Ooit heb ik op het forum wel eens gelezen dat er Porschemotoren zijn met cilinder(wanden) van nikasil en met alusil. Nikasil zou dan de betere optie zijn. Hoe kun je erachter komen wat er, zonder de motor uit elkaar te halen, bij een bepaald type gebruikt is?

Pelican knows it all.....

http://forums.pelicanparts.com/showthread.php?threadid=73286

Cabrio's iha alusil, coupes nikasil.

Nee hoor.

Citaat uit een posting van Wayne Dempsey

Nikasil vs Alusil Cylinders - In 1973 Porsche introduced a new type of cylinder used on the 911 2.7 Carrera RS. Engineered by German manufacturer Mahle, Nikasil cylinders are manufactured out of a dense, aluminum alloy that is centrifugally cast in a mold. The cylinder bore is then electroplated with a very thin layer of nickel-silicon carbide. Originally designed and used on the venerable 1971 917, these cylinders provide several unique advantages over the older-style ones. The primary advantage is that the micro-thin layer is extremely durable, and allows for thinner cylinder wall thickness as a result. As a result, the piston bores can be enlarged without changing the original cylinder head stud bolt pattern. In addition, the reduced friction along the cylinder walls combined with the surface properties of the nickel-silicon coating creates a tighter seal against the cylinder. The result is a slight increase in overall horsepower, due to the increased efficiency. These Nikasil cylinders are the most durable of any of the production cylinders and are highly sought after for engine rebuilds. These cylinders can be retrofitted to the earlier cars, however, you will need to install the updated piston squirters in to your early case (1970 and earlier) if it doesn’t already have them. The piston squirters lower the piston crown temperatures so that you can run the close clearances used by Nikasil or Alusil pistons and cylinders. It’s also important to note that Mahle makes Nikasil pistons and cylinders for 2.2L and 2.4L engines.

In 1974, Porsche introduced the Alusil cylinders, manufactured by Kolbenschmidt. The Alusil cylinders were primarily used as a less-expensive alternative to the Nikasil cylinders. These cylinders are manufactured out of a special 390 eutectic aluminum silicon alloy, and are used with a special iron-plated, ferrocoat piston. Like the Nikasil cylinders, they are plated with a special coating on inside bore. This coating is electrically etched to leave a microscopic layer of silicon particles exposed on the cylinder wall. The iron-plated piston and the silicon-plated cylinder walls operated together to create a durable dual-surface. In addition, the Alusil cylinders have the same thin-wall construction of the Nikasil cylinders, meaning that they too can maintain the same head-stud spacing pattern.

So what are the main differences between all of the available pistons and cylinders? The early biral cylinders can be honed and reused just like other cast-iron cylinders on non-Porsche cars. Starting in 1974, Porsche mixed and matched the Alusil and Nikasil sets, so it’s really the luck of the draw as to which set you have in your car. For the most part, Porsche used mostly Alusil in the 2.7L and 3.0L engines because of the reduced cost of production. The Alusil cylinders, unfortunately, cannot be honed. The honing process destroys the etching layer, and renders them useless. In fact, a general rule of thumb is that the Alusil cylinders are a one-time-use product, and should not be used again if the engine is rebuilt.

Alusil cylinders cannot be reliably reringed. This indeed is a common misconception in some Porsche circles. There are no replacement rings available that are specifically designed for the Alusil cylinders. Of course, throwing out your current pistons and cylinders can lead to the large expense of new ones, so a lot of people reuse them anyway. In some cases, the new set of rings seat fine, and they indeed can be reused successfully. However, you cannot hone these cylinders, nor predict whether the rings will indeed seat properly. The correct action to take is to purchase new pistons and cylinders, otherwise you may be tearing down your engine again in less than a mere 1000 miles. These Alusil cylinders typically have a ‘KS’ Kolbenschmidt logo cast into their base, although for a time, Mahle also made Alusil cylinders. The coating on the Alusil cylinders is non magnetic, so you should be able to tell the difference with a simple refrigerator magnet.

If you are tearing apart your engine for reasons other than worn out rings or valve guides, then you might opt to reuse your Alusil cylinders. This would be the case, for example, if you were tearing down your engine to replace broken or pulled head studs. If this is the case, I would recommend that you take your pistons and cylinders off of the engine, put them high up on a shelf, and don’t touch them until you are ready to reassemble. Don’t pull the pistons out of the cylinders and don’t dislodge or disturb the rings. Of course, you are taking a risk here that you will have worn rings in the near future. However, if your engine is a 3.0L, with 100K on the odometer, then there is a good chance that you can get 100,000 additional miles or more out of your set of rings, cylinders and pistons. I don’t necessarily recommend playing the odds like this, but if you’re rebuilding a good running engine with excellent leak-down numbers for the purpose of replacing head studs or some other non-wear problem, then it might be a good bet.

The Nikasil cylinders can indeed be honed and reused. They typically have a ‘MAHLE’ stamp on the lower side of the cylinder. The nickel-carbide surface needs to be lightly honed with a special silica impregnated tool, or what is commonly known as a grape or flex hone. The surface properties are too hard for normal tool steel honing machines. The Nikasil coating will be ever so slightly magnetic when you place a magnet next to it. The honing process is performed using special tools – either a specific tool designed to hone the cylinders, or a grape hone. Either way, you should only have an expert familiar with the Nikasil cylinders perform the honing process.

Interessant verhaal, Maarten, maar nu weet ik nog steeds niet hoe je dit nu kunt controleren, of is dit niet te checken?

Magneetje, Wim.

Oké

yeah... right

Ik begrijp hieruit dat dit dus zo aan de buitenkant te zien is.

Yep, dat wordt beweerd.

Thx, ga het in het weekend even checken.

911 carrera RS de eerste met nikasil. De eerste 911 2.7 en 911S 2.7 ook nikasil later alusil (G-serie). H-serie (2.7) alles Alusil vanaf 3.0 alles nikasil. (Dit zijn dus de oude G en H series)

Zo zou het moeten zijn. zegge ze

Ja

Alusil versterkt linnen kap en nikasil bekleed stalen dak zeker

nu ja, dat "je kan alusils niet herringen" is een punt van discussie op Pelicanparts... sommigen zeggen van niet, anderen van wel

of het is iets van geluk hebben, of het is iets van manier van werken dat verschilt tussen zij die het geprobeerd hebben

ik heb mijn vorige 944 (alusil) herringt zonder honen, leek me niet nodig, er was nog een mooi honing patroon te zien op de wanden
en dat ding had na revisie een compressie volgens het boekje , die ringen hebben zich mooi gezet...

Zoals het citaat ook al zegt, Nicasil is Mahle, Alusil is Kolbenschmidt. Merktekens van deze fabrikanten zijn vaak ingegoten in de cilinders.


Groet,

Brian Verbeek


www.karrera.net

De 3.0 en 3.2 zijn in een mix gebouwd met Alusil en Nikasil.

Het is in sommige series echt een kwestie van mazzel of pech hebben volgens de literatuur daarover. MAAR er is hoop:

De motoren zijn voor verschillende markten in verschillende versies gebouwd. Zover ik heb kunnen nagaan in eigen speurwerk is de 930/20 motor (3.2) die voor Europa werd gebouwd altijd met Nikasil afgeleverd.
Andere versies zijn wel met een mix Alusil en Nikasil gebouwd.
In de US of Japan is het een kwestie van mazzel of pech, maar van oosrpong in Europa geleverde auto's hebben de 930/20 motor en zouden dus altijd Nikasils moeten hebben.

Check is pas te doen als je de cilinders los hebt:
Onderaan op de voet staat Mahle (Nikasil) of KS (Kolbenschmid / Alusil).

Misschien kan Erwin iets uit eigen ervaring roepen ?
Kom jij wel eens Alusils tegen in een 3.2 ?

[QUOTE=Wayne at Pelican Parts;483189]blablabla

wolf, dat hat Maarten ook al gepost...