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 and DR650 from 1990 to present. Engines using the SACS system were generally regarded as being very durable.

Development

While addressing reliability issues in Suzuki's only

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charged bike, the XN85, the SACS system was first conceived by Etsuo Yokouchi, who looked to

World War A world war is an international conflict which involves all or most of the world's major powers. Conventionally, the term is reserved for two major international conflicts that occurred during the first half of the 20th century, World WarI (1914 ...

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

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

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 A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

. The result was a success. When the GSXR entered development, Suzuki set a goal of 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 Suzuki GSX-R1100 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.

References

Motorcycle engines Motorcycle technology Engine cooling systems {{motorcycle-stub