Cats - how restrictive are they?
08-22-2007, 04:44 PM
#76
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08-22-2007, 04:49 PM
#77
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08-22-2007, 04:53 PM
#78
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that is what I am thinking as well. Modding anything from the cats back I think we yield minimal performance enhancement.
My second dilemna is that I have renntech headers. Similiar to Evosport headers, these headers connect to the stock downpipes which is 47mm wide. These downpipes connect to the primary cats, and it isn't until after the primary cats that the piping expands to 70 or 74mm. Hence the bottleneck isnt just the primary cats. It is also the 47mm piping from my headers to the cats. How do I solve this issue without getting new headers?
My second dilemna is that I have renntech headers. Similiar to Evosport headers, these headers connect to the stock downpipes which is 47mm wide. These downpipes connect to the primary cats, and it isn't until after the primary cats that the piping expands to 70 or 74mm. Hence the bottleneck isnt just the primary cats. It is also the 47mm piping from my headers to the cats. How do I solve this issue without getting new headers?
08-22-2007, 05:16 PM
#79
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SLK55:63.5mm pipe X 2 = 2.5" X2
http://www.supersprintna.com/categor..._model%5D/302/
SLK350: 60mm pipe X 2 = 2.36"X 2
http://www.supersprintna.com/projects/mb_slk_350.php
I bought I believe it was 14 guage wire from Autozone to re-wire my O2's. Plus get some wire loom to protect it. Tape the wires as well and make sure you splice everything back correctly.
Last edited by ProjectC55; 08-22-2007 at 08:13 PM.
08-22-2007, 05:27 PM
#80
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I have two 2.5" cats. Replace your reso with an X-pipe. You can copy Supersprints pipe diameter and path for building your exh. See the one for the SLK350 they have it may very well be the same just a tad smaller in diameter.
SLK55:63.5mm pipe X 2 = 2.5" X2
http://www.supersprintna.com/categor...tegory_id/139/
SLK350: 60mm pipe X 2 = 2.36"X 2
http://www.supersprintna.com/projects/mb_slk_350.php
I bought I believe it was 14 guage wire from Autozone to re-wire my O2's. Plus get some wire loom to protect it. Tape the wires as well and make sure you splice everything back correctly.
SLK55:63.5mm pipe X 2 = 2.5" X2
http://www.supersprintna.com/categor...tegory_id/139/
SLK350: 60mm pipe X 2 = 2.36"X 2
http://www.supersprintna.com/projects/mb_slk_350.php
I bought I believe it was 14 guage wire from Autozone to re-wire my O2's. Plus get some wire loom to protect it. Tape the wires as well and make sure you splice everything back correctly.
Anything I should look out with? Such as disconnect battery when cutting the wires? etc...
Im going to have a shop do it for me, but just in case there are any special procedures that they need to know.
08-23-2007, 12:26 AM
#81
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2004 MB E55 AMG, 2006 Audi A6 4.2, 2008 WRX STI
08-23-2007, 07:10 AM
#82
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that is what I am thinking as well. Modding anything from the cats back I think we yield minimal performance enhancement.
My second dilemna is that I have renntech headers. Similiar to Evosport headers, these headers connect to the stock downpipes which is 47mm wide. These downpipes connect to the primary cats, and it isn't until after the primary cats that the piping expands to 70 or 74mm. Hence the bottleneck isnt just the primary cats. It is also the 47mm piping from my headers to the cats. How do I solve this issue without getting new headers?
My second dilemna is that I have renntech headers. Similiar to Evosport headers, these headers connect to the stock downpipes which is 47mm wide. These downpipes connect to the primary cats, and it isn't until after the primary cats that the piping expands to 70 or 74mm. Hence the bottleneck isnt just the primary cats. It is also the 47mm piping from my headers to the cats. How do I solve this issue without getting new headers?
Go to good exhaust shop...they wont have any probs with making for you nice connecting pipes instaed of Primary CATS...which go from headers to pipe directly with increasing diameter...
08-23-2007, 08:28 AM
#83
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With it open, I lost throttle response and low end torque. There was a slight hesitation. Top end 80mph+ I think I gained some power.
With it closed I felt like it was faster only till about 80mph or so. You could definitely feel the increase in torque.
For sound you can't beat it. For performance, I'd stay away.
Remember, the exhaust is still going to flow through the full system, just some of it will come out the open valve. Also note that I had this mounted where the resonator would be (after the cats and before the muffler). Mercedes and the muffler shop both said I would get a CEL light if I did it pre-cat.
Prior to this, I had an Eisenmann Race muffler. Believe it or not, I could definitely feel the gains from that thing. And I mean both low end torque and top end hp. It was just too loud for every day use and neighbors wanted to kill me lol.
I think the only thing you can do Frank, is to just try out all the different combinations and dyno your car each time. It looks like we're divided on whether primary cats, secondary cats, resonators, mufflers, and manifolds should all be removed/replaced
...
Last edited by ItalianStallion; 08-23-2007 at 08:31 AM.
08-23-2007, 08:59 AM
#84
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This is my final answer.. 
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
08-23-2007, 09:04 AM
#85
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This is my final answer..
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
08-23-2007, 10:57 AM
#86
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Are you still gonna take out the resonators? I tihkn I want to do that ASAP, just afraid of the added noise level. I know my resonator weighs a decent amount. Let us know your dyno reults.
08-23-2007, 11:16 AM
#87
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08-23-2007, 11:24 AM
#88
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This is my final answer..
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
Kleemann headers with Kleemann downpipes that have Cats built into them.
Spoke to Brandon yesterday and it seems that they now sell their headers with racing 200 cell cats in the downpipes. No CEL problems and no OBDII fault concerns. He told me that having downpipes without cats vs with is probably worth 5-7rwhp. Not worth the headache or anxiety of if you ask me.
Its your money my friend...I wouldnt go that route...
You wont gain much...just replace your primaries with 200cell cats and that it...
08-23-2007, 11:25 AM
#89
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01-27-2008, 09:21 PM
#90
There seemed to be a lot of people interested in removing their primary CATs. Did anyone get it done? Some people talked about 200 cell...who sells this and how hard or easy is this type of job for a qualified exhaust shop?
Sorry if the thread answered these questions already.
Sorry if the thread answered these questions already.
03-01-2008, 01:29 PM
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