Ford Fiesta ST
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#353868 - 21/09/11 12:40 PM Cat back vs Normal system
kconroy Offline


Registered: 01/12/10
Posts: 47
Loc: England
Just wanted to know guys whats the difference between the normal full exhaust system and the cat back system. I was looking on JamSport at the full miltek exhaust system and to get a sports cat included its an extra £500 even though its only 350 when you buy it on its own. Can you buy everything seperate to aviod the sting?

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#353869 - 21/09/11 01:01 PM Re: Cat back vs Normal system [Re: kconroy]
ST_Lee Offline
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Registered: 17/09/08
Posts: 8873
Loc: Blackpool
Yes you can buy the sports cat separately from the cat-back mate. Have a shop around for the best deal. You can also get the 4-1 manifold too

Can only think the extra cost is towards fitting but £150 difference is a bit silly

Oh and the difference is more power and better sound!
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#353870 - 21/09/11 01:06 PM Re: Cat back vs Normal system [Re: ST_Lee]
kconroy Offline


Registered: 01/12/10
Posts: 47
Loc: England
What exactly is a cat back? and the only problem im having is finding the centre silencer and the rear one seperatly. Is it worth getting the whole system because of the new 2.5" bore pipes. I just didnt know if to get the de-cat, or to get something alittle more legal ha

I thought that 150 difference is abit strange. lol

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#353871 - 21/09/11 01:12 PM Re: Cat back vs Normal system [Re: kconroy]
ST_Lee Offline
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Registered: 17/09/08
Posts: 8873
Loc: Blackpool
I could have a go at explaining the cat-back, but will leave it to someone more technical than me

I personally went with the sports cat - firstly because of the implications with the - and secondly because it wouldn't pass its MOT and I couldn't be bothered with the hassle of swapping it over every year. Plus, I later found out that as I have a Powerflow cat-back, my system had to be modified to fit it all together, meaning my original cat will no longer match my cat-back without modification
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#353872 - 21/09/11 01:28 PM Re: Cat back vs Normal system [Re: ST_Lee]
steviehouse Offline
Best Non ST Car of the Year 2013/2014

Registered: 10/05/10
Posts: 11614
Loc: Jubail, Saudi Arabia
as said in the ebay bits and bobs thread mate, the 2.5" big bore is suited only for cars above 200bhp

see this for exhaust explanation

http://www.fordfiestast.co.uk/showflat.p...true#Post284227
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#353873 - 21/09/11 01:43 PM Re: Cat back vs Normal system [Re: steviehouse]
kconroy Offline


Registered: 01/12/10
Posts: 47
Loc: England
Right i think i understand now so really all i need to get (for beggining) is the manifold (with built in flexy) then a sports cat and i can keep the standard tail end or get a cat back if i want better sound?

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#353874 - 21/09/11 02:15 PM Re: Cat back vs Normal system [Re: kconroy]
The_Notorious_C Offline


Registered: 23/04/11
Posts: 457
Loc: Aberdeen, kind of.
to fit the standard exhaust you will need to cut it, just in case you think it's a straight bolt up job.
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#353875 - 21/09/11 02:33 PM Re: Cat back vs Normal system [Re: The_Notorious_C]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
Basically if you want your car to pass on emissions and MOT's go for the sports Cat.

If you want to use your car for racing then de-cat is good buy it's been recorded that with the de-cat on the full system you get an extra 2-3bhp then the sports cat. But again varies on each car.

Cat-back, does absoloutely sweet f all performance wise for your car it's oftern the bit which makes the sound a long with the back box depending on the bore of the pipning you can generate raspy sounds, deep, or high pitch like F1 cars (smaller pipe you get can also effect the back pressure to the sports cat you can get a lot of back fire, pops and bangs).

There are two versions available with the Milltek system non resonated which is a clean straight through pipe to the back box or resonated which muffles the sound at high rpm it's useful if you don't want a noisey exhaust system as it can sometimes cut out any noise all together at low RPM (in my opinion the better option)

for the full milltek system you will need the following

-Manifold
-De-cat/sports cat
-Non-resonated/Resonated cat-back
-Backbox

All parts will slot together to make the full system.


Edited by STASON (21/09/11 02:47 PM)

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#353876 - 21/09/11 02:39 PM Re: Cat back vs Normal system [Re: STASON]
ST_Lee Offline
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Registered: 17/09/08
Posts: 8873
Loc: Blackpool
Quote:

Cat-back, does absoloutely sweet f all performance wise




Really? That's odd as Stew made 154bhp with a manifold and filter but I made 172bhp when I had manifold, filter and cat back!!!
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#353877 - 21/09/11 02:51 PM Re: Cat back vs Normal system [Re: ST_Lee]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
It gives a little bit of back pressure or less for the engine it does help the car breathe a little better but we are talking barely any margines for performance.


Quote:

Cat Back

That term refers to the portion of the exhaust from the catalytic converter on back to where it ends at the rear of the vehicle.
They generally use larger pipe than the stock system. Good systems will have mandrel-bent turns that allow the exhaust gas pass with as little back pressure as possible. The mufflers in these kits are often glasspacks to reduce back pressure.

It is more of a improvement in sound than performance, it will help achieve a deeper sound that is lacking in small displacement engines and improves horsepower very little.

An improvement is there but hardly worth the cost as a performance upgrade.





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#353878 - 21/09/11 02:53 PM Re: Cat back vs Normal system [Re: ST_Lee]
ET07 Offline


Registered: 09/09/11
Posts: 169
Loc: Lancashire
Quote:

Quote:

Cat-back, does absoloutely sweet f all performance wise




Really? That's odd as Stew made 154bhp with a manifold and filter but I made 172bhp when I had manifold, filter and cat back!!!




I always thought this was the case. The standard cat is very restrictive (on all cars, not just an ST) and there is a great deal of pressure build up...a sports cat basically gets rid of this pressure build up whilst providing the catalyst properties required of a catalytic converter (and the law), similar to a straight through illegal de-cat. Having a better exhaust manifold with a standard cat-back is effectively pointless as the standard cat is just undoing the work done by the manifold because it can't get rid of the exhaust fumes quick enough. So it would be better to get a sports cat-back and later look into a manifold (unless you can afford the whole sports exhaust system, in which case get that!).

This is just my understanding...feel free to correct me if I'm wrong. I'm still learning as well

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#353879 - 21/09/11 02:58 PM Re: Cat back vs Normal system [Re: ET07]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
it would be interesting to see what people can make with sports cat anf manifold with standard cat back system.

bet that will get some decent flames and bangs.

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#353880 - 21/09/11 08:51 PM Re: Cat back vs Normal system [Re: STASON]
Kaxe Offline


Registered: 01/07/08
Posts: 8157
Full system ftw!
I did the system piece by piece on my old fez. Unlocks all the power!

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#353881 - 21/09/11 09:18 PM Re: Cat back vs Normal system [Re: Kaxe]
gary4vicky Offline
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Registered: 09/05/10
Posts: 4603
Loc: Northampton
full system is good but my mot tester had to really let the car warm up to get it to go through on the emissions with my sports cat. they sound pretty great too
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#353882 - 22/09/11 12:04 AM Re: Cat back vs Normal system [Re: gary4vicky]
ST_Lee Offline
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Registered: 17/09/08
Posts: 8873
Loc: Blackpool
Quote:

full system is good but my mot tester had to really let the car warm up to get it to go through on the emissions with my sports cat




I'd read that too. I made sure I went for a nice drive before I dropped my car off to be tested
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