Porsche m96 crankshaft material

[Tmoose]

Does anyone know for sure?
Info online is scarce, but a few sources suggest or even assert that the M96 (Boxster) crank ( and rods) are pressed metal, not forged steel blanks.

http://www.flat6innovations.com/broken-crank

The wide "flash" lines of the rods and rear(front?) crank throw look like vestiges of a "real" forging process to me.

When Chevy does their premium PM rods they have minimal flashing, like the rod on the right shown here -

http://www.hotrodders.com/gallery/data/500/medium/piston_005.jpg

thanks

Dan T

 

[BrianGar]

Dan,

Your link to image is broken,

But, if its this image you're talking about it looks like a 'regular' forging which gets clocked(twisted) after removal from the last 2 piece forging + flash trim tool,

http://www.renntech.org/forums/uploads/monthly_10_2008/post-34760-1224872113_thumb.jpg

The minimal flash on the rods as with the chevy items could mean they are sintered.

The rods in the 1.8Ts in the VAG range went over to sintered items in about 01-02 so it wouldn't surprise me if the Porsche items were same. Another way to tell if they are sintered rods is if the cap mating surface is a rough finish - it has been cracked off the main rod after boring the big end journal. The rough 'cracked' mating surface provides superior cap relocation without the need for dowels or other. Again, it cuts out a few processes in reference to ground cap faces.

Im not fully sure what you think the different is when you say pressed steel vs a forged blank since the crank gets formed by pressing a heated blank between two forging dies. There are often a few sets of dies, each pair getting smaller, and nearer the net shape as the operation progresses, the last process being the trim tool which slices off the flash extruded at the parting line. This flash is normally 6-10mm wide depending.

I hope this is the information you needed, and that its not a 'mother milk ducks' post for you - if it is apologies.

If you mean something else entirely, the only other 'new' method I know of forming such engine items is done by Bmw, whereby a heated steel tube is fitted into a tool and the tool closed. The tube is then inflated with fluid (60kpsi) and the material conforms to the inside of the tool. The part is removed, and ground at journals and lobes. The hardened steel rings fitted at bearing/lobe locations within the tool before tube installation thus become the wear surfaces and lobes. This makes for a very lightweight camshaft. Im not sure you could make a crank this way though with the hydroforming process.

Brian,

 

[Tmoose]

Hi Brian,

Yep, your link goes to the same crank failure and subsequent pressed metal crank material discussion I was struggling with.
First because of the wide flash line in pictures of the busted crank, and second (naively?) thinking Porsche would NEVER do such a thing.

I believe some PM components are also described as being forged later in the process, although the difference between forging and Hot Isostatic Pressing seems like the kind of thing some marketing groups might twist counterclockwise without a second thought.

 

[BrianGar]

If you want to see some perfect crankshafts - Look at the Ferrari Items, In any of their cars.

The flash on the Boxster crank doesn't really matter, but they are no supercar remember.

Brian,

 

[Tmoose]

Generally the folks experiencing the problem on those m96 threads have put in a batch of track hours.
One seems to be a (the?) specialist catering to owners competing at some level, or wanting to have "competition" engines. His understanding of topics like engine balancing and torsional vibration is kind of thin. So when he said the crank was PM I assumed he may be wrong about that, but wanted to dig into it to be sure >> I << wasn't assuming more than I should (again).

 

[BrianGar]

Further digging shows you are correct re powdered metal crank.

http://www.flat6innovations.com/index.php/broken-crank

Sorry for leading you down the wrong path. I was not aware a crank of said caliber was made using the sintering process. I still dont think this is why they are failing though. Could users have removed the crank damper, or altered flywheel mass?(article seems to point to this too)

Hard to beat a 4340 crank all the same....

Brian,

 

[Tmoose]

Hi Brian,

That is >>the<< guy who is saying the crank is PM.

But......
- I (Google) can't find anything in Porsche literature saying the crank is PM.
- The width of the flashing rib on the rear throw "looks" like a forging remnant to me (unless they PMd the rib so it would look forged, similar to clamshell molded tires sometimes have the "segmented" mold ribs molded in, or low end imported bicycles of the 70s whose thick square cut cast frame lugs had a curvy profile cast in to resemble sculptured lugs).
- The "guy" is ignorant on a variety of other topics ( the crank didn't "shear" off, lots of incorrect balancing and torsional vibration tech intermixing )
- Chevy Performance says they can make a Performance PM rod that is "better" than the famous 350 Chevy forged steel "pink" rod, but offer only cast nodular iron or forged cranks.
- The thin webbed geometry of Porsche 6 cranks does not allow for adding material to compensate for a change to lessened material properties. A stock early 911 crank is so hard and hardened so deep that number stamps are destroyed trying serialize the counterweights.
- Details I know of some specific German engineering (practically automatic crank upgrades of engines as power increases, proper full documentation of heat treatment on ID fans) make me think Porsche simply would not use anything but a forged, hardened crankshaft.

 

[BrianGar]

I see.

Ill admit, I have never heard of a sintered crank - ever, and thought this one slipped through the net un-noticed to me. I cant find anything Porsche either on sintered cranks, which to me means they are not made this way or they would be using it as a marketing slant in some way.
Im going back again to stating what I said originally,(should have trusted my instinct) that they are forged as per normal. Ive since looked at approx 30 Porsche cranks in high res(not phone) and they all show signs of regular forgings all showing 15mm flash lines. A sintered anything wont have such a flash line, and the shape in general is 'smoother' and nearer net shape as it would appear in a 3d drawing for example. Forgings are a little more 'un-even' in general.

''make me think Porsche simply would not use anything but a forged, hardened crankshaft''

^^ Thats what I thought, and still think, the trigger happy search caught me off guard though - sometimes stuff doesn't surprise me considering the 'innovations' that are showing themselves in the new VAG engines. But this one of a sintered/pm crank was pushing it a bit it has to be said.
I call your man out to be wrong, and perhaps disgruntled.
Someone should tell him to tap it and record ring - a cast vs forged vs pm anything all have very different rings when tapped with a small hammer.

Brian,