One sponge or two?

[MrPT]

As you go over 3000 rpm it just starts to sound like some sort of trumpet/trombone combination playing under my dash.

I think that's the idea, although there's definitely a french horn in there as well.

I guess those harmonics are intended to add a but of "motorsports character", reminiscent of Porsche Mezger, older BMW inline 6s etc. Performance engines have more bits that generate noise on top of the fundamental combustion and exhaust sounds (intake, ITBs, solid valvetrain etc).

I found that with two foams out you just get a monotone blare at high RPM and it's seriously loud. With the roof up you can really feel your ear drums getting smashed. Settled for about 2/3rds of the inner foam removed in mine.

[Chris1981]

I had both out for a bout a month... have now replaced the foam nearest the intake as it was a bit too loud at higher engine speeds and actually takes away from the naturally great noise a straight 6 makes, like MACK pointed out it's not an authentic noise so I find it best not amplify it too much!

[MefiEcosse]

Just fitted one of these yesterday, bought it 2nd hand so larger bit foam had already been removed!
I'm happy with the sound at the moment but would like to try some more foam to compare, anyone have any they don't need?

[OntarioZed]

I cut the larger piece of foam in half and placed it at the firewall and left the smaller piece of foam that was located at the intake boot out. I find it sounds nice and growly at higher revs with the top down, but quiet at lower "'around town" revs. With the roof up, however, I still think it's a bit loud at higher revs.

A compromise, but I'm happy at this setting.

[road warrior]

The foam was taken out by Neil for me to try, didn't know there was 2 pieces in there, anyway, I eventually put it back to hear the lovely 6. Now of course I have a dlv back box and love it. Yesterday for shits and giggles I took out the sponge again - and couldn't hear any difference .
I think I will put it back in. Real is always better when.

[tomrdy]

I had the big piece out pretty early in my ownership. Love it. Gives great induction roar when youre on the beans but made pretty much no difference driving lightly (ideal for me).

Recently took the remaining piece out to try and found that there was a bit more drone at lower RPM on load. The on-beans induction was quite a bit louder but not particularly "better" sounding. I also noticed that I could hear a tinnnny intake whistle/high pitch vibration on initial throttle application. Had the same sound in my previous car which had a K&N Apollo and on the Z when I put an open pod in for laughs. The sound really annoyed me and once I noticed it i couldn't un-notice it.

Back to my original set up with the big piece out

[MalNCH]

So, does this just increase the noise in the cabin then ??

Yes, deafens you but everyone outside the car still thinks you have a quiet Z4, completely pointless.

[ben g]

So, does this just increase the noise in the cabin then ??

Yes, deafens you but everyone outside the car still thinks you have a quiet Z4, completely pointless.

Why would you want to have a loud car outside anyway? All you end up doing is pissing off your neighbours and ending up with a keyed motor

My standard exhaust pops and sounds fine.

[Capa]

I like the sound with both sponges out for bimbling about, but in the choopay it's properly loud and quite unpleasant north of four grand. I settled on leaving the smaller one in situ.

[brillomaster]

I've taken one out, works well for me! its a track car, so loud on the inside, but quiet on the outside is perfect as I can hear the engine note more through a helmet to get heel and toe better, but is not going to hassle any drive by noise limits.

Only time it got annoying was along the long uphill Kemmel Straight at Spa, about 30 seconds of doing 6000rpm in 4th gear, not getting any faster

[MalNCH]

So, does this just increase the noise in the cabin then ??

Yes, deafens you but everyone outside the car still thinks you have a quiet Z4, completely pointless.

Why would you want to have a loud car outside anyway? All you end up doing is pissing off your neighbours and ending up with a keyed motor

My standard exhaust pops and sounds fine.

My question would be why do you want a loud car inside that only you and your passenger can hear? So you can pretend you have a performance exhaust?

[ben g]

Yes, deafens you but everyone outside the car still thinks you have a quiet Z4, completely pointless.

Why would you want to have a loud car outside anyway? All you end up doing is pissing off your neighbours and ending up with a keyed motor

My standard exhaust pops and sounds fine.

My question would be why do you want a loud car inside that only you and your passenger can hear? So you can pretend you have a performance exhaust?

That makes no sense. The noise you're hearing inside the car is induction noise. It certainly sounds better than hearing a fart can belting out 120db of aural nuisance.

I just to enjoy pissing my neighbours off when I was 18 and drove a corsa. Not really keen on that anymore.

Also, chuck the roof and windows down and everyone will hear the same noise you do inside the car

For what it's worth, I think I actually put one bit of foam back in mine, as I found it became annoying when driving when both foams were removed.

[tomrdy]

That makes no sense. The noise you're hearing inside the car is induction noise. It certainly sounds better than hearing a fart can belting out 120db of aural nuisance.

+1 on this. I actually really like the idea of the sound generator (this analog/mechanical type, NOT the new-age speaker-driven type).

It's real sound and I am basically having the cake and eating it too - I can enjoy my motor's induction sound, without being a noise nuisance and getting unwanted attention. When I was younger and I had my little Astra with the odd 140hp , I put the loudest intake I could and it was LOUD. Sounded awesome and was great for letting my friends and neighbours know I was about to pull up from a block away.

In saying that, i can definitely appreciate wanting a bit more head-turning-ness sometimes (I won't lie this includes me) but as I've grown older, I've realised the most important person to impress with the cars handling, acceleration, sound etc... is.. surprise.. me. So if I mod/part makes adds to that, but does F**K all for random strangers outside, I'm fine with that

Also with the roof down the sound is literally audible to everyone around you. Drove through a tunnel and giggled like a child.

My standard exhaust pops and sounds fine.

OT: I only recently discovered that our stock exhausts can make some really nice pops in 1st/2nd. I'm like a kid with a new toy in carparks now. Drives my wife nuts while I'm sitting in 1st at 3500rpm