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Discussion Starter #1
Hi there.

I discovered recently that there was a cat on the turbo downpipe on the diesel 159s (1.9 and 2.4).

There are a couple of reasons I'd like to remove mine. By the way, my car already has the dpf removed and a remap.

1) I love the turbo whistle that my old Saab 9-3 Tid used to have (same engine but no cats). I hope removing the catted downpipe on the 159 may give me that lovely sound...

2) A little less backpressure on the turbo may help spool up of the turbo.

3) There is no gas test on the diesel cars at the moment - just a smoke opacity test.

I looked for a replacement decat pipe and found one on Italian ebay. I've duly bid and won.

Now, before I pay, I just wonedered if anyone else had done this or know of any issues.

Many thanks
James
 

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i'd be wary with the new mot checks now in force, checks for a cat is now part of the test and will produce a fail if missing where originally installed when new.
 

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Discussion Starter #4 (Edited)
Cheers gents.

Thats a great thread of Clogz' - I've been reading it for the last half hour! Yes, gains looks very good with no issues reported so far on the AlfaTune ones. The one I've bought looks identical.

Yes, I've heard about the "fail if not installed if one was installed as new" but I also believe the examiner isn't allowed to remove covers/undertrays etc. Without removing the undertray noone is going to know. Also, I have an MOT tester where the original part is "fitted for the test and then removed again" if you make sure the original part is in the boot.

Honestly though, I have a hankering for a 2.4 after reading that thread of Clogz'

James

James
 

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I have been thinking about doing the same on my 1.9 as it made a big improvement doing the same to my 156 jtd, It is a popular mod on the vectra with the same engine, there are a few decat pipes available for them.
I was going to do the same as I did on my 156, buy a second hand cat and remove the insides rather than buying a pipe as I dont think there are mounting points for the heat shield on the replacement pipes.
 

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I have a 1.9 GT and have removed both the pre and main cats (it had no dpf).

I've just refitted my original exhaust as I'm selling the car, I haven't noticed any difference in performance from switching back to the standard exhaust. It's not quite as 'responsive' as it was with no cats and it certainly doesn't sound as good but the real world difference is pretty negligible tbh.
 

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I removed the cat on my 159 2.4.
The DPF is still in place.
Boost response improved.
Max boost actually rose a bit.
Fuel consumption improved marginally.
Regens take a lot les time than before.
 

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I removed the downpipe cat and the DPF and to my opinion it accelerates faster and i got 205km/H out of it instead of 190 stock and its not chiptuned yet but i did close of the egr with a steel plate behind the valve it gives the check engine light but it dousnt go in safe mode. il post some more info of my car later on om at work :D
 

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Discussion Starter #9
Thanks for the info gents.
Well its all bought and paid for now and will be with me in a few days.
It will be fitted along with a few new suspension parts when it goes into the local specialists.
I'll keep you updated with progress.

James
 

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Discussion Starter #14
Evening gents.

It hasn't arrived yet but I'll try and get it fitted as soon as I can after it gets here.

Looking at the pics I'd imagine its mild steel. That's perfectly fine for me as its pretty pointless having stainless so close to the engine. It'll always be the first part to get hot so not much chance of it getting full of condensation and rusting.

I believe you supply a pipe like this one Alfa Tuner. What performance gains (if any) do you notice once fitted? Also (most importantly!) does it give customers that turbo whistle back that I miss so much from other turbo cars?

James
 

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Discussion Starter #16
Well, my (front) cat replacement pipe was fitted today and I'm very pleased with the results.

No engine warning lights of any kind, very little extra exhaust noise, a nice little audible whistle from the turbo (very satisfying) and I think it pulls harder from even lower down the rev range that it did before.

All in all - very pleased!

James
 

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Good stuff Persky. are there any covers over the decat/dpf?

If not I think the only pain will be replacing it before MOT each time!

EDIT: Just checked the link, didn't realise this was the downpipe precat rather than the dpf/cat straight through pipe!
 

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Discussion Starter #18
Good stuff Persky. are there any covers over the decat/dpf?

If not I think the only pain will be replacing it before MOT each time!

EDIT: Just checked the link, didn't realise this was the downpipe precat rather than the dpf/cat straight through pipe!
Yes, its the downpipe cat rather than the combined cat/dpf under the car.

The more I drive it, the more impressed I am with it. The car seems to have lots more power than it did before. I'm 100% impressed - the car is now actually DAMN fast. Just wish I'd had a dyno power check before and after.

James
 

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Hi everyone!!
If i want remove the DPF and replace the original cat with a downpipe on my 159 1.9jtdm without increase HP with a ecu remap, it's better if i put a 200 cell sport catalyst?
 

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Can someone point me in the right direction to a de cat pipe as I’ve found two one by Autolusso and one by JTD performance thanks
 
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