We were lucky enough to spend a significant amount of time on not one, but multiple different Summit 850 E-TEC machines over a 3 month period in early 2016, spanning several different states and even two different countries. Since that time we have additionally been able to spend several hours on our production 2017 Summit 850 E-TEC. That being said, our findings should be fairly accurate in reference to the production units sold to the public.
Face it, we’re all power freaks so we will start with this wicked-hot new engine, the Rotax 850 E-TEC. The new 850 E-TEC engine is not an over bored 800 E-TEC; this is truly an all-new engine, the first one to be designed from the ground up specifically for direct injection technology.
BRP added a number of new-to-the industry features that help complete the performance package. The new 2-piece forged crank shaft has no pins holding it together. Each half of the crankshaft is one solid forged piece of metal instead of a bunch of pieces pressed together with pins holding them in place. This design is stronger and is much more rigid which also makes it smoother. Because it is a forged crank shaft the rod can no longer be pressed on so they are a split design that are bolted together such as on a 4-stroke. The crank uses a positive pressure direct lubrication system which means none of the bearings use grease like previous models did. They now receive pressurized oil through the crank to the inside of the bearing and centrifugal force flings it to the outer side of the bearing. By eliminating the grease the crank has less rolling resistance and is more efficient.
The cylinders now feature a new plasma cylinder coating process that also requires less oil for lubrication yet is still more durable that the previous cylinder design. The piston rings are encapsulated in cast iron for better ring life, technology derived from the diesel industry. Compression ratio stays the same as in previous years @ 12.5-1.
BRP has incorporated a second set of injectors mounted into the throttle bodies which deliver fuel in the mid and upper rpm ranges. They aren’t used at lower cruising speed but act as more of an accelerator pump when a hand full of throttle is pushed, a feature that helps improve throttle response. This move allowed for new lighter, smaller primary injectors on top of the cylinders, which replace the previous units used on the 800. A new RAVE exhaust valve system is 3 times faster than old system. To help operate the additional injectors the ECU is now 2 times faster than its predecessor allowing it to process much more information.
So what does that all mean from a performance standpoint: The new motor weighs around 83 pounds (no clutch) and produces 165 horse and 107 foot pounds of torque, according to BRP.
We have ridden long stroke motors in the past that felt lazy and slow to rev but this motor is unique with a much better feel. The throttle response is very good and revs quickly, which is uncommon for a longer stroke motor. BRP claims the throttle response is 30% better and while we have no idea what process they used to validate this, we would agree that the response is very good. The 850 has better torque in the lower throttle ranges compared to the 800 E-TEC and continues through the upper mid-range where the secondary injectors begin to operate. While the 800 often felt revy down low, the 850 feels much stronger and requiring less throttle to initiate slower maneuvers. Some of the response is due to the reduced inertia of the cranktrain and new pDrive clutch but the overall result is an easier motor to ride. The motor is a blast in the mid-range with ample power to lift the front when needed or for that quick burst needed to get you out of trouble. Riding it through the trees is easier because the extra torque and throttle response takes away some of the effort required from the rider. And it’s fast….acceleration from bottom to mid is instant. Short hillclimbs with little to no run are much easier because of the torque and the snap produced from the 850 E-TEC.
Top end pull is very good but the increased bottom-end torque begins to subside near the upper range. Peak RPM is similar to the E-TEC 800 as it likes to run around 7900 RPM. As with most long stroke motors, this motor is most playful in the midrange and even though it has great top end, it does not have the over-rev that we have seen from the 800 class motors. This is not a problem as the machine will continue to pull hard on wide open stretches or long pulls. Fuel mapping on every machine we rode was crisp and felt production worthy. Fuel consumption is low considering it’s an 850 but we think it uses slightly more than its 800cc little brother – as it should, making more power through the entire rpm range. Even so, we are willing to accept the tradeoff for the increased horse power and performance.
Many mountain sled riders have opted away from electric start in the past because of the weight penalty that has come with it. Electric start can often add 30 pounds or more, but BRP has significantly reduced that number for the 2017 with this new 850. The starter motor is now smaller and lighter, by design it can now be that way. It drives a gear located inside the crankcase which runs through a gear reduction. This prevents the need for a large heavy ring gear mounted to the drive clutch further reducing weight when compared to traditional system. The battery is stored at the rear of the fuel tank with the wires running under the fuel tank.
The battery is where the majority of the added weight comes from, but aftermarket lightweight versions (like EarthX) are available cutting 70-85% of the weight. A 14 pound battery can be replaced by a 3 pound lightweight version making electric start a great energy saver for the rider. Think about it: How many times do you start your machine per ride? Every time you stop to help a buddy did out or stop to chat, every time you pull the cord you use a little bit of your energy. We are willing to bet it’s more than you use throwing around an extra 5-10 pounds of electric start weight on the machine.
For 2017 BRP focused on reducing weight but they did it in such a manner that the weight reduction included other performance benefits and in some cases better durability. Lighter weight rotating parts have less inertia which almost always makes for better handling as is the case here. The pDrive clutch is 2.8 pounds light than the previous version which helps reduce cranktrain (crankshaft, magneto and clutch) inertia 15%.
So, here is a look at the internals: the clutch uses two vertical rollers mounted against the towers instead of buttons. One roller is tapered outward and utilizes centrifugal force to maintain pressure against the tower. This means no more shimming or replacing buttons trying to keep tolerances tight. Most traditional button systems cause friction where the pDrive roller design has none, preventing slop in the towers and never needs adjusted. The new flyweights are very wide and are adjustable allowing the user to adjust rpm when conditions require. Adjusting the flyweights is quick and easy and flyweight removal is not necessary. The sheaves are mounted to an oversized shaft-on-shaft design with larger bushings for less binding and bushing wear.
The end result: lighter weight, more durability and ultimately better power transfer to the ground. BRP has been using this clutch on the production race sleds utilizing the tough conditions of snowcross as their proving grounds. Mountain sleds can be very tough on clutches but we expect good reliability from the pDrive.
BRP engineers also put significant focus on two major areas: rider maneuverability in the cockpit and chassis maneuverability through the snow and the results were achieved by addressing multiple areas of the machine. The new motor is now narrower and has been moved 2.25” closer to the center of the chassis which BRP says reduced side-to-side inertia by 20%.This changed the center of gravity but it also balanced the weight distribution more evenly from left to right. It also makes the machine feel more even when it comes to how much effort the rider inputs when side hilling on the left side compared to the right side. Most machines are easier to pull over to the left than they are to the right and this is because the left side has a higher percentage of the total vehicle weight but the G4 is much better balanced.
The rider now has more room to move about thanks to narrower side panels that are now angled and stepped forward near the knee and thigh area. Each Ergo-step panel as BRP calls them is 2” narrower which helped reduce the overall width of the chassis by 4”.
The foot well has been pushed forward 2.6” and the sides have been opened up for easer foot transition when moving feet in and out of the foot well. The transition from belly pan to running board which is the lowest point of the bellypan now sits 1.75” higher than the previous chassis and the running boards are now 2.25” higher at the rear of the tunnel. The X package comes with extruded machined running boards that provide great traction and stay free from snow better than the previous version. The tunnel now has a beveled shape and is narrower towards the top. The rear of the tunnel is now open preventing snow build up and lets the snow evacuate from the tunnel easier. All of these features help reduce chassis drag in deep snow and allow for better deep snow maneuverability. We were impressed with how much more room the rider has to move around. No more bumping our shins or knees on the side panels when we needed to get forward or on steep down hills and no more accidentally hooking our feet in the stirrups. The other thing you notice is how you don’t need to be swapping sides as often. Since the sled is so well balanced, our riders were able to stay on one side of the sled more of the time instead of constantly swapping sides, going back and forth. This alone save energy over the course of the day, but also demonstrates how much easier the G4 is to ride.
The narrower chassis has less chassis drag and speed scrub caused from deep ruts and will pull itself out of a nasty trench in almost every case. Part of the improved drive comes from the new PowderMax Light 3.5” pitch Flex Edge track. Available in a 154” or 165” length, this track gets up on the snow faster and with less trenching. It is a whopping 10 pounds lighter than the previous 2.86” pitch version and the reduced weight is a major contributor to the new handling characteristics. A ten pound reduction of rotating mass that far away from the center of rotation is HUGE when it comes to how much power it takes to get it all moving, and keep it moving. By some estimates this is almost the same as removing seventy pounds of static mass from a machine, and it feels that way.
The new track is actually very multi-dimensional and seems to work well in just about all conditions. The wider spaced lugs help the track clean out faster and lets each lug bite into fresh snow. Going to a 3.5” drive pitch isn’t just about making the track lighter, there is a significant effect on how the added spacing between the lugs keeps more snow between the lugs and allows each bar to grab and pack the snow. This one is tougher to quantify, but the difference is real and noticeable. The track still has the traditional 16” wide feel that it has in the past but when ridden in deep snow the extra width is appreciated.
The rest of the chassis was re-evaluated to establish where additional weight could be saved or performance could be increased. The bulkhead and perimeter frame have been completely redesigned to be more rigid as well as stronger for better handling and impact protection. If the front end takes an impact the A-arms are the week point protecting the bulkhead. This is now a die-cast front bulkhead, much stronger and lighter, meaning no more cracked S-modules.
The all new RAS 3 front suspension has one more inch of shock travel to help keep the new chassis planted and in contact with the snow. BRP updated the rear suspension and dropped about 2.6 pounds of weight while requiring less energy to roll on edge.
A new heat exchanger design uses less fluid and is an integrated part of the tunnel. The seat is all new with a smaller design, clearly influenced by dirt bikes, and is now easier to maneuver around during gymnastic powder riding. The tank is new as well and no longer requires burping which means no more sitting on the back of the machine to get the air out and the tank full, but it is only 9.5 gallons in capacity – that said, we’re told the fuel pump will now pull more fuel from the tank than before, so it should be about a wash.
The control switches have even been minimalized and moved down to the cowling to help open up the handlebar control area. The new digital gauge assembly is smaller and sits fairly flat in the center of the dash, but with great big digits that are easier to read.
Our riders all commented on how much they liked the new feel of the G4 and the 850 E-TEC. We were able to feel comfortable very quickly and started maneuvering the machine through deep snow and into the more technical situations almost immediately. Most test riders commented that the machine required less anticipation and was more predictable when the rider had to negotiate from one side to the other and less focus was needed when maneuvering around body panel’s and foot position. They also noted that is very rare to lift a leg over from one side to the other and the rider can stay centered on the machine through more diverse riding conditions. The chassis and motor respond quicker to the rider and require less input and energy.
The rear suspension, as it was with the last chassis, is extremely compliant and rides well through all conditions. In fact, the only change we ever made to the rear suspension was going stiffer on the rear springs to help control front end lift while on a side hill. This is one adjustment we have made to all of our Summits over the past few years but the G4 was better than previous models. It didn’t try to stand up on us as much as the 2010-2016 models did. The 165” version stays flatter while the 154” version will lift the front end more and feels more playful in the tighter terrain.
The new G4 sleds still have a Summit feel to them, and for the Ski-Doo loyalist you won’t be disappointed. For the guys who generally have a hard time adapting to the Summit feel, you will be surprised how easy this machine is to ride and how short the adaptation time is. Simply stated, it’s just more agile and it takes less energy to ride. It fits a wider range of riders than previous Summit models have. More power, more torque, easier to ride, easier to make it do what you want it to, it is quite impressive.
The 2017 Gen 4 REV with the new 850 motor is the first time in 20 years that BRP has released a new engine and chassis together as a combination in the same year. It’s a tough job to pull off because so much calibration has to be accomplished. We think the folks at BRP did a fabulous job and the end result is a machine that is both lighter and easier to ride – the most user friendly and best Summit ever made.
By Dustin Pancheri – From the December 2016 Issue of SnowTech Magazine (November 2016)
You might also like our 2017 Summit 850 E-TEC: First Ride! article from the Spring of 2016.