Flapping/ Growling/ YARRR from engine, mature semi-educated post. lol
 

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 shit 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.

Ideas?

Sound I was talking about.

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

Going through the gears.

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

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?

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?

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?

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.

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.

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

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?

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.

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.

Wow.........just wow! :suspect:

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.

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

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?

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.

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.

The part that confused the shit 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.

http://www.autoexe.co.jp/car/Axela(B...m957ximage.jpg

http://www.autoexe.co.jp/products/s_...957xtanpin.jpg

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.

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.

/\ what they said

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.

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

The noise could be vfad related ...

Try diconnecting the vac line to the vfad and see if thaT CHANGES ANYTHING .

We read all the forums before buying one, she redlines it at least once a day after it is up to temp, and she rarely ever drives it in AT mode.

I just went out, did an ECU reset and checked the intake/ airbox. There is nothing that can be flapping, and it is not resonance. I know for a fact that it is going to make the same noise just quieter, once the intake is back to stock. After doing the ECU reset and checkover, i made an attempt to get it real hot. The car got to the point where it had little power, made the noise even as low as first gear and 4500 rpm. It sounds incredibly thrashy. It had a loping idle, and was making an odd quiet sqeaking noise. I let it cool down for 10 minutes, and went out for a 3000-4000 rpm highway drive to get some air through it again... The idle came back to normal, the squeak went away, yet it still made the noise. And last night we were able to get the noise to go away completely... Hmm.

I dont have a stock lower half of the airbox to put on right now, or I would. However, I can almost guarantee it is not that problem.

This is driving me nuts, and now she wants to trade it in for a Miata. I feel bad for getting her into a car which is having odd problems.

And obviously plug it at either end correct? Should I leave the electrical plug on the VFAD control which is mounted on the airbox plugged in?

All you would need to do is disconnect the vac line for the VFAD, behind the throttle body, and cap the fitting.
Then tie the hose off to the side so its not dangling around in the engine bay.
The electrical connection for the solenoid can stay in place.

Just to let you know... by doing this you are allowing the VFAD valve to stay open at all times, so the car will sound louder at lower RPMs.
But it won't harm anything.

i'm not too worried about the sound.

When installing an AEM/ K&N/ etc. intake you would have to do this anyways, correct?

I'm going to try this, and will report back in 20 mins.

Yes... you cap the nipple behind the throttle body also.
But for you, there is no need to remove the hose... just tie it off to the side so its not dangling.

Also - someone suggested it could be the panels in the airbox vibrating . Check this as well by removing them .

You think its better to shove a screw in the hose instead of simply capping the nipple behind the throttle body? :scratchhe

/\ if you have the right cap - no . Who has a cap like that on hand though ? ;)

LOL... I guess some people may not know you can get a variety pack of vacuum caps for a couple dollars at Autozone :dunno:

heh - correct

Capped the VFAD line and removed the panels from the airbox. no dice, same result.

The only things I have not done yet are new plugs/ OEM bottom half of the airbox, for the simple reason that I do not have them.

I notice that the engine bay is crazy smokin hot, I know rotaries run hot.. But i mean this is hot. The coolant temp guage reads normal.

WoW!?!?!?!?!

As started go back to stock and see what happens. Mazda designed the 8 airbox very very well and I can not understand why you would take the VW guys methods into consideration. If your looking for sound then buy a RB or AEM intake new or used in the for sale section (Intakes are available a lot). But before you do anything go back to the stock set up.

One thing you might want to remember is that Mazda designed almost very component on the 8 very well. So well that it's a bitch to gain Hp with simple bolt-ons. Gaining more then 10+ in terms of Hp or Tq is almost impossible without going FI. Sound will not make the car go faster. You have to pay to play , there are no short cuts.

Hope you learn from this mistake. Good Luck

Just went for another drive at higher speeds trying to get some air through the front of the car. It would only keep making the noise, and with the panels in the airbox out... It has never been thrashier.

At this point I give up. We'll be looking for a stock bottomhalf of the airbox for the car, and she'll just have to live with the fact that it does not make as much intake noise.

Her brother is a mechanic, and we're going to get him to do the airbox/ plug the VAFD back in/ plugs/ oilchange/ and rear diff fluid change as the LSD is chattering under low speed parking lot cornering.

As previously stated, with the intake we were looking to gain no power.. Only sound. If mazda designed the car so well, why could'nt they get it to make some real power while getting V8 fuel mileage.

I guess thats why it's her car, and my wagon has a turbo. Thanks for the help guys, if you have any other ideas.. I'll be inclined to hear them out.

Oh Boy.......................... I'm not going to touch that remark I'll let someone else do it LoL

Oh, and before you go have some else work on the the car look at the DIY and printout the info you need to do the repair the right way the first time. Better yet you should try to buddy up with some of the guys in your area that have knowledge in the 8.
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So then you should have done your homework and read through the threads on this site to achieve that.
Plugging the VFAD fitting to keep the valve open at all times is one way to achieve that.
Another is to remove the resonance chamber and plug the opening.

Because a "well designed car" isn't always about HP... only teenagers and people who jerk off to the "Fast and the Furious" movies think that way.
Take the RX8 to an auto-cross event or down some windy roads and you'll understand why the RX8 is in fact a well designed car.

And this is also why the whole intake setup is so complex with SSV, VFAD, APV, and VDI valves.
Because Mazda tried to get as much out as possible from this little 1.3L engine while still complying to federal regulations.

^ :yesnod:

sorry guys.. Did'nt mean to offend any of you. It is a fantastic car down a windy road I will agree. Engine and exhaust wise it is stock, cass just wanted some sound out of it so I made it a sri. Worked well on my ms3 until I ordered all my corksport goodies.

I'm not offended because you're entitled to your own opinion, just didn't want your views on "well designed cars" to be skewed and limited to one category.
Most people here are fine with admitting that our car isn't made for the drag strip, but unfortunately we are constantly paraded by individuals who want to turn it into a "drag car" with minimal effort, money, and experience.

Best thing you can do is what I mentioned above, an aftermarket intake like the AEM or Racing Beat, and/or aftermarket exhaust setup.

There was a theory thrown around a while back that the squeaking noise you describe may be a sign of a bad coil. I haven't read of any verification of this but as I re-read through your posts, it seems to me you may have a classic "weak coil" situation and you are certainly within the mileage range where it is rather common for coil failures.

I do not want you to buy anything, especially something as expensive as our coil kit, on a mere hunch as you may have a few concurrent problems. At the same time, we do know that the BHR Ignition System is a definite improvement over even brand-new OEM coils so if it is something easily affordable, you may want to place it at the top of your list when the current issues are resolved or bad coils are shown to be the cause.

Tell her to hang in there and we will all sort this out so she can resume enjoying her RX-8. :)

Hi Charles. I have seen your BHR Ignition system before. Can you briefly describe the benefits over the OEM?

You should have called me .....I'm sure I've got one around here....I have all my RX8 and MX5 OEM removed parts.

Brian, I'll be in touch... Once I can find your phone number again. I changed phones and lost all my contacts.

Thanks for the help gents, i'll let you know the airbox related outcome.

Out of cursiousity, the diff is starting to chatter under low speed cornering too. Parking lot sort of setting..

I imagine the diff uses 75w90, which I have already.. How much friction modifier should it see? The car is the GT (CDN car), so it has the LSD and good stuff from the factory.

Or with 38,000 km... Should I just add a little more FM to make the chatter go away.

Plugs will be done tonight by me. I had Cass call the dealer and we forwarded Larry the Service manager the Youtube videos. He figures its plugs. After I change plugs, and everything is back to OE the only other thing to do is take it in and have them work with it if the car does not co-operate.

FWIW - Incase someone else has monkey'd with the car before us. What is the correct Coil to Plug wire combination. I've read that the trailings can be backwards and it'll still run, only poorly. True?

Thanks again, and Brian I'll give you a shout after work.