Can someone please explain what a de-cat is?

How do you do it?

Why would you do it?

 

Only asking as a friend of mine has a civic saloon v-tec and he has it de-catted and another friend has a 1.5 DOHC Mirage and he is getting it done to his aswell?

part of the exhaust system is the catalytic converter. its designed to reduce the toxicity of the exhaust gasses by converting carbon monoxide and unburnt hydrocarbons to carbon dioxide (via oxidation with water as a by-product).

The problem is they are expensive and restrictive in the flow of air from the engine. De-catting a car just involves replacing the cats with plain simple pipes, thus allowing the gasses to flow out freely but at the expense of the cars emissions, more power but higer toxin levels.

Another plus to a de-cat is that it allows the unburnt fuel to pass into the exhaust and can give you a nice little flame lol

However, if you do remove the cats and bin them then you will fail emissions on an MOT if its applicable to your car. HTH

Hijack, so in that case then it obviously has benefits, but isnt there rules on when the car was first registered in the uk to wether it has to pass the emmisions or wether it is exempt ???

yes, I'm not an MOT'er or mechanic but i think..... iirc, cars made before 1992 dont have to "pass" an emmissions test at MOT, selected cars made 1992-1993 dont have to "pass" but ALL cars made 1994 on have to pass a preset level of emissions and therefore most de-cats will cause this to fail.

Its all about balance but now that the emissions testing is done by computer direct to VOSA there is no "cheating" the test, you get an immediate pass or fail from the computer.

ok, but is it when the car was actually built or when it was first registered in the uk, mine has bin in the uk for a good few years now, think I remeber seeing that if the car was first registered in the uk before 2000-2001 then it would be emmisions exempt, no doubt someone will tell me otherwise, lol. tend to be wrong alot at the moment, think i'll stick to ships.

i believe the regulations go on the cars date of first use. This seems to back this up.

 

http://www.transportoffice.gov.uk/crt/vehicledrivers/roadsidechecks/randommotemissionchecks/roadsideemissionsandmotstandards.htm#P16_1832

 

First used before 1/8/1975 - Visual test only. Failure for excess idle speed, dense blue or black smoke for 5 seconds at idle or during acceleration up to 2500rpm or half engine max speed whichever lowest.

 

First used between 1/8/75 and 31/7/86 - meter test CO

 

First used between 1/8/86 and 31/7/92 - meter test CO

 

First used between 1/8/92 and 31/7/94 - advanced emission test (CAT) if its running on petrol when presented, to the vehicle specific limits usually around CO

ok, but is it when the car was actually built or when it was first registered in the uk, mine has bin in the uk for a good few years now, think I remeber seeing that if the car was first registered in the uk before 2000-2001 then it would be emmisions exempt, no doubt someone will tell me otherwise, lol. tend to be wrong alot at the moment, think i'll stick to ships.

its when the car was built. mine was imported in 2002 (IIRC) is a 1990 series 1 and decatted with no problems from the mot emissions test.

iirc import zeds even 93 onwards get away with a basic emmissions test because it's not a 300zx, rather a Fairlady Z, which ain't on the systems. Just hearsay though so could be *****cks.

It gets tested as a 300zx but zeds in the uk were only made until 1994 so all 300s only get a basic cat test afaik

im gona decat my 91 tt some people say not to because of the turbo seals but im gona risk it anyway :D

Change the PCV valves *AND* hoses at the same time as a safe guard ;)

so if i get the car decatted it should be ok on the emmision test then?? dont wanna have to put them in again for the sake of an emmisions test

tbh its really hard for a zed not to pass the emissions test decat or not.

thanks very much for clarification

FYI ;)

 

http://300zx.co.uk/forums/showthread.php?t=27060