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      12-15-2011, 01:18 AM   #23
mrow
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Quote:
Originally Posted by smug01 View Post
The secondary cats are required to keep the vehicle emissions in check while the diagnostic is run on the rear O2 sensor. This is required each drive cycle, where the ECU modifies the fuel air mixture into a region that makes the primary cats less effective in reducing emissions. I believe this revised diagnostic was implemented in 2010 regulations.

Once the diagnostic is complete, the primary cats are sufficient to meet emissions. Since this diagnostic will likely complete within the first few minutes of a drive cycle, you should have no problem passing a smog check, based on emissions measured.
My understanding is there is no O2 sensor past the first set of cats.
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      12-15-2011, 02:16 AM   #24
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Correct. The rear O2 sensor I was referring to is the one right downstream of the primary cat. It is the one that needs the diagnostic...which causes emissions breakthrough of the primary cat.
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      12-15-2011, 02:23 AM   #25
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This means that the secondary cat is only necessary to contain emissions for a very short duration during each drive cycle.

So yes, removing it will increase emissions a small amount for a short period of time, but this will not be detectable with a sniff emissions test (since the test is on a warm engine after the diagnostic would have completed).

It is still, technically illegal to remove the secondary cats for on road use, per the letter of the law.
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      12-22-2011, 08:58 PM   #26
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Any videos yet?!
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      12-22-2011, 09:20 PM   #27
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Car came today so I will have vids tommorrow.
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      12-23-2011, 05:31 PM   #28
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Sorry, snowed today and mid-pipe was supposed to be delivered this afternoon. No vids yet.
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      12-27-2011, 04:36 PM   #29
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N55 Midpipe

I swapped my stock midpipe out for a N55 midpipe today. Sounds a little louder.

The N54 midpipe has a couple of nasty bends in it compared to the N55.







Bought the midpipe from a member here.

Randy
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      12-27-2011, 07:37 PM   #30
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I swapped in the factory N55 midpipe yesterday. Going slow (with not infrequent beer breaks), it was an easy 2-hour job.

If you do it, I'd suggest that you also replace the two gaskets that fit between the midpipe and the downpipes.

Neil
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      12-27-2011, 09:22 PM   #31
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Quote:
Originally Posted by MDORPHN View Post
I swapped in the factory N55 midpipe yesterday. Going slow (with not infrequent beer breaks), it was an easy 2-hour job.

If you do it, I'd suggest that you also replace the two gaskets that fit between the midpipe and the downpipes.

Neil
Neil- whats your take on the N55 mid-pipe. I'm torn between the N55 pipe and the Maddad pipes. I'm afraid I'm not going to notice any difference with the N55 pipe - at the same time, I'm concerned that if I go with the Maddad pipes, when I eventually go with downpipes, it might be too loud of a setup.
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      12-27-2011, 09:32 PM   #32
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Have only done one short, rainy commute since installing the midpipe, and didn't notice any significant change in the exhaust note. I will, however, be taking longer drive tomorrow and will post up my impressions.

FWIW, I'm as interested in gaining some cheap horses as I am in improving the sounds.

Neil
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      12-27-2011, 09:43 PM   #33
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Quote:
Originally Posted by MDORPHN View Post
If you do it, I'd suggest that you also replace the two gaskets that fit between the midpipe and the downpipes.

Neil
definitely second this. I did the midpipe (Berk) swap at 3500miles and the gaskets was already falling apart.
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      12-27-2011, 09:45 PM   #34
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Quote:
Originally Posted by MDORPHN View Post
Have only done one short, rainy commute since installing the midpipe, and didn't notice any significant change in the exhaust note. I will, however, be taking longer drive tomorrow and will post up my impressions.

FWIW, I'm as interested in gaining some cheap horses as I am in improving the sounds.

Neil
Thanks for your input- I think I'm going to give the N55 pipes a shot, considering how cheap they are, its not like I have much to lose. Ordering some Akrapovic downpipes tomorrow and my Cobb AP should be here tomorrow as well. Hopefully will gain some low end torque with the AP. When it gets a little warmer outside, I'll do the Helix IC.

Joe
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      12-28-2011, 04:06 AM   #35
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Besides sound does it bring more torque/hp better spoolup etc?
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      12-28-2011, 08:27 AM   #36
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Quote:
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Besides sound does it bring more torque/hp better spoolup etc?
Hard to tell by seat of the pants. I had offered my car to Cobb to develop the AP tune, but due to my hectic work schedule they ended up using other member's cars so we never got to compare the before and after numbers from swapping the midpipe. It has to be a little less restrictive with no secondary cats but how much gain only the dyno knows.
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      12-28-2011, 08:49 PM   #37
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I just finished the install in about 50 minutes ( jack stands and on my back). It feels lighter as it should without two cats gone. I purchased at Tischer BMW - best price.
From a startup and quick rev you get a little more bite (backfire type sound) as rpm's decrease but I can't tell any major difference at idle and on the upswing of the rpm.
I'll be driving it hard tommorrow and will update my post. I expect it to have a nice affect at speed.
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      12-29-2011, 10:46 AM   #38
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Quote:
Originally Posted by Oaktree View Post
I just finished the install in about 50 minutes ( jack stands and on my back). It feels lighter as it should without two cats gone. I purchased at Tischer BMW - best price.
From a startup and quick rev you get a little more bite (backfire type sound) as rpm's decrease but I can't tell any major difference at idle and on the upswing of the rpm.
I'll be driving it hard tommorrow and will update my post. I expect it to have a nice affect at speed.
OK, acceleration sound is much better with the N55 - no doubt. Much meaner, angrier and it now starts to overwhelm the intake and drivetrain sounds. I'm not hearing a major difference in rasp or backfire type sounds on deceleration...thatís ok though since acceleration finally has the bite I wanted. You do get a little burping on deceleration. Does it spool faster? I think so but itís hard to say, it feels like it pulls faster and revís stronger. Drone, both my wife and I thought it decreased at 65mph but the Magnaflow seems to have its own character and decides to drone when it wants too. TBD but it would be great if this was a potential solve.
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      01-03-2012, 08:13 PM   #39
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Quote:
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So adding 2ndry cats to the N55 can't be a good thing?
N55 doesn't need to secondary cats, that engine burns much cleaner than the N54.
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      01-11-2012, 04:52 PM   #40
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How much did you guys pay for those midpipes?

Thank you
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      01-11-2012, 05:12 PM   #41
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Quote:
Originally Posted by Franklin Joseph View Post
definitely second this. I did the midpipe (Berk) swap at 3500miles and the gaskets was already falling apart.
We have done at a handful of R&R to try different mid pipes and exhaust, but still on the same oem gaskets.
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      01-12-2012, 09:02 AM   #42
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Quote:
Originally Posted by EINSER M View Post
yesterday took out the midpipes from the 2012 135 and swapped with the 1M. no change for the 135 but a good amount of pop and rumble for the 1M with the N55 pipes! perfect remove and bolt swap too.
highly recommended simple mod to the OEM exhaust setup!
Now combine with the Y-pipe (resonator delete) from the BMW Performance Exhaust for the ultimate smorgasbord of BMW exhausts. ;-) No, probably that would be too much. And require cutting. But just a thought.
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