[Saintor]

I experience unpleasing droning at mid-high rpm range when it is cold. When hot it is ok.

if you think that the performance exhaust is loud and has drone, sell your car and get a geo metro.

Please do better than this at your next "comment".

[Tee212]

Get a ride with someone with the same exhaust/engine set as you for a fair comparo. What might be annoying you is music to most of the youngins ears or old age is catching up. I tried all types of exhaust setups on 4bangers in my days. The PE on a 335i imo is just too loud for my taste. I enjoy hearing the engine spool and sing but on cold startup idle its embarrassing loud.

btw what you described above is typical of any larger free flowing exhaust.

[bavarian19]

Originally Posted by Delta0311

It's a simple bolt on installation. Doesn't require a BMW engineer to install this thing.

While it is not as simple as a bolt on, there is some cutting of the existing piping required at the right point. Maybe some of the cuts were done improperly.

[TheRox]

Originally Posted by Tee212

Get a ride with someone with the same exhaust/engine set as you for a fair comparo. What might be annoying you is music to most of the youngins ears or old age is catching up. I tried all types of exhaust setups on 4bangers in my days. The PE on a 335i imo is just too loud for my taste. I enjoy hearing the engine spool and sing but on cold startup idle its embarrassing loud.

btw what you described above is typical of any larger free flowing exhaust.

I'm mid-20's =) but also a human being, not one of those people who thinks every car should sound like a thunderclap -- no the sound of the exhaust is music to my ears; I LOVE the character, makes the car less clinical...and appeal to me emotionally.

I know its something about the installation, I need to get under the car:


to quote someone from another forum:

Originally Posted by Originally Posted by [url
http://www.montecarloss.com/SSThunder/engine.html][/url]

Drone in the exhaust is due to the engine driving the exhaust system at its resonant frequency. You can't get rid of it, any length of pipe has a natural frequency, but you can change the frequency (RPM) it happens at. Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose. To raise the resonant frequency of a system, shorten its length. To do this, you can try tail pipes that exit by the wheel (like GM's have), or you can try a muffler with a shorter internal flow path. If you have a true dual system, you can change the natural frequency of the system dramatically by adding a balance tube. If you can't shorten the system, then you can add slightly less than one wavelength of pipe. This will also raise the resonant frequency of the system. The wavelength in a single converter system (not true dual) is a little less than three feet at 3000 RPM. Shortening the system by a foot or so will move a resonance at 2000 RPM to about 3000 RPM.

To move a resonance, calculate the wavelength at the RPM that gives the resonance you want to move. Then calculate the wavelength at the RPM you would rather it be at. The difference is the length of pipe you need to add or delete. Add to lower the RPM, delete to raise it. If you want to raise it but you can't cut any pipe out, then add one wavelength of pipe minus the amount you calculated. This will have the same affect. If you add or subtract a multiple of a wavelength exactly, you will not change the resonant RPM.


Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2

or

Wavelength = 8250 / RPM

Wavelength = standing wavelength
1100 = speed of sound in air in feet per second
60 = convert RPM to Revs per second
RPM = RPM
1/4 = four cylender firings per revolution (make this 1/2 for "true dual")
1/2 = standing wavelength is half the wavelength of a "normal" wave

[mike-y]

you might want to also look into a hemholtz resonator. It's a small expansion chamber that branches off from the exhaust to cancel out natural resonant frequencies. They came on stock S2000s to cancel out drone at certain frequencies.

pics can be seen here. Also, in the link, there is a pic of a 335i or M3 exhaust with the hemholtz resonators from Active Autowerks.

http://www.pro-touring.com/showthrea...onance-exhaust

[topcat87]

what an informative thread.
therox i highly suspect that ur install is correct because most aftermarket systems will have some drone at 2-3000rpm.

intially i thought my exhaust was in contact with the body but it was not im gonna try this branch resonator

[FrankiE90]

if u think it's installation problems
go back to where u had it installed and do an inspection ur self.
- check out the mid section clamps (where the
resonators used to be). wiggle them see if they're bolt'd on tight.
- check out the clamp by the muffler.

worst come to worst - get ur OEM setup back on and drive and see if u
still get drone. just use the clamps from the PE.

and do u have a CAI?

[TheRox]

Originally Posted by topcat87

what an informative thread.
therox i highly suspect that ur install is correct because most aftermarket systems will have some drone at 2-3000rpm.

intially i thought my exhaust was in contact with the body but it was not im gonna try this branch resonator

Yea, I thought about this logic --- if it were drone due to installation, the symptoms would be total ==> I should hear drone at all rev ranges.

Because I only hear it from 2000-2800 rpm..I suspect its the resonant frequency of the pipe...from physics, I recall that at this frequency a pipe starts to vibrate.

So that hemholtz resonator would probably be the solution -- I just don't want to modify my PE at this point. I shall live with it, its not that bad I guess

[TheRox]

Originally Posted by FrankiE90

if u think it's installation problems
go back to where u had it installed and do an inspection ur self.
- check out the mid section clamps (where the
resonators used to be). wiggle them see if they're bolt'd on tight.
- check out the clamp by the muffler.

worst come to worst - get ur OEM setup back on and drive and see if u
still get drone. just use the clamps from the PE.

and do u have a CAI?

appreciate the advice, i'll try to see if its installation

I do not have any cold air intake, other htan the stock setup.

[philsteroni]

I would get your original resonator reinstalled.

[topcat87]

so did a frequency analysis hoping to identify the wavelength of the drone but it seems that my exhaust doesnt really drone it just super effing bassy a seen from the graph.
theres no evident peak just a smooth curve. i guess it just the characteristics of this exhaust

[twistedm3]

Police Chief Hubbard: Is this the gentleman who crashed through Victor Maitland's window? Who disabled an unmarked unit with a banana?

Detective Foster: Yeah, and we're not gonna fall for a banana in the tailpipe.

Axel Foley: [mocking him] You're not gonna fall for the banana in the tailpipe? It should be more natural, brother. It should flow out, like this - "Look, man, I ain't fallin' for no banana in my tailpipe!" See, that's more natural for us. You been hanging out with this dude too long.


Just a little Monday afternoon 'twisted' humor .. to offset the pain

[9378max]

any chance of posting sound clips for us to hear?

[B-737]

OP, when did you get your PE installed? how many miles are on it?

i totally understand where your coming from. I was so much on the fence about going back to stock i left my stock exhaust at the dealer for about 2 weeks while i was making up my mind. then it sat within arms reach in my garage until recently.

If you just hang in there, break it in, roughly 1000-1500 miles, you'll find things will really round out. In the beginning i found that it might have been just a little too loud when starting and raspy when accelerating from low RPM and low speeds. After 1500 miles thats all since gone away. Although my car never experienced any droning, i have found that when i fire it up its no longer too loud, and that overall its quieted down across the spectrum, while becoming a little deeper. no raspieness either.

There were friends (car enthusiast types) who saw my car frequently from when it had stock exhaust since it was new. i never told them about installing the PE, been driving the car around them since, and none of them has even made a remark that it has sounded any different thats the kind of subtle i was looking for.

Im not a very patient guy... but just hang in there for a little longer... you may find that it'll sort itself out. and all your remorse will go away

[TheRox]

FIXED IT!

Despite taking it back to dealership three times for this -- they said it was fine.

I hoisted the back up on rhino ramps...and checked the clamps -- I found the clamps behind the X-pipe to be far too close to each other, close enough that once the car was on, they were probably touching...causing the two pipes to vibrate.

I moved one clamp down, took some force...drove the car around the block and VOILA...very clean engine sound, no real drone that I can perceive.

will test it this weekend on a longer trip...but I am very happy now.

Gotta do it yourself to do it right!!!!

[new2the3]

Originally Posted by TheRox

FIXED IT!

Despite taking it back to dealership three times for this -- they said it was fine.

I hoisted the back up on rhino ramps...and checked the clamps -- I found the clamps behind the X-pipe to be far too close to each other, close enough that once the car was on, they were probably touching...causing the two pipes to vibrate.

I moved one clamp down, took some force...drove the car around the block and VOILA...very clean engine sound, no real drone that I can perceive.

will test it this weekend on a longer trip...but I am very happy now.

Gotta do it yourself to do it right!!!!

Glad you got it fixed, I knew that it was not installed properly. The BMW PE definitely does not drone, its an excellent sounding exhaust.

[TheRox]

Originally Posted by new2the3

Glad you got it fixed, I knew that it was not installed properly. The BMW PE definitely does not drone, its an excellent sounding exhaust.

THere isn't any drone anymore


But if I accelerate (ie. hit the throttle a bit) at 2000 rpm...there is a drone like low frequency purr

Not the nice higher frequency clean engine sound...but a burble...only if I hit the accelerator

is this drone or is this normal?

[E90-07]

It sounds normal when crusing on the highway as soon as i touch the gas you hear a small roar comming outta the back just loud enough to hear over the radio sometimes

[milly]

Im glad you got this figured out, lots of great information on drone in this thread

[Dark_Knight_335]

Originally Posted by TheRox

FIXED IT!

Despite taking it back to dealership three times for this -- they said it was fine.

I hoisted the back up on rhino ramps...and checked the clamps -- I found the clamps behind the X-pipe to be far too close to each other, close enough that once the car was on, they were probably touching...causing the two pipes to vibrate.

I moved one clamp down, took some force...drove the car around the block and VOILA...very clean engine sound, no real drone that I can perceive.

will test it this weekend on a longer trip...but I am very happy now.

Gotta do it yourself to do it right!!!!

Way to stay cool and figure it out. You are the man bro!