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I saw this, and even sent an e-mail to the guy asking how much postage was likely to be - £10 as that was the most Parcel force charge up to 25Kg or dead heavy anyway.

Thing is, its a silencer would you not be better with just a straight pipe if you were going to bother swopping pipes (as uou will have to go to the effort of swopping back each MOT)
 

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Discussion Starter · #3 ·
I dunno how much if any benefit a straight pipe gives you over a silencer- a wee bit I suppose. That difference will however be small compared to the gain you get from removing the CAT.

The main thing is that some people find the cabin noise from a straight through pipe too intrusive on 2.3T's, hence why the likes of Abbott offer the silencer version of cat bypass.
 

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talking to a specialist in edinburgh about this. he said that you need a silencer type pipe. This is due to backpressure ans 'stuff' and how it affects the engine...a straight through pipe alters the pressure hence causes (possible) probs. Could be complete *****! but thought I'd mention it....'cos I know nothing about this maybe someone could explain why it is rubbish?
 

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Discussion Starter · #5 ·
Well, he's sort of right. A car exhaust system is an integral part of the engine and it's tuning and therefore fuel economy, emissions etc etc...

Engines generally "like" a certain amount of back pressure from the exhaust. As I recall, it helps with low-down torque. So, if you removed all the back pressure, then things would probably not be happy. A measured reduction, however, will bring an improvement in responsiveness, and possibly top end power.

This particularly applies to turbo engines. I'm not sure, but I would guess that the majority of the back pressure on the engine actually comes formthe turbo itself. By reducing the restrictions in the exhaust post turbo, you enable a faster spool-up and more top end power. Gas flow is a big thing, and basically anything that can be done to make it smoother and less restrictive will result in more power.

So, a straight through pipe will give better performance compared to a box, but the difference is marginal compared to that achieved from removing the restrictive cat.
 

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Mark/.

On my 1994 9000 2.3T Full blown, I have a non-silencer straight thru pipe instead of CAT, no noise increase or anything, just a lovely quiet purr from rear sports box..
No-one should be taken in by being sold a much costlier silencer-type thru pipe (maybe non-turbos are different, without a turbo to eat up a lot of the initial noises, I dont know).

Andy
 

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Discussion Starter · #7 ·
I've certainly noticed the difference... but then I'm on the full Abbott system on my 93 2.3 FPT. It's quite a lot louder with the straight compared to say having the CAT in or the silencer.

On my last one, a modded 2.0LPT (more like a FPT) I just had the Abbott rear box and the difference was more subtle.

One of the main things you will get with the straight thru compared to silencer is more "popping" on overrun. Some like it, some don't. Personally it always brings a big to my face when I hear it.
 

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My '94 model Aero has a straight through cat replacement and Abbott rear box (older and larger dia. than Andy's). Side by side mine is quite a bit louder than Andy's at idle. It used to concern me but on the move it's not silly, it's something you can get used to.
Nick.
 

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Mark/.
Yep, that popping sound is ok in my book,provided engine is in good nick, and it does it for right reasons .

As Nick says, overall, my system has the cat bypass, and a 3" rear abbott box, but little else. Still restricted from manifold .
(Other priorities Im afraid, just run new head gasket and other stuff in....)

Andy.
 
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