335is with Catted Downpipes Sounds Raspy Above 5K RPM

mawzi · 10-17-2018, 01:30 PM

I installed Cobb catted downpipes on my 335is. It sounds great at low rpms and idle, but quickly turns into Civic-like coffee grinder sound at high rpm.

Anyone has dealt with this problem?

Will replacing the secondary cats with resonators fix my problem?

Jeff@TopGearSolutions · 10-17-2018, 01:39 PM

Technically secondary cats already smooth out sound. It may be your axle back actually causing the rasp? Some noises are inherently unavoidable as characteristics of the engine.

Post a vid.

hellokitty · 10-18-2018, 03:30 AM

See my posts here...

https://www.e90post.com/forums/showthread.php?t=1544141

mawzi · 10-18-2018, 08:20 AM

Quote:

Originally Posted by hellokitty

See my posts here...

https://www.e90post.com/forums/showthread.php?t=1544141

Ya, I was reading this thread. Why did you replace the x pipe though?

hellokitty · 10-18-2018, 09:20 AM

Quote:

Originally Posted by mawzi

Quote:

Originally Posted by hellokitty

See my posts here...

https://www.e90post.com/forums/showthread.php?t=1544141

Ya, I was reading this thread. Why did you replace the x pipe though?

I read that the MF xpipe sounds better than the factory one. Here it is installed. It adds more dimension to the sound especially at the lower rpm range (2-4K rpm)

mawzi · 10-18-2018, 09:24 AM

Quote:

Originally Posted by hellokitty

I read that the MF xpipe sounds better than the factory one. Here it is installed. It adds more dimension to the sound especially at the lower rpm range (2-4K rpm)

Thank you!

mweisdorfer · 10-19-2018, 03:24 PM

Quote:

Originally Posted by mawzi

I installed Cobb catted downpipes on my 335is. It sounds great at low rpms and idle, but quickly turns into Civic-like coffee grinder sound at high rpm.

Anyone has dealt with this problem?

Will replacing the secondary cats with resonators fix my problem?

Yep, replace the secondary cats with 1792 Vibrant Resonators

You will virtually eliminate rasp & drone

mweisdorfer · 10-19-2018, 03:36 PM

Quote:

Originally Posted by mawzi

Quote:

Originally Posted by hellokitty

I read that the MF xpipe sounds better than the factory one. Here it is installed. It adds more dimension to the sound especially at the lower rpm range (2-4K rpm)

Thank you!

Make sure to get a 2.5" X pipe. Magma Flow is good X-pipe.

mawzi · 10-20-2018, 01:10 AM

Quote:

Originally Posted by Jeff@TopGearSolutions

Technically secondary cats already smooth out sound. It may be your axle back actually causing the rasp? Some noises are inherently unavoidable as characteristics of the engine.

Post a vid.

Hard to hear in the video but listen between 4.5K and 6K

hellokitty · 10-20-2018, 01:17 AM

Quote:

Originally Posted by mawzi

Quote:

Originally Posted by Jeff@TopGearSolutions

Technically secondary cats already smooth out sound. It may be your axle back actually causing the rasp? Some noises are inherently unavoidable as characteristics of the engine.

Post a vid.

Hard to hear in the video but listen between 4.5K and 6K

This sound will be completely eliminated with the vibrant 1792 resonators in place of the secondary cats. I used to have the same rasp.

mawzi · 10-20-2018, 01:18 AM

Quote:

Originally Posted by hellokitty

This sound will be completely eliminated with the vibrant 1792 resonators in place of the secondary cats. I used to have the same rasp.

That's great to hear. They're on their way!

b92 · 10-22-2018, 12:01 PM

Quote:

Originally Posted by hellokitty

This sound will be completely eliminated with the vibrant 1792 resonators in place of the secondary cats. I used to have the same rasp.

The sound would get louder and the fumes would smell worse, no?

hellokitty · 10-22-2018, 11:58 PM

Quote:

Originally Posted by b92

Quote:

Originally Posted by hellokitty

This sound will be completely eliminated with the vibrant 1792 resonators in place of the secondary cats. I used to have the same rasp.

The sound would get louder and the fumes would smell worse, no?

Correct to both

mawzi · 10-23-2018, 07:27 PM

Unfortunately, installing the 1792 resonators in place of secondary cats only reduced the rasp by about 30%.

It introduced a couple of new problems though:
-Exhaust smell
-Weird vibrating noise at the end of every rev.

Not sure if things will change after the car is tuned. It's still stock. Gotta wait till next summer.

Before (Only Cobb Catted):

After (Cobb Catted + 1792):

hellokitty · 10-23-2018, 10:07 PM

Quote:

Originally Posted by mawzi

Unfortunately, installing the 1792 resonators in place of secondary cats only reduced the rasp by about 30%.

It introduced a couple of new problems though:
-Exhaust smell
-Weird vibrating noise at the end of every rev.

Not sure if things will change after the car is tuned. It's still stock. Gotta wait till next summer.

Before (Only Cobb Catted):

After (Cobb Catted + 1792):

Do you have the golf tee mod done? Could it be the exhaust valve that's rattling?

mawzi · 10-23-2018, 10:32 PM

Quote:

Originally Posted by hellokitty

Do you have the golf tee mod done? Could it be the exhaust valve that's rattling?

It's not the valve. I tried with and without the T mod. Similar sound.

hellokitty · 10-23-2018, 10:35 PM

Quote:

Originally Posted by mawzi

Quote:

Originally Posted by hellokitty

Do you have the golf tee mod done? Could it be the exhaust valve that's rattling?

It's not the valve. I tried with and without the T mod. Similar sound.

When are you getting the rasp? I did some pills this evening and my setup (which is the same as yours except I'm catless with the MF xpipe) has absolutely no rasp. :/

mawzi · 10-23-2018, 11:10 PM

Quote:

Originally Posted by hellokitty

When are you getting the rasp? I did some pills this evening and my setup (which is the same as yours except I'm catless with the MF xpipe) has absolutely no rasp. :/

The rasp is around 5K when you floor it on 1st gear. Do you have an automatic?

hellokitty · 10-24-2018, 01:14 AM

Quote:

Originally Posted by mawzi

Quote:

Originally Posted by hellokitty

When are you getting the rasp? I did some pills this evening and my setup (which is the same as yours except I'm catless with the MF xpipe) has absolutely no rasp. :/

The rasp is around 5K when you floor it on 1st gear. Do you have an automatic?

I did the same pull as you did just now and don't have the same rasp in 1st gear. I have a DCT...

b92 · 10-24-2018, 10:55 AM

It's gotta be with our iS mufflers, it's such a common problem with downpipes on our platform and the mufflers are really the only difference.

mawzi · 10-24-2018, 03:34 PM

It's really stinky now. Thinking about putting the secondary cats back in, and try to find a location for vibrant resonators after.

mweisdorfer · 10-24-2018, 04:29 PM

Quote:

Originally Posted by mawzi

It's really stinky now. Thinking about putting the secondary cats back in, and try to find a location for vibrant resonators after.

I don't think the resonators are installed right. I think you have a leak in the weld(s)

10-17-2018, 01:30 PM	#1
mawzi Private First Class 20 Rep 183 Posts Drives: 2012 335is MT Join Date: Mar 2018 Location: Toronto iTrader: (0)	335is with Catted Downpipes Sounds Raspy Above 5K RPM I installed Cobb catted downpipes on my 335is. It sounds great at low rpms and idle, but quickly turns into Civic-like coffee grinder sound at high rpm. Anyone has dealt with this problem? Will replacing the secondary cats with resonators fix my problem?
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10-17-2018, 01:39 PM	#2
Jeff@TopGearSolutions 3441 Rep 79,212 Posts Drives: C6 Z06, 09 335i, 10 335xi Join Date: Dec 2008 Location: www.TopGearSolutions.com iTrader: (37)	Technically secondary cats already smooth out sound. It may be your axle back actually causing the rasp? Some noises are inherently unavoidable as characteristics of the engine. Post a vid.
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10-18-2018, 03:30 AM	#3
hellokitty Brigadier General 2894 Rep 3,726 Posts Drives: '17 M3 ZCP DCT Join Date: Jul 2010 Location: Southern California iTrader: (2)	See my posts here... https://www.e90post.com/forums/showthread.php?t=1544141
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10-23-2018, 07:27 PM	#14
mawzi Private First Class 20 Rep 183 Posts Drives: 2012 335is MT Join Date: Mar 2018 Location: Toronto iTrader: (0)	Unfortunately, installing the 1792 resonators in place of secondary cats only reduced the rasp by about 30%. It introduced a couple of new problems though: -Exhaust smell -Weird vibrating noise at the end of every rev. Not sure if things will change after the car is tuned. It's still stock. Gotta wait till next summer. Before (Only Cobb Catted): After (Cobb Catted + 1792): Last edited by mawzi; 10-23-2018 at 07:53 PM..
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10-24-2018, 10:55 AM	#20
b92 Major 540 Rep 1,040 Posts Drives: E92 335is, 6MT Join Date: Feb 2016 Location: Rhode Island iTrader: (2)	It's gotta be with our iS mufflers, it's such a common problem with downpipes on our platform and the mufflers are really the only difference. __________________ 2011 E92 335is, Space Grey/Coral Red, 6MT. RB 2+, Wedge tuned. E85 PI coming soon.
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10-24-2018, 03:34 PM	#21
mawzi Private First Class 20 Rep 183 Posts Drives: 2012 335is MT Join Date: Mar 2018 Location: Toronto iTrader: (0)	It's really stinky now. Thinking about putting the secondary cats back in, and try to find a location for vibrant resonators after.
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