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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 04-16-2016, 06:50 PM   #1
Eric Giles
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ZHP stock exhaust louder/deeper on automatic ZHP compared to a manual ZHP?

I make this question ZHP specific due to the fact that's the two cars I am comparing, plus the ZHP mufflers don't have the adjustable flap that changes the exhaust tone. However, it could pertain to any automatic vs. manual transmission E46.

So, as the title asks...what would be the reason why the factory exhaust system on an automatic equipped ZHP would be louder and with a deeper tone (especially inside the car while driving) than the same factory exhaust on a manual transmission ZHP? Since I purchased my '04 automatic ZHP sedan earlier this year, I have always noticed that my exhaust is fairly loud and deep...much more so that I ever recalled with my '05 ZHP manual I owned years ago. I have been able to verify this since a friend purchased a '04 ZHP 6sp that I haven driven a couple of times.

Now both cars are totally stock as far as exhaust and engine. His car has around 85k miles, mine has 129k miles. I recently changed the Vanos seals, plugs, etc and the sound from mine is the same. Mine almost 'drones' a bit while cruising around 40-45 in town with the RPM's at around 1600. If I drive my friends car at the same speed and in the gear that will get me to 1600 RPM at that speed, I do hear more or a deep tone from his exhaust inside the car but it isn't as pronounced as mine. Otherwise, his car is just very quiet and you hardly ever hear the engine or exhaust. Driving my car, you are almost always aware of the exhaust note at lower RPM's.

I've put my car on a lift while it was running and checked for any exhaust leaks, and there are none. My interior isn't missing any sound deadening material, and hasn't had any other modifications that would allow more noise into the cabin. During my research, I noticed that while all ZHP mufflers have a 32Hz vibration damper installed on the back end of the muffler, realoem.com shows that all automatic equipped ZHP's have an additional 32Hz vibration damper attached to the front end of the muffler as well. So that tells me that for some reason, the automatic transmission contributes more vibration or resonance to the exhaust system...but why is this so?

Anyone have any clues, suggestions, similar experiences, etc? To be honest, I find the extra exhaust tone inside the car a bit annoying...
Eric Giles
'04 330i ZHP

There are few things more expensive than a cheap BMW...

Last edited by Eric Giles; 04-16-2016 at 06:53 PM.
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Old 04-16-2016, 09:29 PM   #2
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Location: TEXAS - Circuit of the Americas doing laps with my M5 and coming in for a pit stop.
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My Ride: 03 330iT SportWagon
I had a 2001 330i M-sport Automatic last year and I noticed a louder exhaust in the car and rpms a little higher for the same speed.

I preferred my 325iT for the lower sound and rpm levels. I was wondering if all 330i's sound that way.
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Old 04-17-2016, 12:13 AM   #3
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Location: Albuquerque, NM
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My Ride: 2002 325i 2004 325Ci
it seems that the non-ZHP automatic E46 also has a louder tone compared to the non-ZHP. I have a 2002 E46 325i 4 dr (automatic) and a 2004 Ci (manual). I've noticed that the automatic is louder, especially in the cold. the Coupe has 85K miles and the 4dr has 56K miles. both cars meticulously cared and original stock. I thought I was imagining the sounds too. The coupe is funner to drive, but the automatic does have a nice sound. Great cars!
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