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When Ski-Doo's REV chassis was introduced a few years back, it set the industry on end, propelling Ski-Doo to the No. 1 sales spot.
The rider-forward position, A-arm suspension and aircraft-style pyramid chassis redefined the modern snowmobile and signaled catch-up time for the competition. The REV instantly dominated racing, and when word of mouth confirmed its handling advantages, Ski-Doo was on its way to the top.
"Product is King" is BRP's engineering slogan, and these days the consumer demands excellence when they turn over fistfuls of dollars for recreational products. REV's design caught the competition flat footed, and in the rush to catch up, several major mistakes put some of the competition further behind. Meanwhile, Ski-Doo gained ever more market share.
But, by last season, it appeared the competition had nearly caught up with more rider forward positions, strengthened chassis and long-travel, A-arm front suspensions.
How to stay on topWith the competition nipping at its heels, Ski-Doo decided that instead of playing it safe, it would up the ante.
Ski-Doo's answer - more power, less weight. Its new 800R engine produced a healthy 155.7 horsepower in last year's dyno test, up nearly 15 hp from that used in the 800 REV, plus, the REV-XP is more than 50 lbs. lighter.
Does going lighter mean a weaker more flexible chassis? Far from it; through design based on knowledge from the aircraft business, the chassis is 21% stronger in twist and 37% stronger in bending.
Strength was accomplished by careful finite computer analysis of load-bearing elements. Prototype sleds were loaded with stress recording sensors, and then hammered on by the company's professional snocross racers, like Blair Morgan and Steve Martin.
Racers were asked to ride as hard as possible, intentionally bottoming out travel and making the chassis slam the ground on landings. Morgan says cornering is much improved and that he could jump and run lines he wouldn't usually be able to with the original REV. As a result of the computer analysis and stress testing, the design of the engine bay, front suspension cradle and the pyramid structure is completely new. Lightweight die-castings and carefully dimensioned aluminum tubing cuts weight while adding strength.
Weight savings usually are not accomplished in a big lump, but from small reductions in many areas. With the XP, the chassis lost 13 lbs. Simpli-fying and eliminating parts saved 8 lbs. on the front suspension, as 78 parts were cut in overall assembly. The steering system also was drastically simplified, reducing the parts count from 133 to only 33, while shedding 5 lbs. Simplifying the rear suspension saved 8 lbs.; a new track shed another 4 lbs.
Replacing solid shafts with larger diameter hydro-formed hollow shafts dropped 8 lbs. from the drive system. Another 8 lbs. were removed from the body and the seat. Some components naturally gained weight, such as a larger driveshaft-mounted brake disc, but all in all, Ski-Doo claims a 51 lb. weight reduction from the REV.
Under the hoodThe driveshaft-mounted brake system is well cooled through a vented shield, and the Brembo caliper has the piston housing protruding into the tunnel for snow cooling. Ski-Doo lowers the engine in the chassis by more than an inch and tilts it back for better centralization too. As a result, new carb intake manifolds were needed to clear the tunnel.
The secondary shaft also was moved up and forward to add an additional 8 inches of clearance for the driver's legs. Hitting the hood with your knees was one of the frequent criticisms of the REV, but thanks to the new secondary clutch location, this is no longer a problem for larger drivers.
However, the new secondary design may be a problem for racers accustomed to quickly removing secondarys to change tuning components. The stationary secondary sheave itself is part of the hollow shaft, and the whole shaft has to be removed with the secondary in order to change springs and helixes.
Ski-Doo has made the process easier by introducing a window in the outside chaincase cover, so, the shaft can be removed and the chain with sprocket held in place by an insert. Most consumers will not have to go through this procedure, but racers would probably trade some added weight for quick access. Rumor has it that the factory racers have such systems, and perhaps this will be available as a racing accessory.
The secondary clutch itself is a new twin track roller design with eight helixes already available as Ski-Doo accessories. A secondary clutch is the highest revving component in the drivetrain, and its large ribbed diameter makes it a prime candidate for windage loses. Ski-Doo engineers measured the windage loss from the REV secondary to be as high as 8 hp. Careful design of the sheaves and ribs on the new secondary reduced the windage loss to 2.7 hp while still maintaining adequate cooling. That's an extra 5.7 horses delivered to the track, and if you figure in efficiency loses in the drive system, it's probably equivalent to 7 horses more at the crankshaft.
Tech rideRiding the REV-XP is a blast. The lighter chassis means you can throw this sled around in a way you may have thought impossible having grown used to increasingly heavier sleds in the last 20 years. It's something you definitely feel, and it adds greatly to the fun factor.
Being this much lighter and with the weight centralized, potential ride problems can happen if the suspension is not adjusted correctly. On a GSX 600, I noticed a tendency to bottom out and pitch strangely across the moguls, rather than soaking up the bumps. This occurred because GSX models have a position sensitive rear shock; the PS shocks have a softer rebound and are calibrated to give a plush ride for the average trail touring rider. This setup is not for mogul busting, for that, you need the X package.
Ski-Doo has addressed individual preferences by making the front shocks' dampening adjustable. One adjuster changes both the compression and the rebound equally to make sure the average trail rider can make the change without getting lost between rebound and compression settings.
The rear suspension also has less of a rising rate, which works better on a lighter sled. With less sprung weight to push back at the suspension, shock calibration and spring selection is going to be more sensitive to driver weight if you want optimum chassis performance. These are new areas of refinement that Ski-Doo engineers are working on, and they'll probably have solutions soon.
There is no doubt that the REV-XP is another step forward for Ski-Doo, and it will likely put some distance between the Canadian sledmaker and some competitors who just caught up to the original REV.