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 To decat or not to decat? this is the question
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domn8
Level 6 User

Joined: 26 Jan 2005
Posts: 159

Posted: Fri Jul 01, 2005 6:05 am

^^^on my valver with K&N and Magnex backbox.

Is it going to make it stupidly loud and will the performance difference be worth it?

any other pros and cons?

Dom
Tranton
Site Subscriber

Joined: 17 Mar 2004
Posts: 342

Posted: Fri Jul 01, 2005 6:10 am

Putting the CAT back on for the MOT is a con. Unless it passes emmissions and your friendly with the tester Laughing You should notice the performance but it won't be massively increased.
domn8
Level 6 User

Joined: 26 Jan 2005
Posts: 159

Posted: Fri Jul 01, 2005 6:19 am

Im assuming there is no need to pay sill ymoney for a K-tec or other brand as they are simply a section of pipe with mounts unless silenced.

Can get them on ebay for 29.99
Leigh_f
Site Subscriber

Joined: 01 Mar 2004
Posts: 458

Posted: Fri Jul 01, 2005 8:02 am

one of the best things i did, gives lovely note (to my sytem anyway!) with mods like this i believe that any performance is a state of mind i.e you'll think it's quicker as it sounds quicker and theoretically should be, but whether it is is a different question
Chris H
Forum Moderator

Joined: 02 Mar 2004
Posts: 19978

Posted: Fri Jul 01, 2005 8:08 am

go fer it
Mad Pierre
Level 10 User

Joined: 18 Jun 2004
Posts: 614

Posted: Fri Jul 01, 2005 9:14 am

http://www.madpierre1.plus.com/vids/VALVER/pierre.wmv

That's the noise It will make with a full Exhaust system. I.e. Only one box. The back one. and with a de-cat on. Note the back box was a sporty one also for the noise.
domn8
Level 6 User

Joined: 26 Jan 2005
Posts: 159

Posted: Fri Jul 01, 2005 9:40 am

Ah Ive seen that before, sounds good
Mad Pierre
Level 10 User

Joined: 18 Jun 2004
Posts: 614

Posted: Fri Jul 01, 2005 9:59 am

Yep it does. Bastard to put up with at time's tho'. That why the cat back on. Nice and loud for small drive's Very Happy . Not so good on long drive's and when you work at 6 am on day's or come home at 3 am at night. On nights, pissing everone off. It also get's all the nob's hangin around your car.
schakal
Spammer

Joined: 27 Jul 2004
Posts: 5717

Posted: Fri Jul 01, 2005 12:48 pm

what about an insides punched out cat ??? i have been told it does not give the same performance but feckin awfull sound Rolling Eyes
Mad Pierre
Level 10 User

Joined: 18 Jun 2004
Posts: 614

Posted: Fri Jul 01, 2005 2:11 pm

Go for a De-Cat if you want. I'm just pointing out, if it loud now. it be a load louder, with a De-Cat. and IMO you only gain on top end power.
Gentle Ben
Site Subscriber

Joined: 07 Oct 2004
Posts: 2281

Posted: Fri Jul 01, 2005 2:56 pm

Yep. Decat reduces back-pressure, reduces torque thus acceleration.
domn8
Level 6 User

Joined: 26 Jan 2005
Posts: 159

Posted: Sat Jul 02, 2005 2:49 am

so whats the decating thing all about then? just big ass noise?
Dan
Site Subscriber

Joined: 28 Jan 2005
Posts: 3547

Posted: Sat Jul 02, 2005 3:38 am

ive noticed on mine in high end revs that it pulls better with a non silenced decat.
JB
Mr Quoter-vator

Joined: 16 Feb 2004
Posts: 7405

Posted: Sat Jul 02, 2005 6:12 am

yawn!
Chris H
Forum Moderator

Joined: 02 Mar 2004
Posts: 19978

Posted: Sun Jul 03, 2005 11:44 pm

don't talk shite ben.
schakal
Spammer

Joined: 27 Jul 2004
Posts: 5717

Posted: Mon Jul 04, 2005 4:59 am

Gentle Ben wrote:
Yep. Decat reduces back-pressure, reduces torque thus acceleration.


Laughing
Gentle Ben
Site Subscriber

Joined: 07 Oct 2004
Posts: 2281

Posted: Mon Jul 04, 2005 8:13 am

Bad explanation, here's another:

The catalytic converter unit places slight restriction on the flow of exhaust gases as they exit the car. Replacing the cat with a section of pipe eliminates this obstruction and the exhaust gases exit the car at a higher velocity (higher gas flow).

If the flow of gas through an internal combustion engine is increased, then an increase in power can be felt and a higher top speed can be attained. The downside is that exhaust back pressure is reduced. Back pressure in the exhaust keeps the air/fuel mixture of the next engine cycle in the cylinders longer, thus allowing more torque to be evolved since the burn is kept in longer.

In short decat = higher top speed but acceleration (0-60 times) will suffer.

The choice, is yours! (In my best early 90's quiz show voice).
Chris H
Forum Moderator

Joined: 02 Mar 2004
Posts: 19978

Posted: Mon Jul 04, 2005 8:49 am

Ben really, I have told you before when you don't know what your talking about don't pretend you do and type anyway!

Also a CAt in decent nick isn;t that much of an obstruction, 90% of them these days are rather blocked.
david3533
Site Subscriber

Joined: 02 Oct 2004
Posts: 1575

Posted: Mon Jul 04, 2005 8:56 am

an amazing fact about cat's, for them to work effeciently the ambient air temp has to be 22deg C! now how many times a year does that happen in the uk? also another fact if the ambient air temp is below the optimun working temp more polutants are generated!!!! just thought I would pop that 1 in Very Happy see i'm full of boring useless rubish Laughing
Gentle Ben
Site Subscriber

Joined: 07 Oct 2004
Posts: 2281

Posted: Mon Jul 04, 2005 11:08 am

Chris, I just state what I have been led to believe, and if what I'm told sounds logical to me, then I'll stand by it.

Where exactly is the flaw in my explanation then?

I can accept when I'm wrong but I don't appreciate being told I have no idea.
JB
Mr Quoter-vator

Joined: 16 Feb 2004
Posts: 7405

Posted: Mon Jul 04, 2005 11:43 am

i smell snake oil...
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