Not really an issue (I believe) but just curious as it has happened twice. First time we had a lot of rain (to the point of there being decent sized puddles to drive through... my exhaust got significantly deeper toned and loud (actually like the sound) and I figured I might have an exhaust leak but it shortly went away. Well, today we had heavy rains again and after driving through a portion of the road with decent sized puddles the same thing happened. I wasnt far from where we were going so once I got the parking lot I revved a couple times then got out and had my g/f rev it... didn't sound different anywhere but towards the back... so nothing from the cat area or anything. Again, it went away. The first time it happened I thought there might have been a crack or something but the fact that it goes away leads me to believe that's not the case.

So.... I'm sure the answer is simple, but what is/could be the cause of this?

this would be a perfect call for "cartalk"....i could just hear the snickering...

snicker snicker

am I missing something? :uhh:

your ears are probably just playing tricks on you

nope.

with my last midpipe it did it too.

beers :beer:

hmm, very strange.
maybe echo off water?

Time to call Agent Molder.

am I missing something? :uhh:
your brain apparently






LOL j/k.....maybe....:squint:

your ears are probably just playing tricks on you

someone else was in the car both times and noted it... plus it's quite hard to miss... doesnt sound even close to the same... the difference is quite significant.

hmm, very strange.
maybe echo off water?

it continued once the car was parked as well...

nope.

with my last midpipe it did it too.

beers :beer:

I do have the RP supercat... my thought was that it would have to do with thermal expansion/contraction but for some reason I'm led to believe that would cause a crack if it was the reason.

wow thats so wierd... I've never heard of that happening on any car

I've noticed something similar up here when it gets colder out. It's more noticable in my 7 then the 8 but either way I don't really care it isn't a significant change just gets a little deeper.

Things that make you go HMMMM......
(bonus points to the person who knows what that's from)(

Nothing unusual. Cold or damp air is dense. And dense air carries the sound better.

I need it to rain here so I can see if I hear a difference.

NO!!!! no rain allowed here.
It'll mess up my perfect zaino job.

as long as it doesn't mess up sevenstock ;)

Things that make you go HMMMM......
(bonus points to the person who knows what that's from)(

C+C music factory?

o_O i asume that it was just a temp leak from the rapid cooling. Mine did that i was driving though deep water and heavy heavy rain (couldnt go over 30 on a hwy). i currently have gasket glue on now to seal mine.

I also have a mid pipe still hot down here

I have RP HF cat on my car and ive noticed the same increase in volume when there is heavy rains down here. It happens maybe 3-4 times a year....I just presumed it was the way the sound was bouncing off the water. Never thought too much of it as it goes away when the rain recedes.

I've noticed after washing my car using those pressure washers when I drive away from the car wash the exhaust note has definitely changed, after a minute or so it goes away. I figured it was the cold water on the hot exhaust pipes causing the weirdness but it doesn't seem to affect anything that I've noticed.

Nothing unusual. Cold or damp air is dense. And dense air carries the sound better.

that may be true but it only happens after puddles pretty much... if the air were the only cause then it would have continued when I went back out 30 min later.

o_O i asume that it was just a temp leak from the rapid cooling. Mine did that i was driving though deep water and heavy heavy rain (couldnt go over 30 on a hwy). i currently have gasket glue on now to seal mine.

I also have a mid pipe still hot down here

that sounds like the best answer... my only confusion about that solution is where the extra noise should come from. My ability to locate it specifically could be off but I'm rather sure it was coming from the exhaust pipes (that is to say it didn't sound like it was coming from anywhere along the exhaust pipe or any of the joints between pipes). This explanation is the one that came up first in my line of logic but the fact it didn't come from along the exhaust path.

So if it is a leak, should the sound come from the area of the leak?

when I had my RP supercat I experienced similar issues. I mostly experienced it when I would drive through puddles only during heavy rains. at first I thought the same thing (exhaust leak) or somehow water was getting inside the muffler or cat. in any case, it didn't happen all the time, it usually went away after a few minutes, and I never had any problems arise because of it.

Has Agent Scully reported in yet?

thing that make you go hmmmm=Arsenio Hall show........"lets get bizzzzzyy"

Taking a wild guess here:
When you lower the car, I think the exhaust note gets a little deeper. I guess it's kinda like getting a deeper bass when you situate your subwoofer in a corner.

When you go through a puddle, effectively, you're lowering your car for a moment.

people keep missing this detail: once I go over the puddle it stays. I pulled into a parking lot that was wet, but there was no puddle to speak of and the effect stayed.

Not really an issue (I believe) but just curious as it has happened twice. First time we had a lot of rain (to the point of there being decent sized puddles to drive through... my exhaust got significantly deeper toned and loud (actually like the sound) and I figured I might have an exhaust leak but it shortly went away. Well, today we had heavy rains again and after driving through a portion of the road with decent sized puddles the same thing happened. I wasnt far from where we were going so once I got the parking lot I revved a couple times then got out and had my g/f rev it... didn't sound different anywhere but towards the back... so nothing from the cat area or anything. Again, it went away. The first time it happened I thought there might have been a crack or something but the fact that it goes away leads me to believe that's not the case.

So.... I'm sure the answer is simple, but what is/could be the cause of this?

My Theory:

I do know your exhaust will have a different "tone" when hot versus cold (at start up) - you tend to notice this on aftermarket/louder exhausts, but not so much on a stock system.

I think the rain is throwing enough water on your exhaust to keep it cooler than usual and thus a different "tone" than you are used too is being emitted.

people keep missing this detail: once I go over the puddle it stays. I pulled into a parking lot that was wet, but there was no puddle to speak of and the effect stayed.

If many people missed that detail, it likely is a problem with wording, not a comprehension problem.

Anyway...
You must have sensitive hearing.
Perhaps the effect is not unlike the acoustic change experienced after snowing, which absorbs sound waves. Most people can sense that, but I'm not sure about sound affected by wet surfaces.

did a lil googling and it appears that it does happen to other cars as well.

maybe it's the cold water from the rain. maybe the splash drenches the exhaust and causes the metal to slightly expand and contract differently altering the exhaust flow. and it stays that way until the heat dissipates the water.

:dunno:

I know this is an old thread..... Did you ever find resolution to this issue. I have the exact same thing with my 09. http://www.rx8club.com/showthread.php?t=204354

I never did. I assumed it was something like an exhaust leak that formed or something. Mine wasn't really a rattle, it was almost like I had an entirely different exhaust installed.

When I made this thread, I had the racing beat dual catback. The volume increase was almost as significant as when I changed the RB catback to the HKS single. Not quite as loud as the HKS, but pretty close. It had a much deeper tone than that, though. I honestly thought a truck next to me had a loud aftermarket exhaust, at first... then I realized it was actually my car making the sound.

http://www.school-for-champions.com/science/sound_over_water.htm

Since the temperature of the of water in a lake or ocean is usually cooler than the normal air temperature, the air just above the water level is cooled by the water. The temperature varies according to the distance from the surface of the water. This gradient of speeds would result in a lens effect due to refraction of sound. That means sound would tend to focus and thus increase its apparent loudness.

Cool air bends sound and thus increases amplitude. It is a strange effect that follows the principles of sound and wave motion.

I assumed that most people knew this... Hope it helps.

So the moral of the story?
Come to DGRR 2012... lol

I never did. I assumed it was something like an exhaust leak that formed or something. Mine wasn't really a rattle, it was almost like I had an entirely different exhaust installed.

When I made this thread, I had the racing beat dual catback. The volume increase was almost as significant as when I changed the RB catback to the HKS single. Not quite as loud as the HKS, but pretty close. It had a much deeper tone than that, though. I honestly thought a truck next to me had a loud aftermarket exhaust, at first... then I realized it was actually my car making the sound.


Same boat, I thought it was a straight pipe m/c riding next to me in the down pour. I am stock with intake and exhaust. My dealer has an open call for me to stop by when it is doing it.

http://www.school-for-champions.com/science/sound_over_water.htm



I assumed that most people knew this... Hope it helps.

So the moral of the story?
Come to DGRR 2012... lol


I am well aware of this but in my case it is not the issue. The noise in my OP, is recorded while sitting in a dry hangar at work. Still get the rattle noise as well as the much deeper tone until it dries up. In my case it took about 5 minutes for the sound to go away while sitting in the hangar. Also, the roads can be just wet, go over standing water at 50 and the sounds comes and stay there for a while. It is NOT sound amplified over water.

I am well aware of this but in my case it is not the issue. The noise in my OP, is recorded while sitting in a dry hangar at work. Still get the rattle noise as well as the much deeper tone until it dries up. In my case it took about 5 minutes for the sound to go away while sitting in the hangar. Also, the roads can be just wet, go over standing water at 50 and the sounds comes and stay there for a while. It is NOT sound amplified over water.

I wasn't replying to your rattle... I was commenting on 8 Maniac's post referring to his RB exhaust being louder in the water.

I wasn't replying to your rattle... I was commenting on 8 Maniac's post referring to his RB exhaust being louder in the water.

Gotcha, sorry 'bout that. Just wanted to make sure that I give as many details as possible.

It's been a while now, so I don't remember exactly, but it wasn't after every rain and it wasn't specifically over puddle when the change in sound was noticeable. The parking lot I had pulled in didn't have any standing water, though it was wet. I've been in that lot many times while it's raining or has been wet, and it never had the same effect.

That's why I believe it's not an issue related to changes in sound reflection from the environment, but something that was causing a temporary change in the actual exhaust sounds. It only started during heavy rain (enough for water to collect on the roads) and persisted in areas with no standing water and after the rain had slowed or stopped. It never started with light rains.

Hiyas maniac, but I had the same situation as you. I noticed it only when it rain really hard, and the hollow noise would come the mid of my car it seem. Every time i press on the gas, it would make this deep hollow noise.

heh for mine. it was with a cheap catless pipe, the front copper gasket was leaking slightly, didnt have this issue after when i got the racing beat mid pipe and new gaskets. same noise as when one of the rear spring loaded bolts on the rear of the mid pipe came loose.

I miss my rx8 sometimes lol

Then it seems like czar's explanation about different thermal conductivity of stock exhaust component mating with the aftermarket exhaust component causing a temporary leak, is the best candidate yet.

Wild speculation follows. Don't laugh.

I'd expect the air at the top portion of the exhaust to be relatively drier than on the bottom due to heat rising and the absence of ambient air due to the floor. On a rainy day, perhaps the ambient air below the exhaust emphasizes the difference and causes the exhaust pipe to arc like a bow. And since the stock exhaust component is different metal, it bends differently, causing the mating seam to open up a crack?

I've started noticing a deeper tone on my exhaust. This is my first winter with my 8 (well I live in northern California so I might actually be exaggerating with the term "winter"). Anyway, my 8 is completely stock and up to date maintenance. Since the heavy rain and colder temps my exhaust has been deeper but as far as I can tell the change in tone is coming from the back. I guess my questions are mostly geared to 8 Maniac:
- did the issue resolve it self?
- did it ever lead to bigger issues down the road?

I realize my situation might be different since my care is stock but I wanted to give this a shot. I also could just be paranoid. I've only had my car for 7 months and am still learning. Sorry for the thread bump and thanks in advance for your replies.

The "issue" would go away before I'd finish the drive, usually. I think it may have been there once when I turned the car off. I don't think it ever lasted 30 minutes. Also, the change was somewhat sudden. I had always been driving around prior to the change and then suddenly it would get deeper and MUCH louder. Like I mentioned... The first time it happened, I thought it was a truck next to me with a loud exhaust. It took me a few minutes to realize it was my car. Someone was with me at that time and they didn't even notice it was my car.

I think it's fairly normal to hear changes in tone with significantly different temperatures, which is what I assume you are hearing. My car ended up needing an engine replacement after I sold it, but I seriously doubt that was related to the exhaust sound issue. The car had relatively high mileage for an 04 and it had a lot of miles on it since I originally had this issue appear.

lots of speculation here...

I have a stock exhaust and same happen when it rain / the road still wet..

so I think it's more related to sound deadening stuffs..maybe it lost it's ability/purpose when wet?

I read on other thread that there's some kind of a layer of metal sheet underneath that act as sound deadening..

Not sure about this so..calling sound deadening expert..

your ears are probably just playing tricks on you

lmao ^

snicker snicker

a well deserved razzing ... :lol2:

Higher humidity. Coarser sound.

Maybe a little more incomplete combustion due to the wet air.

what kind of exhaust are u running. i know when i had the greddy sp2. warm days it would seem mild then on cold days a litttle louder but when it rains it seems like the sound just got like some turned the volume up. but i really think it has to deal with how dense the air quality is at the time.

A long time ago, a friend of mine was experiencing this same issue. After much head scratching and speculation, we began to experiment. To make a long story short, I'll just get to the final experiment... We intentionally put water into the tailpipe and viola! We replicated the change in the tone of the exhaust sound. It is water in the muffler that causes this phenomenon.

These are the hypothoses that we came up with... Varying water levels in the muffler cause the total atmospheric volume of the muffler to change. There are several variables that affect the amount of water in the muffler such as: humidity, tire spray from road surface, splashes from puddles, etc. etc.. Even where the water is in the muffler as the car moves, turns, hills, acceleration/deceleration and what not, can change its resonant properties. As the temperature of the muffler increases, the water evaporates and changes the resonant properties as the water level changes. When the water is at a certain level combined with the muffler (and exhaust gases) at a certain temperature, the water may boil, thus causing a drastic change in exhaust pressure which will also change the resonant properties.

Hope this helps to bring everyone some resolution.

thanks for the replies! it's definitely been wet here in the bay area. my 8 runs the same except for the deeper exhaust tone. definite head scratcher but i'm glad to know it's nothirng that serious.

The only serious issue would be possible rusting and subsequent holes due to said rusting.

Hey guys, I have a similar problem with rain...
The faster I drive, the harder it rains. I'm serious. It's like I control the rain cloud with my gas pedal. I have to click my wipers to a faster speed the faster I go.

It's crazy. Seems to happen in my other car, too, so maybe there's something defective with both of them. Do I need a new windshield? I hope its not the engine going bad.

I filled my muffler/exhaust with water on a couple of occasions to steam clean my exhaust. It got louder:Eyecrazy:

Holy four year old thread Batman!

I filled my muffler/exhaust with water on a couple of occasions to steam clean my exhaust. It got louder:Eyecrazy:

Holy four year old thread Batman!

Steam cleaning? Who cares? I control the weather with my accelerator. What about my problem?

Steam cleaning? Who cares? I control the weather with my accelerator. What about my problem?


You get bigger problems!

Hope I dont get banned for this but.

He hates you!:squint:

multiple reasons, the most significant one (in my opinion at least) would have to be..;
rain droplets- as the sound waves travel away from the source, rain droplets in the air refract some of the waves back away resulting in hearing something better than when its not raining as more of the sound wave is being reflected back towards you. the heavier the downpour, the more droplets, the more sound you will hear. (this concept can be observed when comparing a noise in a open field and then again at the same volume in a enclosed environment like a bedroom or inside your car. the waves will hit the walls and come back creating the illusion of it being louder)

hope that makes sense and helps
edit: nevermind, saw a super thread revival.. lol

You get bigger problems!

Hope I dont get banned for this but.

He hates you!:squint:

inorite?

multiple reasons, the most significant one (in my opinion at least) would have to be..;
rain droplets- as the sound waves travel away from the source, rain droplets in the air refract some of the waves back away resulting in hearing something better than when its not raining as more of the sound wave is being reflected back towards you. the heavier the downpour, the more droplets, the more sound you will hear. (this concept can be observed when comparing a noise in a open field and then again at the same volume in a enclosed environment like a bedroom or inside your car. the waves will hit the walls and come back creating the illusion of it being louder)

hope that makes sense and helps
edit: nevermind, saw a super thread revival.. lol

Nerd.