I'm going to decat the car soon and was after help. Do I go custom straight through or get a S/S cat back off the shelf so to speak and put in decat down pipes. Also there is the query regarding back pressure problems that can be caused by decatting, anyone know more?

Apparently it can cause your seals in tub to blow as the position that the tub seals have been worn in will be changed as the pressure will change thus making them try to re-seat themselves on a new position..this is what may cause a failure.

 

Having said that...Im getting full de-cat fitted anyway as tubs will need doing oneday anyway...so its a good excuse if they go :)

 

Dont know anything about the catback systems :rolleyes:

 

This maybe of some interest on a similer subject:-

http://www.300zx.co.uk/forums/showthread.php?p=437917#post437917

I'm going to decat the car soon and was after help. Do I go custom straight through or get a S/S cat back off the shelf so to speak and put in decat down pipes. Also there is the query regarding back pressure problems that can be caused by decatting, anyone know more?

 

 

Keep your cat pipes and your cat back system separate. This gives you flexibility in the future may you require to repair or replace a section.

 

If your worried about the tubs seals then just add a cat back system for now and maybe a pair of cat pipes with built in "sports cats". Although these offer improved flow characteristics over standard cats, they also provide a certain degree of BP.

 

The BP vs Tubs seals theory is only really apparent with standard tubs/seals. If you have after market tubs then there is a good chance your seals have been upgraded.

just dug this up:

 

http://www.300zx.co.uk/forums/showthread.php?t=45053&highlight=generic

Max Power mentioned something about losing or gaining back pressure but I've left the mag at work so I'm not sure if it's the seals I'm concerned about. I will look tomorrow.

there is less restriction in the exhaust piping so you lose back pressure

Decat = Turbo seal failure - fact or fiction. ;)

 

Here u go : http://www.300zx.co.uk/forums/showthread.php?t=37089

Max Power mentioned something about losing or gaining back pressure but I've left the mag at work so I'm not sure if it's the seals I'm concerned about. I will look tomorrow.

 

If you have a TT you want as little backpressure as poss, no backpressure would be ideal. No restrictions = maximised gas flow = faster turbo spool

 

If you have an N/A then the correct amount of backpressure is essential, due to the exhaust gas scavenging effect. Removing all backpressure from an N/A would make it loud but the performance would more than likely be awful. We have spent a long time researching the characteristics of exhaust backpressure on the N/A recently, using an in house Dyno and many different pipe lengths. The results were very noticeable

 

The only reason to maintain backpressure on a TT is to protect the turbo oil seal. If you have a low mileage healthy engine then the chances are you will be ok de-catting. If you de-cat and the seals go, then they were on the way out anyway. Like anything on the Z its just a matter of time.

Okay then I have a 91 UK TT. Opinions please, should I or shouldn't go for a decat?

ive gat a 92 with 124k on the clock so maybe not a good idea ???? maybe it is i dunno but wanna do it

Okay then I have a 91 UK TT. Opinions please, should I or shouldn't go for a decat?

 

Ask yourself "why do you want to do it". Is it because you really need that extra 15-20hp, or is it because you can :D .

 

If you think that by gaining an extra 15-20hp will end up costing you £1-2k to fix then I think the decision is simple. You know your car better than anyone else, hence the choice is completely yours.

If it is more power you require, on a TT the above HP gains can be easily obtained by other means.

 

In short if you are uncertain then don’t do it, on the other hand removing the cats does provide a better driving experience.

Tricky one is'nt it :headvswal

I'm definitely going to get a S/S exhaust, possibly custom, and then I will get an induction kit at some point so may not need to risk decat.

So what exhaust would others recommend? I want some more noise and probably quad pipes but bigger than standard.