de-cat

podu · Post by **podu** » Wed Sep 20, 2006 8:44 pm

has anyone made one for theirs,would any pipe off any model fit on my sri turbo cos gonna cut cat off it for de-cat and keep my original cat for the mot.

Blue406 · Post by **Blue406** » Wed Sep 20, 2006 9:18 pm

Why go through the hassle?

Davva2004 · Post by **Davva2004** » Wed Sep 20, 2006 10:15 pm

Less back pressure = more BHP! Turbo cars don't need back pressure like NA cars do, NA cars use the contrictions in the exhaust to create waves of pressure down the exhaust pipe which helps suck all the exhaust fumes out of the cylinder, it's called scavenging. Because turbo cars force fill the cylinders they run less overlap on the cams as the engine doesn't need to suck in it's own air fuel mix. Turbo cars produce more power with a freeflow exhaust, for example on my RS Turbo replacing the stock 2" pipe with two silencers for a 3" pipe with one unrestrictive backbox gave me 15bhp @ fly.

Post by **Welly** » Thu Sep 21, 2006 8:56 am

Too true, Turbo's respond well to a free flowing system, NA cars can suffer a loss of torque with some 'performance'

systems.

A decat effectively removes a restriction in the system so things just happen a bit quicker, this can 'free up' a few BHP's although the real benefit is the way it delivers the power afterwards.

GeordieBoy · Post by **GeordieBoy** » Thu Sep 21, 2006 11:53 am

Have a look at buying a CAT for your car and gutting the insides of it b4 fitting. Then when it comes to MOT time you can just swap over to your proper CAT as with petrols you need it for the MOT.

I've been quoted £120 for a De-Cat for my HDi from AAS Exhausts.

podu · Post by **podu** » Thu Sep 21, 2006 6:54 pm

is the cat seperate to the front pipe or is it part of the front pipe?
mate works with stainless steel pipe so can get some 2-3inch pipe to make decat if it's seperate from down pipe,possably make some for others too if it works ok.!

=|[PsychoPoet406]|= · Post by **=|[PsychoPoet406]|=** » Sat Sep 23, 2006 1:24 pm

I'm sure Ascar used to quote £35 for a decat pipe. It's only a bit of pipe after all.

niz406 · Post by **niz406** » Sat Sep 23, 2006 5:29 pm

Do you want stainless or mild steel ?

If your gonna do a DE-Cat do it properly !

podu · Post by **podu** » Sun Sep 24, 2006 12:41 pm

was gonna use stainless, gonna get an old cat off a scrapper and use flanges off it so easier to put on n off for mot time.probably have to make hole n weld on a bolt for probe to go in unless its b4 the cat have'nt looked properly yet.

dougspug · Post by **dougspug** » Wed Oct 18, 2006 11:23 am

unfortunately 406s have two lambda sensors,before and after the cat be prepared for your eng management light to be on all the time,and fail mot if tester spots it.

niz406 · Post by **niz406** » Wed Oct 18, 2006 11:43 am

dougspug wrote:unfortunately 406s have two lambda sensors.

D8's don't

And tbh he wants to put the CAT back on for the MOT, otherwise he wouldn't need flanges as he could cut the CAT out and weld in another box of pipe joint !

nipper76 · Post by **nipper76** » Tue Nov 07, 2006 12:26 pm

ok just to simplifie this...(im learning) if i take the cat off its going to improve performance...?
dose this work with Turbo diesels??
and can you do the job witout to much mucking around.... cutting etc
whats this de-cat pipe?? is it something you can buy that saves cutting and boddging?
soz if i sound dumb lol

Davva2004 · Post by **Davva2004** » Tue Nov 07, 2006 1:53 pm

nipper76 wrote:ok just to simplifie this...(im learning) if i take the cat off its going to improve performance...?
Not always... turbo petrol engines yes, NA petrol engines it's more complicated as you tend to lose torque.
dose this work with Turbo diesels??
Erm... pass. I would presume that the principle would be the same as a turbocharged petrol engine though.
and can you do the job witout to much mucking around.... cutting etc
Yes, by buying a decat pipe.
whats this de-cat pipe?? is it something you can buy that saves cutting and boddging?
It's a pipe that is the exact length of the cat housing with the correct flanges on it, you just unbolt the cat out of the exhaust system and bolt in the decat pipe. That way you can swap it back for MOT time because no cat equipped car will pass the emissions section of an MOT test without a cat fitted.
soz if i sound dumb lol
Not at all!

Post by **Welly** » Tue Nov 07, 2006 3:03 pm

Funny isn't it, no one seems to know anything about exhaust systems on Diesel engines and whether they can be improved upon or whatever.

(I don't mean you Davva, best mate, I just meant generally, you know)

Been bothering me for ages that.

nipper76 · Post by **nipper76** » Tue Nov 07, 2006 6:21 pm

sounds fairly simple

thankyou ... Davva2004
now heres one for you... do diesels have cats?? no not the furry kind lol
1 diesel fanatic says no... but some1 else says they do.
hmm???

and if you take it out... dosnt that make a high risk for toxic fumes??
cheers