The first snowmobiles made do with as little as 5 horsepower (3.7 kW) engines, but engine sizes and efficiency have improved drastically. In the early 1990s, the biggest engines available (typically 600cc-800cc displacement range) produced around 115 hp (86 kW). As of 2010, several snowmobiles are available with engines sizes up to 1,200 cc, producing 150+ hp, as well as several models with up to 1,000 cc engines producing closer to 180 hp (130 kW). Recently, some models are turbo-charged, resulting in dramatic increase of engine horsepower. Snowmobiles are capable of moving across steep hillsides without sliding down-slope if the rider transfers their weight towards the uphill side, a process called side-hilling.
Mountain sleds permit access in remote areas with deep snow, which was nearly impossible a few decades ago. This is mainly due to alterations, enhancements, and additions of original trail model designs such as weight, weight distribution, track length, paddle depth, and power. Technology and design advances in mountain snowmobiles have improved since 2003 with Ski-Doo’s introduction of the “REV” framework platform. Most two-stroke mountain snowmobiles have a top engine size of 800 cc, producing around 150 hp (110 kW), although some 1,000 cc factory machines have been produced. These may not be as popular as many 800 cc models outperform them because of weight and an increase of unneeded power.