...and wow, it sure makes a difference! However, it almost sounds like a switch: normal when cruising, but an immediate loud, throaty growl when gassing it above 3k RPMs. For those who have done this retrofit, is the sudden shifting in sound character, between pre-retrofit and loud growl, normal?

Side note: I had both foam pieces removed, but put the small one back in after I got back from my test drive, and I haven't gone back out yet.

Thanks!

Yeah, with both pieces removed or just the small piece still in, it sounds like a switch.

IMO, it sounds much better with about 40% of the big piece in and with the small piece out.

With both pieces out on my 3.0Si I always get asked by passengers what intake I have. It is somewhat obnoxious and drones but it doesn't bother me to where I'd put the foam back in. I would though if I got exhaust.

Where does one buy one of these. I have an '06 3.0i without one.

In the DIY forum there is a post on sound generator retrofit and it has the part numbers. Take the part numbers to your local dealer or any oem parts store (pelicanparts.com mileoneparts.com) and buy the parts listed.

O.K., let me get this right! All of you are making adjustments to your sound generator because you want to hear more cabin noise? It does not improve performance of your Z4! It is also not possible for exhaust to enter in unless you have and exhaust leak and it would come in from the cabin vents. The sound generator only flows fresh air. The only thing this sound generator does besides making more sound in the cabin, is redirect air from the throttlebody and intake. The best thing to do is remove it, seal the hole and allow your engine to have more air. This would then give you an improvement and an all around better sound that can be heard from both inside the car and outside. Just let the car breath!

I'm sure the engine is still getting plenty of airflow.

As am I (the car breaths fine), as the generator is a sound tunnel and doesn't flow much air. Sure there may be a slight bit of wiggle to the air flow, but Huge doubt that it's robbing performance, especially after talking to a design tech with BMW and finding the intake flows quite a bit more air than is used.

And yes, those of us that have the generator remove some or all of the foam to suite our sound tastes. I like a little louder noise at high revs.

This is the part where someone might try and tell us what we like...



But then maybe you're right...

Toss up a couple of Dyno charts with and without foam and with and without the generator and show us what damage we're doing to the performance.


We'll wait right here:)

i didn't like the sound so i took it out...

BMW's factory tuned exhaust sound plenty nice

O.K., let me get this right! All of you are making adjustments to your sound generator because you want to hear more cabin noise? It does not improve performance of your Z4! It is also not possible for exhaust to enter in unless you have and exhaust leak and it would come in from the cabin vents. The sound generator only flows fresh air. The only thing this sound generator does besides making more sound in the cabin, is redirect air from the throttlebody and intake. The best thing to do is remove it, seal the hole and allow your engine to have more air. This would then give you an improvement and an all around better sound that can be heard from both inside the car and outside. Just let the car breath!

the soundgenerator is actually a membrane that vibrates as the butterfly valve opens. There is no air going to the cabin whatsoever. SG or not makes absolutely no difference to performance.

I removed the large piece of foam in my 3.0 and made a video :)

But I'm not yet allowed to post links...

youtube.com/watch?v=_d9KqoxetNg