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.
While addressing reliability issues in Suzuki’s only turbo charged bike, the XN85, the SACS system was first conceived by Mr. Estuo Yokouchi who looked to World War II era aircraft for inspiration. Like air cooled motorcycles, Radial engines 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 horsepower (75 kW) 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.