cobalt

I have been looking at a lot of cast aluminum and magnesium parts from Porsche lately and I am shocked at the lack of quality. I spent 30 years casting parts for the DoD, airplanes, helicopters, race cars, cosmetic and ornamental etc etc.

It isn't that difficult to cast a decent aluminum or magnesium casting but what I am finding is IMO unacceptable amounts of gas porosity in aluminum parts and magnesium parts riddled with microshrinkage actually more like extreme shrinkage. I honestly will come out and say whoever cast the Mg fans shouldn't be in business.

I recently purchased a 996 Cup car intake plenum loaded with gas porosity and a 993 magnesium fan with extensive shrinkage to the point is clearly visible through the factory paint.

I understand this is common for many automotive parts but the prices of Porsche's and their parts I would expect better. It doesn't take much for a foundry to control its processes and when producing parts in large volume far easier to prevent shrinkage by properly gating the parts.

Here are some examples please post if you have others to share.



You can clearly see the excessive amount of porosity in this casting on the machined surfaces. These might look good but they show signs of core shift poor sand mix and nothing was done to slurry the core parting lines to make a clean internal chamber. Don't get me started on the ridiculously oversized parting lines and poor cleaning job. Surface roughness due to poor sand control as well.






^^^ the white dots are gas bubbles possibly from an improperly cured core, improper venting of outgases from the core or improper melting and degassing of the aluminum prior to filling the mold.

The shrinkage in this fan is criminal IMO. If I was making these they all would have been scrapped.











This is from a 1996 40k mile 993 engine. The paint is not damaged and has filled the voids. For a rotating part this is completely unacceptable IMO.

I thought the Germans were supposed to be good at this??

GTS Sully

The packages of hamburger and hot dogs buns are a nice touch!

r911

This cannot be done by Germans. They must be outsourcing it to one of the "suspect countries."

Thx for posting the info tho.

cobalt

Parts are marked with OE stamp and made in Germany. I was shocked.

wareaglescott

Well as 99% of us that read this are completely uneducated on the technical aspects that you mention how do this translate to the performance/durability/lifespan of the parts?

You say this is common for automotive manufacturers. Does the part meet the expected industry standard? If it performs and lasts as expected then the fact that 'they show signs of core shift poor sand mix and nothing was done to slurry the core parting lines to make a clean internal chamber" doesn't really bother me or mean much to me.

cobalt

It all depends. .

Longevity will suffer as porous surfaces will trap contaminants and accelerate corrosion. The real concern is the fan. It is rotating part and this is clearly a stress riser, so yes. If the paint is compromised and moisture attacks it can fail quite quickly and since it is on the backside may go undetected and make a hell of a mess one day. These are prone to failure. I had not seen this on the early cars as much as the 964 and 993 on up parts. Years ago people used to break blades by putting a pry bar in to loosen or tighten the belt. I always assumed this was the case with these as well and now I am thinking it is as much a manufacturing issue for some of the failed fans posted.

I can't say what standards if any are employed. Based on what i know I would have to say there was no QA of any type. This would not meet the bare minimum of a Grade D casting for foundry control for non inspected parts and I would reject on visual inspection alone.

r911

Are the parts made in Germany? or is just the box marked that way?

wareaglescott

Interesting. thanks for the additional feed back.

cobalt

I was looking at bunch of 70's mag cases and other early cast parts yesterday and it seemed the quality was much better. So this seems to be more common with parts made in the 90's on up so far. If anyone has any similar parts they would care to share I would be interested in seeing them.

r911

Maybe contact VWAG - I'm sure they are looking for ways to pay off their pollution fines, so maybe cost-cutting on their Luxo-SUV Division (which used to be called "Porsche") is one way they are doing it...

GTgears

Steve Weiner-Rennsport Systems

They have cut more than a "few" corners,........

They are cutting FAR FAR more now in the quest to control costs and maximize ROI.

In many cases, QC is either non-existent or outright laughable so finding decent parts is both a full-time job and the biggest challenge of my career.