Cylinder Honing Information

[snowman]

The following sites have very interesting info on cylinder honing. Free literature is offered that details how Flex hones work and why they are the way to go for final honing or reuse of cylinders that can be honed.

http://www.brushresearch.com/Index.cfm?FuseAction=home.TechnicalBooklets
http://www.brushresearch.com/Index.cfm?FuseAction=home.FlexHoneTools

These hones are relative inexpensive (about $50 typ) and are available thru many auto parts stores as a special order iitem. They are also suitable for home use with no special skill required to operate, fool proof, and almost impossible to damage anything, unless you have Si cylinders.

Hear your engine break in within the first 5 minutes of running! ( sound changes from soft booms, to very sharp bangs)

[Wayne 962]

No-no on Nikasil cylinders though!

-Wayne

[speeder]

Same with Alusils. That covers any 911 built since 1973(?).

Mr. Snowman, since you aspire to be an expert on 911 motors, and be taken for one, why don't you read some books and try to talk to some of the big-name engine builders? Jerry Woods and Walt Watson, (Competition Engineering), are two of the most respected for good reason, they have serious stats (#s) behind them. Don't know if you could get any of their time, but I have and it protects me real good from misinformation.

You mentioned personal attacks in another thread, I do not wish to flame you here in any way, but it seems as though you are an experienced engine builder w/o much specific air-cooled or Porsche experience. Is this correct? Take care,

[Jim Sims]

I'm confused; I thought any of the cast iron lined and Nikasil cylinders could be honed (but the Nikasil only with special procedures and abrasive - normal stones don't work). Only the Alusil can't be honed at all? Please clarify. Jim Sims

[724doorE]

Straighten me out Jim on this if I misfire, but I belive all nikasil should not be honed due to the nickel particles being dislodged by the procedure. As I understand it, the particles are "stood" up during the plating process and part of their purpose is to hold oil on the cylinder surface. Once honed, holding the oil film is not possible to the same extent.

I didn't realize nikasil was used on any cast iron liners, I thought it was used only with the aluminum lines (on the production engines). We also have the " chromal" racing engine jugs to think of from the 906 onwards.

Don't forget Porsche, Mahle, isn't the only mfr to use the process, I belive it has been common practice on small bore bikes since at least the early sixties and I would be willing to bet money that our buddies in the aircraft engine building industry were the first to use this technique for this purpose. I wouldn't be surprised to discover that, for example, the old wwII Pratt Whitney radials used this idea that might have contributed to their legendary ability to keep running after being shot up, having a jug blown off, no oil, etc.

ramble on....

[island911]

I believe the Nikasil can be honed, (as Jim says; "with special procedures and abrasive') but that does NOT mean they should be honed as part of a rebuild. . . .with the hard nickel/silicon surface, they don't wear like cast-iron pistons, and you only have ~.004" of hard surface (as new). So (IMO) one had better have a very clear idea about what they are trying to accomplish, (and how it's done) for a hone to ever touch a Nikasil cylinder.
BTW; I believe Mahle invented the process.

My speculation on why Nikasil can be honed (on the rare/weird occasion) and the Alusil can not, is in the mechanical structure of the surface. Nikasil has the silicon carbide in a nickel matrix, where as the Alusil has the silicon carbide self-supported. (Alusil surface is created by etching away the aluminum, leaving the silicon)

[724doorE]

Ahh, thanks Island, you saved me from looking it up!

[Wayne 962]

Sorry, I meant to say, "don't do it yourself" - you should use a special diamond hone. Good info on honing though Snowman - good find. I did a bunch of research for the book, here's an excerpt from page 54:

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, 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 between the piston rings and cylinder wall. 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 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 replacement Nikasil pistons and cylinders for 2.2 liter and 2.4 liter 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 have 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 cylinder walls operated together to create a durable combination. 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 (Figure 3-17). 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 etched 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 re-ringed. 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 leads 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 between Alusil and Nikasil cylinders with a simple refrigerator magnet. The Nikasil coating will be ever so slightly magnetic when you place a magnet next to it.

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 on an low-mileage engine. 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 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. You should only have an expert familiar with the Nikasil cylinders perform the honing process.

-Wayne

[snowman]

"The Nikasil cylinders can 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. You should only have an expert familiar with the Nikasil cylinders perform the honing process."

The info refered to is the grape, flex hones cited here. And why did I bother saying EXCEPT for Si??? no one seems to have read it. I even cited "cylinders that can be honed"

Whats going on here? I refered to some of the most expert people in the world on cylinder honing, cited that they had free literature, and noted that if you can use their product it is very forgiving. Its also used BIG time by the bike crowd with their air cooled and almost identical cylinders.

[80sc man]

I am fairly new to this board and am trying to learn about porsche engines as I have just come from the chevy world. I would really appreciate it if you all could cast away your personal "fits" with eachother. It makes it kind of hard to learn and have fun while doing it when I have to sort through all these cutdown letter to eachother.

[island911]

Originally posted by snowman
. . .
. . . And why did I bother saying EXCEPT for Si??? no one seems to have read it. I even cited "cylinders that can be honed"

Whats going on here? . . .

"Si"
. . . which is short for "Silicon,"
. . .which may contextually imply "Silicon-Carbide,"
. . ..which is used in a Nickel metal matrix by Mahle
. . .for one of Mahles cylinder-lining products called Nikasil.

Snowman, you are assuming every reader will have the background to make the inferential jump from "Si" to a product called "Nikasil" or "Alusil."

Now do you see why I call your posts half-baked? This posts, of yours, may be gramatically correct, but inferentially false, to some. . . . kinda Clintonian, in a way. You don't want THAT, now do you?

[snowman]

Whats half baked about reading some info on honing? Straight from the source, not me. I kinda see the root of the ignorance here. Must be a Democrat and kinda think that everyones an idiot or something and needs help figuning out 6th grade stuff.

[island911]

Originally posted by snowman
. . . Must be a Democrat and kinda think that everyones an idiot or something and needs help figuning out 6th grade stuff.

Considering the grammar and spelling here, I would say "6th grade stuff" is a stretch.

[snowman]

Must be a democrat, can't argue the subject, change it.

Opps sorry about that, could be any kind of leftist pinko, commie, same difference.

Anyway I thought this was an engine building forum, not a spelling, grammer, flame fest or whatever.

Heres a novel thought, why not talk about rebuilding Porsche and related engines?