Why does my SV6 have 4 catalytic convertors> are they all neccesary? Power robbing?

[mike249cc]

while underneath my car i noticed it has 4 cats.
2 up front near pedals which a a trapezium shape
2 near the middle before it joins to the rear exahsut with are smaller!
are theya ll neccesiarly?
can some be removed if so what are the consequences?
thanks

[Dz811]

are they all necessary? NO

is it legal to take them out? NO

could you get rid of the ones near the middle because there's no oxygen sensor after them without damaging anything or throwing error codes??... yes, yes you could...

[NickVR]

They were put there in the late VZ models to meet the Euro 4 emissions from memory.

Yes it would be illegal to remove them.

[mike249cc]

how much louder would it be to remove the rear ones, ? what performance/ sound differenece would i notice?

[acarmody]

You will notice the sound of about a $10,000 fine being sent in the mail too you. And it gain you performance from your legs as you learn to peddle or walk everywhere.

[VKCOMMO]

You will notice the sound of about a $10,000 fine being sent in the mail too you. And it gain you performance from your legs as you learn to peddle or walk everywhere.

Thats about the full & correct answer

[db_notso]

lol pretty sure the REAR ones are just hotdogs not cats only the fronts are honeycomb and you will only get find if over 110decibels (i think may have changed too 95db's)
i am 90% sure of this as recently replaced a system and the exhaust guy said they were dogs only
question is was he upselling or is it true?

nope just checked my "info"
is stainless shell
three way monolith type
cat material extruded cordierite
one per bank so 2

[mike249cc]

so db_notso are u saying that the front ones are cats and the rear ones which dont have any sensors following them are just resonance chambers?

[db_notso]

from my manuals (gregory)
modded ones i get normall have two cats where front ones are and nothing whgere doggies are and are really noisy!~

could always just ask an exhaust shop over the phone they would know without having to look down the pipe or trust people you dont know on the internet (i know piece of mind counts these days )

[Not_An_Abba_Fan]

The cats are the larger ones up near the manifolds, the ones under the car are just resonators.

[mike249cc]

so with this new knowledge what does everyone think it will sound like with out the reear resonace chambers

[VzVzVz]

Taking cats out is really not a good idea. I've had a mate who got his car inspected by the highway patrol. They jacked the car up and used a lazer thermometer to check for a difference in temp between the cats and the pipes. It's pretty serious.

I've contemplated it, but not worth it. My dads old Porsche used to have no cats, but that thing was very rarely driven on the road.

[mike249cc]

i thought we just establish that the chambers toward the middle of the car with no sensors after them were not cats?

[Not_An_Abba_Fan]

Removing the RESONATORS will give the car a raspy ricey sort of note. Especially if you have a 2 1/2" single exhaust system.

[soop]

Will sound like utter shit.
If you could make it sound good for nothing, Big brands would be out of business.

[db_notso]

checked with the raptor vz guys today the rear ones are deffinatle not catylic converters
qouted him below
"they have an outer honeycomb design in them to allow you to have sufficient backpreasure so catylic converters can heat up they do rob power but not much at all
when removed the exhaust drones save your money for a catback and better more flowing rear muffler and if possible full sytem for performance"

[mike249cc]

i have a 2 1/2 inch twin cat back. what would it sound/ go like with it off?

[db_notso]

well an exhaust (or intake) is only as free flowing as its smallest point
i just save up and get full sytems my last 2 cars

[mike249cc]

yea i am keen on extractors very wsoon, what would you guys reccomend for value for money?