Cat Question, not the four leged furry type

[dean]

Hi all

I recently acquired a new down pipe that does not have a catalytic converter and was going to swap it onto my car when i eventually get round to doing the cylinder head. I have welded a union on to take the oxygen sensor, but i was looking at the cat from my donor car and it is empty?!?!?!?
I was under the impression that a catalytic converter had a honeycomb to increase the surface area and give a more complete chemical reaction. I wanted to remove my cat and fit this straight through pipe to overcome the restrictive nature of this honeycomb, but there doesn't seem to be any point if they are just an empty box!
Does this sound right or is something amis here, the cat from the donor is a genuine psa part and date stamped 92 which is the year the car was manufactured, so i would guess original.

Dean

[DerekW]

Hi Dean,

I'm sure you're right. I always understood the cat was based on a honeycomb coated with some exotic metal - platinum, osmium, germanium, geranium or something. Do you think it's possible that, in the interests of standardising the exhaust pipes, PSA might have used plain expansion boxes for markets that did not legally require a cat?

Was a cat a legal requirement in the UK in '92?

Derek

[dean]

Hi Derek

Yes, from 09/92 all cars sold in Britain had to have a cat, and the donor (identical to my car) had an oxygen sensor which are only fitted to cars with a cat?!?!?!?

[colinxm]

Hi Dean, a good trick is to bash out the honeycomb (it's quite brittle) to remove the restriction while still maintaining the pretence of a cat for the MOT man who'll be looking to see if there's one fitted - this may well be what a previous owner has done :-)

Regards Colin.P

[onthecut]

Hi Dean.

Odds on the honeycomb had collapsed, partially or completely blocking the exhaust and someone simply broke the rest and removed the remains. I don't think you will fool the MOT guy though --- the emissions kit will pick out the difference in the exhaust gases.

Mike.

[dean]

Hi all

My car doesn't have to have a cat because it was registered before 09/92 so i can remove it and it will not affect the mot at all, also because of its age the cars emissions are allowed to be at a slightly higher level than post 09/92 vehicles. As regards the honeycomb within the spare cat, i cannot see any rusted mountings within the housing, and it feels totally smooth inside, I'm sure you are right Mike but i couldn't see any evidence of anything being in there in he first place, which just got me wondering, because i have never actually taken the time to peer into a cat before.

Regards Dean

[DerekW]

Lucky you, Dean. You'll get more power and lower fuel consumption without a cat.

Derek

[dean]

Fingers crossed, and with valves that dont do their level best to eradicate any sign of compression (exaggeration) it should be like another car when its done

Dean

[Zaphod]

truth is many cars can pass the emissions test without a cat fitted at all. and its a falicy you need on fitted to the car to pass, as long as the emissions are within limits you will pass. my turbo CT is well within despite having no cat at all

[citroenxm]

Interesting post..

My 1990 H reg 24v V6 as you all know has 3 'cats'!!

When I get back round to restoring the car slightly, ie: replace manual box, weld sills at the rear, I have EVERY intention of removing ALL 3 'cats' as the exhaust needs attention before next mot, and seeing what results I get.. As its a 1990 theres no need for the cats to be there in the first place!

I guess in your case, Dean, the honey comb has been removed for better flow through of the exhaust gasses

Rgds
citroenxm