Charlie944

Hello all, I wanted to fill everyone on my most recent track event at 944Fest. The clutch I noticed would slip when sitting in traffic doing the stop and go game in heavy congestion. I encountered two pretty good sized traffic jams. I was not slipping it hard at all during those times either and would try and just let the car idle in first gear going 3mph. At the track I turned down the boost to about 8-10psi and drove pushed it no harder then half throttle. I did not notice any slipping during those times. The car was cold (no street driving) and then went right to the track so I think the clutch never got a chance to heat up big time.

For instance after a beautiful traffic jam coming into Chicago the clutch would slip with barely any throttle applied while upshfting (no boost whatsoever). After it cooled down a bit from high way driving it did better but would give way when under mild boost.

I spoke with Dave and Kennedy Engineering (KEP) and he stated that they have had terrible luck with Fidanza's warping under heat due to the Aluminum has almost twice the rate of expansion that Steel does. Hence causing the flyhweel to bow and flex in a "U" shape therefore causing a irregular mating surface.

Here are some pictures of my clutch all apart and I noticed on the pressure plate that only half of the surface shows wear and the other half shows the machine marks from the resurfacing.

To recap what I have for components: Sachs pressure plate modified my Markus Blaszak for 30% more clamp force, Feramic iron disc, and Fidanza flywheel.

http://forums.rennlist.com/upload/p1010098_copy1.jpg

http://forums.rennlist.com/upload/p1010099_copy4.jpg

http://forums.rennlist.com/upload/p1010100_copy1.jpg

http://forums.rennlist.com/upload/p1010101.jpg

http://forums.rennlist.com/upload/p1010102_copy2.jpg

http://forums.rennlist.com/upload/p1010103.jpg

I did notice all that black dust (sintered iron from disc) too inside the flywheel.

I will try and throw a dial indicator on the flywheel on it tonight and post results soon.

This makes clutch job number 4 for me this year!!

Charlie944

Opps that was Dave @ Kennedy Engineering.

2bridges

Did you put a square on it??? My gut questions that because it's aluminum is the problem..... Thare are tons of race cars in all types of racing that use aluminum flywheel to reduce rotating mass.....

If you get more detail I would be interested.

mblaszak

We have seen a number of problems with the Fidenza flywheels, not the least of which is warpage. Remember, that for Aluminum to be as strong as steel, it needs to be 4x as thick... that is basic physics... but the Fidenza is NOT 4 x as thick, it is the same as a steel flywheel...

The second problem we are running across is that nobody is balancing the Fidenza flywheels. The manufacturer states they are CNC machined and therefore balanced... well guess again. You know that Steel Trigger setscrew they use, it weighs 3.10 grams... and that translates to about 4 pounds of unbalance at 6500 RPM. Now add to that a steel facing... rivits.. and you have less than a balanced unit to be sure.

Now to the issue of an iron or copper faced clutch disk... I wonder out loud... why? The Coeff of friction on steel to steel is pretty low... which is why trains use steel wheels on steel rails... For HP clutches we use... Kevlar to 500 HP.... copper to 700 HP and then Ceramic to 1000 HP.... and we do NOT use steel disks for anything....

Not sure if this helps you any... hope it does....

testarossa_td

Always good to have tech info!

2bridges

AMEN TO THAT!!

jacklet

soooo is the balance the reason for warping? i ran an alum flywheel on a true 450 horse early camaro no probs-it wasn't any thicker than a steel and we flat out abused the s#%t out of that car never balanced the flywheel although there were no set screws in it-if i'm reading this correctly the wheels are balanced when machined but not after the installation of the friction face or set screws?
if they are balanced after this will it work?

jacklet

why on earth did you ever use an iron disc? that may be the prob? that's gonna generate a lot of heat-i would think?

Charlie944

I put a square on the flyhweel last night and it checked out okay. I did not see any gaps and I was tyring to stick a .010" feeler guage underneath the square and it would not go through. Also tried shining a light on it to see if there was any gaps due to warpage and again nothing. Now granted this was done when the flywheel was a room temperature. When it starts to heat up is when I was having the problem so I would be curious to see what the Fidanza would look like when it is hot. I had this same problem when I ran a windowed Kevlar disc (solid Kevlar ring on the outer most circumfrance with pucks of Kevlar on the rest of the disc) like this disc was also wearing most on the outside edge like my Feramic disc. I still had the Fidanza and same pressure plate with the Kevlar disc.

As to why I went with the Feramic disc; it has the highest heat resistance of any other clutch material made today with a coefficient of 0.7. This coefficient doesn't change with temperature as many clutches do until after 900 degrees and has a melting point of 1600 degrees to tolerate even the most extreme use. Fuerthermore, when this disc wears it exposes new layers of friction material so unlike other discs where if they slip they end up being toast and need to be replaced. Also it dissapates heat very well and I was expecting the Al flywheel to do the same because it is Aluminum. But perhaps it does so at a price....warpage.

jacklet

hmmmmm, is the pp straight?

Charlie944

I put the same square on the pressure plate and did the same checks and I seen no problems. Again this was at room temp. I did alterante tightening the pressure plate bolts when drawing it onto the flywheel so I did not bind it or get it ****-eyed. I am perplexed by it as well all's I know is that I have uneven wear across the mating surfaces on the disc, pp, and flywheel. And that is slips when it gets hot nut when colder it grabbed well. So that is why I am going to go back to my steel flywheel and try a Kennedy Pressure Plate.

special tool

One of the best products I ever bought for my 951. I have over 10,000 miles on mine with organic disk, kevlar disk and copper/ceramic disk.
Guys who REALLY know clutches know that cop/ceramic eats flywheels for breakfast - not mine. The REPLACEABLE lining on my Fidnaza is almost new looking. Had my fingers on it last week, as a mattter of fact.
This is 10,000 plus miles on a car with 475/425 hp/tq on LOW BOOST, also.
.....and I am not cruising aound on low boost all the time, believe me.

Charlie944

Thank you everyone for your replies!

I do love the flywheel and the ease of rev matching.
I was thinking that I could bolt the clutch assembly together on the floor and put some plasti-gauge on the flywheel surface and on the pressure plate surface (at different spots) to check for any irregularities. That way the pressure plate is exhibiting pressure on the disc and flywheel. Because right now in a static state nothing is showing any warpage.

Charlie944

Well I put some green plasti-guage (.001" - .003") at the 12, 3, 6, and 9 o'clock postions on both the Fidanza and on the pressure plate. One on the inside area of the friction ring and on on the outer edge on both the flywheel and pressure plate.
On the Fidanza I noticed a consistent .0015" on the outside edge (where it shows wear) and a varying .002" to .003" on the inner edge. Meaning that there is a .0005" to .0015" fluxuation in gaps between the inner and outer edge of the Fidanza flywheel. On the pressure plate it varied .0005" from inside to outer edge.

I then bolted everything to my steel OE flywheel and ran the same test. On the flywheel it was consistently .0015" on both inside and outside edges and on the pressure plate everything was .0015" as well.

Bolts were all torque to their 18ft/lbs spec and alternated tightening for a even clamp down.

Dal Heger

Looking at the picture of the flywheel, it looks like the friction surface isn't centered on the flywheel. It looks like it's an ellipse according to your picture. It looks like you're grabbing aluminum from the flywheel itself instead of staying on the friction surface.

Dal.