Ok guys. I have experienced a strange sound like when getting crushed ice from a fridge when driving during rain. I feel the sound coming from the drivers side, middle of the car ish. It only does it when I press the accelerator as soon as I raise the pedal it stops. Touch the accelerator again even slightly and the noise comes back again. After a while, it disappears.

I experience it today after driving through a puddle and about a month ago during rain as well. No CEL during the condition, car runs and starts fine.

Spark plugs replaced last Thursday. Radiator flushed and using water wetter about 6 months ago. Seafoamed a week ago.Transmission oil and diff oil changed about 6 months ago with Amsoil 75w-90 GL4 and GL5 respectively.

What could be causing this issue / sound?

My Rx8 is a 2005 MT with 61k miles. Mods in my sig. Premix 5 qts of Amsoil Saber Pro every fill up with 93 octane. Pulls strong.

 

Best guess is that it's your intake sucking in water that is trying to get cleared up.

 

That makes sense since I'm using the Revi ram air duct. It just scares the **** out of me cuz I don't want this engine to die.....not now at least.

 

might want to read the thread that's been floating around regarding WW...

 

errr....what's WW? can you point me to that thread?

 

https://www.rx8club.com/rx-8-discuss...nation-238912/

 

I run WW with straight water and don't have that oily type gunk in my cooling system.

 

Yup, you are fine. It is coolant + water wetter that is the problem. I was going to comment on it in my first post till I realized that you are in PR, and probably never see freezing temps to worry about having to have coolant.

 

Correct, that is why I removed it. Coldest I see here in the caribbean is mid to high 70 degrees. All my cars run straight tap water with WW and I check the PH often, if it's not pink-ish I add a little.

However, next change I might try this one.

AMSOIL - AMSOIL Dominator® Coolant Boost (RDCB)

I'm becoming an Amsoil freak, lol.

Back to topic.

RIWWP, I checked the filter box to TB intake tube yesterday after your post and it was bone dry. If it did suck water, anything left evaporated while the car was sitting there. Anyway, I cleaned the MAF, just in case. Im going to remove the plugs this thursday to check em after a week of regular driving and also check the rotors for any carbon buildup, wetness and such.

Any other possibility? What type of symptoms do damaged mounts create? I feel the noise coming from that area in the drivers side.

 

Damaged motor mounts make idle vibration worse, usually if you turn on the AC and the vibration goes from poor to bad, it's motor mounts.

If you ignore the water component, the other possibilities are chewing apex seals (doesn't seem like it from your description of the engine behavior) or intake valve fluttering (again, doesn't seem like it).

 

Yeah, that's what I was hoping not to hear. But why during wet contitions only? Car starts fine and pulls fine to 9krpms.

Ok, so I'm going to hold on to the spark plug verification and do a compression test this weekend with a regular tester.

I downloaded the RX8 Compression Calc Android app, which I belive someone from this forum made, to get the corrected results. Neat app BTW.

 

Yeah, I don't think it's anything other than the water. Underhood temps usually sit around 180-200F, so it will evaporate any water pretty quick. Anything else that makes that kind of noise would also be messing with your power delivery, and will do so regardless of wet or dry. That you have an aftermarket intake further improves the likelihood of just some water ingestion.

 

RIWWP, confirmed....must be water ingestion. I was driving right now under heavy rain and the sound came back....heavily. Lift the throttle and the sound is there but barely. Arrived at my destination let the car idle until sound dissapeared. Rev it a couple of times and shut it down.

Wow...talk about effective intake. How can the water get past the filter so easily?

 

Easy. Low pressure from the engine on the internal side of the intake, higher pressure outside, tries to suck stuff in. Water molecules are bigger than air molecules, but still smaller than the filter gaps.

Be wary of anything your bumper doesn't completely clear, even a wave of water hitting the filter wrong and you could ingest enough water to crack the block. It's been known to happen more than once. Always water to the splash pan or higher, always an aftermarket intake. Volume of water for 1 face is larger than the capacity at full compression and the uncompressibility of water plus the force of the car's weight with engaged drivetrain moving forward is enough to crack the block.


For reference:
https://www.rx8club.com/rx-8-parts-s...e-asap-196770/
https://www.rx8club.com/trouble-shoo...ed-8-a-222466/

 

I've had no problem with my RB duct + stock intake box. For a little extra insurance, I enlarged the drain holes at the first bend in the duct as well as the holes upstream of the filter in the airbox. If you're using an intake other than stock or RB, there's less space for the water to drop out of the airstream before passing the throttle body.

 

Thank you RIWWP and HiFlite999 for your comments.

RIWWP. As soon as it started raining heavily I turned off the radio and AC to confirm it was water ingestion. I drove the car as careful as possible once the noise started since I was afraid to break it. I lifted the pedal a couple of times and barely touched it to keep it moving. Definitely, no puddle swimming for this 8.

Thanks for the tip HiFlite. The Caribbean isn’t always sunny, we get a lot of rain too. So, I will need to do similar mods to my RB ram air intake. What about installing one of those filter socks? Will that help?