[Renalicious]

Ok, as promised, I went up to the local mountain today with my Edirol and did a couple of quick passes to record the ever-o-so-described rattle caused by light weight single mass flywheels. In this case it is the newly installed RS Barn flywheel, new clutch, etc. As a bonus, we hear a well heated stock exhaust as well.



check below for new sounds.

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[Scott Collins]

[quote name='Renalicious' post='37306' date='Jun 21 2007, 09:21 PM']Ok, as promised, I went up to the local mountain today with my Edirol and did a couple of quick passes to record the ever-o-so-described rattle caused by light weight single mass flywheels. In this case it is the newly installed RS Barn flywheel, new clutch, etc. As a bonus, we hear a well heated stock exhaust as well <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />



Please forgive the clipping in some of these! I promise I will record better quality passes this weekend.



http://www.renalicious.com/Sounds/first%20gear.mp3

http://www.renalicious.com/Sounds/second%20gear.mp3

http://www.renalicious.com/Sounds/inside.mp3

http://www.renalicious.com/Sounds/revving.mp3 (Clipped a bit)



I kept the revs under 3000 since it only rattles between around 1700 to 2500 (In my case at least)[/quote]

Ren,



That's very cool. How did you do the recordings?



#3, from inside the car, sounds like a few wild turkeys got loose and were trying to get out of the car. Is that the rattle that everyone talks about?



The performance must be amazing, rattle or not, right?

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[Renalicious]

I used the Edirol R1, placed on the ground and did a couple drive bys. It's a handy little device with good pick up, and various immediate processing effects which I failed to use to get better results. It's one of those simple carry around devices that I've always wished I had when I was a kid hehe



The rattle is just that, it sounds like something is loose in the back and it's vibrating under deceleration. It can be difficult to capture the true extent of the sound, but at least you get the gist of what to expect if you get a non dual mass flywheel. Basically if you don't know what the sound is, you'd be inclined to think there was something wrong with the car <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />



About the performance, I can feel the difference in the response of the car: it feels more willing to get going when you step on the gas. So far this is my only major mod, so I can't say that the difference is night and day, but I do feel something. Throw in the airbox mod, exhaust, and Pete's chip then I'm sure the car will feel really alive <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[Renalicious]

Alright, here are some new better quality sounds.



Clearly audible is that rattle at around 2300 RPM

http://www.renalicious.com/Sounds/Startup%...d%20revving.mp3



First gear drive by

http://www.renalicious.com/Sounds/first%20gear.mp3



Second gear drive

http://www.renalicious.com/Sounds/second%20gear.mp3



Rattle while idling with clutch in and out to show the difference

http://www.renalicious.com/Sounds/Idle%20chatter.mp3



Hope this helps answer some questions about how a light weight flywheel will sound in our cars <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[flwbyu]

Hmmm. That sounds a little disconcerting. ;-d

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[mitch968]

Great job with the recordings, Ren. That's just how my fidanza flywheel sounds, though I don't really hear any difference clutch in/out at idle (at least from inside the car). I imagine you had the recorder outside back by the gear box for that one?



Any vibrations felt in the cockpit on deceleration? I have enough of a vibe in the low 2k range on decel, that I just clutch in or downshift to avoid coasting in that range.

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[flash]

i hear a difference - depressing the clutch makes it go almost completely away



the aforementioned vibration is there on mine, but since i don't rest my hand on the shifter (very bad habit, and the hands stay away from the shifter unless i am actually shifting) i don't notice the vibration

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[Renalicious]

I can feel the vibration through the seat. When I'm driving with the windows up and the music on it's really the only difference. Nothing too serious, but it reminds me that "Oh yeah, that car is making odd noises now. I should get it out of gear and use the breaks so people don't think this thing is falling apart" <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[sasilverbullet]

Thanks for the recordings! Now I know for sure that I'm staying with the OEM flywheel...

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[flash]

did you balance the flywheel and pressure plate first?

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[Renalicious]

Nope, I didn't do anything before, I assumed the shop would have read the instructions and acted on whatever needed to be done. The vibration is very minor, and really only happens when decelerating. It's proportional to the amount of noise coming out of the gearbox. I figure it's the sort of thing that the DMF dampens out with it's springs, etc.

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[flash]

arrrrgh - i hate that - most shops won't do it becuase it means the car up on the rack another day - it is VERY important though - this vibration can lead to damage - this is a very standard thing for any single mass flywheel, and they should know it



i hate to say this, but unless they provide a receipt from the machine shop or something else showing it was balanced, i would make them pull it, balance it, and put it back in - the flywheel is not balanced from the factory, nor is the pressure plate - they need to be done both individually and together

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[mitch968]

I don't believe this is necessarily a balancing issue. I had my shop (a local highly trusted p-car specialist) send my assembly to be balanced by a local machine shop. They balanced the pieces individually and together and I have this same vibration Ren is talking about. I have also spoken with others who have the single-mass, had it balanced, and have similar issues.

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[flash]

ok - let's be sure we are talking about the same vibration - if it only occurs during the 2k range, more on decel than accel, it isn't balancing - if it occurs across the rpm range, it probably is

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[mitch968]

Yup, only on decel in the low 2k range. Smooth everywhere else. It feels more like hitting a resonant frequency, rather than something out of balance. It sounds like this is what Ren is describing as well, though I expect his may be less due to the greater mass of the RSBarn flywheel.

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[flash]

ok - i still would have balanced it though - imperceptable harmonics do ugly things, and cost power



i think i need to have pete include a note in the flywheel box

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[Renalicious]

I'll be going back to the shop sometime in the next couple of weeks for a car checkup, so I'll ask them if they balanced it, and what it would cost to get it done. I think there were instructions to do it, but it's was more of a "Good practice" type thing.

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[flash]

yeah - i thought he would put that in - opinions vary on "good practice" or "necessary" - having seen what happens on other engines, and knowing about the oil pickup tube issues on this one, and adding to that the fact that they went to great lengths to deal with harmonics on this engine, i lean on this one to "necessary", where on some other engines i would only feel "good practice"



balancing a flywheel and pressure plate is only about 75 bucks

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[Fox944]

My PowerHaus lightweight Flywheel also makes this rattle.

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[flash]

any single mass flywheel with no damping anywhere should make the same noise in the transaxle for the same reason - the porsche motorsport unit does too

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