[SILVY968]

In the recent article by FLASH in 9 Magazine, Vol3 No 4...

" ...removing the 40 pound so-called "vibration damper""

Question is what does this device do and what happened when you remove it?

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[6spcab]

[quote name='SILVY968' date='Sep 24 2005, 09:58 PM']In the recent article by FLASH in 9 Magazine, Vol3 No 4...

" ...removing the 40 pound so-called "vibration damper""

Question is what does this device do and what happened when you remove it?

[right][post="10247"]<{POST_SNAPBACK}>[/post][/right][/quote]



Oh boy, here it comes.

<img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />

Here is a link with both sides of the topic. I removed mine and noticed no difference in terms of handling, however I did this when I installed larger and heavier (10 lbs heavier rear) tires/wheels so I saved 30 or so lbs in the back. Some call it dead weight, others say it balances out the heavy muffler on the left side of the rear end, and others say the car will fall apart over time if taken out due to harmonics. Some also recommend that it is not removed if you have a stock suspension setup. All I know is that it is a heavy piece that is slowing me down and that removing it made no difference in my handling setup or vehicle vibrations.

Lee



http://65.61.16.109/forum/topic.asp?TOPIC_ID=10696

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[SILVY968]

Yes, I heard about the "vibrations will destroy your car if removed" story too.

What I would like to see is an article written by Porsche about it. These guys, in my opinion, know what they are doing and would not design, build and install a 40 pound lump into their cars without a good technical reason. The muffler is in the exact place on the driver's side, so maybe it counterbalances the weight from side to side, but how does the extra weight stop damaging vibration?

Anyone ever read anything from Porsche about it? I just read thru the Porsche factory lit and there is no mention of the weight and it is not drawn in on the x-ray drawing of major components.

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[SILVY968]

Lee,

Read the threads.

Mine stays in.

Thanks for the info.

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[flash]

i just did an interview with probably the most renowned expert on these cars that was very enlightening - i'll be writing the article in the next few days - bottom line, i feel VERY good about removing it

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[6spcab]

[quote name='flash' date='Sep 25 2005, 12:09 PM']i just did an interview with probably the most renowned expert on these cars that was very enlightening - i'll be writing the article in the next few days - bottom line, i feel VERY good about removing it

[right][post="10266"]<{POST_SNAPBACK}>[/post][/right][/quote]



Yep, I feel good each time I step on the gas! 40 lbs does make a difference. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[SILVY968]

OK FLASH,



Based upon your comment I look forward to reading about this!

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[Beachboy]

I'm a coupe guy so I stand outside this "discussion" but I am a mechanical engineer and I can add one small bit of information that might add light (or fuel). It is a common misconception that steel can fatigue from vibration. In order to lose strength it must be stressed to it's yield point. That varies by alloy and structure, etc. Take any steel bar and bend it a bit and it bends back, everytime for millions upon millions of reps. Bend it once just a bit too far, past it's yield point, and it does not return to it's original point and it's internal structure is permanantly altered and weakened. Aluminum is quite different and is subject to fatigue strength loss with high repitition low level stress.

I guess that applies here in whether or not when removing the ballast/dampener causes chassis flex past the steel unibody yield points, I doubt it.

That said it is a very reasonable assumption that added vibrations would affect all sorts of electro-mechanical and mechanical systems on the car in a negative fashion over time.

It is also obvious that removing 40 lbs is going to make the car more responsive. Whether you can feel it on the street or not is purely subjective.

But then, it's pretty obvious that there is an almost constant and linear inverse relationship between adding performance and reliability/resale value. The most valueable cars in resale are pure stock and not driven very much. IMHO The poor owner never had the joy of driving his fine car very much and it has always been a mystery to me that owners of such cars are so proud of how little they have driven them. I guess they like looking at them better than driving them, not my cup of tea.

So it comes down to whatever floats your boat, which I think has been clearly stated. No need to rock the boats any further.

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[Greimann]

Brian, that is a good technical point about steel fatigue. I think those concerns may have been over blown by other factors as well.



The actual issue is really about chassis dynamics and NVH (noise vibrations and harshness).

I believe the weight is a tuned mass damper designed to kill second order harmonics that upset the chassis stability.



Here is a very interesting thing I turned up. Looks very familiar.

tmd.pdf Size: 485.97 KB  Downloads: 76

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[Beachboy]

That's really interesting, a '94 date of issue probably means it all started a few years before that with mostly Japaneese listed as previous researchers.

The harmonics dampening makes sense, I assume you're talking about low frequency stuff that would cause tank slapper (old motorcyclist term) type results.

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[S_Cal968]

This is nothing new... I also participate in a forum for classic Pontiac Firebirds [67-69] and the guys with "verts" have discussed this same topic. Those that have removed the dampener reported a resonate harmonic vibration at a given speed. Some are willing to compromise the vibration for reduced weight and others re-installed the weight. As mentioned its a personal preference. Depending on several variables the driver may never experience the vibration.

From a technical standpoint, it would be interesting to see what the long-term affects are. Even after extensive pre-producion testing, I'd bet the tuned damperner is added for ride quality more so than body structure reliability.

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[Beachboy]

That may be true but I could also see it affecting suspension dampener performance and longevity of electronic gear.

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[SILVY968]

Very interesting Patent to read!!!

I took mine out, along with the spare and jack ( AAA member ).

I have noticed a very anoying vibration around 60 ish MPH right after the removal.

My PM checked the alignment just for fun and all is well.

My fuel consumption did not go down, so I'll put the damper back this weekend and report.

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[flash]

thanks brian - that is exactly what every single mechanical engineer has said so far



nice article dave - thanks - supports the contention that no chassis damage will occur as a result of removal



given the frequencies it may be dealing with 10-17 hz, i seriously doubt any electronic gear will be affected



i can't wait to write this article

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[SILVY968]

FLASH was, and always seems to be right.

The damper was put back in with no ride change.

The culprit was lower tire pressure than normal. With 18" wheels and lo profile tires there is a happy medium between poor ride with too little and poor ride with too much air pressure.

The weight comes out for good. My new AAA card arrived, so out stays the jack, compressor and spare. Minus 107#.

Can't wait to read the article that FLASH has been threatening to write.

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[bibbetson]

Anyone know what the USA inner bumpers and shocks weigh both front and rear? not the bumper covers, but the aluminum I-beam bumper that sits behind the bumper cover. I'm considering removing these from my DE car, but want to be sure the weight reduction is worth it.

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[flash]

front bumper and shocks are 16 lbs (shocks are 3lbs each)



i i remember right, the rear bumper is 16 lbs by itself - shocks are the same 3lb each



i felt it was well worth it - my front assembly is completely absent (like taking a bowling ball out fo the front)



the rear assembly has seem some serious mods - pulled 9 lbs out and still have a functional rear bumper

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[bibbetson]

Bob,



Can you elaborate on what you did for the rear. There is a lot more going on back there. The bumperettes connect to the bumper. Also the bumper cover is supported at the bottom by braces off the bumper so that it doesn't flap in the wind. I was thinking of putting in a lightweight aluminum 'C' channel and then connecting the bumberettes and bumper cover to that.



Comments?

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[flash]

you have a PM

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[968 Cab]

I removed the 40lb damper from the Cab and found the car "livelier" (subjective for sure) but definitely a little peppier - that plus the airbox mod has made a formerly sluggish car much more driveable around town. I also removed the spare, jack, etc but do have a big ADS amp, Bazooka Sub and 10 CD changer back there that in total weighs as much as the spare.



The 968Tip is much better around town from a standing star now, so I'm happy with leaving the weight out. No longer need to shift into 1st every time to avoid embaressment at the stoplight!



The 968cab seems to be pretty sensitive to tire pressure - more so than my 951TurboS coupe - just a few lbs low and the car rides very rough - as in severely flat spotted tires. I have new Yoko ES100's on 17" Boxster twists on the car and find they run best around 36 psi cold.

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