I have recently bought a new exhaust and am thinking about de-catting it.. I have heard a few people mention about problems with doing this as it affects turbo-spooling...

I'm guessing the standard exhaust has restricters in it and is all adjusted and set perfectly for the turbos.. so all I want to know is, how people get away with de-catting their twin turbo zeds, do they fit restricters in the de-cat pipes themselves to try and compensate? -

 

Also, the AIV system... what is that for?.. and do I need it?..

 

Cheers!

The cat its self is the retrictor, so to decat a car and then put a restrictor into the exhaust would simply make your cars emissions worse...

 

The issue with decatting these old cars is that the turbo seals will be failing with age and cats can go somewhere to holding the required backpressure in order to keep these seals intact to some extent. In reality the cat is masking a problem thats already there, but the cats mask the problem and limit its affect on the car. When decatting its often the case that these seals and you'll begin to experience smoking from the cars exhausts.

 

If i were you i wouldnt decat it (too many horror stories from people that have done it) unless you've got the funds to rebuild/replace the turbos should this problem become apparent.

 

If you do some searches on the forum you'll find other peoples experience with this issue.

decating is good performance wise,

 

i decated mine, not sure if i can notice a difference greatly,

 

maybe it does spool a bit sooner and is more responsive, but im not sure.

 

i think it might of bein all in my head, as i knew id freed up the exhaust system :D

 

 

if turbo seals are on their way out then its not really worth it,

 

on my S13 it smoked with a standard exhaust on boost, put a decat full system on and it literally poured out with smoke.

 

new turbo then, but on cars like that isnt too difficult to change. the Z is a different matter tho!

 

if you are sure your turbo is healthy go for it tho :)

its up to you but dont then do what i did and wind up the boost as well,as yourll be doing what ive spent the six months doing because i cant afford someoneesle to do it taking engine out to rebuild tubs

its up to you but dont then do what i did and wind up the boost as well,as yourll be doing what ive spent the six months doing because i cant afford someoneesle to do it taking engine out to rebuild tubs

 

why, was your fine/non smokey with them off?

 

but then very smokey on increased boost? on boost or on idle aswel?

I think there was a poll on here asking about smoking after a de cat, IIRC most owners did not get smoke after de catting.

yea if your cars healthy it should be fine,

 

if your decat and it smokes it just shows the cats were hiding the problem!

why, was your fine/non smokey with them off?

 

but then very smokey on increased boost? on boost or on idle aswel?

 

just the same ,but i think with the decat and the extra boost there then is a possible weak spot whitch i think in my case took the later .once rebuilt with better tubs im going to leave it set to 1.4bar

so, if the turbo seals go.. can't you just get better newer ones?.. and the moral of the story seems ot be.. the newer/less miles the car is/has.. then generally the better the condition of the turbos are.. which seems kinda obvious.. my car has done 38,000 miles.. i'm hoping it should be fine to de-cat it.. how much if it all goes t1ts up?