dynamho

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.

8 Maniac

iTrader: (1)

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.

Jax_RX8

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.

dynamho

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.

NgoRX8

iTrader: (1)

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.

bhammer

I know this is an old thread..... Did you ever find resolution to this issue. I have the exact same thing with my 09. https://www.rx8club.com/series-ii-technical-trouble-shooting-160/strange-noise-204354/

8 Maniac

iTrader: (1)

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.

reddozen

iTrader: (1)

http://www.school-for-champions.com/...over_water.htm

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

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

bhammer

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.

bhammer

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.

reddozen

iTrader: (1)

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.

bhammer

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

8 Maniac

iTrader: (1)

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.

alfy28

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.

czar

iTrader: (3)

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

dynamho

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?

a12chan6el

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.

8 Maniac

iTrader: (1)

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.

tonik

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..

chickboiii85

lmao ^

TeamRX8

iTrader: (25)

a well deserved razzing ...

Are-Ex-Eight

iTrader: (1)

Higher humidity. Coarser sound.

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

sauceyI986

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.

Joe-the_tattoo_artist

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.

a12chan6el

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.