To decat or not to decat? this is the question

Level 6 User Joined: 26 Jan 2005 Posts: 159

^^^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

Site Subscriber Joined: 17 Mar 2004 Posts: 342

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.

Level 6 User Joined: 26 Jan 2005 Posts: 159

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

Site Subscriber Joined: 01 Mar 2004 Posts: 458

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

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

go fer it

Level 10 User Joined: 18 Jun 2004 Posts: 614

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.

Level 6 User Joined: 26 Jan 2005 Posts: 159

Ah Ive seen that before, sounds good

Level 10 User Joined: 18 Jun 2004 Posts: 614

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.

Spammer Joined: 27 Jul 2004 Posts: 5717

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

Level 10 User Joined: 18 Jun 2004 Posts: 614

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.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Yep. Decat reduces back-pressure, reduces torque thus acceleration.

Level 6 User Joined: 26 Jan 2005 Posts: 159

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

Site Subscriber Joined: 28 Jan 2005 Posts: 3547

ive noticed on mine in high end revs that it pulls better with a non silenced decat.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

yawn!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

don't talk shite ben.

Spammer Joined: 27 Jul 2004 Posts: 5717

Gentle Ben wrote:

Yep. Decat reduces back-pressure, reduces torque thus acceleration.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

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).

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

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.

Site Subscriber Joined: 02 Oct 2004 Posts: 1575

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

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

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.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

i smell snake oil...