Two years ago, Ski-Doo introduced the first production turbocharged 2-stroke engine in the snowmobile world. Today, the manufacturer is taking things a step further by introducing the 850 E-TEC Turbo R, which develops 180 hp.
That’s an increase of 15 hp or 9% over the previous 165 hp engine.
This engine, which is still only available in mountain snowmobiles, allows the rider to benefit from the 180 hp up to an altitude of 8000 feet. At that altitude, the naturally aspirated 850 E-TEC develops 55 hp less. This difference in power is anything but negligible.
This gain in power is largely explained by the average increase in supercharging from 1.5 psi to 2 psi compared to the 165 hp turbo version. Thus, we’re talking about a boost of between 1.5 and 6.5 psi on the Turbo R.
In terms of mechanical components, there have been some changes. Here they are:
New engine head
One might think that this change was to increase the compression ratio. Instead, it seems that the goal was to improve spark plug cooling. It’s interesting that the Turbo R version now uses the same spark plugs as the naturally aspirated 850 E-TEC.
New injectors
Here, we can believe that the manufacturer wanted to have more efficient injectors in order to obtain the desired power. Indeed, more power necessarily implies more gasoline to be injected in the cylinders.
New air box
This change was probably motivated by two factors. First, by changing the chassis, the shape and location of the air box had to be modified. Secondly, the increase in power may have required an increased volume of the airbox. It is not surprising to see this modification for the 850 E-TEC Turbo R.
Increased power increases the stress on the drivetrain component. So Ski-Doo uses some stronger components in the pulleys. In addition, the drive chain is now also stronger.
The Summit Turbo is approximately 18 pounds heavier than the naturally aspirated versions. The power gain offsets this weight gain as the power to weight ratio goes from 2.72 (naturally aspirated) to 2.48 lb/hp (turbo) in the 154″ version. That’s a 9% drop in the power-to-weight ratio, which is far from negligible.
When will the 850 E-TEC Turbo R be used in trail models?
That’s a question we can’t answer of course. Personally, I would be very curious to try this engine in a Renegade X or X-RS for example.
So I will add this wish to my gift list for next Christmas… What about you?
