Nikasil or Alusil?

[Greg White]

How can you tell if you have Nikasil or Alusil cylinders? My pistons and cylinders are out of my 84 Euro Carrera and appear to have some of the linning comming off of the top edge. If they are Nikasil, is this the linning comming off? If they are Alusil (which I think is not a linning) what is this deteriation?
Thanks, Greg

[Bill Verburg]

Actually Nikasil/Alusil refers to the cylinders, but since each needs its own special pistons it really doesn't matter much. Look for the manufacturerers stamp Nikasil is made by Mahle, Alusil by Kolbenschmidt, As far as I know all European 3.2 were Mahle Nikasil, 10.3 cr

[Early_S_Man]

Although Alusil piston & cylinder sets are available from both KS and Mahle (so-called "LS" sets) ... the Euro 3.2 only have Nikasil sets listed in the spec book!

[robs]

Hello,

I never found a stamp on my 1980 SC 3.0 Euro cylinder set that indicates if I have Mahle Nikasil or KS Alusil. Can I see it with the motor in the car ? Has anyone a photo showing what (and where) I have to look for ?

The Motor type is 930/09, number 6304239.

Thanks,

[1980SC]

I'd also like to know what I have in my 1980 930/09 # 6301010, but I don't think you can tell from the outside.

Rob
1980SC euro

[Bill Verburg]

According to the spec book Mahles were nikasil and KS were alusil



The info thats supposed to be on the cyl base is as follows



unfortunately it's often not there, I just looked at a set in my garage, the manufacturers stamp is missing. Though JE kindly put their stamp on the bottom of the pistons

[Greg White]

OK, I've got one of the sets in front of me. It is a mahle set with the letter "P" to the right of that. The cylinder also has a "5" in a triangle as shown in the previous post and a Part number of "95ZN1 W8". Does this help to identify?

[Bill Verburg]

The 5 in the triangle is the height group, the # in the middle between the Mahle stamp and the height group is the cylinder tolerance B in the last diagram. It should be a # 0,1,2,3

[Greg White]

Bill, according a machine shop in NJ, if these are Alusil then they can be honed and reringed. The top edge (about 5/8" in from the top) has what appears to have a delamination of something. This bothers me. I'm trying to detirmine if I need a new set of pistons and rings. I am interested in a long term reliable solution for this rebuild. Thanks, Greg

[john walker's workshop]

nikasils delaminate, generally at the top edge, alusils don't, because they're not coated.

[Greg White]

Can you hone and reuse Nikasil cylinders that are delaminating?

[joeycatt]

Nikasil's can be renewed (much less expensively than replacing)by US CHROME
Their web site is: http://www.usnicom.com/usbig31.html
They claim to use the same process as Mahle, and will renew a cylinder for $115. There is an additional cost for machining , if the cylinder is damaged - I think around $40.
They say that they will renew the cylinder, remachine it to within .0002" accuracy. They asked me to also send my pistons - they renew and custom fit the cylinder to the piston.
I've not used them yet - but will likely try it this winter, when the 3.0 gets renewed. Good tech service and competent help available when I called them. That alone is a real +++

[Wayne 962]

I fell like I have posted this at least 3 times on this BBS in the past month, but here it is again:

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.

-Wayne

[Greg White]

Hi Wayne, thanks for all the good information, but I still don't have and answer to my question. Should this honing process be used on cylinders that have the nikasil coating comming off around the top of the cylinder? Or are these scrap? see the attached photo. Greg

[Doug Zielke]

Hey Wayne.......
This winter, I'm going to be taking the heads off my 3.0, due
to a recently discovered broken head stud.
I read your info about leaving Alusil cyls and their pistons
and rings alone if the motor is otherwise healthy. Mine is,
and I do not want to re-ring if I find Alusils in place when
I take it apart.

You say to pull the cylinders off along with the pistons, so
as not to disturb the rings. OK I get the point of this good
advice, but how *exactly* do you do this? I mean, you need
room to push out the wrist pins. What is the trick? Please
tell me the detailed method. I'll still be buying your book,
anyway, even if you tell me the secret.

[Wayne 962]

Minus one point for Greg using an image that is even too big for my own monitor!

Doug,

See here:

Wednesday's Engine Rebuild Teaser Pic...

-Wayne

[speeder]

So other than the magnet test, there is no other sure ID as to which you might have? (Since Mahle made Alusil also and sometimes jugs have no manufacturer ID?). TIA.

[Wayne 962]

My magnet works every time.

Odd are, if the cylinders are Mahle, they're Nikasil. If they are KB, then they are Alusil. It's not always the case, but most of the time it is...

-Wayne

[Greg White]

Sorry for the giant image, it was the first time that I have tried to attach a file. Be that as it may I, I am still looking for someone who knows about the delamination of the nikasil. From what John Walker wrote this may not be so unusual. Any help would be appreciated. Greg nomoregiantimages White

[john walker's workshop]

from the photo, it looks like the delamination goes into the area that the top ring covers, so they're trash. usually you see it just at the top edge, where the bore has a slight bevel. even then, there's no way to know if it will get worse or not.