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06-26-2011, 01:56 PM | #1 |
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Anyone's N52 have secondary cats?
My understanding has been that the N51 has an extra pair of cats in addtion to the cats in the exhaust manifolds. It also is supposed to have lower compression and the two stage intake manifold to make up for any power loss from the extra cats and lowered compression.
The different exhausts can be seen in the attached images from real oem. I noticed my 128i has the secondary cats shown for the N51 but does not have the two stage intake. According to my VIN I'm supposed to have an N52 and the block is stamped N52B30 right next to the serial number. I'm curious to know who else has these extra cats on an N52. |
06-27-2011, 12:13 PM | #3 |
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My car is N51-equipped and it has the secondary cats under the car. It also has the 3-stage intake manifold, secondary air injection, and an ozone-fighting radiator coating, all of which help it achieve the SULEV II EPA rating. I can't verify the reduced compression ratio, but it's heavily rumored that the N51 does have a lower compression ratio than the comparable N52. I can tell you from personal experience piloting both engines that the N51 has a slightly but noticeably different power curve than a comparable N52.
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06-27-2011, 03:53 PM | #4 |
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I'm bummed that my car has the secondary cats but no 3-stage intake. My engine is clearly marked as an N52B30AE. Why would it have the extra cats?
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08-18-2011, 05:54 AM | #5 |
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This brings up questions
I also have a 2011 6MT sport pack
My exhaust system looks like the lower picture you posted. I saw in an earlier post that the n52 has ULEV and n51 has sulev II on the emissions sticker. Mine says ULEV II. I'm not too sure where the engine serial number is on my car, but I would guess I have the same setup you have. One question would be is it legal to eliminate one stage of a two stage system? Which one would you eliminate? How do I tell if I have a three stage intake? Last edited by rvsixdriver; 08-18-2011 at 10:43 PM.. |
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08-18-2011, 07:12 AM | #6 |
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According to the EPA's website, there are actually three versions of the 128i engine in the U.S.: Bin 5 N52 (Federal), ULEV II N52 (CARB), SULEV II N51 (CARB). This spans the entire E82 U.S. production (i.e., 2008-present). I'm guessing the CARB version of the N52 has the secondary cats and the Federal version does not.
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08-18-2011, 10:45 PM | #7 | |
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Last edited by rvsixdriver; 08-18-2011 at 11:26 PM.. |
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08-19-2011, 09:27 AM | #8 |
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Unless BMW made a change for the '11 model year, the U.S. N52-equipped 1-series does not have the 3-stage intake manifold.
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08-19-2011, 11:59 AM | #10 |
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cats or 3 stage manifold?
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08-21-2011, 05:42 PM | #13 |
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It might be that the cars with the secondary cats are SULE cars (ie CA specs). ?
The three stage intake manifold is also called: DISA. IF you google that you will find lots of info about how it works. BMW has used that DISA intake manifold on lots of other models as well. Some of the German tuners can reprogram the two stage intake (DISA too) to make a big Hp increase. Normally they can get around 275 PS with just a chip tune on a N52. |
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08-22-2011, 09:30 AM | #14 | |
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Last edited by AW128i; 08-22-2011 at 10:44 AM.. |
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08-22-2011, 10:23 AM | #15 | |
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Also.... I think all Military Car Sales (MCS) orders get the ULEV cars - incase a service memebr is from one of those states that require ULEV spec/cars. |
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11-25-2012, 11:56 PM | #16 |
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sorry to bump an old thread guys but I wanted to hear everyones opinion on this since I don't know.
My car, an N52, has the lower picture from above, meaning I have both primary and secondary cats. I live in Texas, which I'm not even sure is a carb compliant state or not. Anyways, I was wondering what happens if the secondary or primary cats are removed(pick one, not both). I read online that removing the first set would yield the biggest gains as they are the most restrictive, but would it cause a CEL to occur or something of that sort? Would I fail the emissions test? I read that removing the second set would yield little to no gain in power and just slightly increase the noise your car makes, and it also wouldn't produce any CEL or anything. Therefore, its not "worth it" to remove them, unless you want more sound. I was just curious because I was searching through the forums and found this. I always wondered why my car has two sets of CATS, and if removing one would be beneficial or not. Edit: Funny that my car has two cats and is considered ULEV-II.. it smells of gasoline when I turn on the car initially >_>
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11-26-2012, 07:01 PM | #17 | |
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11-26-2012, 07:10 PM | #18 | |
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EDIT: I have my old exhaust in the garage. the secondary cats are definately not there, so they are in the car to what I have
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Last edited by Greenkirby21; 11-26-2012 at 08:12 PM.. Reason: added images |
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11-26-2012, 09:01 PM | #19 |
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I stand corrected. I thought the mf went all the way to the manifold. But since you do have the mf it would be easy for a muffler shop to just cut them out and put strait pipe in line. As long as the downstream o2 sensor is before the secondary cats there would be no cel either.
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11-26-2012, 09:27 PM | #20 | |
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Here in Texas, my county requires yearly emissions test, but they are done via OBD-II port. I will probably pass by the dealership (if I can be sneaky) and see what their exhaust looks like underneath for the other 128i. If the other 128i on the dealership lot are missing these catalytic converters, then I will feel completely fine and should be able to remove them without any problems : ). I looked at our 2012 X3, and that also has secondary catalytic converters(bottom picture says its for ULEV2 vehicles) Wheras my moms car, a 2012 335i, has just the primary(but its an N55 and I think those come with a straight pipe since many people do N54 + N55 midpipes) i just find it funny that putting my vin on realOEM also shows I shouldn't have them
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Last edited by Greenkirby21; 11-26-2012 at 09:34 PM.. |
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11-27-2012, 01:08 PM | #21 |
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You should do us all a favor and get a dyno done before and after. I'd really like to know what gains can be had from removing those extra cats. Not that it would be the same on my N51 but it would still be nice to have real numbers.
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12-09-2012, 03:29 PM | #22 | |
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+9 HP and +3 Torque http://www.e90post.com/forums/showthread.php?t=703329
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