156 GTA Decat ?

Quick question

Does anyone know where i can buy a set of decat pipes for a 156 GTA?

Phil

Just go to your local custom exhaust place they could probably knock something up for not much cash.

Will a decat pipe increase the exhaust noise?

I suggest you get local exhuast shop to custom make a straight thru pipe instead knock the inside out. In case you don't like the sound and smell you can always go back. Yes it will increase noise.

Autodelta do them I think, at least they put some on my car.
Don't think they are on the website, maybe give them a buzz next week (I know Jano is on hols this week).


Don't know how much they were, in my case they were a FOC "sorry" for being late doing some work on my car.

They don't increase noise too much I think.
A little more noisey when cold perhaps.

Cheers,
TB

TB - did removing the cat give a worth while increase in power?

This was just a teeny part of a large set of changes so I can't tell in isolation their effect personally.

However I think I recollect Jano mentioning that it gave 11 lb/ft torque extra.
I think the car has to be remapped to gain the most of the decat, and also I believe the 11 lb/ft is in addition to whatever the remap itself would give without the decat.

Please take these figures with a pinch of salt since it was a long time ago and my memory may not be accurate

Cheers,
TB

Originally Posted by Pascs

TB - did removing the cat give a worth while increase in power?

Will the car go through the mot without the Cat pipe on?

no

So you would have to put the cat back on for the test, would a high flow sports cat be better?

Thanks for all the info lads...Very much appreciated...Will get a decat sorted for her and let you know how i get on..If i get a chance i will throw her on the rollers before and after...

Phil

Originally Posted by oldboy

So you would have to put the cat back on for the test, would a high flow sports cat be better?

yes and yes. I think the full supersprint system comes with those....

I think it depend on how many cats are disabled and wether the car was remapped appropriately.
My recollection is that there should still be 2 cats functional.

I was told by Autodelta that it would still pass the MOT, basically all they were doing was bringing things down from "Alfas corporate allotment of emmisions" to the minimum required to pass the test.
Basically a standard car straight from the factory will be way cleaner than actually required for the test.

I'll find out in about two weeks time for sure when I have my equivalent test which does give a full PPM emmisons readout.

Cheers,
TB

Originally Posted by oldboy

Will the car go through the mot without the Cat pipe on?

it has to have a cat visable as well as passing the emissions test

Originally Posted by ukoldschool

it has to have a cat visable as well as passing the emissions test

Sorry Ukoldschool, but the cat isn't a legel requirement in the UK at this moment in time. Neither is it a requirement at this moment in time in the UK to fulfill the homologation requirements for passing an MOT.

The MOT regulations only stipulate that your car passes the relevant cat test. Some cars between 1992 and 31st of July 1995 are cat test exempt, which will be shown when putting in the data in the new MOT system.

Still, it is in most of the cases not possible to pass emissions when removing the cats. Also, it has to be remembered when removing the cats the post lambda sensor needs to be disabled in the software.

Onr more problem might arise in the future quite frequently will be the road side emission test, which can be as expensive as inconvenient when found exceeding emission standards.

My 156 GTA has the full supersprint system fitted with cat by-pass and it passed it's first mot a few months ago

The supersprint system doesnt have a cat bypass - it has a high flow cat: http://www.supersprint.com/prodotti/753700.jpg

UK we may be talking about different cat components.
I don't know the full details of the cat layout in the GTA so apologies for the fuzzy wording of this post

I do still have a supersprint hi-flo cat on my car, I presume this is the primary cat.
The cat components that were disabled on my car were (I thought) earlier up the exhaust chain nearer the manifolds.

The GTA has either 3 or 4 cats I believe, I can't remember which.

It was other catalytic components than the main cat that was disabled in my case..

Cheers,
TB

Originally Posted by ukoldschool

The supersprint system doesnt have a cat bypass - it has a high flow cat: http://www.supersprint.com/prodotti/753700.jpg

That looks a lot different to mine, I only have twin exit

GTA - thats a 147 system its virtually the same as a 156 other than the backbox and a shorter and slightly different centre box.

Is there any other company than Supersprint that makes race cats for the GTA?

Probably not of any use but the supersprint cat itself is made by HJS Motorsport.

Best bet is to have some/one made up by a local exhaust shop as suggested

...or if you're feeling experimental... a simple Y-pipe, with a spacer attached to the post cat lambda using a spark plug arrestor(?) or similar to fool the ecu that the cat is in working order, something like these crazy folk do on vwvortex.


Back to the supersprint, tested mine just recently, with ss manifolds worth a good 5-10 lbft from 2500rpm to the redline and 8whp at the top end, more of a growl under load soundwise.

TB, do you get error messages now that you removed the cats on the manifolds?

I really cant recommend a cat bypass to anyone. Had one on my Elise, and although it improved the sound and used to make it pop and bang on the overrun, power increase was negligable, plus you had the hassle of having it refitted for MOT's...emissions used to go off the scale if it wasn't fitted.

Then there is the whole 'legality' issue. Its not illegal as such, but I'm pretty sure you'd have some issues with the insurer if you removed it, and if you had an accident I'm sure they'd try and use it as a reason to wiggle out of paying.

For £250, I'd get a sports cat/hiflow cat...so much easier.