Broken M96 crankshaft- X-51s fail too!

[blue2000s]

Originally Posted by Lil bastard

There are several things to consider when using pressed metal tech to form a part. Pressed metal pieces perform best under compressive force and much less so under tensile force or torque (twisting). This is what surprises me about using this tech for a crank, seems to be one of the least suitable environment.

But, I'm no Porsche engineer, so they must know something I don't. Either that, or the bean counters have veto power over the engineers, which come to think of it, maybe isn't all that much a stretch.

But, with CNCing being all the rage today, it would seem that they could get a cost (and reliability) effective alternative going that route with a forged billet.

Then again, a little perspective may be in order - this is the 1st crank failure that I'm aware of and it occured in an extreme application (racing). Still, it was the X-51 part. I can more easily see the stock crank using pressed metal, but am really astounded to see it adopted for the premium, race purpose part.

Cutting billet parts is expensive because of the time and wasted material. Definitely more expensive than powdered metal.

[tholyoak]

The X51 engine is no different on the bottom end. It is a series of top end modifications, heads, cams and intake, porting etc. Bottom end uses the same parts as the regular 3.6.

While the M96 motors have some issues, personally I don't see this failure as one of them. The 964 based motors have seen crank failures at the track with their true drop forged cranks. To me this is an issue of running a street motor on the track at sustained high rpm for over 12k miles without tear down and inspection or balancing of reciprocating masses.

-Todd

[Brucelee]

Originally Posted by tholyoak

The X51 engine is no different on the bottom end. It is a series of top end modifications, heads, cams and intake, porting etc. Bottom end uses the same parts as the regular 3.6.

While the M96 motors have some issues, personally I don't see this failure as one of them. The 964 based motors have seen crank failures at the track with their true drop forged cranks. To me this is an issue of running a street motor on the track at sustained high rpm for over 12k miles without tear down and inspection or balancing of reciprocating masses.

-Todd

Now we are back to that old debate about whether running these engines hard is GOOD for them.
Based on that theory, the cars that are tracked should be totally flawless??

[tholyoak]

Big difference between lugging these engines along at 2k rpm on the street and using a street engine as a race motor without modification or testing.

-Todd