ALUSIL CYLINDERS
Alusil is a hypereutectic aluminium-slicon alloy (AlSi17Cu4Mg). The composite material contains approximately 77% aluminium and 18% silicon. This alloy was created in 1927 by Schweizer & Fehrenbach in Germany and was then further enhanced by the engine component company, Kolbenshmidt.
The product Alusil is not a coating process but a treatment of the aluminium surface by either chemical etching or a honing and lapping process will expose a very hard silicon precipitate namely ‘silica’ thus rendering the abundant silicon particles on the aluminum surface to act as a wear layer for the pistons and rings.
The Alusil aluminium alloy is commonly used to make linerless aluminium alloy engine blocks. The silicon surface has excellent porous qualities, enough to hold oil, also acting as an excellent bearing mate surface. BMW switched from Nikasil coated cylinder walls to Alusil in early 1997 to eliminate the corrosion problems that they were experiencing caused through the use of fuels containing fluctuating levels of sulfur found in countries around the globe.
Sulfur found in these array of fuels has had a negative impact on Nikasil which causes the breakdown of Nikasil linings causing premature engine failures. ‘Nikasil Plated Cylinders’ problems are subject to cracking, peeling and pitting. This has become an undesirable surface for the harsh environment of piston and ring to bore wear, where scuffing is the order. Many vehicle and motorcycle manufacturers have followed suit and refrained from using the Nikasil process of cylinder bore plating for obvious reasons outlined above.
ALUSIL has become the futuristic material of the new millennium and has found a stable and lasting impression on vehicle manufactures and motor engineers through trial and error and science. This is a product that not only has excellent lubrication qualities but helps keep cylinder walls and piston ring surfaces cooler together with excellent wear characteristics.
In essence Nikasil has no better characteristic other than an extremely hard surface, but this alone cannot make up for the problems it has shown up over the years of its reign. It’s following is still maintained by an off-road motorcycle following, due to the fact that the single cylinder barrel and piston is easily changed between race heats and provides a readily ‘quick fix’ solution. A Nikasil sleeve or re-plating should cost you between R1500 and R2500. Alternatives such as Chrome Molly sleeves are a good alternative for Moto-X with good performance characteristics. Blue Print Engineering in Johannesburg can assist you with all your motorcycle re-sleeving requirements.
Automotive Engines using Alusil piston sleeved blocks include:
- Audi 2.4 V6
- Audi 3.2 FSi V6
- Audi 4.2 FSi V8
- Audi 5.2 FSi V10
- Audi/VW 6.0 W12
- BMW N52 i6
- BMW M60 V8
- BMW M62 V8
- BMW N62 V8
- BMW V12
- Porsche 928 V8
- Porsche 928S i4
- Porsche 944 i4
- Porsche 969 i4
- Porsche Cayenne V8
For more information CLICK HERE “Engine / Parts / Specialist Engineering Services” or Call Centre : 0861 7777 22
