At Replika Maschinen, inc. our primary business is improving airflow and volumetric efficiency primarily via porting of the engines air passageways. However, we also seek to improve volumetric efficacy by improving the quality of the air or fluid charge by lowering the temperature of that charge to gain more oxygen per volume. Air is the working fluid of internal combustion engines, so air is the fluid I am referring to here. When we lower the
temperature of our working fluid/air, it becomes more dense. One of the ways in which we lower the temperature of the inlet charge and engine and achieve this volumetric advantage is through the world of THERMAL COATINGS.
 
     Around the end of the Second World War the need to go higher, further, faster enveloped the defense and
aeronautical industries. These desires spawned a metallurgical revolution in exotic materials. But along with these exotic materials for air frames and more powerful engines came new problems of protection. Corrosion resistance, noise suppression, friction reducers, thermal barriers and thermal dispersants were invented or modified to address these new concerns. The automotive racing industry discovered these substances sometime in the 1970's. However, as they soon learned, racecars and their engines are not jet-propelled aircraft and vice-versa. Coatings that worked just perfectly in the sustained and controlled environment of aerospace often meet its match in an automobile engine. Zirconia based ceramics for example, have very different expansion rates, 4.16x10-6, when compared to aluminum alloy at 13.7x10-6 over temperature ranges of 80 to 800 deg. F. Fortunately there were individuals who saw the benefits and worked hard to develop coatings specifically for the automotive industry. These are what we here at Replika Maschinen, inc. and other facilities around the world use and are what we will concern ourselves with as the topic of conversation to follow.

Turbo Compressor Housing

     But first, what are thermal coatings and what do they do? Thermal coatings come in two basic categories; thermal dispersants to help get rid of heat and thermal barriers to block heat. Thermal dispersants help the coated part shed heat faster than that part normally would dispense with were it bare or un-coated. Thermal dispersants are generally exterior coatings and therefore primarily work via convection, but conduction is also involved. Convection is the transfer of heat by the laminar or turbulent motion of a liquid or a gas from one region of space to another. The convection style transference of heat as it relates to the automotive type world would include radiators, oil-coolers, brake calipers, rotor carriers and hubs, exhaust systems, turbocharger/supercharger housings and air and liquid cooled engines. Conduction is the transfer of thermal energy through a material or between two bodies in contact. This would apply to heat transfer between cylinder and cylinder head or any two or more parts in contact with one another. So for our pop quiz, which theory of thermal heat transference covers lap dancing?

Miata 1.6 Cylinder Head

     THERMAL DISPERSANTS as the name implies, reduce or remove excessive heat. As mentioned earlier, a large
majority of an engines potential heat energy ends up as waste. An engine must dispense with this excessive heat
or else burn up. Coated cylinder heads dispose of excessive heat at a far greater rate then un-coated heads.
Reducing the onset of engine killing detonation, lower intake charge temperatures and less chance of blowing head
gaskets due to cylinder head warpage and walk are just a few more advantages. Engines work on heat but this
heat must be properly dealt with. Too little and the engine will not operate in an efficient manner, too much and it
will melt down.
 
     In early 1998, the INDY LITES organization decided to conduct a test of their then current oil cooler and thermal
dispersants. They had the oil cooler thermal dispersant coated, it was then tested on and off the track. They
experienced a 15% reduction in oil temperatures; the smaller older coated oil cooler out performed its newer and
larger replacement. All INDY LITES teams now run coated oil coolers. In NASCAR, Bill Elliot and many others, run
coated radiators to help reduce internal engine and engine bay temperatures and improve aerodynamics via smaller
radiator openings. Brake parts and systems can also be coated. Obviously the faster heat is dissipated the less
likely the chance of fade or out rite failure. As a side benefit, coated parts shed dirt and rubber and are far less
likely to plug up, as readily as un-coated parts will.
 
     In our next article, we will discuss Thermal Dispersants and Dry Film Lubricants. For further information on the
subject of thermal coatings, please feel free to visit us at; www.ReplikaMaschinen.com.

Thanks, until next time,
Don Redmon, Replika Maschinen, inc.

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