911 SC 3.0 Aluminum Flywheel ID & Recommendations

[cpcooper]

I posted this in 911 Technical Forum, but this may be more appropriate place.

Anyone recognize this aluminum flywheel? It was an eBay impulse buy I made when I had my '78 SC apart, and I chickened out on installing it when I put the car back together. Not so sure now. Looking at other posts here, guys are happy with aluminum flywheel AND aluminum pressure plate. Thinking of going that direction, but can't find any information on this flywheel and there are no names or stamps on it. It is all aluminum, with no steel insert for the clutch surface, although the clutch surface has a rough finish somehow applied over the aluminum.

[chris_seven]

You need to be really careful when considering Aluminium Flywheels.

I have seen one burst quite recently. It was manufactured in the UK and had clearly not been 'stressed' correctly.

The flywheel you have bought doesn't look too bad but if you can't find the manufacturer it may be an idea to make some basic calculations to make sure it won't burst or fatigue.

I would also suggest you carry out a basis hardness test to try to determine the 'strength' condition of the alloy used.

A good 2000 or 7000 Series alloy in a T6 temper should be about 175 HV or 85 HRB.

Stresses should be less than 150MPa to avoid fatigue failure.


The 'wear' face where the clutch grips is also worrying.

It is conventional to rivet a cast iron plate to this surface as if it is plain Aluminium it will wear very quickly.

The RSR Pressure Plate is Aluminium but it was 'flame' sprayed with a Tungsten Carbide coating. If it has a hard coating it may work quite well.

Kennedy still make this type of plate but I am not sure about its like compared to a Sachs Clutch with a Aluminium Housing and cast iron pressure plate.

I would be interested to know the weight of this Aluminium flywheel as we make a RSR style steel flywheel which weighs 2.8kkg.

[faapgar]

Hi,that looks like a flywheel made by Dave White.I have one in 6 bolt style that weighs 3.5 lbs.Clutch service is sprayed with a Plasma coating and is very durable.Weigh your flywheel & post the weight.Merry Xmas to all.Fred

[cpcooper]

Yes, weighs 3.5 pounds. Searched "Dave White flywheel" and didn't get much besides this thread.

[racing97]

They stopped producing those units I believe they were made in FL. The wear surface was way to aggressive.
regards

[cpcooper]

I kind of wondered about that... flywheel and pressure plate friction surfaces are usually pretty smooth. This feels like maybe 180 grit sandpaper. Still might be interesting to try though; 3.5 pounds and the car isn't driven much. Faapgar, what do you think?

[chris_seven]

If they have been plasma sprayed they would need grinding after this process had been carried out or they would be quite rough.

Grinding of this face would be quite costly as the TiC coating is extremely hard and a diamond wheel would probably be needed.

[racing97]

It has been plasma sprayed, and the disc life is terrible. But it is nicely made and quite flat some of the 6 bolt are big on the overlaying crank flange and shake horribly.

regards

[cpcooper]

How terrible disc life? 5K miles would be terrible disc life, but 5-10 years driving for this car. On the other hand, I looked at some other aluminum flywheels available with iron insert but they are 6 pounds, almost double the weight of this one. But... seems like the the disc wear issue could be further aggravated with compensating for a light flywheel in traffic. Maybe heavier one would be good compromise. Still, 3.5 pounds is intriguing.

[chris_seven]

Is the poor clutch life because they weren't ground?

TiC should be quite hard and should be quite wear resistant and if it is smooth it shouldn't really chew up the clutch disk.

At 6lbs I am not sure that the Aluminium Flywheel with a Cast Iron Plate is worth the effort.

We make 9 bolt flywheels similar to the RSR style and they weigh 6.3lbs and are made of Chromoly.

We make a 6 bolt version that is 6.1 lbs.

If you look at the inertia the differences between the solid aluminium and the 'scalloped' steel the weight differences are less important.

[faapgar]

Hi,I used one with a 6 puck metallic disc and have not had any problems with wear but I do not have to deal with traffic as it is a rural area.With a 6 puck design clutch release is in or out.Probably not conducive to Southern California lifestyle.Al light resurface to smooth the surface would help for traffic prone areas.

[racing97]

Unground, it is so abrasive that it ears the disc up with in a few track days. I don't know why they sprayed it and left it so ruff.
regards

[cpcooper]

Wonder if, as racers, they might have intentionally left it rough to for better grip. I had an AASCO aluminum flywheel in a 3.2 Boxster and could always smell clutch after spirited driving. Replaced disc and pressure plate with best I could find and same thing only less. I think I'll show it to a couple of machinists I know and see what they think about smoothing it out a little. If I do run it, it's going to be with an aluminum pressure plate... well, I assume the pressure plate itself will be iron, but the cover aluminum.

[9146GUY]

This is what the Dave White flywheel looks like. I have the last of them. They are plasma coated and work very well. I have a 6 bolt version in my 914-6 GT race car and it has been run for many seasons without any issue.
Send me a PM if there is any interest.

[cpcooper]

Yes, yes, that's it! How long are the bolts? Stock pilot bearing? Are you running aluminum pressure plate?

[chris_seven]

Originally Posted by cpcooper

Wonder if, as racers, they might have intentionally left it rough to for better grip. I had an AASCO aluminum flywheel in a 3.2 Boxster and could always smell clutch after spirited driving. Replaced disc and pressure plate with best I could find and same thing only less. I think I'll show it to a couple of machinists I know and see what they think about smoothing it out a little. If I do run it, it's going to be with an aluminum pressure plate... well, I assume the pressure plate itself will be iron, but the cover aluminum.

No - that really wouldn't be sensible as the stick/slip characteristic would be unpredictable and very hard to manage.

The vibrations that would also tend to be introduced could also become a nightmare and could cause other damage.

You want a clutch to grip in a controllable and repeatable manner.

We grind the friction face of our new flywheels to ensure consistent behaviour.

If you roughen the surface then you will lose contact area and the engagement of the clutch will suffer. It may snatch and judder but it will probably take less torque to make it slip than if the flywheel were correctly ground.

If you Boxter clutch slips so badly you can smell the clutch then the contact pressure must be too low and you are causing damage.

I would look at the geometry and try to measure the load/deflection behaviour of the pressure plate.

I would have thought that a well made correctly coated and ground Aluminium flywheel should work quite well and if has been well designed should be very good.

[9146GUY]

cpcooper. This flywheel used the 928 Bolt PN 928 102 151 01 and the stock bearing. From your picture you appear to have the steel ring that is used under the bolts. You must use it. You can use either a steel or aluminum pressure plate because the "body" of the aluminum pressure plate still uses a steel surface to contact the clutch disc. You can use almost any type of disc, puck or regular.
Hope that answers all your questions
Steve

[cpcooper]

Thanks Steve/914-6GUY, I just posted an ad for WTB pressure plate. Got me thinking about 914-6's, so I looked them up; seems like I missed the boat there too, out of my league. Here's a 914-8 for $5K in my neck of the woods.

1973 Porsche V8