpipe and get hold of a s/h mid cat. That way, you could use your current mid pipe for track days, whilst leaving the cat in for "everyday" use
 

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Discussion Starter · #12 ·
Thanks - that sounds like a great idea - I'll need to see how much an 2nd hand mid cats go for as that could almost negate my savings if they are too pricey.

I also noticed in previous discussions that there was a potential I could pass the MOT without a cat, but this may be down to pre-'92 cars being subject to a less stringent test than my '96.

In addition - I am assuming the performance of the JT3" without a cat (or even with a bypass silencer as opposed to straight pipe) will exceed than of the sport and racing JT cat systems??
 

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Faero I have a MY95 aero with the cat as a seperate item.I have a JT exhaust on order and have arranged a date for fitting,if they can split the sections,you are welcome to what you want.PM me
 
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