what is a decat?

theballboy

Tuner
Points
60
Car
mondeo tdci
Sorry I have no idea but wnat to know basically what is a decat?
Also - what is a cat-back exhaust?
Thanks
 

pgarner

TC ModFather
Points
417
From
Lockerbie, SW Scotland
Car
Octy smoke machine
the cat is the catalytic converter
a decat is basically a straight through pipe that replaces this.
cat back is basically everything from this back - midsection and back box
 

theballboy

Tuner
Points
60
Car
mondeo tdci
Where can I find more info? It sseems that a decat can produce more torque or hp? What is the purpose of having a cat in the first place?
 

pgarner

TC ModFather
Points
417
From
Lockerbie, SW Scotland
Car
Octy smoke machine
google will open a whole doorway of knowlage ;)

a decat can release power by de restricting the exhaust.
the cat itself had to be fitted to every car after 91. the cat uses precious metals to remove/convert the harmful gases in the exhaust.

in petrol cars its hard to remove the cat as these are tested for emissions CO, NO are two of the main ones
however in a diesel its easier to remove as these are smoke tested which the cat has bvery little to do.

but dont expect massive gains. on the mondeo you should feel faster spool however
 

obi_waynne

Administrator
Staff member
Moderator
Points
1,137
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
By Spool PG means here the rate at which the turbo kicks in and spins up.

A sports cat is a better option IMHO as it keeps the cars emissions road legal. Gains are similar to a decat though but a sport cat does cost a bit more.

Does the TDCI even have a catalyst though? I thought that they had a DPF (Diesel Partical Filter instead?)
 

theballboy

Tuner
Points
60
Car
mondeo tdci
Im not sure exactly but I think it does. Does that mean that a decat would have no advantage gains?

Also and importantly, how does this affect MOT if done?
 

obi_waynne

Administrator
Staff member
Moderator
Points
1,137
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
A decat or removing the catalyst will improve exhaust flow and will in most countries fail an annual inspection test.

Sports cats are designed to flow better - they usually have a larger surface area for air to flow through and still perform the useful emission improvements keeping the car legal. A good sports cat is usually larger than the standard one and has larger cells inside.
 
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