Revolution….that’s what they’re calling it again. And, that’s really what it is. I haven’t seen this substantial of a change in the Ski-Doo model line up since 2003 with the release of the original REV (they told us then it was going to start a revolution, and it did).
Ski-Doo engineers started with a clean slate and developed the engine and chassis together. The reason for this was to eliminate any potential for compromise based on having to make a previously designed part work in this new platform. Even though parts interchangeability could have saved them costs, every effort was made to remove weight, increase horsepower and provide improved mobility and agility. So how well does this sled really work? With one day of riding on it, I have to say it is REALLY good.
The real heart of this new platform is the engine. Said to provide 165 horsepower and 106.6 ft/lbs of torque (10 horse more than an 800 E-TEC), this engine is a real powerhouse. It has many unique new features that are first to the snowmobile industry like Direct Bearing Oiling, Plasma coated cylinders and Booster injectors just to name a few. This engine flat out works well. It is very responsive and pulls super hard on top. The throttle has a very linear feel allowing precise control.
After sitting through the tech session on a Thursday night and then actually getting to see the new sleds, waiting to ride them the next day was reminiscent of the night before Christmas as a small child. I was so excited that sleep came difficult to me even though I was extremely tired from a very long day of travel. I kept waking thinking about the different innovations that Ski-Doo engineers had brought to the table with this new model. With a new chassis, new tracks, a new engine and new drive clutch, Ski-Doo really upped the ante with this model.
From the first blip of the throttle, I knew I was going to like this sled. The engine snapped to attention and pulled extremely hard. It was very responsive. The chassis had great manners too. To get this sled to do what you want requires much less rider input. Even though this takes time to get used to (it is very easy to over-ride), I really like this new chassis – a lot. I found that I didn’t have to jump from running board to running board nearly as much as the previous Summit. And it was much better balanced side to side allowing me to initiate an aggressive sidehill maneuver about as easily on either side (on previous models is it always more difficult to pull the sled up to the throttle side because the mass is shifted more to the brake side making you lift more weight or more fully commit going toward the throttle side). I can see where at the end of the day the rider will have much more energy and will be able to continue to ride more aggressively throughout the day. It also opens up more opportunity for more aggressive maneuvers in areas that previously were thought to be difficult or impossible to ride.
This sled really shines when you drop in the deep stuff. One thing I really like about it is when you are getting close to being stuck, you can shift your weight quickly, grab a handful of throttle and the sled will pop right back onto the snow and continue on. It is very forgiving and truly makes you a better rider. Getting the sled to do what you want it to is now even easier as it is more responsive to your inputs. Tricky situations are less difficult to navigate and get through. You can’t help but smile at how you feel so much more confident and able to enjoy the ride even more.
You really notice how the sled lets you put it into a sidehill so much further and easier than before. I loved how the new narrow chassis would not tend to lift the track out of the snow when placing it at severe angles on a steep slope. It allowed me to focus more on my line rather than other mechanics of keeping the sled on the slope. This is a very significant change for mountain riders.
The new track with its new wider lug spacing and lug pattern seems to penetrate the snow better than their T3 track without trenching (in deep snow). These sleds excelled in all conditions they were exposed to that day. I didn’t realize how much I truly liked them until I jumped back onto an XM chassis and found out just how much Ski-Doo has progressed in the engine, chassis and track department. The difference is substantial enough that I’m having a difficult time wanting to ride my T3 Summit again… and I really liked that sled.
At the end of the day the best way to describe the new Summit is agile, responsive, confident, powerful, playful, and just plain fun. Combined with the added torque, power and durability of the Gen II E-TEC 850 it looks like Ski-Doo is pulling out all of the stops with their 4th generation REV Summit X and Summit SP.
Lighweight: 25 pounds lighter than a Summit 154 x 2.5” track.
PowderMax Light Tracks are still 16” wide and retain the Flex Edge design. The pitch of the track is lengthened to 3.5” which allows more snow to be placed between each lug and improves traction in deep snow. It also reduces the number of lugs and reinforcement bars required in the track which reduces weight. This track is an amazing 10 pounds lighter than an equal length 2.5” lug track.
Running Boards: Summit SP models get a stamped aluminum running boards and X-package models get extruded aluminum boards. Each has strategically placed holes for snow evacuation and a rear kick up with boot traction. I liked the extruded boards of the X-package models best as they had less flex. This allowed my weight inputs to the boards to be more immediately realized rather than the board flexing a bit before the input was realized. It may seem like a small thing, but it is noticeable. The running boards are also 0.6” per side narrower for less drag in the snow.
Open Toe Hold: The new Summit models have an open toe hold area. This allows the rider to place his foot 2.6” farther forward as it is not blocked by the belly pan side area. This helps in initiating aggressive sidehill maneuvers and I quite liked it.
Narrow Belly Pan / Chassis Design: The belly pan at the footrests is a full 4” narrower than XM models (2” per side). And at the knee area, the chassis is 6” narrower (3” per side). This narrower design keeps the bellypan from dragging in the snow as much at extreme lean angles and when popping up on the snow in really deep conditions. It was very noticeable to me how much less it would hang up. This is a very welcome change to mountain riders.
New heat exchangers in the tunnel utilize Friction Stir Welding (FSW) to provide more efficient coolant passages with lots of cooling surface area front and rear (where it is most effective) with little in the middle. This is done by using this new FSW welding process to fuse the lower stamped cooler section to the bottom of the tunnel. The top of the tunnel acts as the top of the heat exchanger as well. This new process improves cooling efficiency along with being lighter weight.
Rotax 850 E-TEC Engine: This new engine is found in all of the GEN 4 REV models from the Summit to the Renegade and MX Zs. It has so much new technology packed into it that it would take a full chapter of a book to do it the justice it deserves. I will touch only on the high points for this article.
It has an 82 mm bore with 80.4 mm stroke providing 849.188 cc of displacement. Compared to the old engine the bore remains the same and the stroke is lengthened to attain the extra 50 cc displacement (800 E-tec is 82mm bore with a 76 mm stroke which is 799.5 cc displacement). It is claimed to have 10 horsepower more than then 800 E-TEC which Ski-Doo says is 165 horsepower (we feel this quoted number is very realistic considering the extra displacement and technology packed into this engine). It makes its peak horsepower at 8000 to 8100 rpm.
This new 850 E-TEC Engine uses second generation E-TEC direct injection. While the method of injecting fuel into the engine is similar, the whole system has been refined. Booster Injectors have been added to the intake. When you snap the throttle in mid to high rpm areas, the boost injectors add fuel to increase the response. The throttle bodies are also 35% closer to the cylinder and are 10% lighter even with the booster injectors. They are said to also add throttle response.
A new eR.A.V.E. exhaust valve system is used on the new 850 engine. The valves still have 3 distinct positions as the engine rpm varies but they now open and close 3 times faster than on the 800 engine. This also adds to the snappy response of this engine.
The Electronic Control Module (ECM) is 2 times faster on the 850 than the 800. Its microprocessor now cycles at 32 million cycles per second.
The engine has been significantly narrowed up to place it in this narrower chassis as well as to reduce weight and centralize mass from side to side (have equal weight on each ski). This was done by re-designing the magneto and recoil housing to reduce the overall width on the right side. The width of the left side has been reduced with the addition of the pDrive clutch which is 11 mm narrower than a TRA. The cylinder uses a Siamese cylinder design (transfer ports utilize opposite sides of the same wall) to keep it as narrow as possible. It has also been lowered and moved back in the chassis, but utilizes the same drive belt. The new front heat exchanger allowed this to happen.
The pDrive clutch is another feature we could spend a whole chapter on as well. It is 11 mm narrower than a TRA and 15% lighter (2.8 pounds). It is claimed to have a reduction of 30% in rotating inertia. The design appears to be very efficient replacing TRA sliders with friction free rollers in the pDrive. And to top it off, it uses a shaft-on-shaft design which allows tighter tolerances. Oversize rollers have needle bearings instead of bushings and the open design reduces heat from its fan action (this means cooler belts and better rpm stability). Dust, debris from belt wear and rust are also not kept within the clutch as much where it is an open design. The pDrive weight uses a pivot point that is on an acentric that allows for “Clicker” changes for changes in elevation and snow conditions. I’m excited to spend more time with this drive clutch.
The cylinder bores now feature a new Plasma coating. This coating is semi porous (like a sponge) which allows it to retain oil on the cylinder wall and reduce oil usage. This Plasma coating is also a better conductor which better draws the heat from the combustion chamber and piston better improving performance, consistency and durability. Its expansion rate is the same as the aluminum cylinder allowing it to maintain the same shape as it heats and cools. This is a really significant change that has the potential on its own of revolutionizing the snowmobile industry.
The engine utilizes Direct Bearing Oiling with a forged two part crankshaft (similar to a 4-stroke) that has internal oil passages that feed oil directly to where it is needed most (at the main bearings and lower rod bearings) and then allows the centrifugal force to push it (or fling it) to the other bearings, cylinder wall and piston rings. The bearings and other engine parts are oiled and protected with much less oil used. Oil is applied directly where it is needed most and then distributed from there. The two piece forged crank is said to have less flex and improved rigidity and durability.
The piston uses Ring Carrier Piston Technology which is essentially a cast iron over-molded insert that has high wear resistance to ring movement and pressure. This ensures a tight seal through the life of the ring.
The air intake has sound attenuating baffles in it (much like modern cars). I found the intake sound level to be very acceptable. It was not annoying at any rpm or speed. That is a trait I appreciate.
The exhaust is all new utilizing a lighter weight muffler and fully insulated heat shield to help bring the internal pipe temperature up quickly to improve consistency and performance.
Oil efficiency is said to increase by 34% and fuel efficiency is said to be about the same as the 800 E-TEC. For mountain riders, fuel range is always a consideration. I have found on the 800 E-TEC that I seldom have to carry fuel as other sleds I ride with run low or out before I do. The less fuel and oil I have to carry with me the better as the sled is lighter. But I still want plenty of range to get me into the backcountry and back with ample fun while I’m there. The fuel tank is slightly smaller, but the effective capacity is greater (no burping required) and for those really long rides, Ski-Doo now offers an even larger 4-gallon fuel caddy (that should be enough for any rider to absolutely exhaust himself).
By Jerry Matthews, SnowTech Mountain Test Staff
You might also like our 2017 Summit 850 E-TECH – Long Term Test Article.