My cats are gonna be history, just as soon as the new front pipes turn up. What happens with the O2 sensors ? Just disconnect ? Fit them into the new pipes ?

 

The O2 sensors are on the pre-cats (or downpipes, depending on year).. I seem to remember yuo saying you didn't have pre-cats..

 

Either way the answers the same - leave where they are (or if you're replacing the precats/DPs, put them into the new ones)...

 

The car wont run (very well!) without O2 sensors

 

Az

 

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Stage: Rather Ill

You will have temp sensors on the cats which just need disconnecting though. And some sort of pipe that blows fresh air over the cats to clean out i think. Just disconnect and remove these aswell but dont block ends.

AIV valves - big pipe going into the back of the CAT...

 

You can actually remove the solenoids, reed assembly and all pipework if you like.. (they're just a PITA anyway, and with no CAT,s have nothing to do! Might as well eliminate a bit of troublesome vacuum hosing)..

 

The EGT's, I thought they were on the precats?

 

Az

Right really thick person here. What do I need to do to get rid of my cats? Is it easy, that do I need and where can I get it from?

I have a 1991 UK TT, with a Mongoose exhaust.

 

Stuart

Woop woop, really thick person alert

Only kiddin' Stuart...

 

You need, basically, a set of pipes to replace the CAT's (available from.. Well at a guess, Johnny, amongst others)..

 

The only complication on the Z is that the CATs have AIV inlets into them -, no problem really, just remove the AIV system is the best thing to do (it's a pile o' crap anyway, Nissan got rid on 93/94 onwards)..

 

And the EGT (Exhaust Gas Temp) sensors.. Not too sure what you do with these I have a feeling the ECU monitors them, could be wrong though and dont have the wiring diagrams with me...

 

Az

 

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Stage: Rather Ill

i know this information can probably be found easily elsewhere, but since we're on the subject...

 

what's the latest year that you can legally remove the cats from your car? and what kind of performance increase (or decrease even) can you expect?

If it's a UK car and it was supplied with Cats then you can't legally remove them - period.

 

If it's an import which is not explicitly listed in MOT testers book (i.e. a grey import as opposed to a parallel import, I'd guess) then they should perform a non-cat emissions test.

 

Whether it's legal to remove a cat from a car in the UK is unclear, but my guess is that it's not legal. Although it is possible to buy a car imported from Japan that does not have a cat and that will pass the import test (MOT), but probably not the SVA if it's a more recent model.

 

 

Clear as mud ....

I'd always heard that the law was if it was manufactured before '92, you could remove the CAT's no problem (UK or not), but if manufactured after '92, and originally had CAT's, then they have to be present..

 

However, my 1994 CAT-less Renault just passed an MOT with flying colours Just have to know the right tester.....

 

Az

I have read in my local MOT centre that you can remove the CATS off your car if it is pre K reg (1993) If the original spec had CATS K reg or after, they must remain on. I have asked this when I got my MOT and there where posters about on the wall of the MOT centre

 

Stuart.

Hmmm, I thought that cats were more,should we say 'optional' before a certain year (say '92) and after that all cars sold in the UK were fitted with them. But my understanding was that if the car came fitted with them then they may not be removed.

Zeds don't have EGTs They do have O2(lambda) sensors though - these are straight after the turbo on the exhaust where it bends down to go under the car - if you look down the back of the engine you can see them sticking up. As far as I know they are on the turbo extension pipe - not the exhaust so shouldn't be a problem. AIV hoses - remove them like Az says

 

CheerZ,

 

Andy

So what are the two little steel braided hoses/wires connected to the cats ? Are they the cat temp sensors ?

The hoses that run along side the exhaust are the AIV hoses. They are about 1 and a half inches thick if that helps.... They basically dilute the exhaust with fresh air to reduce the emissions.

 

CheerZ,

 

Andy

Hate to argue, but my Z (Jap TT) DID have EGT's. Its a late 92 - also has no AIV valves etc.

 

When I made the cat bypass pipes, I just made a new flange for the sensors and put them back in. Seems that you can get away by just disconnecting them, but I wasn't sure at the time. If you decide to keep them, you'll need an M12*1.25 tap to thread the holes, and they're a bugger to get hold of.

Well I love to argue :d bring it on baby

 

If you had EGTs they had been added afterwards - the only temp sensing that is done on a standard car oin the exhaust is the cat overheat warning......

 

CheerZ,

 

Andy

300 zx does not have EGT'S as standard, never has never will