cstishenko

Hey guys, fairly new to the forum..

We've got an 06 6 port 6AT RX8 with 38,000km and it's making an odd sound.

It is a sound that has gone unheard, until we put an intake on the car. I've read about MIAC, and the coolant restrictor. It is neither of those issues. In neutral while revving it up it sounds wonderful, no sand in a blender, no MIAC. There is definately no detonation either, I have a MS3... I know what that sounds like :p

The car always runs good 94 Octane fuel and Mobil 5w20 with ambient temps around 10-20 celcius (50-70*F)

The sound cannot be heard in first gear. In second gear and up, it sounds like a flapping raspy sound coming from the intake anywhere above 5500 rpm. Now, if you press the throttle to WOT and let off repeatedly you can sometimes get it to clear up and sound proper. Which I find weird.

While it is making the sound, it seems to have a little less power too. I've read my fair share of posts now, and users are saying it's everything from poor fuel, to plugs/coils/wires, to my engine is toast. I'm looking for some real advice before spending real money.

Now, the car does not have the MSP16 update done. There are no stickers in the enginebay/ under the hood/ door sills. We have not spoken to the dealer about whether it does or does not, as they are hard to deal with.

Before the intake, we did not hear it. Now it's audible, and it's bugging the **** out of me.

I'll also be doing the Coolant Bypass mod for the Throttle Body soon aswell.

Thoughts? Ideas? Where Should I look? I'll post up a youtube vid of the sound as soon as the weather clears up a little.

cstishenko

Ideas?

cstishenko

Sound I was talking about.

http://www.youtube.com/watch?v=BZr_lPjnsIA

cstishenko

Going through the gears.

http://www.youtube.com/watch?v=h1wn86c4tiY

cstishenko

And to mention, it is definatey heat related. Before the needle reached half, we would it out through the first three gears and the sound WAS NOT there... So we're not sure.

Anyone have ideas?

cstishenko

Replaced Coils and Wires. Did not get a chance to do plugs, and did not want to yet as theyre non returnable items.

Coils and plugs DID NOT help. Can anyone else help me?

Mazurfer

What is the intake you put on?
How many screens are you using?
Have you checked all the hose connections and made sure they are all good?
When you put on the intake, did you remove the VFAD?

Put the old one back on and see if it goes away?

cstishenko

The intake is actually a K&N panel filter, with a hole cut in the lower section of the airbox for a bit of sound.

So in other words, consider the car to be stock.

cstishenko

So, Could this be something to do with the VFAD? It sounds to me like the cars can sometimes be finnicky without the VFAD functioning properly. Some say uninstall it completely or leave it stock.

cstishenko

We also use 5w30 non synth oil, and 94 octane.

cstishenko

went for a drive tonight and after about 10 mins on the highway at 120 km/h the noise went away completely! I could not get it to duplicate the sound even after repeated hard pulls through 2nd and 3rd.

got back into town, went for dinner and guess what? Its baaaack. This would tell me its likely not mechanical?

Jon316G

iTrader: (1)

So you say the sound didn't occur until you put in an intake (which later you claimed its just a K&N filter).
Have you tried to go back to the OEM filter to see if the noise continues?

Then you said, "with a hole cut in the lower section of the airbox for a bit of sound".
Please tell me I somehow read this wrong and you didn't actually cut a hole in the airbox itself.

And don't try to blame other components like the VFAD... if it worked before you messed with it, chances are good that its something YOU actually did.
But if you really want to go chasing intake valves, I know a good DIY on checking the valves that'll keep you busy
Seriously though... I would "undo" everything you did and see if the sound is still present.

invasion08

iTrader: (7)

Its the hole you cut into the lower section of the airbox. You wanted a bit of sound? Well now you got a bit a of sound and you do not like it. I bet if you fix the hole you cut, the sound will go away.

Mazurfer

Wow.........just wow!

cstishenko

like a swiss cheese airbox, many guys in vw culture do it for a little bit of added sound.

there is no reason why it should make such noise with merely an open element air cleaner.

what your telling me is that with any SRI it is going to do the same.

keep in mind it is heat related. Hotter it gets, the more the sound is there.

cstishenko

we did not have the sound before with the intake being stock because it has been rather cold until recently. We bought the car in december! I've had the hole in there since later jan. Once it got hot out, it happened so I don't think it can be blamed on the intake.

last night I don't think it did it because doing 100 for 10 mins in the countryside means ambient temps of maybe 8 degrees celcius. We haven't seen over 20 C

invasion08

iTrader: (7)

Well if you do not think its the hole you cut into the airbox, try fixing the hole first and see if the noise goes away. If it does not go away then its not the hole causing the noise and if it does then it was the hole. What is good for the VW people does not mean its good for the RX8 people.

Would you be able to take a picture of your airbox so i can see what you really did?

cstishenko

With the intake modification, it has only made the noise since it became warm out. There was no issue before.

The only thing i could think of is that the two panels that you can unscrew from within the airbox lid are rattling?

I'll post a pic when I get a chance to snap one, and put the airbox back to stock as soon as I find a new lower half to borrow.

Mazurfer

I would guess that it MIGHT be the disruption of the airflow caused by the holes, but only one way to find out for sure.

cstishenko

The part that confused the **** out of me is that it went away completely when we were on the highway last night.

Got back into town, got it upto temp... Boom the noise was back. It is something heat related.

And being that it is heat related, this is why it would'nt make the noise during dec/jan/feb too. It's been progressively getting worse, but it has also been getting progressively warmer too.

My dealer is confused as hell too, as no matter how many holes are in the airbox... It should'nt make that noise. The holes in the airbox just make the noise very apparent.

It is basically the arc/autoexe modified stock airbox i've made.

Charles R. Hill

iTrader: (7)

I don't think it good social graces to argue with the very people who have been around this car for a LOT longer than you have when they are trying to help you. If you think weird sounds after modifying anything on the intake of the RX-8 is a new concept around here, think again.

The intake system on the Renesis engine was designed for maximizing airflow and minimizing resonance and noise. Mazda spent TONS of money to make the Renesis a smooth, quiet, engine and their efforts have likely been undone for very little money and even less forethought.

If there is ANY area where the RX-8 needs no help, it is definitely the intake system and it is best to leave it alone.

Easy_E1

iTrader: (2)

You should have heard my 4port AT with the AEM. That was some funky sounds there.
I think your just hearing a frequency resonance change in the intake.

Brettus

iTrader: (2)

/\ what they said

cstishenko

The problem is that this is not my car. It's my live-in girlfriends. She understands everything about warmup, oil quality, fuel quality and driving style with the renesis. However, I don't drive it much until there is an issue.

Thanks, I will take your advice and get it back to stock asap... However, I personally do not see how modifying the intake could create such a noise.

Create a loss in performance? Most likely. The girlfriend just wanted some extra noise out of it, unfortunately it has turned into an undesirable noise.

Now i'm asking this, so I can take a look elsewhere while waiting for a new lower portion of the airbox from my dealer.

Are there butterfly valves or anything in the intake manifold that are solenoid activated? I'm thinking as it gets hot, something may be malfunctioning causing it to make the noise. It seems as though when it is done making the noise it picks up a little power.

Watch the video and think of everything it could possibly be, you all know these cars better than I. Keep in mind it is definately heat related. The car operates perfectly in every way, except for this noise at WOT from 5000 rpm - 6500ish.

We have had a CEL in the past, however it went away on it's own within the same day. I have no way to check it, and the AccessPort from my MS3 won't check cel's on the rx8.

I'm going to change the plugs, just to be proactive with this project. And do a reset of the ECU to see if that helps. If we can get this problem nailed, we may even be interested in a set of your BHR coilpacks to increase reliability.

Easy_E1

iTrader: (2)

How often does she redline the car? Does she drive in AT mode or Manual?