Advanced Technology


Robin America works with its industrial customers to design and engineer engines for specific applications. It has several lines of general-purpose engines, and among them are series that feature chain-driven, overhead camshafts (OHC) and several other component designs also employed in Subaru automotive engines. Here’s an overview of Robin engine technology.



Hemispherical Combustion Chamber


Hemispherical (hemi) chambers allow an engine to have a higher compression ratio, which translates into greater power combined with improved fuel efficiency.


Intake and Exhaust Valves


The engine’s valves work more efficiently because of the reduced number of parts between them and the engine’s crankshaft. Plus, due to the hemispherical combustion chamber’s cylinder head design, the valve ports and spark plug can be positioned for optimal flow of the air/fuel mixture and combustion. As a result, the engine offers increased power and lower emissions over an overhead-valve design.




The use of OHC in small, general-purpose engines is unusual. (Note that all Subaru Automotive engines sold in the United States have OHC designs.) Most general-purpose engines have overhead valves, which utilize pushrods. Overhead-valve engines are slightly less expensive to manufacture, but OHC technology offsets that with a number of advantages.


OHC engines with hemispherical combustion chambers tend to breathe better: They take air and fuel into the intake and push out exhaust gases more efficiently than pushrod engines do. In addition, the Subaru Robin OHC engines have fewer moving parts than overhead-valve engines, which contributes to easier starts and quieter operation.


The cam chains are designed to carry oil to the camshafts and valvetrain from the crankcase, which lubricates better than an overhead-valve engine’s splash technique.


Component Materials


Pistons, cylinder walls, timing chain, and rocker arms are all constructed for strength and durability.


Heavy-duty piston rings slide along cast-iron cylinder liners within the aluminum block.


The timing chain is manufactured by a company that makes timing chains for high-revving motorcycle engines. The chains are made of hardened steel, and they operate at reduced noise levels.


Rocker arms are also made of hardened steel to help increase durability and reduce maintenance.


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