De-cat, does and donts for heaps of scrap

Hello,

Looking to decat my 3.9 (early K Reg)

Other than the pipes (that need a pair of nuts for the lambda sensors adding) and a resistor, do I need anything else ?

Keeping reading that a non cat Fuel module/ECU is needed.

Since they are as rare as rocking horse raisins, what do i need to do ?

Only looking to do it the once,

Did it start life with a CAT? The law changed a year or so ago, so if a vehicle was produced with a CAT it now has to have one for the MOT. Don't know if there are any exceptions. Your MOT tester may not know if it had one or not, so you may well get away with it. (It might be more than a year and I may be wrong - someone will correct this hopefully)

having seen the build documents, theres no mention, at all,

Microcat gives both options as well so anyones guess....

If your car was first registered in or after 1993 it MUST have a cat fitted.

wammers said:

If your car was first registered in or after 1993 it MUST have a cat fitted.

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He's ok by a year then?

Jonnyb1990 said:

having seen the build documents, theres no mention, at all,

Microcat gives both options as well so anyones guess....

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TBH I think it's very hard for testers to tell. I think there were times when some models were fitted with them and some not in the same year. You might be able to tell by looking up the VIN number, but no tester is going to go to that bother.......I reckon.

Al2O3 said:

He's ok by a year then?


TBH I think it's very hard for testers to tell. I think there were times when some models were fitted with them and some not in the same year. You might be able to tell by looking up the VIN number, but no tester is going to go to that bother.......I reckon.

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He did say early K. Obviously as he has Lambda sensors and a cat ECU, was fitted as standard with cats. Would therefore be illegal to remove it.

wammers said:

He did say early K. Obviously as he has Lambda sensors and a cat ECU, was fitted as standard with cats. Would therefore be illegal to remove it.

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My mistake, should have said he's unlucky by a year. Should have had a closer/longer look at the car reg to year web site I googled

Al2O3 said:

My mistake, should have said he's unlucky by a year. Should have had a closer/longer look at the car reg to year web site I googled

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As far as i can see K prefix ran from 1st August 1992 until 31 July 1993. All vehicles first registered in 1993 had to have cats fitted, they became compulsory in that year. They cannot be removed. Some vehicles had them fitted before that date, but if they were fitted as standard they cannot be removed either. There are two provisos, any vehicle manufactured in or after 1993 MUST have a cat fitted. And IF a cat was fitted as standard equipment it MUST have one fitted regardless of year. .

Build date is Dec 91, sold date is June 92

Jonnyb1990 said:

Build date is Dec 91, sold date is June 92

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You can try it.

Jonnyb1990 said:

Hello,

Looking to decat my 3.9 (early K Reg)

Other than the pipes (that need a pair of nuts for the lambda sensors adding) and a resistor, do I need anything else ?

Keeping reading that a non cat Fuel module/ECU is needed.

Since they are as rare as rocking horse raisins, what do i need to do ?

Only looking to do it the once,

Click to expand...

I know I'm a bit late to this one but really why bother? you're not going to see any real difference in performance or economy.

FWIW, I'm guessing the ecu is a 14CUX so all you need to do is change the tune select resistor so the ECU will use a non-cat fuel map. Remove the cats from the exhaust, adjust the MAF and that should be about it. Whether or not that's legal for MOT type reasons I don't know, my '91RRC on a J is non-cat so an early K plate could be too I suppose??