RT930turbo

Page 2.5

hopsis

That pdf does indeed state on page 2.5 that Cayenne Turbo engines are alusil coated, no such thing said about naturally aspirated engines on page 2.3

Still doesn't confirm it either way.

RT930turbo

This applies to both versions, where there are differences between the two in each subsection (e.g. Pistons) it is called out specifically. All the M48 4.5L and 4.8L engines are Alusil.

dihmels

Cool. Nice rock just flipped. Thanks for the document @RT930turbo

And yes, page 2.5 is referring to both NA and Turbo engines as it also covers the crankshaft, motor mounts, torque brace, etc. So it seems to be fact, IMO. The turbo engine torque chart is misleading as it seems to indicate a new "turbo" section.

J'sWorld

Doubt any new discoveries are going to be made unless Porsche or Jake Raby decide to release a bunch of data.


The PDF that Ernie posted is pretty credible it just needs to be read correctly. You can check out my post history, and I'm lazy so I'll allow you to prove me wrong.

^^^^

dihmels

Another bit from this document, that I am sure has been mentioned before, is that although it is clearly indicated that the block and cylinder material remain the same (AlSi17Cu4Mg)
, and no change were made to the cast positions for the S and forged for the TT, all of the second generation 4.8 liter engines have iron coated pistons.

oldskewel

Nothing in there says anything is Alusil coated. Because nothing is.

The whole entire block is an Alusil casting. The document does not actually use the term "Alusil" but calls the block "Aluminum" when being brief and "AlSi17Cu4Mg" when being specific. AlSi17Cu4Mg is Alusil. https://en.wikipedia.org/wiki/Alusil

It is a hypereutectic alloy, primarily of Aluminum (78%) and Silicon (17%). Hypereutectic means that the Silicon not fully soluble in the Aluminum, so basically there are extra Silicon crystals in the material. Through a finishing process, the Silicon in the cylinder walls is exposed to provide a harder surface. But there is no coating added, no liner, and again the whole block is Alusil.

And BTW, no this is nothing new. Not a great discovery. Anyone who knows about this knows it and is probably tired of saying it (see post #50 above) each time this comes up.

I cited a magazine article earlier in this thread with info from one of the main guys who used Alusil in block manufacturing, trying to keep the information here grounded. But on the interwebs, his statements carry as much space as everyone elses and are quickly washed away, like the Aluminum on a cylinder bore. When anyone new comes in to try to learn about this issue, 95+% of the information they quickly find is wrong, whether they know it or not. And it generates further information, upping the percentage. Really, just for fun, whatever you think you know now, go back through this thread and see how much of it is completely wrong or irrelevant.

dihmels

@oldskewel I agree with you 100%. There is even a mention of a different alloy used for the blocks 2008+. Also apparently not true. Personally I'm not looking for the "one answer" to the issue. I am more or less discovering many opinions and a few facts. I am curious about though about the use of iron coating on the pistons 2008+ for both S and TT.

Forums are and education system. When you start a researching subject you really are the student. As you learn you may become a teacher of other new students or may be happy with your new found knowledge and walk away. Those who choose to become permanent students and never graduate to teacher should have walked away a long time ago. I'm not speaking to anyone directly but if you find yourself annoyed by this, or any other thread, walk away. If you've graduated to teacher then be prepared to teach the same curriculum to any new students that may sign up. JMO

hopsis

This is good info, I personally don't mind finding out I've been wrong. All I've learned from this topic is mostly from internet forums and I guess it happened exactly as oldskewel stated above.

RT930turbo

I enjoy sharing the knowledge I've gained. I dont post too often, but those of us that have been all the way into a cayenne engine are somewhat few and far between on the forums.

Not many folks overhaul M48s, but for anyone crazy enough to go down the path I am willing to help. When I went down this road it was very helpful to talk to others that have been there done that. I spoke with several on this thread, and we exchanged notes and the result was fantastic.

At the end of the day, these are just engines.


-Artie

dihmels

My next search will look more like "How to get the engine out of the bay through the front?"

Flat6 Innovations

Note-
Alusil isn't a coating. The block is made from monolithic Alusil entirely.

Wisconsin Joe

^This.

Same as the 928 block.

Incidentally, same as the old Vega block. The one that always blew up.
However, that was an overheating issue. The heads were designed very poorly and would overheat & warp.

928s & Cayennes are very susceptible to damage if they are allowed to overheat. But something has to go wrong for that to happen.

19psi

Bought my first used car in '86 when I was in 10th grade....a '77 Vega. By '76 Chevy got it right after tweaking the engine into what they called the "Dura-Built". I bought mine with 60K miles on the odometer, beat the hell out of that car for 5 years and it didn't burn any oil between changes when I sold it at 125K miles.

It took Chevy 5 years to iron out the bugs and there were recalls and revised warranties for the early years. And technically, the block wasn't so much the problem.
Seems it took Porsche at least 7 years to correct the scoring issues (at least with the Cayenne) and of course no owning up to it. And considering the Vega came out in 1971 and the 928 in 1978, you'd think a proper aluminum block with high silicone content would be a no brainer for any manufacturer 3 decades later.

I'd love to know what went on behind the scenes at Porsche in the mid 00s when engines started crapping out under warranty. You just know the blocks were being sent back for analysis. Were they at a loss as to what was causing the scoring? Did they know right away that it was a bad tolerance issue? If so, why did they do nothing about it until '09 or '10?

v10rick

GM needed the engine to last just long enough until body cancer finished it off.