[Runnin'Rich]

I’ve fitted the euro 130i sound generator to my e91 328i.
I could barely hear the difference.
I can only think the 130i must have less sound insulation so the driver can hear more.
I attached a hose from the sound generator and ran it out the hood into the drivers window. It sounded amazing, just like the Z4 sound generator that directly pipes through a factory hole in the firewall.
There is no hole in the e90 firewall so I attempted to pipe the sound closer to the driver. I cut a hole into the plastic which surrounds the wiper mechanism and piped the sound in there. This did not help much in terms of volume.

Mine is LHD, I know there is holes in the firewall for the RHD equivalent. But they are blocked by the ebox and exhaust heat shields.

Does anyone have an idea of where I could get a 1-2” hole in the firewall without cutting metal?

Thanks
PS I’m not interested in K&N filters or silicon elbows for more intake sound

[pcmrsage]

I just want to understand, why a sound generator? Downpipe would sound so much better.

[Runnin'Rich]

No Down pipe on 328i
Not interested in exhaust mods either for sound

[PhaceN52]

I'm totally interested in this too, even thought of removing some firewall insulation

[The Nightman]

Maybe you could try to mimic the BMW Performance intake's "air guide" that pipes induction noise past the hood seal near the driver?



https://www.e90post.com/forums/showthread.php?t=195658

Cutting a hole in the airbox for a Dinan style air ram hose adds a lot of induction noise too.

[Efthreeoh]

I have both an N52 Zed 3.0si with the sound pipe and an N52 E90. I'm not sure it would make that much difference. The exhaust on the Z4 comes in much better than the intake noise. Hacking the E90 firewall is a bit risky for such an experiment, IMO.

[Runnin'Rich]

Originally Posted by The Nightman

Maybe you could try to mimic the BMW Performance intake's "air guide" that pipes induction noise past the hood seal near the driver?



https://www.e90post.com/forums/showthread.php?t=195658

Cutting a hole in the airbox for a Dinan style air ram hose adds a lot of induction noise too.

Thanks for the reply.
The original poster who fitted that US Performance Intake stated that it didn’t make a noticeable sound increase. I already went through to the wiper mech which is closer to the driver than the air guide without success

[Runnin'Rich]

Originally Posted by Efthreeoh

I have both an N52 Zed 3.0si with the sound pipe and an N52 E90. I'm not sure it would make that much difference. The exhaust on the Z4 comes in much better than the intake noise. Hacking the E90 firewall is a bit risky for such an experiment, IMO.

Did you remove the foam from your n52 sound generator pipe to make it loud?

[PhaceN52]

Originally Posted by Runnin'Rich

I can only think the 130i must have less sound insulation so the driver can hear more.

You're right, that's exactly why
https://www.realoem.com/bmw/enUS/sho...diagId=51_5851 part n.7
https://www.realoem.com/bmw/enUS/sho...diagId=51_5526

on the E90 it seems like the rubber panel behind the dash and heater core inside the cabin, maybe hacking the central part and leaving it intact where it serves as a gasket on the steering shaft, coolant and ac pipes and so on it can increase engine noise, but damn... not that straight forward

If it could be doable at least without disconnecting the pipes from the hvac unit i'd give it a try this spring, but from what I remember doing the core I'm not sure, and then there's the unknown about road noise, I'd like hearing the engine, not tires rolling...

[Runnin'Rich]

Thanks for the post PhaceN52
I didn’t think about the heater gasket.
It looks pretty tight to get a sound pipe between the AC/coolant lines. I will investigate further. I agree on your road noise point

If you have an Auto transmission I think it’s possible to use the hole that is for clutch master cylinder to brake reservoir line. I unfortunately have a 6MT so it’s taken.
There is a RHD equivalent but I think it’s tight behind the ebox, I will investigate today

[Efthreeoh]

Originally Posted by Runnin'Rich

Thanks for the post PhaceN52
I didn’t think about the heater gasket.
It looks pretty tight to get a sound pipe between the AC/coolant lines. I will investigate further. I agree on your road noise point

If you have an Auto transmission I think it’s possible to use the hole that is for clutch master cylinder to brake reservoir line. I unfortunately have a 6MT so it’s taken.
There is a RHD equivalent but I think it’s tight behind the ebox, I will investigate today

It's not as simple it seems. The Z4's system is designed into the car from the getgo. It's a straight pipe with attenuation foam to enhance the sound. Some type of pipe that snakes around is going to provide a completely different sound.

[colorado.e9x]

Solution: cold air intake with heat shield. I put a gruppe m rep on my bone stock 328 and the induction noise was superb

[Runnin'Rich]

Originally Posted by Efthreeoh

It's not as simple it seems. The Z4's system is designed into the car from the getgo. It's a straight pipe with attenuation foam to enhance the sound. Some type of pipe that snakes around is going to provide a completely different sound.

Yeah I’m sure a BMW sound expert tuned the generator diameter (or maybe just made it as big as possible to fit) then experimented with some different foams till he got the best balance of deep Induction sound without injector ticking.

I Put a 24ft (7.32m) pipe from my sound generator out the hood down the side of the car and fed it into the drivers window. The diameter was half inch larger than the original sound generator pipe.
It sounded awesome just like the videos on YouTube of people removing the foam from their Z4 pipe.

Maybe a smaller pipe / smaller hole will reduce lower frequencies, who knows? Maybe I’ll hear more injector tick. I don’t really mind as long as I can hear some more engine sound along with it

[The Nightman]

Maybe try to see where all of the plugs are on the firewall:


https://www.realoem.com/bmw/enUS/sho...diagId=51_6037

Maybe #11 plug? It is 30x36mm apparently. Part # 51711872829

https://www.realoem.com/bmw/enUS/par...&q=51711872829

Might be above the brake pedal and used by MT though: https://www.zpost.com/forums/showthread.php?t=664934

[Runnin'Rich]

Thank you for posting Nightman
I think i found the hole you’re referring too but the RHD one! (clutch master cyl to clutch slave line pass through) Which is great becuase it’s empty on my car.

I removed the plug it’s about 15mm size hole. I used a hook ended pick to thrash open the insulation on the other side. I then poked a line through, it came out below the cabin blower fan behind the glove box.

I now need to find some suitable pipe. I bought some wire protection conduit, but it’s split for feeding over wire so it doesn’t transfer sound. There was clear PVC fish tank pipe but I’d rather get something that looks like black conduit.

[PhaceN52]

That's great, have to try it too
Did you torn off the insulation? review needed soon

[The Nightman]

Check out the photos of the firewall in this eBay listing: https://www.ebay.com/itm/124808691079

[Runnin'Rich]

Thanks for the images Nightman.

It looks like I’m using the only hole available. Wish I could use the massive ones blocked by the ebox.

So I did some testing with different size pipes.

I went to the plumbing section at my local hardware store and bought a dishwasher adaptor. I upsized the diameter using insulation tape until it was snug in the sound generator.
I then pulled the red pipe (13mm OD) through from the engine side using a piece of plastic air line duct taped to it.

The red pipe was a tight fit into the dishwasher adaptor.

So for context when driving with the 2-1/4” pipe from the sound generator into the cars window, I found the experience similar to a k&n filter with an open air box, except with more volume at WOT. If you drive with minimum throttle the car sounds stock. Going with mild throttle you get some deep grunt sound, which works great for blipping the throttle for down shifts. If you go WOT the noise is much louder like your ears are inside the airbox!!

Now when using the smaller diameter pipe the experience was a bit different.
There was no difference in sound unless I was at wide open throttle.
The car sounded stock when blipping the throttle to 4K for down shifts.
Doing a WOT pull in 2nd gear, I got induction sound from 4000rpm onwards, at 5k the sound went very loud!! Like a crazy resonance. And maintained till red line.
I felt like I had lost the deeper tones from 2500rpm to 4000rpm, but still the CSL noise barks in at 5000rpm!

The next test I cut a longer section of the 2-1/4” pipe and then stepped it down right at the hole with a short section of of the red pipe. Driving with this setup gave me some deeper tones back at lower revs. It was also a good deep tone from 4000rpm onwards, a nice smooth bark up to the redline. It was like the original 2-1/4” pipe but just quieter. It was harder to hear the grunt on blips but it was still there. I’m guessing becuase of the restriction in diameter and the fact the pipe exit is behind the dash there is reduced volume. When I did the big pipe test I wedged the pipe in the passenger seat with the outlet pointed at my face!! No wonder it was louder.

I then did a third test where I removed the red pipe completely and just pointed the 2-1/4” pipe at the open 15mm hole. On test drive It sounded pretty much stock, I could hear a little bit of grunt at WOT from 5k onwards but very quiet. So it’s important that the pipe work is totally sealed going into the firewall.

So in conclusion, the larger the diameter pipe the better it sounds no matter the length. If you step down the diameter the narrow pipe needs to be short or you will loose sound at lower revs and on blips.
The pipe work must be sealed properly or you’ll loose volume
If you have a 6MT there is only one hole easily accessible which is small at 15mm.

I’m gonna work on a permanent solution.
The 2-1/4” pipe is too large to feed under the cowl. So I’ll order some smaller Diameter non-split conduit and some kind of elbow for entry through the hole.

[Runnin'Rich]

Here’s a better shot of the ~15mm hole and it’s surroundings.
That’s an AC pipe in front of the opening

[Runnin'Rich]

So I bought some new plumbing parts and had another attempt.
Got a smaller diameter sump pump hose at 1-1/4. It came with an adapter with a thread. I screwed it into the connector piece and then dremelled off the outside ribs. I also shortened the length so it didn’t contact the surface inside the generator. One lap of insulation tape got a snug fit.

For the firewall end, I firstly trimmed off half of a plastic A/C line clip. I cut a 1-1/4 elbow and then used double sided foam and a zip tie to secure it around the hole. I tucked the pipe under the strut bars.

Sounds great so far but wasn’t able to get WOT test as roads were icy.

[Runnin'Rich]

Also the hole I’m using is not for the clutch slave line, the exact spot on the opposite side of the car has a bolt through it. Maybe it supports steering coloumn?

[Runnin'Rich]

Here is a comparison test with and without the sound generator piped with 1-1/4” to the small hole.
I’m completely happy with it. No foam needed. Just a nice deep tone from 3000rpm with no resonance.

https://youtu.be/3Aa2x_puBrI?si=REs9AQ24--5QATV2