The Suzuki Advanced Cooling System (SACS) was developed by Suzuki engineer Etsuo Yokouchi in the early 1980s. The system was used extensively on GSXR model bikes from 1985 through 1992. Suzuki continued to use the system in its GSF (Bandit) and GSX (GSX-F, GSX1400, Inazuma) lines until the 2006 model-year. Engines using the SACS system were generally regarded as being very durable.

Development

While addressing reliability issues in Suzuki

Suzuki

is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...

's only turbo charged bike, the XN85, the SACS system was first conceived by Mr. Estuo Yokouchi, who looked to World War

World war

A world war is a war affecting the majority of the world's most powerful and populous nations. World wars span multiple countries on multiple continents, with battles fought in multiple theaters....

 II–era aircraft for inspiration. Like air-cooled motorcycles, radial engine

Radial engine

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...

s used in many early aircraft suffered from heat and reliability issues. To overcome these problems, aircraft engineers often used oil jets aimed at the bottom of an engine's pistons to carry away excess heat. Following their example, Yokouchi decided to apply the approach to motorcycles. The result was a success.

When the GSXR entered development, Suzuki set a goal of 100 hp for a 750 engine and, due to known heat-related problems in high-power air-cooled engines, determined that air cooling alone would not be sufficient. Therefore the SACS system was applied to the bike's design and was eventually carried over to all larger GSXRs. The final GSX-R SACS engine appeared on the GSXR1100 in 1992, later bikes featured water cooling.

Mechanics

The SACS system uses high volumes of engine oil aimed at strategic points of the engine, like the top of the combustion chamber, which are not typically well served by air cooling alone. In order to provide enough oil for both cooling and lubrication, the system uses a double-chamber oil pump, using the high-pressure side for lubrication of the parts (crankshaft, connecting rods, valvetrain), while the low-pressure, high-volume side provides oil to the cooling and filtering circuit. The oil removes heat from hot engine parts through direct contact, is pumped away and subsequently routed through the oil filter, followed by routing through an oil cooler before being returned to the main sump.