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The Secrets behind Nickies™ How are Nickies™ different from a factory aluminum cylinder? There were three varieties of aluminum cylinders installed from the factory by Porsche. First biral cylinders with aluminum fins cast around cast iron liners. Then there were early aluminum cylinders, utilized a ferral or chromal plating. Later, Porsche turned to Mahle's Nikasil and Kolbenshmidt's Alusil. Although both were aluminum, that's where the similarity with "Nickies™" ends. So how are Nickies™ better?
What makes Nickies™ the
latest step in the evolution of the aircooled cylinder?
In the development phase of LN Engineering's Nickies™ cylinders, we were considering casting our cylinders, but we were unhappy with the attention to detail that is left out of typical castings. Even with the best of castings, there are limitations. Stock Porsche cylinders were cast. While advantageous for mass production, there are downsides to casting. First, casting poses a big difficulty to a strong grain structure. Our billets are from a special extrusion, custom-made by Alcoa, allows for the strongest possible grain pattern, making for a much stronger and thermally conductive material while being much less brittle than casting alloys, so they are more forgiving to high cylinder pressures and detonation. Through advanced metallurgy, material science, and engineering, LN Engineering's Nickies™ cylinders provide:
What’s
Wrong with
Cast Iron Cylinders?
All stock VWs, Porsche 914s, and early Porsche 911s and the vast majority of modified ones use cast iron cylinders. One of the major problems with cast iron cylinders is that they are thermally overloaded! This includes commercially available big bore kits in the popular 1720cc 86mm bore size. Note that the aforementioned 911T has the only 911 engine ever to receive cast iron cylinders due to its detuned, low performance nature. These engines, at their maximum 2.4L, had just an 84mm bore and produced about 22hp per cylinder, and that’s with a superior cooling air system. Even the Porsche realized that cast iron cylinders were not sufficient with their early adoption of biral, ferral, chromal, and nikasil cylinders. It should now be apparent why the challenge of keeping your aircooled engine "cool" is a daunting task! Cast vs. Billet - It's easy to see why Nickies™ work so well.
I've heard of biral cylinders. How do these perform?
An alternative to replating existing
liner-less cylinders is to "sleeve" them. This process requires the cylinder to
be over-bored significantly (to the point of reducing the structural integrity
of the aluminum) and then a ductile iron or chromoly sleeve can be pressed in
with an interference fit. This is superior to cast on fins in that if sufficient
interference is used, the liner physically cannot separate from the cooling
fins, which will lead to increased life of the "biral" cylinder. The superiority
of this conversion ends here. From a cooling standpoint, this is a step in the
wrong direction. Interesting side note: LN Engineering did at one point offer biral cylinders, dubbed "Biral Babies," as an alternative to our Nickies, but due to their high manufacturing cost to provide a quality biral cylinder without the drawbacks of their cast counterparts, they could not be sold competitively when compared to our Nickies™. Nickies™ also worked better, which is an added plus. Why Aluminum Cylinders?
How does a ferral coating or chromal plating differ from Nikasil? Historically, the first way to allow the use of solid aluminum cylinders was developed in 1951 by Mahle. This was "Chromal", which used a hard chrome plating on the bore of the cylinder. Many aircraft have since used this over the years, too. The big problem with this plating is that it is highly prone to chipping - although in a low-performance, light-duty, low rpm aircraft engines it proved satisfactory, it was a problem to destroy the chromal plating on a Porsche cylinder on a hard run. In addition, chromal platings tended to shed oil, required cylinder walls to be "dimpled" to force oil to stay on the cylinder walls. This also leads to flaking or cracking of the plating. Similar in wear characteristics, Porsche used a flame-coated "ferral" coating. Needless to say, this is an unsatisfactory solution, and it ultimately led to Mahle's development of Nikasil in 1967. To this day, high end Porsche engines utilize this Nikasil plating process. Not only does Nikasil allow the total elimination of poor-cooling cast iron, but it also is harder and more oleophilic (oil-liking) than cast iron. In fact, diamond tooling is required to hone these cylinders! This allows superior lubrication, reduced friction, and superior wear characteristics. We feel so strongly about our Nikasil process, that all our cylinders come with a lifetime warranty on the plating. No cylinder commercially available comes with that promise! If you have chromal or ferral cylinders, let us rebuild them or convert them to big bore cylinders! Is Alusil the same as Nikasil? Which one is better? Nikasil, while it is the best solution around, it is also the most expensive. Reynolds and Kolbenschmidt developed a process that still uses cast iron rubbing on aluminum, but flips it around from a typical engine. Instead, they plate the aluminum piston and let it ride in the aluminum cylinder. To reduce wear on the cylinder wall, a high-silicon aluminum alloy is used on the bore. The Chevrolet Vega was among the first of the vehicles to use this new idea. Needless to say, history speaks for itself: the Chevrolet Vega engine had many, many problems due to this process, ranging from excessive wear to overheating to outright engine failure. As with the Vega, heat is the enemy of Alusil and was promptly replaced by Nikasil cylinders until Porshce went to water-cooled in the late 90s. Soon after Porsche began to use Nikasil on 911 and 911S engines, they reverted to the use of Alusil to save money. The high-performance Carrera engine never got this treatment - it stayed Nikasil. The use of Alusil was limited, and the factory went back to Nikasil after not too long due to the superior performance and longevity of Nikasil. With exception of lower end watercooled Porsche engines like those in the Boxster which use a modern version of Alusil called Lokasil, high end Porsches like the GT2, GT3, and Carrera GT utilize Nikasil. There is quite some debate concerning the rebuildability of Alusil cylinders going back to the etching/honing process done to the raw aluminum bores and re-ringing. This is not an issue with Nikasil, as it can be readily re-honed or stripped and replated if required. Case Study: Hummel Aviation
LN Engineering was approached by Hummel Aviation with a desire to have a two-cylinder alternative to typical four-cylinder power plants in their Ultra-light and Experimental aircraft. There were three primary objectives:
Why use Nikasil plating? Aluminum pistons rubbing on raw aluminum cylinders doesn't work. There are three primary solutions to this problem. Nikasil, or Nickel Silicon Carbide, is the most tried and true of them all. It is a special plating originally developed by Mahle consisting of silicon carbide in a nickel matrix. Since its inception, it has been used in every high performance automotive niche from aircooled engines to NASCAR to Formula One and even water-cooled OEM engines, and there’s a reason why. Not only does it allow the total elimination of poor-cooling cast iron, but it also is harder and more oleophilic (oil-liking) than cast iron. In fact, diamond tooling is required to hone these cylinders! This allows superior lubrication, reduced friction, and superior wear characteristics. We feel so strongly about our Nikasil process, that all our cylinders come with a lifetime warranty on the plating. Not even Mahle cylinders come with that promise! I've heard that BMW had problems with Nikasil in the U.S. market? Refining the Alusil process is a major focus of automotive engineering today due to the price and complexity of Nikasil plating. Some attempts to modify the tried and true, yet expensive, Nikasil process resulted in chemical incompatibility with high-sulfur fuels. It seems that there simply is no way to make it cheaper without compromising quality and durability. BMW had problems with their Nikasil blocks in the US where the fuel has a high sulfur content, whereas Porsche had zero problems in the 2+ decades Nikasil was used. Many also neglect the fact that BMW also uses Nikasil in their motorcycles, to this day, without fail. In fact, the company we use has been plating for years and years without incident in the US where high-sulfur fuels live and comes with a LIFETIME WARRANTY with our Nickies cylinders. I've heard there aren't any good rings for use with Nikasil bores? Considering the wide range of bore sizes we've made our Nickies cylinders in, it's been critical to find rings that are designed to work with nikasil. In fact, we have quite an extensive array of ringsets from Porsche's original equipment manufacturer Goetze, to many that are supplied by JE Pistons. In fact, the use of nikasil allows for lighter tension, thinner rings, with better ring seal than rings thicker, higher tension rings typically used with cast iron bores, for greater HP improvements and longer ring life! I'm thinking of doing a rebuild myself. Is there any recommended reading?
Part I can be found at: http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm Part II can be found at: http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-2.htm For the VW Type 4 or Porsche 914, I would suggest visit Jake Raby's Aircooled Technology at http://www.aircooledtechnology.com and the Type 4 Store at http://www.type4store.com for their instructional DVDs on rebuilding your type 4 engine. They have a high performance engine assembly DVD in the works for 2008/2009 and also offer engine kits for the VW Type 1 and Type 4 featuring our Nickies cylinders for easy assembly with no special tools required. Do I still use head gaskets? What base shims do I use? Aircooled engines rely on a metal-to-metal seal at the head/cylinder interface. With cast iron cylinders, this poses a problem. The thermal expansion of cast iron is much lower than that of aluminum, so when the engine gets hot, the heads get bigger than the cylinders and the seal “moves,” which is a primary cause for symptomatic compression leaks. An aluminum to aluminum sealing surface allows for the omission of copper head gaskets, for even better sealing! When both pieces are aluminum, they expand at the same rate so the seal can remain intact! Like the 3.2 Carrera cylinders that used a taper on the sealing surface to create a gradient in the clamping loads which improves sealing and helps to form a "carbon seal," we duplicate this taper to improve head sealing and eliminate the need for gaskets on all our cylinders. Our cylinders can still be used with your choice base shims in either steel, copper, or even aluminum.
LN Engineering now offers custom base shims for our 1800 and 1883cc big bore kits and we can also do custom thicknesses with just a short 3-5 day wait in most cases, made to order. We stock .010, .020, and .040 sizes for immediate delivery.
LN Engineering also offers custom thickness base shims for our slip-fit and machine-in cylinders for the 964 and 993 Porsche 911 engines, in any thickness, in steel or copper. Contact us at 815-472-2939 or info@LNengineering.com to bring your “tried and true" Aircooled engine to the new standard of precision performance!
Website last updated Feb 1st, 2008. Contact webmaster at info@LNengineering.com Copyright LN Engineering LLC ©2008 |
A quick
survey of performance aircooled
engines will find that VWs are unreliable, but the Porsche 911 is so
reliable
that in both production and racing they last forever.
Porsche tackled this problem by using
“biral” cylinders to overcome the limitations of cast iron ones up to 32hp per
cylinder.
Although the liner is stronger, it wears about two to four
times as fast Nikasil and also reduces thermal conductivity significantly,
almost cutting cooling capability by 2/3rds. Modern ductile cast iron is
stronger than the casting aluminum alloys used for cylinders, which increases
rigidity, reduces wash-boarding, and reduces warping. Nickies, made from the
finest extruded aluminum custom made for LN Engineering by Alcoa, is 100%
stronger than the casting aluminum used by the factory and 35% stronger than the
best ductile cast iron available. There is no finer cylinder available for your
aircooled engine.
Although biral cylinders are
a significant
upgrade over cast iron cylinders, extreme racing conditions (starting
with Porsche’s 1971 917) or ultra-high performance
street machines (starting with Porsche’s 1972 Carrera)
required more.
Wayne
Dempsey, owner of Pelican Parts and publisher of 101 Projects, has provided an
excellent must read guide to rebuilding and upgrading your 911 engine, "How to
Rebuild and Modify Your Porsche 911 Engine", which is available from Pelican
Parts or your local book store. Wayne has provided a sneek peak in the form of
Pelican's Technical "Time to Rebuild?" article, which covers many aspects of the
process. Regardless, this should be your first read before diving into a rebuild
or considering doing it yourself. Even if you don't need a rebuild, it's good
reading. 
LN Engineering Nickies™
are Proudly 100% Made in the USA!