Regarding N55 stock exhaust & post cats.

prima_materia · 03-14-2017, 06:02 PM

Quick question. I've seen on numerous threads where people mentioned having resonators and/or post cats on their N55 335i? I'm confused on this because while some claimed this, others claimed the opposite? Just confused, because when I installed my catless DP and looked over the exhaust I never noticed resonators/ post cats.

Also, in the Bentley manual under the exhaust section for the N55 I don't see anything in the descriptions or diagrams for resonators or post cats? I noticed post cats and resonators on the N51, N52, N52KP and N54 though.

Apologies if this has been covered, but like I said - both parties were claiming opposites, so that's mainly why I'm asking.

Even though I was under the car I can't remember, so that's partially why I'm asking also.

Cheers

Kevin39 · 03-14-2017, 08:16 PM

Hmm, I was under the impression that only the Rwd n55s didn't have secondary cats. Mine doesn't. But I thought the xdrives still did. Maybe someone else can chime in.

Redfire03 · 03-14-2017, 09:47 PM

Above is correct based on my understanding.

2wd = no secondary cats
AWD = secondary cats

I have an x drive and removed my secondary cats.

prima_materia · 03-15-2017, 03:16 AM

Hmm, see this is odd, because I have an 11' xDrive and I don't think I have secondary cats. I have access to a garage, I'll get it on the lift here in a couple days, genuinely curious.

I could easily be wrong, but it's been bugging me lol.

prima_materia · 03-15-2017, 07:49 AM

I stand corrected, looked under the car and it does indeed have post cats. :P

STR8-6IX · 03-15-2017, 07:02 PM

Quote:

Originally Posted by Kevin39

Hmm, I was under the impression that only the Rwd n55s didn't have secondary cats. Mine doesn't. But I thought the xdrives still did. Maybe someone else can chime in.

Quote:

Originally Posted by Redfire03

Above is correct based on my understanding.

2wd = no secondary cats
AWD = secondary cats

I have an x drive and removed my secondary cats.

Quote:

Originally Posted by PrimaMateria

Hmm, see this is odd, because I have an 11' xDrive and I don't think I have secondary cats. I have access to a garage, I'll get it on the lift here in a couple days, genuinely curious.

I could easily be wrong, but it's been bugging me lol.

all e90's have secondary cats. my N52 equipped f10 has them (i removed them

)

ANMVQ · 03-15-2017, 07:09 PM

Does removing the sendanry cats do anything other then change tone? And emissions? Being MA I don't need any headaches

DrRobert · 03-15-2017, 11:24 PM

Not sure how the x-drives are configured, but I know that in my 2011 E90 335i the OEM downpipe contains two cats in series. In other words, I think the primary and secondary cats are both in the DP.

prima_materia · 03-16-2017, 03:24 AM

Quote:

Originally Posted by DrRobert

Not sure how the x-drives are configured, but I know that in my 2011 E90 335i the OEM downpipe contains two cats in series. In other words, I think the primary and secondary cats are both in the DP.

Yeah, for my XDrive, right after the downpipe, not much farther after down the way there's two post cats.

EB89 · 03-16-2017, 05:22 AM

Quote:

Originally Posted by STR8-6IX

all e90's have secondary cats. my N52 equipped f10 has them (i removed them

)

This is not true, N55 RWD does not have cats in the mid pipe

All N54 cars and N55 X Drive have mid pipe cats.

Kevin39 · 03-16-2017, 06:32 AM

^Yep.

Quoted text is incorrect.

Quote:

Originally Posted by STR8-6IX

all e90's have secondary cats. my N52 equipped f10 has them (i removed them

)

DrRobert · 03-16-2017, 01:32 PM

Quote:

Originally Posted by STR8-6IX

all e90's have secondary cats. my N52 equipped f10 has them (i removed them

)

Quote:

Originally Posted by EB89

This is not true, N55 RWD does not have cats in the mid pipe

All N54 cars and N55 X Drive have mid pipe cats.

You are both correct. Like I said above, N55 RWD does have secondary cats, they are in the downpipe after the primary cat with an O2 sensor in between them.

STR8-6IX · 03-16-2017, 01:36 PM

Quote:

Originally Posted by DrRobert

You are both correct. Like I said above, N55 RWD does have secondary cats, they are in the downpipe after the primary cat with an O2 sensor in between them.

im confused here.. why didnt they all just get secondary cats after the o2 sensor? if anything, wouldnt the x drive version have secondaries inside the downpipe due to fitment issues with the xdrive?

however, I know that the f10 an f30 do not have secondaries (they are probably in the downpipe) but rather, a resonator and muffler. what is this for, cost cutting? better airflow?

my 2011 528i with the n52 has an exhaust system exactly like the e90 328i. I deleted my secondary cats and installed a magnaflow muffler. very happy with the sound.

DrRobert · 03-16-2017, 01:42 PM

no idea. I just know this because I had both cats removed from my DP and had a HJS high flow cat retrofitted into it. There are definitely 2 cats in the 2011 E90 RWD DP (and the same DP is used for the 135i too). I have pics if you don't believe me.

9krpmrx8 · 03-16-2017, 01:46 PM

DrRobert · 03-16-2017, 01:54 PM

Quote:

Originally Posted by 9krpmrx8

Perfect. The hole in the middle of the stock DP on the left (just below the bracket) is for the O2 sensor. There is one cat in the top half and another in the bottom half inside the cylindrical part of the DP, on either side of the O2 sensor.

DrRobert · 03-16-2017, 02:22 PM

OK, here is the DP from my 2011 335i:

Cat #1:

Cat #2:

Kevin39 · 03-16-2017, 06:53 PM

Here's the secondaries I'm talking about. Mine doesn't have that. I wouldnt consider the downpipe as two separate cats either.

prima_materia · 03-16-2017, 07:00 PM

Quote:

Originally Posted by Kevin39

Here's the secondaries I'm talking about. Mine doesn't have that. I wouldnt consider the downpipe as two separate cats either.

Yup ,that's exactly how my setup is for my 11' xDrive.

And yeah, when I think of the stock dp I don't think of it being '2 cats'.

EB89 · 03-22-2017, 07:35 AM

Why would anyone think of the downpipe as two cats in a N55?

DrRobert · 03-22-2017, 08:03 AM

Quote:

Originally Posted by EB89

Why would anyone think of the downpipe as two cats in a N55?

Because it has two cats in it.

prima_materia · 03-22-2017, 08:03 AM

Quote:

Originally Posted by EB89

Why would anyone think of the downpipe as two cats in a N55?

Lol, exactly.

03-14-2017, 06:02 PM	#1
prima_materia Private First Class 58 Rep 165 Posts Drives: 11' BMW 335i Sedan XDrive LCI Join Date: Jan 2016 Location: Ohio iTrader: (0)	Regarding N55 stock exhaust & post cats. Quick question. I've seen on numerous threads where people mentioned having resonators and/or post cats on their N55 335i? I'm confused on this because while some claimed this, others claimed the opposite? Just confused, because when I installed my catless DP and looked over the exhaust I never noticed resonators/ post cats. Also, in the Bentley manual under the exhaust section for the N55 I don't see anything in the descriptions or diagrams for resonators or post cats? I noticed post cats and resonators on the N51, N52, N52KP and N54 though. Apologies if this has been covered, but like I said - both parties were claiming opposites, so that's mainly why I'm asking. Even though I was under the car I can't remember, so that's partially why I'm asking also. Cheers Attached Images __________________ JB4 ISO Map 7 @ 20psi, MHD/BMS e85 BEF, ISO_14 Firmware, xHP Stage 3 TCU Flash, Flex Fuel Adapter, Rev3 Connect-Kit, 50% e85 mix/93 octane, K&N drop-in filter, ER Chargepipe, JB4 CAN-flap disabled, VRSF Catless DP, VRSF 7in. FMIC, Last edited by prima_materia; 03-23-2017 at 03:44 AM..
	Appreciate 0 Tweet Quote

03-14-2017, 08:16 PM	#2
Kevin39 Lieutenant 164 Rep 411 Posts Drives: 2011 E90 N55 Join Date: Feb 2016 Location: Indiana iTrader: (0)	Hmm, I was under the impression that only the Rwd n55s didn't have secondary cats. Mine doesn't. But I thought the xdrives still did. Maybe someone else can chime in. __________________ E90 N55 RWD 6MT MHD Speedtech EFR7670 MFactory LSD
	Appreciate 1 GripAndRip83.50 Quote

03-14-2017, 09:47 PM	#3
Redfire03 Enlisted Member 10 Rep 46 Posts Drives: 2011 335I Xdrive M-Sport Join Date: Jun 2015 Location: Denver iTrader: (0)	Above is correct based on my understanding. 2wd = no secondary cats AWD = secondary cats I have an x drive and removed my secondary cats.
	Appreciate 1 GripAndRip83.50 Quote

03-15-2017, 03:16 AM	#4
prima_materia Private First Class 58 Rep 165 Posts Drives: 11' BMW 335i Sedan XDrive LCI Join Date: Jan 2016 Location: Ohio iTrader: (0)	Hmm, see this is odd, because I have an 11' xDrive and I don't think I have secondary cats. I have access to a garage, I'll get it on the lift here in a couple days, genuinely curious. I could easily be wrong, but it's been bugging me lol. __________________ JB4 ISO Map 7 @ 20psi, MHD/BMS e85 BEF, ISO_14 Firmware, xHP Stage 3 TCU Flash, Flex Fuel Adapter, Rev3 Connect-Kit, 50% e85 mix/93 octane, K&N drop-in filter, ER Chargepipe, JB4 CAN-flap disabled, VRSF Catless DP, VRSF 7in. FMIC, Last edited by prima_materia; 03-15-2017 at 03:26 AM..
	Appreciate 0 Quote

03-15-2017, 07:49 AM	#5
prima_materia Private First Class 58 Rep 165 Posts Drives: 11' BMW 335i Sedan XDrive LCI Join Date: Jan 2016 Location: Ohio iTrader: (0)	I stand corrected, looked under the car and it does indeed have post cats. :P
	Appreciate 0 Quote

03-15-2017, 07:09 PM	#7
ANMVQ Lieutenant 114 Rep 399 Posts Drives: 2011 335XI Sedan Join Date: Sep 2015 Location: Work :) iTrader: (0)	Does removing the sendanry cats do anything other then change tone? And emissions? Being MA I don't need any headaches
	Appreciate 0 Quote

03-15-2017, 11:24 PM	#8
DrRobert Normal Person 148 Rep 862 Posts Drives: 2011 E90 335i Join Date: May 2014 Location: paradise iTrader: (0) Garage List 2011 E90 335i [0.00]	Not sure how the x-drives are configured, but I know that in my 2011 E90 335i the OEM downpipe contains two cats in series. In other words, I think the primary and secondary cats are both in the DP.
	Appreciate 0 Quote

03-16-2017, 01:42 PM	#14
DrRobert Normal Person 148 Rep 862 Posts Drives: 2011 E90 335i Join Date: May 2014 Location: paradise iTrader: (0) Garage List 2011 E90 335i [0.00]	no idea. I just know this because I had both cats removed from my DP and had a HJS high flow cat retrofitted into it. There are definitely 2 cats in the 2011 E90 RWD DP (and the same DP is used for the 135i too). I have pics if you don't believe me.
	Appreciate 0 Quote

03-16-2017, 01:46 PM	#15
9krpmrx8 Clean is the new cool, keep it that way. 808 Rep 1,685 Posts Drives: 11' Alpine White 335i Sedan Join Date: Jan 2016 Location: San Antonio, Texas iTrader: (0)
	Appreciate 0 Quote

03-16-2017, 02:22 PM	#17
DrRobert Normal Person 148 Rep 862 Posts Drives: 2011 E90 335i Join Date: May 2014 Location: paradise iTrader: (0) Garage List 2011 E90 335i [0.00]	OK, here is the DP from my 2011 335i: Cat #1: Cat #2: Last edited by DrRobert; 03-17-2017 at 11:05 PM..
	Appreciate 0 Quote

03-16-2017, 06:53 PM	#18
Kevin39 Lieutenant 164 Rep 411 Posts Drives: 2011 E90 N55 Join Date: Feb 2016 Location: Indiana iTrader: (0)	Here's the secondaries I'm talking about. Mine doesn't have that. I wouldnt consider the downpipe as two separate cats either.
	Appreciate 0 Quote

03-22-2017, 07:35 AM	#20
EB89 Brigadier General 541 Rep 3,131 Posts Drives: 2011 335i e92 DCT Join Date: Sep 2015 Location: Australia, NSW iTrader: (0) Garage List 2011 BMW 335i e92 [0.00]	Why would anyone think of the downpipe as two cats in a N55?
	Appreciate 0 Quote