We have a final process now where we know exactly how to repair the Cayenne engine affected with piston and cylinder scuffing.

We will bore your block from between 0.010" to 0.020" to remove the gouges, plate it with NiCom (Nikasil) back to near-original dimensions, have custom Arias forged pistons made to our specs, and supply them to you with new piston rings designed for Nikasil.

Our pistons are specially manufactured to fit on the stock rods. All you need is an engine gasket set, a set of bearings, and put it together!

In addition to a SUV-saving repair, these forged pistons are much stronger than the stock cast pistons, and the Nikasil-over-Alusil composite is tough-as-nails for your block!

More information here:
http://www.928motorsports.com/servic...ock_repair.php

 

What about the affect of sulfur in gasoline in the U.S. on nikasil?
I seem to remember BMW had a lot of failures and had to abandon nikasil.

 

Keep in mind that not all NiCom processes are the same. We are having no issues, and neither is Mercury Marine or Harley Davidson - who NiCom all their high-performance engines. I use them as a reference because they are American manufacturers and certainly their customers are using American fuels.

Note the many pictures of Harley cylinders being NiCom plated in the pictures on this page:
http://www.928motorsports.com/services/uschrome.php

 

$5000.00 is not cheap.

 

Nope. Unless your comparing it to the cost of
a) replacing it with another Cayenne, or
b) buying a short-block from Porsche (which will likely do this again.)

 

Carl, I'm sure you are aware of the theory that many scored cylinders on modern Porsche engines are due to different rates of expansion of the piston and cylinder at initial warm-up from a cold state. Will your kit also prevent a re-occurrence of scoring due to this issue?

 

DMany people don't realize that asking for more than 100k miles from a set of 2618 forged pistons is not likely. You could get a lot less. They are setup looser all together and they are softer. The ring lands and skirts will wear much faster than a cast or hypereutectic pistons. You could get some piston slap at cold startup. Talk to your builder about these issues.

Used and unscuffed pistons can be had on eBay, any decent engine builder should be able to take some measurements and tell you whether you could reuse your old ones.

Don't forget, the Cayenne rod big end is not resizable due to the cracked cap manufacturing and parting line. For the motors that have seen a lot of high rpm and miles this could matter.

 

I'm thinking about having a torque plate made and offering it for rental so that any good engine builder could sleeve the block properly.

How many people think this is a good idea?

 

I have always thought this was a better theory than the "sulfur in the fuel" theory.

The answer is YES, because of the skirt coating on the piston (not present on the OEM pistons), the different piston to bore clearance we run, and the lower abrasion presented by the Nikasil vs the Alusil. For these 3 reasons, yes.

 

I haven't seen an engine with badly scored cylinder walls yet that had good pistons. They are scored too, in a near-matching pattern. And suppose you did put a piston with scored skirts in a cylinder with a good cylinder wall. That cylinder wall will be quickly damaged as a result... It'd be like doing the repair half-way. Smooth cylinder walls, scored pistons... I wont do it.

 

Gotta go guys - my weekend is calling! So if there are other posts and questions I will see them next on Monday.

Have a good weekend!

 

Thanks for offering this service, Carl. I for one, although I have a 2008 CTT, will sleep better knowing I have a reasonable solution if I develop this problem. $4700 is way better than the $$$$ replacement!

Cheers,
TomF

 

I have heard that US refiners have reduced the Sulfur content in fuel. So this may not be a problem it once was. I'm certainly no expert in this area but always curious about engine design. It seems that getting an aluminum block to wear as good as cast iron has not been simple. It is interesting that Porsche moved away from Locasil back to Alumasil.

 

Was it determined cylinder scoring was caused by:

~ Bad piston oil scraper rings?
~ fuel/chemical makeup?
~ Particulate matter entering combustion chamber?

 

Not in this case.

I have not come to a firm decision what is causing it yet, but I do have my doubts about it being caused by high-sulpher content in the fuel.

Early specualtion was that it was caused by the cast pistons they used in the non-turbo motors.... because he turbo motors had forged pistons and they were reported to be fine. Until the Turbo Cayenne's started showing up the same way also...

Another speculation is the ambient temp where the car is kept. Like a car in SOCAL, for example. Might get into the 50's at night. So even a "cold" engine is relatively warm compared to up here, where a piston has to go from below 0 to operating temperature (big range). That theory has holes in it too.

We dont know everything that Porsche does. They might know that the problem engines came from boring machine or shop A and the engines from boring machine/shop B have no trouble. If it is internal like that, we'll never know because the truth will be buried. For example: look carefully at the circumferential lines near the bottom of the piston skirt in the picture on Post 10 above - those sipes are deliberate, from the factory, and meant to hold oil up on the cylinder wall... interesting..... wonder what they know/knew that they are not sharing.