ZHP stock exhaust louder/deeper on automatic ZHP compared to a manual ZHP?

[egiles14]

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 rcwells purchased Ruby ('04 ZHP 6sp), and I drove it 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 rcwells 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...

[az3579]

No two cars are alike. That is all I've got to say about that!

Sent from my LG V10 on Tapatalk

[egiles14]

No two cars are alike. That is all I've got to say about that!

Sent from my LG V10 on Tapatalk
Well two cars will have their differences yes, but there has to be more to this than explaining it away like Forrest Gump lol! The fact the automatic has an additional vibration damper has to play a part in it I think.

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[az3579]

Well two cars will have their differences yes, but there has to be more to this than explaining it away like Forrest Gump lol! The fact the automatic has an additional vibration damper has to play a part in it I think.

Sent from my Nexus 6 using Tapatalk

Sorry to say, I've got a contradiction to that theory. When I test drove Shawn's OB/NB automatic ZHP for him quite a while back, that didn't sound any different than any other ZHP I've been in with a stock exhaust. If the extra vibration damper had anything to do with it, it would have sounded different, but it didn't.

[egiles14]

Sorry to say, I've got a contradiction to that theory. When I test drove Shawn's OB/NB automatic ZHP for him quite a while back, that didn't sound any different than any other ZHP I've been in with a stock exhaust. If the extra vibration damper had anything to do with it, it would have sounded different, but it didn't.

That's the feedback I was looking for. I wouldn't think there would be that much difference in the loudness of the exhaust just because of the transmission. I was thinking there must be something with my car for there to be such a pronounced difference...now I just have to find out what might be causing it.

[az3579]

That's the feedback I was looking for. I wouldn't think there would be that much difference in the loudness of the exhaust just because of the transmission. I was thinking there must be something with my car for there to be such a pronounced difference...now I just have to find out what might be causing it.

Well, you do know what they say about BMW exhausts... they get louder (and better!) with time!
Just listen to an E30 325i that still has its stock exhaust to know what I mean. :)

[egiles14]

Sorry for bumping this thread 10 months later, but I can confirm that YES, a ZHP with an automatic transmission definitely creates more exhaust 'noise' inside the car while driving. It's probably best to call it more of a drone, and it may be due to the extra load of the torque converter and the automatic transmission.

I was able to verify this again due to now owning another '04 ZHP with 6sp manual that I immediately noticed being quieter on the inside than my previous automatic ZHP. A friend and I recently replaced the engine in a '05 ZHP (original engine was overheated), and upon driving it the increased interior exhaust noise was immediately apparent.

So that's two different manual transmission ZHP's, and two automatic equipped ZHP's that I drove in this 'test' with the same results. In the end it really doesn't matter at all, but it does answer my original question and I guess it is some useless information lol.

[holyc0w]

Is this at the same RPM?

I would expect the automatic to spend more time at lower RPMs.