The Heart of Snowmobiling

Going higher, farther

Published in the September 2008 Issue White Out & Wide Open—The Blog LANE LINDSTROM
"1960 Ski-Doo authentic snowmobile with the original Kohler engine.
"2009 Ski-Doo Rotax 600 H.O. E-Tec engine.
"2009 Arctic Cat Z1 Turbo motor.
"June, 2007 Polaris two-stroke engines waiting to be shipped to from Osceola, WI, engine assembly plant to Roseau, MN, where they'll be mounted into vehicles.
"1998 Ski-Doo High Altitude Compensation system for Summit mountain sleds.
"1997 Yamaha engine factory in Japan.
"2003 RX-1 Mtn. shows rear exiting exhaust.
"2002 Polaris Frontier four-stroke

The engine is the heart of a snowmobile. Who would argue otherwise?

Without an engine it's nothing more than a toboggan. And while toboggans can be fun, we prefer sledding uphill, not just downhill.

Perhaps nothing has evolved over the years more on a snowmobile than the engine.

Consider J.A. Bombardier's first snowmobile, or even David Johnson's first attempt at an over-the-snow Polaris vehicle. Johnson went down to the local hardware store in 1955 and bought a 9 hp Briggs and Stratton for what was later to be known as Number One, while in 1959 Bombardier used a Kohler 4-stroke that offered up a heart-stopping 7 hp at 3600 rpm.

Today's snowmobiles offer a variety of engines from kids, 120 sleds with 5 hp (which still go faster than those early machines) to much bigger ones with 150 hp or more . and just about everything in between. Snowmobiles go farther, faster and are more efficient and cleaner than sleds of yesterday, thanks mostly to the evolution of the engine.


We'll admit right up front that there are few differences in the engine in a mountain sled and a trail sled. All snowmobiles, regardless of whether they are designed for deep snow, trails (or both) or as a workhorse, share the same engines with a few minor changes, such as altitude compensators, which are exclusive to mountain sleds.

It's because of the importance of the powerplant to a snowmobile that most of the attention in the design and build of a sled is focused on that one area. Stands to reason.

Look at where we can go today compared to the early days in the industry. In The Legend of Polaris, authors Jeffrey Rodengen and Richard Hubbard said of David Johnson's first test run on the snowmachine with the Briggs and Stratton engine, "The first ride was not all that impressive. The machine was slow (it went about four miles per hour) and hard to maneuver. It didn't take long for it to get stuck in a snow bank."

Thanks to today's technology, mountain machines are going places few thought possible, up mountains and through feet-not inches-of deep powder. The engine usually determines where you're going to ride. Got an 800cc or a 1000cc? You'll tackle just about anything. Even with today's 600cc engines, mountain riders can go farther into the backcountry than we ever could before the advent of mountain machines.

Yes, today's long snowmobile tracks have something to do with where today's mountain sleds can go, but without sufficient power to turn that track, well, refer to the toboggan comment.

It's not just the horsepower that makes today's snowmobile engines so impressive, it's the technology and reliability that stand out as well. Many mountain riders don't even give it a second thought to ride miles and miles off trail and into the backcountry. In fact, most like it better when there's not a trail in sight.


As already mentioned, two of the early engines used in snowmobiles were the Kohler and Briggs and Stratton, highlighting the fact that in snowmobiling's fledgling years, engines for the various sled manufacturers came from a variety of different companies. J.A. Bombardier, in 1961, also used the German-made JLO two-stroke. The next year Bombardier signed an agreement with Rotax-Werk AG, an Austrian company, to exclusively use those engines, which included a 163cc with 7 hp and 247cc with 8 hp. They were one-cylinder, two-cycle engines. In 1970, Bombardier bought the Austrian company Lohnerwerke GmbH and its subsidiary, Rotax-Werk, and later renamed it BRP-Rotax. Rotax continues to supply Bombardier Recreational Products with its snowmobile engines today. Rotax also manufacturers engines for a variety of products including motorcycles, aircraft, marine, ATV and Kart.

In 1966 Polaris inked a deal with Fuji Heavy Industries to provide engines for the Roseau-based snowmobile manufacturer. Fuji was just one of many Polaris used, though, as is pointed out in The Legend of Polaris. The book, which provides an excellent history of Polaris' first 50 years in business, points out, "Its 1969 snowmobile line gave customers more choices than they ever had before. It included four basic models . but the machines came with a choice of 22 different engines from six different manufacturers-Wankel, Hirth, Sachs, JLO, Kohler and Fuji."

Polaris, too, has narrowed down the list of its engine suppliers. Presently, Polaris engines are built in Germany, Wisconsin and Saitama, Japan. The Saitama, Japan, location is where the Fuji engines Polaris uses are manufactured. Fuji is also the manufacturer of Subaru cars, among other products. About 68 percent of Polaris engines are built domestically in Osceola, WI. For a look at how engines are manufactured in Osceola, SnoWest Magazine showed the process in photos in its January, 2009 issue. The move to manufacture engines in Osceola began in the late 1990s and spilled over into early 2000 and now accounts for about two-thirds of engine production for Polaris.

Arctic Cat also used various companies to supply engines during the early years, including Wankel, JLO, Kohler, Sachs, and then, in 1971, Kawasaki. Just four years after signing the deal with Kawasaki that relationship ended and Cat turned to Suzuki as its engine supplier, a relationship that has endured over the years and continues today. Suzuki engines are manufactured and assembled in Hamamatsu, Japan.

What are the chances that Cat will bring its engine manufacturing to the United States? Cat is already building ATV engines in the U.S. so is it logical to expect the company to do the same with its snowmobile engines? "There are no plans to build Arctic Cat snowmobile engines at Arctic Cat or anywhere in the U.S.," Greg Spaulding, Performance Engine group leader at Arctic Cat, said. "But my thoughts are that it would be very challenging and exciting to do so."


Yamaha has always used its own company-built engines, which are manufactured in Japan near the company's headquarters in Iwata City, which is south of Tokyo. Yamaha has used a great deal of technology derived from its well-respected motorcycle engines and transferred that to its snowmobile engines.

It made sense for the snowmobile manufacturers who used so many different engine companies to make a move to fewer engine suppliers. Keeping enough of the right parts on hand had to be a nightmare for dealers and other service people.

The move by some snowmobile manufacturers to bring engine building in-house seems to have had a simple motive: improved quality control. When a snowmobile manufacturer builds its own engine it allows that manufacturer to maintain tight quality control, something that was clearly pointed out during a tour last summer of the Polaris engine manufacturing plant in Osceola. Al Hogen, director of operations at Polaris' Osceola plant told SnoWest, "By buying components from outside sources and assembling it ourselves, we can control quality. We control our own designs and costs by having our own assembly plant."

Controlling costs and improving and maintaining quality control are two important factors as engines continue to evolve. In years past, the goal to engine development was to build horsepower and improve efficiency. Those goals haven't really changed for present snowmobiles but they are vitally important to snowmobile manufacturers, especially in today's climate of trying to lure more people into the sport. Achieving the goals of increased horsepower and efficiency were joined in later years by a need for improved reliability and increasing Environmental Protection Agency regulations.


Changes over the years to engines used to power snowmobiles have been vast and it's a tough challenge to choose what have been the best improvements or the biggest changes to date. Certainly the advancement of computer-aided designs has been a huge help to those engineers whose job it is to make a better engine. New and different uses of metals has also got to somewhere in the equation of engine evolution. Heavy steel engines have given way to aluminum and other metals that are not only lighter but dissipate heat (one of the engine's biggest enemies) quicker. Those are just two out of a myriad of changes that have taken place over the years in engine development.

It was clear, though, as mountain riding became more popular (the snowmobile masses were still centered in the middle of the country in the 70s and 80s) over the years that engine development needed to quicken if it was going to appeal to more areas where elevation came into play. To make a snowmobile work at elevation, you had to tinker with it, such as change the jets and gut the airbox to account for changes in altitude and/or temperatures. The purpose of gutting the airbox was to get more air into the engine, because as you gain elevation, air gets thinner and makes the engine run richer, which, in turn, would cause the engine to sputter (bog) and run poorly. The trick was to get the right air/fuel mixture for the different elevations you were going to ride in and try to account for the change in temperatures. The goal then, as it still is today, is to properly mix the maximum amount of fuel with the maximum amount of air for the maximum horsepower. Too much fuel would cause the engine to bog while too much air would cause the engine to burn down.

Adjusting your sled to work at different elevations was not something everyone knew how (or even wanted) to do. Mountain riders needed an engine that would do that for them.


There was a lot of cheering when fuel injection was first introduced back by Polaris back in 1992. Cat came out with its own version of fuel injection in 1993.

Bret Rasmussen, who owned a Polaris and then Arctic Cat dealership for years before selling it and recently starting Snowmobile Research Services, has been around the industry long enough to know how big a deal it was for snowmobiles when fuel injection was introduced. He explained, "In pre-fuel injection days an engine could be tuned for 2,000-foot variances but you also had to be aware of temperature changes, which in the mountains, could be several degrees in just 1,000 feet. If you wanted your sled to run optimally, or at all, you had to be willing to change jets for the conditions. Fuel injection was big. We no longer had to tune our fuel systems for altitude changes."

In simple terms, fuel injection meant more precise fuel delivery, which along with meaning not having to adjust your fuel system, meant fewer emissions. As Rasmussen pointed out, with a fuel injected system, when you chop the throttle, fuel delivery stops, unlike in a carbureted model.

Cat's Spaulding said he thinks there are several important changes to snowmobile engines over the years and that fuel injection is certainly one of them. He has other ideas, too, such as the impact of exhaust pipe temperature sensors.

Another industry insider, Mark Brozina, agreed that fuel injection was a big bonus for snowmobile engines, especially for the West. Brozina, who has been in the snowmobile industry for 38 years, the last 20 of it with Yamaha, said, "Fuel injection has allowed engines to produce more horsepower without sacrificing bottom-end driveability. With the bigger throttle bodies you could get more air into the engine." Interestingly enough, Yamaha never did use EFI (electronic fuel injection) on its two-strokes but does on its four-stroke snowmobiles.

Today, Cat offers batteryless EFI technology on its Suzuki engines while Polaris has its Cleanfire injection system, introduced on the 2005 900 RMK.


Ski-Doo uses a system that performs basically the same function as fuel injection in that it compensates for altitude and temperature, beginning back in 1994 with the High Altitude Compensator (HAC). HAC was introduced on the 1994 Ski-Doo Summit, the first snowmobile dedicated solely to mountain riding and the two millionth snowmobile produced by Bombardier. The HAC was described as a system that countered the carburetion richness that can occur because of altitude and temperature changes commonly found in mountain riding. A diaphragm in the HAC would flex in response to air pressure changes (remember air gets thinner as you climb and vice versa), mixing more or less fuel with air in the carburetor. Essentially HAC was a mechanical process controlled by pressure. HAC was replaced by an electronic system in 1998 when the Digital Performance Management system was introduced on a Summit engine. The DPM uses electronic solenoids to monitor temperature and altitude and then feed the information to a microchip, which adjusts carburetion to create an ideal fuel/air mixture. An electronic primer and enrichener is also part of the DPM. A natural byproduct of such systems as the DPM was improved fuel economy because the engine is running optimally instead of poorly where more fuel would be used. DPM also eliminated the need for a manual primer or choke.

Whether it is fuel injection or a DPM, those systems add a sometimes significant cost to the development of snowmobile engines. Despite that cost, we don't know of anyone who wants to go back to the old days of carrying a bunch of jets around in his pocket and stopping every so often to swap jets out.

Years before fuel injection was introduced on snowmobile powerplants, liquid-cooled engines made their debut. Prior to liquid-cooled engines, snowmobile powerplants were cooled by fans, which were probably adequate for smaller displacement engines, but as horsepower increased, so did the need to keep the engine cool. As mentioned before, heat is an engine's biggest enemy.

It was in 1976 that Ski-Doo, near the end of the season, made a limited production run of 25 units of the Everest. The five-port, two-cylinder 444cc engine was liquid-cooled, a first for Bombardier, which claimed the new liquid-cooling "improved performance and reduced noise levels."

Brozina, a regional service rep for Yamaha, said fuel injection and liquid-cooled engines are two of the biggest advancements made in the engine department. He said, "Liquid-cooling improved durability, Engines were more consistent and maintained more consistent temperatures." By maintaining more consistent temperatures, horsepower increased. "Horsepower went up," he said. "Horsepower was more a byproduct of the liquid-cooling, not a direct result, because temperatures were more consistent. Engines no longer had major temperature swings." Other benefits of liquid-cooling, Brozina said, was noise reduction in the engine and durability was improved.


Rasmussen said liquid-cooled engines were definitely an improvement in engine evolution. He also made an important observation as to how that affected sleds for the mountains. Rasmussen said, "Engine development for mountain sleds had to do more with horsepower, so fan-cooled engines went away for the mountain segment earlier than they did for the trail segment."

The cost to develop a liquid-cooled engine is also higher than fan-cooled engines, which most likely explains why all engines weren't liquid-cooled right after the technology was introduced. For example, remember that Ski-Doo first offered a liquid-cooled engine in the Everest in 1976. In 1978, there were three liquid-cooled Rotax engines. It wasn't until 1993 that more than half of Ski-Doo's snowmobile lineup offered liquid-cooled engines.

Today, the greatest majority of snowmobiles are liquid-cooled with only two models in the mountain segment fan-cooled, the Polaris Trail RMK and Ski-Doo Summit Fan. Those two models are considered entry-level snowmobiles and are less expensive (meaning they're a price point option for some) than the liquid-cooled models being offered.

One of the obvious byproducts of liquid-cooling and fuel injection/altitude compensating systems, as Rasmussen and the others pointed out, has been horsepower. If you were to ask a snowmobiler who rides the mountains and deep powder what are two of the most important features of a mountain machine, the answer will most likely be horsepower and light weight.

Engine developers have done a masterful job of coaxing more and more horsepower out of two- and four-stroke engines as they have evolved over the years. Of course, horsepower is not a mountain-only feature. Lake racers and hardcore trail riders in the Midwest love to go fast. Where horsepower has allowed trail riders to go fast, it's allowed western riders to go higher and through deeper snow. That horsepower has come for a variety of places, not just the two mentioned: fuel injection and liquid-cooling.


Rasmussen said, "As two-cycle engine technology evolved, they were able to get more horsepower out of the engines and more durability because of the materials used to design and build the engine. And that has allowed for bigger displacement engines." Cat presently owns the title of the biggest displacement two-stroke with its 999cc engine, commonly referred to as a 1000.

Polaris, too, commented about the horsepower and what engine builders have been able to produce over the years. "The most important change to two-stroke engines has been the steady growth in power density or horsepower per liter, even as emissions levels have gotten tighter," Polaris officials said. "This has allowed Polaris snowmobiles to keep a competitive advantage in the 600, 700 and 800 classes we play in today. Going forward, continued power density increases will be a challenge as pressures on fuel economy and reliability outweigh performance in some segments."

Development, no doubt, will continue as snowmobile manufacturers work to meet EPA restrictions, continue to look for ways to shave weight and make engines even more reliable. "The ability to design and build ever-increasing high output designs by having and selecting the materials to keep them lightweight at these output levels," is the challenge of those engine engineers, Polaris officials said.

As has been mentioned, the EPA is more closely scrutinizing snowmobile engine emissions. Snowmobile manufacturers have risen to the challenge and are meeting those new regulations, but new regulations are coming out for 2010 and 2012 models.


With what has happened in the past with the EPA and what is looming in the future, we posed the question of how much of the snowmobile engine's design is being "dictated" by that federal agency.

Cat's Spaulding said, "The recent and future EPA rulings have had and will have a definite effect on our engine design and development and all for the good as our engines will be cleaner and more efficient. Specifically, engine development, along with emission regulations, require us to spend engine development time reaching the performance targets we set, and at least an equal amount of time again using the fuel more efficiently to achieve the emission targets while maintaining or improving performance targets."

He explained how this is accomplished at Arctic Cat. "This is done simultaneously during the development process by not only measuring the torque and horsepower output for performance, but also such things as hydrocarbon and carbon monoxide outputs, trapping efficiencies, air fuel ratios and a host of other efficiency measures. Performance targets can be achieved by testing and developing such things as port time area, port shape, combustion chamber shape, flow paths and shapes, intake reed areas, flows and fuel mapping, ignition timing and ignition functions and especially exhaust system design, to name a few. But by closely monitoring the emission outputs during these development tests, the entire engine design and specifications can be optimized for both performance and clean emissions."

Polaris officials responded this way to that same question. "The reductions in emissions levels have caused us to implement various new systems on our two-strokes and led us to launch four-strokes as another alternative. The evolution of two-stroke injection engines was jump started to meet emissions, even though there are performance and fuel economy benefits to both. The EPA emissions requirements obviously play a role in the PT product plan."

Continued development, as has been evident in the past with the rising cost of purchasing a snowmobile, will most likely again increase as manufacturers strive to meet EPA regs. Of those regs, say Polaris officials, "It has and will continue to affect designs. Material cost is greater, overhead to develop, test, monitor, record and communicate emissions results to comply to standards increases cost. The effort to complete this has come from the resources that also develop the engines. Vehicle cost to the consumer will increase while trying to maintain vehicle performance the snowmobile customer expects."


While Yamaha engines are technically regulated by the EPA, just like the other manufacturers, meeting EPA regulations isn't an issue with the Japanese company because, as Brozina points out, "a four-stroke is inherently cleaner than a two-cycle engine."

Yamaha, with the introduction of the RX-1 in 2003, started down the road of four-stroke only snowmobiles and today no longer manufactures any two-stroke snowmobiles. It's a decision that created quite a stir in the snowmobile industry but was generally accepted by snowmobilers, except, perhaps those who live and ride in the mountains. Four-strokes are generally cleaner than a two-stroke but they're also generally heavier, too.

"Yamaha knew the biggest challenges (with going four-stroke only) were going to be acceptance and weight," Brozina said. "We knew it was going to be more a challenge but we felt we could meet the challenges we were going to run into."

Weight was the only perceived challenge Yamaha would face when it decided to use four-strokes only. "Basically, the perception was four-strokes couldn't make the kind of horsepower customers were expecting but Yamaha has been able to do that." That evidence comes courtesy of the Apex Mtn., which offers up 150 hp.

To be fair, Arctic Cat, Polaris and Ski-Doo also have four-strokes in their lineup but still lean heavily on two-strokes as the meat of their lineups. Two-strokes have an obvious weight advantage compared to four-strokes.

While the two-stroke takes a beating for "being a dirty engine," Ski-Doo has taken that challenge head-on with its new-for-2009 H.O. E-TEC engine.

"We feel strongly that lightweight, clean two-strokes with their serious weight advantage are here to stay, especially in the performance segment," François Tremblay, director of marketing, Ski-Doo snowmobiles, said earlier this year.

That's where Ski-Doo's E-TEC comes in.

Ski-Doo and Rotax first developed the E-TEC's direct injection two-stroke technology in Evinrude outboard engines. That technology won the Clean Air Technology Excellence Award from the EPA. What makes this technology so interesting is that fuel is injected directly into the cylinder under extremely high pressures, which, among other benefits, lowers emissions.

Also, during what is called the Stratified mode, when the engine is first started up and running at idle, which is about 1200 rpm, a tight cone of fuel is injected into the cylinder, using a third less fuel than at higher rpm and it's injected right before the spark. The fuel combusts before it gets a chance to disperse. All that means is during that mode this 600 uses the fuel of a 200cc engine at idle. It's also at idle that the machine sounds like four-stroke-very quiet. Ski-Doo is also taking on the notion that four-strokes offer better gas mileage than a two-stroke, what with the E-TEC claiming to get 21 mpg. There are lots of reasons to get excited about technology such as what the E-TEC offers, but perhaps the biggest reason is because it shows what's possible with a two-stroke. As for the emissions of snowmobile engines, it's common knowledge these days and you can find it on the EPA's website. If you're interested, log on to:


For Ski-Doo, the E-TEC, along with its four-stroke 1200 4-TEC engine technology, the future is here.

But what about the other three of the Big Four?

For Yamaha, Brozina said, "Yamaha is going to continue to work on horsepower and weight. The weight savings will most likely have to come from the chassis area and from other design and manufacturing techniques." One such manufacturing technique, one that Yamaha is already using, is Control Flow, which Brozina explained is a process for casting aluminum which allows for the building of stronger parts without the weight penalty.

Polaris sees the next five years this way. "The phase-out of emissions reduction for carbureted two-strokes," Polaris officials said. "Two-stroke injection technology will be a balance of semi-direct injection and direct injection. More four-strokes with a heavier emphasis and more tradeoffs on fuel economy versus performance and more flexible calibrations due to regional fuel composition, such as ethanol."

As for 10 years out, Polaris officials said, "Fuel-injected two-strokes and EFI four-strokes will probably be the menu going forward. There may also be new technology such as electronic CVTs, etc. Customer expectations will keep getting higher, so fuel economy, reliability and performance will be the drivers of new engines."

Cat's Spaulding said, "Here's what I see in the snowmobile engine future for the next 5-10 years. Two-strokes and four-strokes will be used by most snowmobile manufacturers. The basic operating principles will remain the same on two-strokes and four-strokes. Power per liter of displacement will be reduced in order to help improve efficiency yet maintain performance. The rest of the future work will be developing new functions and components to improve on what we already know should be optimum."

And what is optimum? "Optimum may mean using all the fuel supplied to an engine to produce its power, leaving nothing unburned and wasted, lubricating the moving parts of this engine with little or no excess lubricate, reduce or eliminate the feel of vibration and reduce noise levels to the absolute minimums possible, given the mechanical noises inherent in a snowmobile chassis."

Then Spaulding added, "The goal may be easy to define, but achieving those goals will take creative, intelligent engineering and much development."

We haven't even touched on what influence the aftermarket has had on snowmobile engines, but Rasmussen posed this question as to the future of snowmobile engine development, "Let's speculate on the future of mountain sled engines. I see the aftermarket using turbos. Does that mean OEMs will as well?" We've seen what turbos and superchargers have done for today's snowmobiles, particularly Yamaha sleds where horsepower figures have been pushed to well past the 200 mark and even close to 300.

But aftermarket products are a story for Mod-Stock Competition.

Looking back over the evolvement of snowmobile engines, there has been a wide range of engine displacements and horsepower ratings over the years. Consider, just as an example, that in 1971, Ski-Doo engine displacements (with horsepower figures) were 247 (12), 292 (22), 299 (15), 335 (20), 399 (24), 437 (35), 635 (40) and 771 (65). Today, those displacements seem to have settled on the following in the mountain segment:

Arctic Cat 999cc, 794cc, 599cc

Polaris 795cc, 700cc, 599cc, 544cc

Ski-Doo 799.5cc, 597cc, 594.4cc, 553.4cc

Yamaha 1049cc, 998cc, 499cc

No snowmobile engine is perfect and some have had their share of issues over the years, but for the most part, we're pretty pleased with what we're riding today. We don't have to think too hard to remember the days of carrying jets in our pockets (or better yet in a Ziploc bag), staying close to the trail for fear of getting stuck somewhere we can't get back from and spending all day trying to bust over a hill that today we fly over with even the smallest mountain machines.

Five or 10 years ago we never dreamed we would be riding the great machines we are today. So how can you not be optimistic about what the next five or 10 years will bring?

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