[jyeah]

Hi All,

In hindsight, I should never had attempted this after the droning I experienced with the OEM PE. However, I took the plunge and installed a brand-new Akrapovich Evo SS exhaust system for my 2010 335i N54 with automatic transmission.

With only a slight load, around 1600-2100 rpm, the car exhibits a low frequency drone (bass-like) and gets louder the more load you put on the car. It's not deafening, but it's certainly not quiet either. At times, it can cover the music I'm listening to in the cabin.

I was wondering if anyone else that has the Akrapovich also noticed this? Before I took the plunge, most reviews indicated that the Akrapovich did not drone, either with a MT or an AT.

Suggestions on how to eliminate the drone would be awesome, as I have searched through the internet and people have posted different attempts at eliminating drone from other exhaust systems.

I love the sound of the Akra from 2100 rpm and up, but the bass-like drone can get annoying.

I have an AR catted DP as well in front of the system.

Thanks for any advice (even if you say I should go back to stock)!

[jyeah]

I also contacted Akra and they suggested to go back to stock DP's. They mentioned that they cannot guarantee drone-free if the system is not stock. However, I vaguely remembered they came out with their own version of catless DP as well.

There are no exhaust leaks and there's nothing touching the heatshield, etc (not a rattle).

[Myrder]

you are bound to get some drone in a completely catless system. Trying putting some resonators on to minimize the drone.

[BigHoncho]

I had exactly the same problem, massive drone and vibration from 1500-2000rpm, even with stock secondary cats welded in (also have the stock downpipe without cats). The only solution was to weld in the stock pre-muffler of a E90/E91, but be careful it has 60mm inlets and the akrapovic has 65mm. In the end the evolution system was heavily modified, I would not do it again.

By the way: how did you fit the front pipes bracket? Mine didn't fit because the AT has a different dimensions, so I used the stock bracket, which doesn't fit perfectly with the akra 65mm pipes.

[lamia2super]

try dynamating the trunk and if the that small compartment bet. the rear seat is vibrating you can mod it or remove the lid. only option really if you don't want mod or change the exhuast

[jyeah]

Originally Posted by BigHoncho

I had exactly the same problem, massive drone and vibration from 1500-2000rpm, even with stock secondary cats welded in (also have the stock downpipe without cats). The only solution was to weld in the stock pre-muffler of a E90/E91, but be careful it has 60mm inlets and the akrapovic has 65mm. In the end the evolution system was heavily modified, I would not do it again.

By the why: how did you fit the front pipes bracket? Mine didn't fit because the AT has a different dimensions, so I used the stock bracket, which doesn't fit perfectly with the akra 65mm pipes.

My front pipes bracket barely fit.

Got it to fit by adjusting the two bolts that mounted the bracket to the transmission. The bolt furthest away from the pipe was adjusted to a higher position and the closer one to a lower position on the mount. That allowed the bracket to be slanted/angled very slightly downwards. I would say there's only about a 1-2 cm clearance from the heat-shield.

By "stock pre-muffler" section, which section do you mean? I still have my stock exhaust. I can probably chop the section needed and weld it in.

Thanks.

[jyeah]

Originally Posted by lamia2super

try dynamating the trunk and if the that small compartment bet. the rear seat is vibrating you can mod it or remove the lid. only option really if you don't want mod or change the exhuast

My trunk was already dynamatted a while ago to dampen the noise from solid differential bushings.

I'll see if it's still resonating with the rear seats removed.

[BigHoncho]

Originally Posted by jyeah

My front pipes bracket barely fit.

Got it to fit by adjusting the two bolts that mounted the bracket to the transmission. The bolt furthest away from the pipe was adjusted to a higher position and the closer one to a lower position on the mount. That allowed the bracket to be slanted/angled very slightly downwards. I would say there's only about a 1-2 cm clearance from the heat-shield.

As I said, I used the stock bracket. Akrapovic told me there is no known fittment issues for AT vehicles. But as you can see at the BMW parts lists, there are different part numbers für the MT and AT versions of the bracket. So its not possible that one bracket fits both transmission cases and Akrapovic denies that!

Originally Posted by jyeah

By "stock pre-muffler" section, which section do you mean? I still have my stock exhaust. I can probably chop the section needed and weld it in.
Thanks.

I mean the middle section, the so called "center muffler with pipes":
http://bmwfans.info/parts-catalog/E9...enter_muffler/

The E92/E93 has an x-pipe (kind of) and the E90/E91 has an muffler instead, that reduced the drone dramatically. I bought an used E90/E91 muffler and welded it into the Akra Evo pipes... that not how its meant to be, but it works perfectly.

--
Here is another picture that shows what I mean:
https://dl.dropboxusercontent.com/u/...ust_system.png

[jyeah]

Originally Posted by BigHoncho

As I said, I used the stock bracket. Akrapovic told me there is no known fittment issues for AT vehicles. But as you can see at the BMW parts lists, there are different part numbers für the MT and AT versions of the bracket. So its not possible that one bracket fits both transmission cases and Akrapovic denies that!



I mean the middle section, the so called "center muffler with pipes":
http://bmwfans.info/parts-catalog/E9...enter_muffler/

The E92/E93 has an x-pipe (kind of) and the E90/E91 has an muffler instead, that reduced the drone dramatically. I bought an used E90/E91 muffler and welded it into the Akra Evo pipes... that not how its meant to be, but it works perfectly.

--
Here is another picture that shows what I mean:
https://dl.dropboxusercontent.com/u/...ust_system.png

Thanks,

Did you use the full center muffler with pipes or just part of it?

Also, the bracket does fit for automatic transmission. I'll take some pictures in a few days when the car is on the lift to show you.

[Killerfish2012]

Originally Posted by jyeah

Hi All,

In hindsight, I should never had attempted this after the droning I experienced with the OEM PE. However, I took the plunge and installed a brand-new Akrapovich Evo SS exhaust system for my 2010 335i N54 with automatic transmission.

With only a slight load, around 1600-2100 rpm, the car exhibits a low frequency drone (bass-like) and gets louder the more load you put on the car. It's not deafening, but it's certainly not quiet either. At times, it can cover the music I'm listening to in the cabin.

I was wondering if anyone else that has the Akrapovich also noticed this? Before I took the plunge, most reviews indicated that the Akrapovich did not drone, either with a MT or an AT.

Suggestions on how to eliminate the drone would be awesome, as I have searched through the internet and people have posted different attempts at eliminating drone from other exhaust systems.

I love the sound of the Akra from 2100 rpm and up, but the bass-like drone can get annoying.

I have an AR catted DP as well in front of the system.

Thanks for any advice (even if you say I should go back to stock)!

There are two things that you need from your stock exhaust system that seem to have been eliminated by akrapovic.

1. oem resonator
2. oem secondary cats which double as silencers
3. To some extent--> Oem mufflers

Without these two components in the exact same position, and configuration as your oem cat back, you will have serious drone issues.

[jyeah]

Originally Posted by Killerfish2012

There are two things that you need from your stock exhaust system that seem to have been eliminated by akrapovic.

1. oem resonator
2. oem secondary cats which double as silencers
3. To some extent--> Oem mufflers

Without these two components in the exact same position, and configuration as your oem cat back, you will have serious drone issues.

So I'm thinking would just 1. OEM resonator as suggested by BigHoncho be enough or do I really need to weld in the secondary cats as well.

It almost makes more sense to just put in the OEM pipes and just keep the Akrapovic mufflers at this point.

Instead of hacking up the stock pieces I'd probably look into installing some Vibrant resonators, or something, instead:
http://www.e90post.com/forums/showpo...1&postcount=44

Either that, or make your own Helmholtz chambers

Or as you mentioned, go with the factory "mid-section" and Akropovich mufflers on the end of that.

[cstmx_ryder]

Put the OEM exhaust back on is the ONLY way to avoid drone all together. Aftermarket exhausts ALL have drone, no matter how you look at it.

Another way to deal with it is run the rpm a little higher in each gear than you normally would, maybe a couple hundred rpms higher....

Wanting NO drone on a aftermarket exhaust, is nearly impossible. That's just like saying, I want a sports car that can get me 30-35 mpg (aside from Tesla), it isn't likely to happen. More like one, or the other.

My .02

[Killerfish2012]

Originally Posted by jyeah

It almost makes more sense to just put in the OEM pipes and just keep the Akrapovic mufflers at this point.

Ditto. See my thread for my exhaust set up. The only droneless setup is aftermarket mufflers welded on to the oem catback. It's not just about simply welding in resonators and secondary cats. It's about where they are positioned on the exhaust. The oem resonators move the drone to a different rpm, and the secondary cats, while being relatively free flowing, change the exhaust note, and help muffle the drone.

[BigHoncho]

Originally Posted by Killerfish2012

Ditto. See my thread for my exhaust set up. The only droneless setup is aftermarket mufflers welded on to the oem catback. It's not just about simply welding in resonators and secondary cats. It's about where they are positioned on the exhaust. The oem resonators move the drone to a different rpm, and the secondary cats, while being relatively free flowing, change the exhaust note, and help muffle the drone.

I think its all about the silencer/resonator in the middle. I tried the deletion of stock secordary cats, metal race-cats und stock kats, all without much change in drone and vibration. The only thing that changed the game was the OEM silencer/resonator in the middle. I even use HJS metal cats with it now and its almost free from drone.

[BigHoncho]

Originally Posted by jyeah

Thanks,

Did you use the full center muffler with pipes or just part of it?

I used almost the full section, I chopped it right behind the two holder and made a nice transition from 60 to 65mm to the muffler in the back.

I have to say, its a shame to cut those akrapovic pipes, but there is no other way to get rid of the drone.

Originally Posted by jyeah

Also, the bracket does fit for automatic transmission. I'll take some pictures in a few days when the car is on the lift to show you.

Thanks :-)

[Killerfish2012]

Originally Posted by BigHoncho

I think its all about the silencer/resonator in the middle. I tried the deletion of stock secordary cats, metal race-cats und stock kats, all without much change in drone and vibration. The only thing that changed the game was the OEM silencer/resonator in the middle. I even use HJS metal cats with it now and its almost free from drone.

The resonator is not a silencer. According to BMW the name of the secondary cat is: catalyst/silencer. Resonators move the rpm occurrence of drone, so that it's not present at highway speeds.

[BigHoncho]

Originally Posted by Killerfish2012

The resonator is not a silencer. According to BMW the name of the secondary cat is: catalyst/silencer. Resonators move the rpm occurrence of drone, so that it's not present at highway speeds.

However, the cats didn't change much, but the muffler in the middle did.

[JAL0988]

I have the same issue with my Remus. I avoid it by driving in Sport Mode. It keeps the RPMs higher and the low bass drone is barely noticeable. I think if you go to any aftermarket exhaust, it'll drone.

[BD_F22]

Originally Posted by JAL0988

I have the same issue with my Remus. I avoid it by driving in Sport Mode. It keeps the RPMs higher and the low bass drone is barely noticeable. I think if you go to any aftermarket exhaust, it'll drone.

+1 on sport mode that's what I do with my AE exhaust

[jyeah]

Originally Posted by BD_e92

+1 on sport mode that's what I do with my AE exhaust

Well, even sport mode doesn't help that much in LA traffic.

[jyeah]

Originally Posted by Killerfish2012

The resonator is not a silencer. According to BMW the name of the secondary cat is: catalyst/silencer. Resonators move the rpm occurrence of drone, so that it's not present at highway speeds.

Yeah, my main question is if it's shifting the rpm occurrence of drone, where is it shifting to?

I'm considering three options right now:

1) Try cutting and welding only the center muffler (resonator) section in
2) Add back in the secondary cats in addition to the center muffler
3) Switch the midsection pipes back to my stock pipes

The thing was, I had the full evolution system welded when I had it installed because the pipes did not seal well and had exhaust leaks (due to heat expansion) that high temp RTV silicone did not solve.