dual mass flywheel: LUK vs SACHS..?

[JFP in PA]

Originally Posted by truegearhead

Are you sure that was due to the LWFW and not due to the fact that these motors are made of explodium?

Visit Jake's website and read all about it. Yes, this was caused by the use of a lightweight flywheel, and the engine is actually an X51 version with all the oil system enhancements. When these things go bad, they go very bad..........

[truegearhead]

Originally Posted by JFP in PA

Visit Jake's website and read all about it. Yes, this was caused by the use of a lightweight flywheel, and the engine is actually an X51 version with all the oil system enhancements. When these things go bad, they go very bad..........

Just read it, scary story. However it's just one case, at the beginning on the articule he states that hes never seen such an extreme failure. It seems low risk to me, that was also a very high powered race car with 12,000 track miles! Definitly something to consider but it doesn't seem probable.

[jb92563]

Thanks for the explanation of the DMFW.

So you say the DMFW can wear out, what symptoms of that would you notice, just out of curiosity.

So are there light weight dual mass flywheels as well?

Seems prudent to keep the harmonic balancer function but at the same time a lighter weight would allow faster acceleration of the engine.

So if I understand correctly the LWFW does NOT have any harmonic balancing functionality?

I also wonder if the flywheel balancing can be done dynamically on the engine or statically before its attached?

Perhaps that is indy mech thinking and only worth it for racers if at all?

[JFP in PA]

Originally Posted by jb92563

Thanks for the explanation of the DMFW.

So you say the DMFW can wear out, what symptoms of that would you notice, just out of curiosity.

So are there light weight dual mass flywheels as well?

Seems prudent to keep the harmonic balancer function but at the same time a lighter weight would allow faster acceleration of the engine.

So if I understand correctly the LWFW does NOT have any harmonic balancing functionality?

I also wonder if the flywheel balancing can be done dynamically on the engine or statically before its attached?

Perhaps that is indy mech thinking and only worth it for racers if at all?

A lightweight unit is a single mass with no dampening capabilities.

Yes, flywheels can be balanced by a competent balancer (requires special fixtures); but having the flywheel correctly balanced does not do anything for harmonic dampening, that requires the dual mass.

[DennisAN]

Originally Posted by jb92563

So you say the DMFW can wear out, what symptoms of that would you notice, just out of curiosity.

From Project 44 in Wayne Dempsey's book:

Now, it's time to turn our attention back to the flywheel end of the engine. Porsche Tech Bulletin 8/02 1360 says to check the dual mass flywheel by twisting it approximately 15mm to both the left and the right, checking to make sure that it returns to its approximate starting position. If the flywheel can be twisted beyond about 15mm with no noticeable increase in spring force, or if it cannot be twisted at all then it probably needs replacement.

[Slate 01]

Good stuff, guys, thanks to JFP and others for sharing on the subject. I was totally into the idea of a LWFW but now won't even consider it. I don't track the car and I can live without the faster revving engine.

[Bigsmoothlee]

I plan to run a lightweight aluminum flywheel ( after taking to a machinist to balance ) and a SPRUNG clutch disc.

[DennisAN]

Originally Posted by Bigsmoothlee

I plan to run a lightweight aluminum flywheel ( after taking to a machinist to balance ) and a SPRUNG clutch disc.

IIUC Porsche combined the effect of the front pulley harmonic balancer AND the springs in a traditional clutch disc in their dual mass flywheel. I suppose you could put on a single mass flywheel if you use a "sprung" clutch disc and a harmonic balancer belt pulley up front.

[JFP in PA]

Originally Posted by truegearhead

Just read it, scary story. However it's just one case, at the beginning on the articule he states that hes never seen such an extreme failure. It seems low risk to me, that was also a very high powered race car with 12,000 track miles! Definitly something to consider but it doesn't seem probable.

We have seen one as well, not as bad as Jakes, but bad enough; plus two complaints of drivability and vibration issues after the install of a lightweight unit, both of which were traced to significantly out of balance flywheels. We also had one in the shop that would not start after a DIY lightweight install that turned out to be problems with the CPS shutters on the flywheel. Some of the lightweight units just are not very well made.