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New Product: 928 Aluminum Lightweight Flywheel

 
Old 03-23-2005, 02:20 PM
  #16  
Gretch
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Not the news I was hoping for, but sounds like progress is being made.....I suppose my GT clutch will last a bit longer.........

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Old 03-23-2005, 09:00 PM
  #17  
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Carl,
Add the timing ring!!!
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Old 03-23-2005, 09:03 PM
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John - did you read the threrad? I'm working on it!
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Old 03-23-2005, 09:10 PM
  #19  
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Why yes I did. Just trying to add to the line of people wanting a twin disk flywheel w/ a timming ring on it.
Nice work!
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Old 03-23-2005, 11:37 PM
  #20  
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John - what we are trying to do is make one flywheel with the timing ring receiver grove in it - and then you can press the timing ring gear of your choice onto it (early or late teeth numbers). Will that do?
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Old 03-24-2005, 04:25 AM
  #21  
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i have a machine shop in the process of exchanging timing rings, apparently its not that easy! will there be compatability issues between the alloy flywheel and steel timing ring?
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Old 03-24-2005, 07:04 AM
  #22  
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Will that do?
Maybe.
drnick makes a good point about securing the steel timing ring to the flywheel.
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Old 03-24-2005, 09:30 AM
  #23  
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Got it - good info - I'll be sure to take that into the design. I'm getting a late-model flywheel w/timing gear in my hands now so I can study it.
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Old 03-24-2005, 02:02 PM
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carl, the timing ring im adapting is from an automatic flywheel as i think these are easier to remove. the machine shop im using is recomendind that we 'turn down' the auto flywheel in order to remove the ring intact and without damage.
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Old 03-24-2005, 02:30 PM
  #25  
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keep in mind that the S4 to 84 clutch converson saves about 20lbs of rotating mass. (no one experienced any issues of any running problems) now, we are going to 15 lbs vs a 25 lb clutch and flywheel package. still not a big deal when you look at the entire rotating mass of crank, pistons, harmonic balancer, etc.

when car mentions that there is no HP gains, it really "Depends" it depends on the rate of acceleration. (ie 1st gear or 5th gear) faster the acceleration , the more hp it will save. obviously, carl is refering to the "rev-up " factor. yes, it will rev in neutral faster, as those accel times are generally in the .25 to .5 second range vs the time in 3rd gear going from 60 to 115mph of about 6-8 seconds.

Its always good to loos 10lbs. because its rotating, and depending on the diameter, it can be like loosing 20lbs as far as net acceleration if it was in the car. just as tires and wheels packages of saving 5-10lbs on a 25" diameter can equal double the weight if it was in the car. (not 5-8x)
Your rule of thumb is way off. (i.e. 7 X) but then again, it depends on the diameter of the rotating mass. If its rotating on the wheel its generally 1.4x if its rotating on the tire, its 2x (double), as if the mass was in the car as far as accelerating rates. ive also removed AC, smog pump and driven fan, and we didnt see more than a couple of HP. (most of that was the driven fan) the smog pump is nothing (ever spin one?) ac is a little more than that, and the driven fan is substantial, but think about it, what does it take to make that much air flow with the slip clutch? im sure, the twin fan set up is doing the same thing, and those forces are from two 10 amp fan motors (ie sub 1hp for both). If i added u all the stuff i removed off my 86 and used these types of calculations, i would be putting 400hp to the wheels equivilant! (but we all know the truth)
List:
15lbs per wheel tire package over previous , 60lbs total
smog pump
driven fan
a/c
20lbs off the clutch

if you use the 7:1 calcuation, thats 80lbs of rotating weight or equiv. 560lbs saved or 56hp, then add the loosely talked about 10hp for the fan, 10hp for the ac, 5hp for the smog pump and you would have 80 hp gained (saved) this just aint the case folks!

One drawback to the flywheel , is not you cant store as much energy in the flywheel when you drop the clutch, as you could for the drag racers, and thats a trade off you have to investigate. also, i wonder about racing applications and its resistance to warping.

Mk


Originally Posted by Vlocity
Hi Carl:

Do you expect any stalling issues? One of the big problems with the 911 variants (964 especially)
is that the lightened flywheel accelerates quicker but also decellerates guicker. Some of the vehicles will not maintain the momemtum of the engine when coming back down to idle and the engine stalls.

Curious if you have seen any issues. I've deleted my AC, air pump and pulley driven fan and there is a huge difference in the accerleration of the engine. I used to race snowmobiles and the old rule of thumb was the 1 pound of rotating weight was equal to 7 pounds of regular weight in the dynamics of the sled.

Best regards,

Ken
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Old 03-24-2005, 02:49 PM
  #26  
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Its good to know there will be somewhere to go when I get through my two new clutch kits for my 78 and 89. Both are using the 80-86 system, and we'll see how they hold up to my driving when I get them on the road.
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Old 03-25-2005, 09:59 AM
  #27  
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Hi Mark:

The 7 time notation I made in context concerned snowmobiles. Snowmobiles have a huge amount of rotating mass. They have an engine, two heavy clutches, chain case and a track which alone weighs up to 10% of the entire weight of the sled. We would then put several pounds of carbide tipped studs in the track for traction which increased the rotating mass even more. The number I used has been quoted by snowmobile engineers and race gurus for years and is a given in the snowmobile world. Eventually we went from steel to aluminum backers on the track studs and then down to nylon. We even shaved the track lugs to remove a few pounds of rubber. One benefit from shaving the track was that we found we had less of a fan effect in the bulkhead of the sled and this increased our speed. The other dynamic issue with a tracked vehicle is that as the speeds increase the track which is run in an oblong shape, wants to be round....more frictional losses.

One of my favorite sleds was a Skidoo Mach one which I hid a Nitros bottle on. I had to grind my own clutch ramps for the clutches to act properly, but when dialed in the sled would run through 550 feet at over 97 MPH. Fun ride on Ice.

Again. the example I quoted was for a snowmobile and the dynamics of that type of a vehicle are very responsive to a little change in rotating mass since there is so much of it and it is such a high percentage of the units overall weight.

As for my comment and question on the stalling...I own a 964 (C-4) with 45,000 miles and I lurk on the 964 board while I feel more at home here. If you look on the 964 board you will see that there is a current very active thread on the stalling issue.

Best regards,

Ken
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Old 03-25-2005, 11:04 AM
  #28  
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I'll say it again - you do not add (or preserve) mass to rotating parts to prevent stalling.

That's BS.

They will find an idle pot that is leaking, an electric decel valve that is not working (that is what GM uses) or a vacuum leak, or an idle stop set too low, or an idle mixture set too lean, or an idle air bleed screw set too far in (lean).

Stalling on sudden lift from the throttle is a tuning problem, not a rotating mass problem.
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Old 04-03-2005, 11:47 AM
  #29  
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It doesn't look like the timing gear is goping to be a problem.

I received my 88 AT flywheel with timing gear from 928 Intl (thanks boys) to examine and cut up - and here are a few pics.

Notice that the mounted height of the timing gear (distance from the crank moutning flange to the timing gear) is identical to ours, and also notice that the outer diameter of our aluminum flywheel and the inner diameter of the timing gear are the same.

I am giving this over to my machinist now, and we will make one up for you.
Then we can test it.
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Old 04-03-2005, 02:20 PM
  #30  
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Like Tom Said - THats 60-1 timing wheel will help those that will have aftermarket systems. =ME<-

Hmmm.
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