When driving through really heavy rain, has anyone else noticed that the exhaust gets noticeably louder and deeper than when in the dry? My dad had the idea that the cool water shrinks the hot exhaust, causing a change in sound. For those that don't know, exhaust pipes grow several inches hot vs. cold so this sounded plausible to me, especially with the muffler/resonator so close to the wheels.

Anyone else hear this or have another reason?

PS this is a stock 05 MCS manual.

 

Your dad's theory sounds very plausible to me, especially because I have seen Magnaflow exhausts grow about an inch after hard driving.

Also, the air passing through the exhaust would have higher water content due to increased humidity and that may play a part too.

 

I noticed the same with my car. While it seems at first to be caused by water cooling and contracting the exhaust, I notice this happening mostly in very hard rain. The 'rooster tail' of road spray that the car throws off might act as a reflector of sorts, causing the sound to bounce back towards the rear of the car and sounding louder. Just a theory!

 

I've noticed it too. On one trip I thought to myself, there must be a car with a really loud exhaust next to me. No other cars in sight...it was mine.

 

OK so I'm not crazy!

The rooster tail thing doesn't fit because it happens at low and high speeds....creative theory though!

 

I've also notice this... And it gets louder (and more "weird") when the A/C in on...

At least, I'm not the only one

 

I noticed this on my MC before I changed to the
MiniMania (aka Ultrik) CAI.
I figured the resonator box got waterlogged and
temporarily changed the intake (not exhaust) sound in my case.

 

Sorry, I didn't see anyone write that!

 

Yes I noticed it as well.
My theory is that with the water all over the surrounding surfaces, it is making the sound bounce off the the object rather than the object obsorbing some of the sound.Kind of like the effect of a room with hardwood floors compared to a room with wall to wall carpet.

 

Try this, especially with a performance exhaust- With a garden hose, stick it in the exhaust tip and turn on the water- fill up the exhaust system with water until it cant hold any more, and then start the car- it initally belches out a crapload of water, then drive- loud as hell! Good times...

 

"Pipes grow several inches." SEVERAL INCHES? , how could I have missed this until now. I often drive with PDXmini, and while my MCS may not be "hung" with an aftermarket exhaust, other member have various high perf exhausts, and i have never noticed their pipes extending by "several inches".
It borders on sexual harrassment!

 

I looked up exhaust expansion and found that it's more like 2-3 cm of growth in length. It's significant enough that slack is designed into cold exhaust systems so that things do not hit when hot.


GT6, you're right, no one said I wasn't crazy....they only confirmed that they are as crazy as me.

 

er, I will take your word for it....

B

 

You've got it - it's the acoustics. Everybody else here has been smoking some funny stuff.

 

I've had the same experience with the louder exhaust noise when raining heavily. At first I even thought I might have put a small hole in the exhaust at some point. Glad its not that

Anyhow, it does seem like additional resonance from the water to me (now that I know its not a hole )

 

[QUOTE][You've got it - it's the acoustics. Everybody else here has been smoking some funny stuff. /QUOTE]


Why doesn't it happen to other cars then?

 

Just thought I'd post a follow-up on this since I was cleaning up my thread subscriptions.

I exchanged my stock exhaust for a Milltek and get a similar louder exhaust noice during hard rain. Seems to support the acoustics theory, but no explanation as to other cars not getting the same noise.

Maybe cat / flex / header related?

BTW, the Milltek also grows a couple of cm/in when hot, as posted in this thead for the Magnaflow. Check my gallery if you want proof.