Building Boost Part 2: In the Real World
An Inside Look at Building The World's Most Powerful OEM 2-Stroke Turbo
Since the 1997 RMK 700, the RMK has been on a steady march toward deep snow excellence. From the Vertical Escape to the IQ, Pro, and AXYS, the RMK has been singularly focused on being the best off trail, deep snow snowmobile in the industry.
“We’re always pushing to expand the boundaries of deep snow performance, allowing riders to push their personal limits and the machine’s capabilities to new levels not possible before. Seeing the progression of RMK capability and knowing what they empower our riders to do over the last two decades has been amazing!” said Sampson.
Today, there are three tenets of RMK that guide all future development – a sort of Three Commandments of RMK. They aren’t metrics or specs, but three snowmobile characteristics that are held above all else: Instant Lift, Effortless Control, and Immediate Response.
“When we talk about our “Key Tenets” we are thinking about what our riders crave. They want the sled to instantly pop out of the snow and start moving forward (Instant Lift) without getting stuck, along with being able ride all day in the best terrain with the least amount of effort (Effortless Control). Immediate response really covers all aspects of the snowmobile and rider interface. From the first press on the throttle, to the pressure on your toes, to the input in the bars, all acting precisely, instantly and predictably every time, building confidence in the machine and rider, pushing the boundaries of capability.” Sampson added.
The last decade of RMK development has been marked by lightweight technology purpose built around the deep snow rider. The Rider Balanced Control of the AXYS platform places riders in the ideal riding location, allowing for unrivaled control in really technical terrain. The lightweight platform and powerful 800 Cleanfire H.O. and 850 Patriot engines made them the best power to weight vehicle on the snow. The Matryx and Matryx Slash take that to the next level, with truly advanced ergonomics and rider interfaces, all purpose built around that same technical, extreme backcountry rider. The Matryx Slash tunnel, rear bumper, and cooling system enhances those tenets, improving the lift and control of the sled in deep conditions.
When the RMK team sat down to discuss what riding a turbocharged RMK could look like, one statement was agreed to among the entire group: No Compromises.
“We knew that we had the next level of lift, response, and control with the Matryx RMK and the 850 Patriot. When we began work on the boosted version, we refused to compromise the ride and handling we had with the NA version.” — Cody Kofstad, Program Leader
The aftermarket kits on the market made good power at elevation, sure, but they also made the sled slow to react, unpredictable to ride, and were temperamental at best depending on the weather and the conditions. The reputation in the market was a turbo kit made power, and came with a host of compromises – trade-offs the RMK team, and RMK riders, wouldn’t accept.
The mission for the entire team was clear: a turbo RMK must feel like an RMK should in all areas on the snow – not just make it more powerful at elevation. The testing in the lab had been positive until this point, however there is no replacement for on-snow riding. In December of 2018, the Medusa project hit the mountains.
“The first few months of testing and riding were really tough. We struggled through a lot of control and calibration challenges to just get the sleds to run the same each day. We weren’t going to settle for anything less than NA response with turbo power.” said Hedlund.
The late winter and early spring of 2019 brought a lot of testing and developing for the team. They had all of the big pieces in place: the vertical turbocharger, external wastegate, intake reed valve, and control strategy was on the development sleds they were working on. As they say, however, the devil is in the details. Was he ever.
The sled had to work in all conditions and terrains. It couldn’t just work on the trail or in the big open meadows, it had to go from tight trees to a steep hillclimb and on the trail home without skipping a beat. Countless software and hardware tweaks and iterations were made, with the development team spending thousands of hours in the Rocky Mountains trying to get their creation to run consistently in every terrain mountain riders can find.
“We were getting new software almost every day, taking what we had learned and applying it forward. We knew we had something, we just had to figure out.” Dallas Blake commented.
Snowmobile development is a seasonal activity, of course. When the last of the snow in North America is gone in May and June, the work that can be done without snow is the focus of the summer and fall. In Roseau, the engineers have a full wood chip track at their disposal, built to replicate riding as best they can. Radiators are fitted on the top of the tunnels, and what work can continue outside does. Going into the fall of 2019, the team really started to feel like they had something. They had gotten the first turbo sled to pass sound regulations testing that summer, a substantial hurdle in bringing a sled to production. Things were looking good in the lab, with the calibration and controls improving every day.
The first provisional patent filings were submitted in the fall of 2019, and the team kept marching to a model year 2022 launch. After 12 years of hard work, things were looking up. They went into the 2019/2020 riding season with a long list of pieces to finish, from exhaust and intake to turbocharger oiling and more. This would be their last full winter before the launch, with only a few months in 2021 before the sled went public. No one was more aware of that date than the development team.
Months were spent riding, testing, developing, and trying to finalize designs. The exhaust muffler with integrated turbine diffuser went through further development, along with the reed valve and turbo system itself. The calibration and software were a continuous improvement exercise, all in the name of making the sled work in every riding situation. In the late winter and early spring of 2020, designs were progressively finalized, knowing that there was only one winter left between then and launch. The Medusa program had hit every milestone and passed with flying colors. With a strong validation plan already in the works, Patriot Boost was green lit for a model year 2022 launch.
The 12 months before a product launch is focused on final validation of the production components. The prototype and development sleds worked extremely well to that point, but complete validation of the final designs was required prior to releasing it to customers. The team knew that Polaris riders would push the sled as hard as they could – and they had to ensure it would be up to the task.
The summer of 2020 saw production engine components progressively arrive in Roseau, with lab validation in full swing. The lab environment allows the team to push the engines beyond anything possible in a snowmobile, ensuring they are durable and reliable in the real world. The endurance dynos featured turbo engines spinning at wide open throttle for hours on end, with countless sensors and data loggers measuring, recording, and analyzing everything going on with the engine.
Validation isn’t for the faint of heart. One failure can lead to an issue that brings the team back to the drawing board, indefinitely delaying a public launch. Much to the excitement of the Medusa project team – the new engine validated well in the lab. Really well.
“We did so much work upfront, ensuring the design and hardware was right, down to the last detail. When we got it into the field and into final validation, it performed incredibly well. It really was rock solid all the way through.” added Buchwitz.
The engine calibration is greatly dependent on altitude, with the turbo making progressively more boost as altitude climbs and air density changes. That meant the team had to validate the sled at every elevation it might see, from sea level to 12,000+ feet.
Turbo sleds left Roseau and headed to all corners of North America: the middle elevation of Montana and Wyoming, the towering peaks of Colorado, Chic Choc Mountains of Quebec, the maritime snow in Alaska, and the sea-level backcountry of the Upper Peninsula, Michigan. The development team racked up the miles fully validating the sleds in this diverse set of terrain and conditions, ensuring that no matter where the customers rode, they were met with consistent, strong performance.
15 years after the first ride to investigate the potential of a production turbo engine, the game-changing patriot boost was ready to go.
“When we found stable combustion through SmartBoost, we knew we unlocked a whole new level of performance — and a whole new way to access new terrain.”— Marty Sampson, Snowmobile Product Director
