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diverzeusy
Hockenheim


Joined: 10 Nov 2012
Posts: 714
Location: Doncaster UK


PostPosted: Tue Apr 18, 2017 5:49 pm    Post subject: Reply with quote

Of interest to me too, any more info on this one anyone may have, has I'm embarking on a Kline exhaust, it came with 200 cell and bypass pipes but do not know which to fit?
My two major concerns being noise and MOT passing 😁
All this to install after the Dinslaken jaunt Thumb
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Demort
Sepang


Joined: 21 Mar 2015
Posts: 2932
Location: Sussex


PostPosted: Tue Apr 18, 2017 7:20 pm    Post subject: Reply with quote

My limited experience of 200 cell cats is they will pass an mot if hot enough and no running faults .. 100 cell and no .. not the ones i have seen which to be fair isnt many !
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996ttalot
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Joined: 21 Sep 2009
Posts: 1212
Location: Horley Gatwick


PostPosted: Tue Apr 18, 2017 8:18 pm    Post subject: Reply with quote

diverzeusy wrote:
Of interest to me too, any more info on this one anyone may have, has I'm embarking on a Kline exhaust, it came with 200 cell and bypass pipes but do not know which to fit?
My two major concerns being noise and MOT passing 😁
All this to install after the Dinslaken jaunt Thumb


What model car?
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Drew1209
Trainee


Joined: 31 Aug 2016
Posts: 65



PostPosted: Tue Apr 18, 2017 8:47 pm    Post subject: Reply with quote

My car a 99 C4 3.4, one of the early egas cars.

As commented on above, I'd also like to thank everyone for there input especially PPBB very informative.
 
  
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diverzeusy
Hockenheim


Joined: 10 Nov 2012
Posts: 714
Location: Doncaster UK


PostPosted: Wed Apr 19, 2017 12:11 am    Post subject: Reply with quote

996ttalot wrote:
diverzeusy wrote:
Of interest to me too, any more info on this one anyone may have, has I'm embarking on a Kline exhaust, it came with 200 cell and bypass pipes but do not know which to fit?
My two major concerns being noise and MOT passing 😁
All this to install after the Dinslaken jaunt Thumb


What model car?

Hi My car is 996 turbo 2000
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Wed Apr 19, 2017 8:24 am    Post subject: Reply with quote

I thought I might chime in to give a little more info for early 3.4 NA owners. As has already been mentioned, there is no such thing as a requirement for backpressure. If you look at motorsports where there is no noise restriction, such as drag racing, frequently open stubs are used because these offer the least resistance (the least backpressure if you will). The thing with exhausts on four stroke engines is that they need to be designed to give the greatest exhaust velocity. The faster you can get the exhaust gasses out of the engine, the more power you will make.

In order to achieve this an exhaust needs to be designed with a diameter that is sympathetic to the volume of gas produced. If the bore is too big then you will actually slow down the gasses in much the same way that a river slows down when it widens. Obviously, at different revs then engine produces different volumes of gas, so the ideal exhaust would vary in diameter in line with revs. Until this fantasy pipe is invented we need to settle on a compromise diameter of pipe.

If you are going catless, you will see bigger gains than going with 200 cell cats all across the rev range. This is not just because the cat matrix isn't in the way, but also because the bulb in the exhaust that holds the cat takes energy (velocity) out of the gas by slowing it down where it widens at the start of the cat and then another restriction is faced at the other side of the cat where it tapers back to the normal exhaust diameter.

To get maximum power out of a 996 NA exhaust, the mufflers would also be changed to something that used a straight through design, such as the After Hours one:
https://www.6speedonline.com/forums/automotive-parts-accessories-sale-wanted/232933-996-after-hours-sport-exhaust.html

The only problem with this is the very tight radius of the bend between the mufflers. Although the design is much less restrictive than the normal 996 muffler, more power could be released by increasing that radius.

I'm currently toying with getting something made in the after hours style, but replacing the first muffler with a 200 cell cat, and running the manifold direct to the cat & muffler on it's own side. If I can get the radius of the bends in the exhaust large enough (basically 6" or greater) then I could lose a collossal amount of weight from the rear of the car, and gain somewhere in the region of 15-20 hp.

As regards lamda sensors, I strongly advise you run them. Without the fine tuning of the mixture that they provide you may have trouble with rough running. I'm speaking from recent personal experience with my early 3.4 car here. Even with a decat pipe, I would still keep the lamda sensors. With one of my lamda sensors out of action recently, the bank it was on failed the emissions test for the MOT, and the car only passed because the tester then tested the bank with the working lamda sensor.
 
  
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Wed Apr 19, 2017 8:26 am    Post subject: Reply with quote

Also, if you decide to install decat pipes and intend to put in the cats for the MOT, make sure you use all stainless nuts & bolts. This will preserve your sanity when you come to swap them around.
 
  
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Harv
Suzuka


Joined: 18 Sep 2014
Posts: 1001



PostPosted: Wed Apr 19, 2017 3:18 pm    Post subject: Reply with quote

What a great thread this has turned into.

I really like the idea of the after hours system, especially from a weight reduction aspect.

For the later cars with post cat 02 sensors then a pair of these will be required unless you have their function coded out.

http://m.ebay.co.uk/itm/Lambda-O2-Oxygen-Sensor-Extender-Spacer-for-Decat-Hydrogen-M18-x-D4-hole-STEEL-/201887030200?hash=item2f01679bb8%3Ag%3AGqEAAOSwt7pXOKVC&_trkparms=pageci%253A45c665ca-250a-11e7-a95d-74dbd18058fc%257Cparentrq%253A868f01f815b0a7854ed88dc4fff36f51%257Ciid%253A3
 
  
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Martin996RSR
Trainee


Joined: 08 Dec 2016
Posts: 81



PostPosted: Wed Apr 19, 2017 3:46 pm    Post subject: Reply with quote

The After Hours mufflers are much louder than the stock ones, so that's something to bear in mind. Also, I reckon that you wouldn't see much change from £1200 if you bought & imported them, whereas I think you could probably get a pair made for about £500 at a custom exhaust fabricators in the UK.
 
  
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Demort
Sepang


Joined: 21 Mar 2015
Posts: 2932
Location: Sussex


PostPosted: Wed Apr 19, 2017 7:44 pm    Post subject: Reply with quote

I was told about lambda sensors with mini cats or a work around for a de cat with post cat lambda sensors fitted ..

Either search lambda sensor with mini cat or a link i found about it here ..

No idear if it works or not but its just a thought to stop an eml light.

http://www.redlineperformance.co.nz/products/exhaust/o2-oxygen-sensor-spacer/o2-oxygen-sensor-spacer-with-mini-cat/

EDIT ..

Pretty much what Harv said Embarassed
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996ttalot
Approved Trader


Joined: 21 Sep 2009
Posts: 1212
Location: Horley Gatwick


PostPosted: Wed Apr 19, 2017 8:24 pm    Post subject: Reply with quote

diverzeusy wrote:
996ttalot wrote:
diverzeusy wrote:
Of interest to me too, any more info on this one anyone may have, has I'm embarking on a Kline exhaust, it came with 200 cell and bypass pipes but do not know which to fit?
My two major concerns being noise and MOT passing 😁
All this to install after the Dinslaken jaunt Thumb


What model car?

Hi My car is 996 turbo 2000
The problem with the decat is not passing on lamba etc, but on CO normally. I would make the assumption it will fail the MOT although we have got them through with tuning.

If you want the best performance then decat is the solution, then 100 cell and then 200 cell. I am sure Felix will swop out the 200 cell cats for you.

As to CEL, decat or 100 cell will needing coding in the DME.

As to noise, the best sound is from decat, then 100 cell, then 200 cell etc. The noise level will rise with decat being the loudest, but to be clear, the noise level with the Kline is very consistent until you are on boost regardless of decat, 100 or 200 cell.

Ken
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996ttalot
Approved Trader


Joined: 21 Sep 2009
Posts: 1212
Location: Horley Gatwick


PostPosted: Wed Apr 19, 2017 8:26 pm    Post subject: Reply with quote

Martin996RSR wrote:
I thought I might chime in to give a little more info for early 3.4 NA owners. As has already been mentioned, there is no such thing as a requirement for backpressure. If you look at motorsports where there is no noise restriction, such as drag racing, frequently open stubs are used because these offer the least resistance (the least backpressure if you will). The thing with exhausts on four stroke engines is that they need to be designed to give the greatest exhaust velocity. The faster you can get the exhaust gasses out of the engine, the more power you will make.

In order to achieve this an exhaust needs to be designed with a diameter that is sympathetic to the volume of gas produced. If the bore is too big then you will actually slow down the gasses in much the same way that a river slows down when it widens. Obviously, at different revs then engine produces different volumes of gas, so the ideal exhaust would vary in diameter in line with revs. Until this fantasy pipe is invented we need to settle on a compromise diameter of pipe.

If you are going catless, you will see bigger gains than going with 200 cell cats all across the rev range. This is not just because the cat matrix isn't in the way, but also because the bulb in the exhaust that holds the cat takes energy (velocity) out of the gas by slowing it down where it widens at the start of the cat and then another restriction is faced at the other side of the cat where it tapers back to the normal exhaust diameter.

To get maximum power out of a 996 NA exhaust, the mufflers would also be changed to something that used a straight through design, such as the After Hours one:
https://www.6speedonline.com/forums/automotive-parts-accessories-sale-wanted/232933-996-after-hours-sport-exhaust.html

The only problem with this is the very tight radius of the bend between the mufflers. Although the design is much less restrictive than the normal 996 muffler, more power could be released by increasing that radius.

I'm currently toying with getting something made in the after hours style, but replacing the first muffler with a 200 cell cat, and running the manifold direct to the cat & muffler on it's own side. If I can get the radius of the bends in the exhaust large enough (basically 6" or greater) then I could lose a collossal amount of weight from the rear of the car, and gain somewhere in the region of 15-20 hp.

As regards lamda sensors, I strongly advise you run them. Without the fine tuning of the mixture that they provide you may have trouble with rough running. I'm speaking from recent personal experience with my early 3.4 car here. Even with a decat pipe, I would still keep the lamda sensors. With one of my lamda sensors out of action recently, the bank it was on failed the emissions test for the MOT, and the car only passed because the tester then tested the bank with the working lamda sensor.


Nice post Thumb
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Phil 997
Yas Marina


Joined: 05 Dec 2015
Posts: 8501
Location: Bournemouth,Dorset

2009 Porsche 997 Carrera 4S

PostPosted: Wed Apr 19, 2017 8:33 pm    Post subject: Reply with quote

996ttalot wrote:
diverzeusy wrote:
996ttalot wrote:
diverzeusy wrote:
Of interest to me too, any more info on this one anyone may have, has I'm embarking on a Kline exhaust, it came with 200 cell and bypass pipes but do not know which to fit?
My two major concerns being noise and MOT passing 😁
All this to install after the Dinslaken jaunt Thumb


What model car?

Hi My car is 996 turbo 2000
The problem with the decat is not passing on lamba etc, but on CO normally. I would make the assumption it will fail the MOT although we have got them through with tuning.

If you want the best performance then decat is the solution, then 100 cell and then 200 cell. I am sure Felix will swop out the 200 cell cats for you.

As to CEL, decat or 100 cell will needing coding in the DME.

As to noise, the best sound is from decat, then 100 cell, then 200 cell etc. The noise level will rise with decat being the loudest, but to be clear, the noise level with the Kline is very consistent until you are on boost regardless of decat, 100 or 200 cell.

Ken


Ken great input thank you Thumb I often wondered about this and what would happen if I changed out my 200cell big bore for the same but 100cell and what extra BHP etc .mine is a 997.1
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Locosaki
Silverstone


Joined: 03 Jul 2016
Posts: 131
Location: Fife


PostPosted: Thu Jun 15, 2017 8:24 pm    Post subject: Reply with quote

Drew, did you ever get round to this ?

I'm on standard boxes also and was wondering if there is any gain in fitting 200cell cats and keeping standard boxes ?
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