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The Secrets behind Nickies How are Nickies different from a factory aluminum cylinder? There were three varieties of aluminum cylinders typically found on aircooled engines. First biral cylinders with aluminum fins cast around cast iron liners. These perform more like cast iron cylinders. Then there were early aluminum cylinders, utilized a ferral sputter or splatter-coat or chromal plating, typically identified by its dimpled bores. 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?
Case Study: What makes Nickies the
latest step in the evolution of the aircooled cylinder?
While developing Nickies cylinders, we considered various casting materials and processes. Even with the best of castings, there are limitations. Stock cylinders were cast. While advantageous for mass production, there are downsides to casting. First, casting poses a big difficulty to a strong grain structure. The strength of a cast cylinder is limited by the casting alloy used, as are other critical properties that affect a cylinder's performance. Our alloy, especially extruded for LN Engineering by Alcoa, allows for the greatest strength, best grain structure, increased ductility, and thermal conductivity. Through advanced metallurgy, material science, and engineering, LN Engineering's Nickies cylinders provide:
Whats
Wrong with
Cast Iron Cylinders?
All VW, Porsche 914, and early Porsche 911 models use cast iron cylinders. One of the major problems with cast iron cylinders is that they are thermally overloaded! 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 thats with a superior cooling air system. Even Porsche realized that cast iron cylinders were not sufficient with their early adoption of biral, ferral, chromal, and later Nikasil plated aluminum cylinders on Porsche engines. 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.
Cast vs. Billet - It's easy to see why Nickies work so well. I've heard of biral cylinders. How do these perform?
Although biral-type aluminum finned iron-lined cylinders do typically cool better than cast iron cylinders, the superiority
of these cylinders ends here. From a cooling standpoint, this is a step in the
wrong direction. Nickies are 35% stronger than the best ductile iron available, debunking the myth that steel sleeves are needed for strength. Nickies also make more horsepower!
Interesting factoid: LN Engineering once offered biral-type cylinders, dubbed "Biral Babies," (shown above) as an alternative to our Nickies. Why no sealing rings or provisions for o-rings? Although some factory Porsche cylinders have provisions for head gaskets, sealing rings, or o-rings, our Nickies cylinders do not come with any for several reasons. We've found through evaluation of cylinder failures, that these sealing ring grooves cut into the sealing surface of the cylinder at the head can leave the cylinder prone to failure due to the thinner cross section of aluminum left to seal against the head. Likewise, we've found that o-ringing the case or cylinders at their bases rather than using sealant eventually leads to nagging oil leaks down the road. Use of Curil T or Curil K2 is a time-proven solution to sealing cylinder bases. Why Aluminum Cylinders? Although biral cylinders are a significant upgrade over cast iron cylinders, Porsche started using solid aluminum cylinders all the way back in 1951 in its production cars, before cast iron and later biral-type cylinders were first used on later Porsche 356 and 912 models followed by 2.0 through 2.4 liter 911 models. a cylinder with better cooling was still required for performance models- they turned to solid aluminum cylinders to fill that need for added cooling and longevity! Aluminum conducts heat FOUR TIMES as well as cast iron. How does a ferral coating or chromal plating differ from our NSC or Mahle's 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, these chrome platings did not fare so well in engines turning higher RPMs. 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 to cast iron, Porsche used a thin flame-coated (also known as sputter coating) "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 NSC nickel silicon carbide composite plating process, that all our cylinders come with a limited lifetime warranty on the plating. No cylinder commercially available comes with that promise! Here are some examples of what happens when you use second rate cylinder plating:
Is Alusil the same as Nikasil? Which one is better? Nikasil, or it's similarly performing NSC (nickel silicon carbide composite) plating, while the best solution around, it is also the most expensive. Reynolds and Kolbenschmidt developed a process that still uses cast iron or similarly clad piston rubbing on an etched high-silicon aluminum bore. The Chevrolet Vega was among the first of the vehicles to use this new material technology. Needless to say, the Vega did not have a good reliability record and only limited 2.7 and 3.0 liter 911 models adopted Alusil cylinders, later replaced by Nikasil cylinders except on water-cooled models. Porsche's newest Boxster and 911 models use a modern version of Alusil called Lokasil while Porsche models like the GT2, GT3, and Carrera GT still utilize Nikasil platings in their bores. There is quite some debate concerning the re-useability of Alusil- type 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. An Alusil cylinder can also be plated with a Nikasil or NSC-platings to allow reuse of these type of aluminum cylinders with conventional pistons and rings. Case Study: How do you solve the problem of thermally overloaded two-cylinder small aircraft engines?
LN Engineering was approached by a small-aircraft manufacturer 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 our NSC plating? Aluminum pistons rubbing on raw aluminum cylinders doesn't work. Originally developed by Mahle, the Nikasil process used by Mahle or our similar silicon carbide composite NSC plating, consist of silicon carbide in a nickel matrix. Silicon carbide is used partly for its uniform particle size, and partly for its hardness. Silicon carbide is second only to diamonds in hardness and therefore provides excellent wear characteristics. The reason diamonds cannot be used is their high cost and the fact that we would have no way to hone it. NSC particle size is a Gaussian distribution of about 3 microns. This size is important so that the coating will not affect the internal components of the engine and too large of a particle will affect ring wear. Another major reason that silicon carbide is used is that it is oleofilic or it has a natural tendency to absorb oil, which in turn helps the oil retention of the coating. The NSC coating is an electroplated process that uses an electrical current to adhere the nickel and silicon carbide molecules to the aluminum. The process does involve dipping the entire part into the plating solution, and an electrical current must be present to start the plating process. Coating thickness varies with each cylinder and is determined by the amount of time it is in the tank as well as the amount of power used. The industry standard of plating thickness is between .003" to .005". Due to the hardness of the coating and its silicon carbide content, we must use diamonds to hone the cylinder bore. An important part of honing the coating is to provide a proper surface finish. If too rough, ring wear will be harsh, and if too smooth, the rings will not seat properly. Oil retention in the bore can also be negatively affected if the crosshatch is not the proper depth. A surface profalometer is used to check the roughness average (RA) and the depth (RPK & RVK & RK ) of our honing patterns to ensure proper engine performance and can be ordered in Ra varying from 3-4 to an average of <20. We feel so strongly about our NSC process, that all our cylinders come with a limited lifetime warranty on the plating. No other manufacturer has such a warranty. I've heard of problems with Nikasil and high sulfur fuels in the US. Refining the Alusil process is a major focus of automotive engineering today due to the price and complexity of Nikasil plating, hence the proliferation of Lokasil or similar high-silicon etched aluminum blocks used by many manufacturers . 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 8 and 10-cylinder aluminum Nikasil blocks as did Jaguar 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. Peeling coatings can be caused by many factors including improper prep or poor plating response of the aluminum alloy used. When the coating is applied properly the nickel will bond stronger to the aluminum than the aluminum bonds to itself or about 25,000 psi. In other words, the coating has higher tensile strength than the aluminum does. Because of this bond, when seizure occurs and plating comes off, there is often aluminum that comes off with it. Coatings will most often peel as a result of substandard materials being used, or when a processing error occurs. The best solution is to use the best materials possible and to monitor the plating process very closely and to have good quality control checks to ensure each and every Nickies cylinder performs up to its expectations. Why have I heard there aren't any good rings for use with Nikasil or NSC-plated 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 ring sets from Porsche's original equipment manufacturer, Goetze, to many that are supplied by JE Pistons and other ring manufacturers. In fact, we typically use lighter tension, thinner rings, which seal better and wear better than the higher tension rings typically used with cast iron bores. Even chrome rings can be run on our NSC plating, which has shown excellent compatibility with many low-tension chrome rings. Total Seal now even offers many rings designed for use with exotic platings, like Nikasil or NSC-plated bores, as found on our Nickies. Why have I heard complaints about JE Pistons? A few years back JE had a few problems with one particular forging, but it was quickly remedied with a new forging and revised pin oiling setup. But this was for a very small group of bore sizes and limited applications. Most of the issues we have observed are from running the clearances too tight when using a JE Piston in a factory Mahle cylinder. Where a Mahle piston best suits a Mahle cylinder, the proprietary alloy used for our Nickies cylinders is designed for optimal piston to cylinder clearance using JE's forgings. In the better part of a decade, cannot say that we can attribute a single failure to use of a JE Piston, as a Mahle piston would have likely failed in the same scenario. As a leader in the Porsche community, LN Engineering's focus on quality, service, and support is evident, and begins with you. Let us help you succeed. 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!
Contact webmaster at info@LNengineering.com If you are having problems contacting LN Engineering, please email us at lnengineering@gmail.com, Copyright LN Engineering LLC ©2002-2010. *LN Engineering features a nickel silicon carbide composite coating similar in appearance and performance to Nikasil, a trademark of Mahle Corporation, backed by a limited lifetime warranty. Porsche, Boxster, 356, 911, 914, 986, and 996 are registered trademarks of Dr. Ing. h. c. F. Porsche AG. All other trademarks and copyrights are property of their respective owners. All rights reserved. This content may not be used for any commercial use without express written permission of LN Engineering LLC, and possibly other copyright or trademark owners. |
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 iron or ductile-iron liner is stronger, it has a much lower thermal
conductivity than a fully aluminum cylinder. Iron or biral-type
cylinders have higher friction coefficients and as such, wear faster
than Nikasil or NSC-plated aluminum cylinders do, on top of not cooling as well as fully-aluminum cylinder.
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