THE LARGEST BMW 2-SERIES FORUM ON THE PLANET
| 10-24-2017, 10:34 AM | #177 | ||
1004
Rep 1,653
Posts |
Quote:
 Quote:
  |
||
|
Appreciate
0
|
| 11-07-2017, 02:57 PM | #179 |
|
New Member
5
Rep 12
Posts
Drives: 2016 235i RWD Coupe
Join Date: Sep 2017
Location: Central Florida
|
Any Black Friday special deals coming?
Interested in mid pipe + muffler delete with the carbon fiber tips. RWD, M-Performance diffuser. Shipped to 33811
__________________
 |
|
Appreciate
0
|
| 11-07-2017, 03:04 PM | #180 | |
|
1004
Rep 1,653
Posts |
Quote:
|
|
|
Appreciate
0
|
| 12-15-2017, 04:42 PM | #182 |
|
Private First Class
 52
Rep 109
Posts |
Hello,
i'm running the Fabspeed Sport Cat Downpipe + Resonator delete + Muffler delete and i have vibrations inside cabin between 1500 and 2000 / 2200 RPMs especially in Comfort mode. I installed myself all the parts and everything is properly in place, no metal to metal contact, all the line is " free in the space ", all the heat protections have been removed to let the maximum space. These vibrations are very annoying especially on long ride, it resonates on the cabin and i can feel them on my seat. It's not droning because the droning appears between 2500 and 3500 RPMs and i can perfectly feel the difference between the drone and the vibrations. The vibrations seem to result of low frequencies. All the bottom of the trunk is fully covered with Focal BAM system to avoid vibrations but anyway, still vibrating. Does someone get this kind of situation ? Thank you very much. |
|
Appreciate
0
|
| 12-15-2017, 07:18 PM | #183 | |
|
Lieutenant Colonel
 
1165
Rep 1,931
Posts |
Quote:
Yes, we all do. After 2 years, i finally took it off for a tuningwerks muffler, so much happier. no more annoying drone at all. Still pops and bangs, but is much more neighborhood friendly. If anyone wants a like brand new fabspeed muffler delete with new clamp, PM me or check the classifieds. $500 for pickup or $600 shipped.
__________________
www.nybmwcca.org
Current Cars: 1995 M3 Coupe Manual Alpine White 1997 M3 Sedan Auto Cosmo Black Metallic 2018 x3 m40 Auto Grey Metallic |
|
|
Appreciate
0
|
| 12-16-2017, 05:27 AM | #184 |
|
Private First Class
52
Rep 109
Posts |
" Unfortunately " i have also planed to replace the muffler bypass by a normal muffler ... because everyday driving is sometimes giving me the migraine.
But i'm a little bit frustrated because the sound generates by the muffler bypass especialy on high RPMs is exceptional. Somebody at a workshop near where i'm located told me that a resonator on the midpipe could stop the vibrations at low RPMs and solve this problem and so could make possible to keep the muffler bypass. What do you think about that ? |
|
Appreciate
0
|
| 12-20-2017, 10:18 AM | #185 |
|
1004
Rep 1,653
Posts |
Other than the muffler bypass what else are you running? Adding a resonator might help but it might also talk away the 'exceptional" sound at the higher end RPM's as well.
|
|
Appreciate
0
|
| 12-20-2017, 01:19 PM | #186 | |
|
Private First Class
52
Rep 109
Posts |
Quote:
I think the resonator will retain the low frequencies which generate drone at the low RPMs but not so much in the higher end RPMs ( because frequencies at these high RPMs are different and the resonator should not retain the typical higher frequencies which generates the exeptional sound ) Last edited by Bibopp; 12-20-2017 at 01:30 PM.. |
|
|
Appreciate
0
|
| 12-21-2017, 11:27 AM | #188 | |
|
Private First Class
52
Rep 109
Posts |
Quote:
|
|
|
Appreciate
0
|
| 12-22-2017, 02:14 PM | #189 |
|
Major General
 5543
Rep 5,366
Posts |
People often fail to understand the R&D extent automakers go to reduce drone and general NVH all the while trying to deliver a sporty, smooth sound in the performance models. The public and many aftermarket parts companies often assume that because an OEM part visually looks restrictive then it must be. They rarely do any testing to prove their theory. Automakers rarely leave power on the table when it comes to intakes and exhausts. The most restrictive part on a turbo BMW exhaust is the catted DP. Everything else is more than up to the task to handle hundreds more HP without much restriction.
When you start removing resonators and mufflers and adding light thin-walled tubing, you'll certainly introduce more drone potential. Automatics are especially effected by this because they spend far more time laboring along the lower rpm ranges where drone is prevalent. Adding exhaust noise is almost always a compromise when it comes to NVH. With that said, I'm surprised that so few BMW aftermarket companies don't employee Helmholtz resonators to reduce drone on their high flow exhaust systems. It can really, but again, most companies don't have the staff and resources to understand where to place the Helmholtz resonators and size them correctly. They're more into the business of bending and welding pipe and making filters on a stick LOL
__________________
The forest was shrinking, but the Trees kept voting for the Axe, for the Axe was clever and convinced the Trees that because his handle was made of wood, he was one of them.
Last edited by XutvJet; 12-22-2017 at 02:20 PM.. |
|
Appreciate
0
|
| 12-22-2017, 04:16 PM | #190 |
|
1004
Rep 1,653
Posts |
I am sorry but I have to disagree Xutvjet. We have a very long process when it comes to R and D with our after market systems. We start off by dynoing the car stock. Next, we take the parts off the car scan them into the system run computerized test on them. Create 3D print of the piece to see it and see how we can change it but still keep it in the same envolope. After that we actually create different models of whatever part we are creating and dyno test them on the vehicles. Once we figure out the part we like the most for sound and performance is when we will actually put it in our production line. If you look on our website you will see that we have dyno graphs for most of our products to show what they will do for your system.
On to drone it is a very difficult issue because sound is also very subjective. You might hear something that someone else does not hear. If you are running catbypass or muffler bypass you are going to receive huge gains in performance but you will have to give somewhere else. |
|
Appreciate
0
|
| 12-23-2017, 08:53 AM | #191 |
|
Private First Class
52
Rep 109
Posts |
XutvJet, so any idea where a resonator must be at his best efficient place to reduce drone between 1600 and 2000 / 2200 RPMs ?
Does the exhaust drone formula is right to get the resonator lenght ? Find on Reddit forum : " Exhaust drone is a problem I've been dealing with and most of the time people solve it by trying various mufflers, resonators, and sound deadening until they like the outcome. There is, however, and exact science to eliminating drone: calculate the drone wavelength and cancel it with a resonator tube. You can also use the sound frequency to buy the correct sound suppression material since the better ones have different material for different frequencies. Here's the formula to get the tube length: ((343)/(RPM * 4 * (1/60))) / 4 Just replace RPM with the RPM where drone is at its worst. E.g. ((343)/(2500 * 4 * (1/60))) / 4 = 0.5145 meters For drone at 2500 RPM you need to weld a capped exhaust pipe 0.5145 meters in length before your muffler, as perpendicular to your existing pipe as possible (it should look like a T). It's as simple as that. Although it's often called a j tube, it's actually better if it's straight, as the more it bends the more sound bounces back before reaching the full length. The j shape comes from having to fit it in small spaces. If you can't weld, with this number you can tell any exhaust shop what to do. Tip: if you just want the frequency for buying the correct sound suppression, use this part: 2500 * 4 * (1/60) = 166.67 Hz (replace 2500 with your drone RPM) For those who are curious, here's the formula breakdown: 343m/s is the speed of sound 4 is the number of pulses per rev the engine makes (a V6 would be 6, but some engines fire two at once, so a V8 would still be 4). 1/60 to convert from minutes to seconds. /4 divides the wavelength by 4 to get the length of tube that will cancel out the frequency. " |
|
Appreciate
0
|
| 12-23-2017, 11:16 AM | #192 |
|
Major General
5543
Rep 5,366
Posts |
^That's outside of my pay grade. LOL. There is a science to the location and size of these resonators. Most companies put them in the vicinity of the muffler. Sometimes just aft of the downpipe(s). Or both.
It takes some experimenting but the end result is these systems are extremely effective at reducing drone. |
|
Appreciate
1
mikeyymonster526.00 |
| 12-23-2017, 02:26 PM | #195 |
|
Private First Class
52
Rep 109
Posts |
I will install a made to measure 2nd part midpipe with a resonator included, the workshop where i will do it tell me it should stop drone, they already experimented aftermarket exhaust on M235i with drone problems if only straight pipes from downpipe to muffler deleted are installed. They told me drone is " normal " because of the physical conception of an full straight pipe line.
|
|
Appreciate
0
|
| 01-09-2018, 07:05 AM | #196 |
|
Private First Class
52
Rep 109
Posts |
Just installed a made to measure resonator. Resutls : drone killed
I got very very important and annoying vibrations / droning waves on all the cabin, some plastics vibrated and i felt them on my seat between 1500 and 2200 RPMs. Everything is now OK, highway cruising is now possible ! The sound is now a little bit quieter and has changed between 5000 and 7000 RPMs ( less rough ). I was feared to loose this rough note but i had to make a concession such the drone was present. |
|
Appreciate
0
|
| 01-09-2018, 09:28 AM | #197 | |
|
1004
Rep 1,653
Posts |
Quote:
 |
|
|
Appreciate
0
|
| 01-10-2018, 01:20 PM | #198 | |
|
Private First Class
52
Rep 109
Posts |
Quote:
|
|
|
Appreciate
0
|
 |
| Bookmarks |
|
|
