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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Fri, Nov-10-2017, 09:38:55 PM   #31
terraphantm
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

I wish I still had my US headers to take a direct measurement now. Maybe I am mistaken.

Also for whatever it's worth, this is a 620 vs 200 cell. 400 should be in between I suppose



Edit: This one is apparently 400 cell, which to my eye looks noticeable more dense than the US one in that other thread. But I admit the Euro one in that thread also looks even less dense

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Old Sun, Nov-12-2017, 01:30:43 PM   #32
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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Originally Posted by terraphantm View Post
I wish I still had my US headers to take a direct measurement now. Maybe I am mistaken.

Also for whatever it's worth, this is a 620 vs 200 cell. 400 should be in between I suppose



Edit: This one is apparently 400 cell, which to my eye looks noticeable more dense than the US one in that other thread. But I admit the Euro one in that thread also looks even less dense

Yea I was going to say in those awe pics above the 200 cell cats do not looo lik the 200 cell cats in the other thread. The 400 cell cat pic def looks less dense then the 600 cell pic above

So are you thinking that the USA cats have a higher cell count then the euro ones?
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Old Sun, Nov-12-2017, 01:36:06 PM   #33
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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I would not assume the change in placement is trivial without proof.



Losses scale up.



Terra says he has compared them IRL.
Well I would assume placing a restrictive cat near the collector in the header was the leading cause to the power reduction from the euro to USA m3


Regarding the scaling question my question is really do to the different size in the cats. If the USA cats have a higher cell count but have a shorter body then the euro cats with a lower cell count but a longer body. Will that really effect the restriction in exhaust flow since the exhaust is traveling through a shorter body but with a higher cell count?
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Old Sun, Nov-12-2017, 04:10:38 PM   #34
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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Regarding the scaling question my question is really do to the different size in the cats. If the USA cats have a higher cell count but have a shorter body then the euro cats with a lower cell count but a longer body. Will that really effect the restriction in exhaust flow since the exhaust is traveling through a shorter body but with a higher cell count?
Maybe. Assuming 200cpi vs. 400cpi, a square inch of 200cpi = 14.14 cells x 14.14 cells, and a square inch of 400cpi = 20 cells x 20 cells. The 200cpi (assuming square cells, which they are not in reality) cells have 0.0707" sides, while the 400cpi's cells have 0.05" sides. 0.0707" per side * 4 sides * 200 cells = 56.56 in^2 of surface area per square inch of cross-section that is in contact with the exhaust flow per unit length along the body. 0.05" per side * 4 sides * 400 cells = 80 in^2. Assuming the per unit length loss coefficient is the same for the two different cells, the 200 cpi would have lower losses than the 400 cpi as long as it's less than 80/56 = 1.43 times longer.

You'd also have to look at the losses associated with transitioning the freestream exhaust into and out of the cells. I think it's logical to assume that higher cell density = higher losses, but I'm not sure of any sensible way to compare without learning those loss coefficients through experiment. That's not all of the variables, but probably two of the biggest assuming same placement of the cat.

Last edited by m3 hal; Sun, Nov-12-2017 at 05:27:45 PM.
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Old Sun, Nov-12-2017, 05:01:24 PM   #35
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

We are never going to know lol. Every one f these threads goes the same way. For piece of mind I'm just getting 200 cells and welding them into the section 1. Done.
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Old Sun, Nov-12-2017, 09:51:56 PM   #36
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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In fact, the only reason BMW put the cats near the engine in the first place was to meet CA emissions standards.
fwiw, euro cats always passed the sniffer tests when CA smog checks still required them for this platform
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Old Sun, Nov-12-2017, 10:38:08 PM   #37
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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fwiw, euro cats always passed the sniffer tests when CA smog checks still required them for this platform
That's different than cold start emissions requirements for manufacturers.
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Old Sun, Nov-12-2017, 11:35:50 PM   #38
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

Is there a way of cleaning older cats?


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Old Sun, Nov-12-2017, 11:42:42 PM   #39
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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That's different than cold start emissions requirements for manufacturers.
yes even with a functioning SAP there's a noticeable smell during cold startup with euro cats that you don't get with usdm headers
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Old Mon, Nov-13-2017, 03:07:21 AM   #40
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Default Re: OEM cats vs Euro Cats vs CSL Cats vs ALL other cats

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yes even with a functioning SAP there's a noticeable smell during cold startup with euro cats that you don't get with usdm headers


Is there, really? I never smelled/noticed a difference.


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Discussing OEM cats vs Euro Cats vs CSL Cats vs ALL other cats in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)