1M exhaust drone problem

[HP Autosport]

Originally Posted by rapter

Very interesting

Curious, are you selling your modification to the market?

Could you take some in car sound samples with both systems?

Question about your mid pipe system: essentially the system removes the two cats and replaces them with straight pipes?

Yes, it is available now.

See post# 70 for photos of the mid-pipe.

There is too much cabin noise at speed for anyone to hear the difference between the two pipes.

Originally Posted by ray101381

and CEL's with your mid pipe system? is a tune required? any performance gains that are noticeable? is it a straight forward bolt on with no modifications?

No, no CEL at all since the mid-pipe is behind the secondary O2's. And not tuning is required.

There may be a little gain in HP and TQ from removing the two secondary cats, but we have not verified it yet. The aftermarket system is lighter than the oem unit if that matters. No other modification is needes, just a straight replacement.

[johnsfb]

I see discoboy1 has now started a poll regarding this problem.
The latest word from my dealer is that there is no directive from BMW on this issue.

Mine was better for a while but it's now about as bad as ever so I have made an appointment with an exhaust specialist for the 14th June to see if he can fix this drone.

I will post result.

[VO1M]

Originally Posted by johnsfb

I see discoboy1 has now started a poll regarding this problem.
The latest word from my dealer is that there is no directive from BMW on this issue.

Mine was better for a while but it's now about as bad as ever so I have made an appointment with an exhaust specialist for the 14th June to see if he can fix this drone.

I will post result.

So the exhaust swop didn't really make a difference then.

I think it's just a natural resonance characteristic of the standard exhaust system similar to what the original MkIV Golf R32 suffered. The only cure for that particular issue was a Milltek replacement system!

It would be nice to know if the HP mid pipes really do cure the problem.

[1erMCoupe]

Hi,

just wanted to bring that thread back into discussion. Any news on this? I am thinking if the plastic bin in which the battery is mounted is amplifying the drone. I mean the exhaust is directly mounted aside this bin. Its maybe worth trying to put some antdrone matat around the battery.

[rapter]

Originally Posted by 1erMCoupe

Hi,

just wanted to bring that thread back into discussion. Any news on this? I am thinking if the plastic bin in which the battery is mounted is amplifying the drone. I mean the exhaust is directly mounted aside this bin. Its maybe worth trying to put some antdrone matat around the battery.

To clarify, your thoughts are that the empty cavities in the truck are amplifying the resonance of the exhaust in the vehicle?

Maybe... It is a good idea and worth investigating. I will try some things out and get back to you

[HP Autosport]

With near 5000 miles on the Berk Mid Pipe we decided to put the OEM mid pipe back on to see if the drone is indeed there and our conclusion is that the OEM mid pipe drones more than Berk and spread over a wider rpm range.

The Berk Mid Pipe is not going back on the car anytime soon...Stay tuned for the next exhaust mod!

[1erMCoupe]

@rapter: Yes

I was testing with a OEM midpipe and the one from Eisenmann. I dont think that the midpipe is the problem. After that i tested the midpipe from Eisenmann and the eisenmann exhaust and ster that a test exhaust. And the drone was back and even increased. While cleaning up the trunk i thought this damn plaistic bin where the battery is placed looks like a big resonance body. I have ordered now a noise protection mat for testing.

[scaramanga]

Originally Posted by 1erMCoupe

@rapter: Yes

I was testing with a OEM midpipe and the one from Eisenmann. I dont think that the midpipe is the problem. After that i tested the midpipe from Eisenmann and the eisenmann exhaust and ster that a test exhaust. And the drone was back and even increased. While cleaning up the trunk i thought this damn plaistic bin where the battery is placed looks like a big resonance body. I have ordered now a noise protection mat for testing.

Will be interesting to see if this reduces/cures the drone...

[oldBMWguy]

I just picked up my 1M from the PC in South Carolina on Tues.-- have 700 miles on the car, and have the drone from 2200 rpm to about 2600 rpm under light load. If you let off the gas the drone almost stops. --- so I guess the newer production cars still have the same problem [if we can get BMW to acknowledge that it IS a problem!]

[Robcut1]

If I am not concerned about HP gain, what would be my best and simplest option for the quietest ride possible without ripping out the interior and adding weight significant with Dynomat, etc.?
I don't much care about pops, burbles, growls, and definitely hate drones, and resonances!

[RussDC]

My does the same thing! Over 2000 miles so far. Keep us posted if and when you fix the problem

[1M Fan]

I installed about 1.6 sq/ft of Second Skin Damplifier and had some success. My testing was limited this evening and it wasn't gone completely, but it did resonate less frequently. I'll should know more tomorrow. I don't think it is just the battery box. The batter box may amplify the sound, but I suspect the source is sheet metal based. I did put a piece in front of the battery box too. That actually made a noticeable difference in my knock, knock test as in the hole panel went from a metallic ring to a thud.

Damplifier is a butyle based mass loader similar to Dynamat Extreme, but a little thinner.

there are a couple of other areas I may put some on. the factory has some dampening on the trunk floor panels at the very back, but the one on the left, still has a metallic ring to it when I knock on it. I may put some on the heat shield against the muffler too. The damplifier is rated to 500 degrees F and it can be used on the exposed under carriage.

[sparoz]

Interesting, keep us posted. . I might just try to strap a pillow to it and see if it makes a difference .

[1erMCoupe]

I filled the bin with all i found ... foam, cloths and i had also some success. Its much better now. I think with a good noise protection mat it will improve.

@1M Fan: I think your right...its not only the battery bin...the whole trunk is amplifiying. I will also put some anti drone mat arround the battery bin.

[Jante82]

How hard can it be to create an exhaust that is drone free? Just build it so that the resonance frequency is moved to a rpm that is above 4000 rpm. If you have some drone at WOT@4500 rpm, who cares? But at motorway speed and rpm between 2000-2800 it is very annoying.

[///1M]

Originally Posted by Jante82

How hard can it be to create an exhaust that is drone free? Just build it so that the resonance frequency is moved to a rpm that is above 4000 rpm. If you have some drone at WOT@4500 rpm, who cares? But at motorway speed and rpm between 2000-2800 it is very annoying.

Yes, yes, yes! I'm staying tuned!
Hoping for a resolution.
The drone is so unfortunate.

[1M Fan]

Let me define two terms as I use them. Everyone may not agree, but at least you'll know what I'm trying to fix.

Exhaust resonation is when the frequencies the exhaust system creates causes other parts of the care to vibrate. This is what I'm working on. Adding small amounts of a "mass loader" in the right spots will cure this. In the 1M the resonation comes and goes between 2000 and 2500 RPM.

Drone is the eritating tone an exhaust system creates in specific RPM or load range. there isn't much you can do to fix it but change the exhaust.

What I've done so far seems to have made the resonation better. It seams to be mostly in the 2100 - 2350 RPM (65 - 70 MPH) range which I don't use much. I'm going to add another 1 - 1.5 sq/ft in a few places tonight and see what happens.

As mass loaders go, the Second Skin products are very good. A thin piece of material will do a lot to control sheet metal vibration.

[HP Autosport]

Originally Posted by 1M Fan

Let me define two terms as I use them. Everyone may not agree, but at least you'll know what I'm trying to fix.

Exhaust resonation is when the frequencies the exhaust system creates causes other parts of the care to vibrate. This is what I'm working on. Adding small amounts of a "mass loader" in the right spots will cure this. In the 1M the resonation comes and goes between 2000 and 2500 RPM.

Drone is the eritating tone an exhaust system creates in specific RPM or load range. there isn't much you can do to fix it but change the exhaust.

What I've done so far seems to have made the resonation better. It seams to be mostly in the 2100 - 2350 RPM (65 - 70 MPH) range which I don't use much. I'm going to add another 1 - 1.5 sq/ft in a few places tonight and see what happens.

As mass loaders go, the Second Skin products are very good. A thin piece of material will do a lot to control sheet metal vibration.

Something else you can try if the drone really bothers you is to clamp weight at various sections of the exhaust until the drone is gone. It's an old trick to reduce exhaust resonance.

[mikewills]

What about a rubberized undercoating spray on the underside of the trunk...above the muffler area.

[1M Fan]

That is an option. It is very hard to remove if it is ever needed. The factory has it in some locations.

Originally Posted by mikewills

What about a rubberized undercoating spray on the underside of the trunk...above the muffler area.

[1M Fan]

Good to know! I never thought about that. The note/tone of the exhaust is fine to me.

Originally Posted by HP Autowerks

Something else you can try if the drone really bothers you is to clamp weight at various sections of the exhaust until the drone is gone. It's an old trick to reduce exhaust resonance.

[HP Autosport]

Originally Posted by 1M Fan

Good to know! I never thought about that. The note/tone of the exhaust is fine to me.

The weights, added in the right locations will just reduce or change the resonance. It's more like a changing harmonics.

OEM manufactures do that all the time, even BMW.