Technical Take-Away: Engine Efficiency
We’ve written much about E-TEC the last 20 months or so and Ski-Doo’s latest 2-stroke engine technology continues to impress us with its incredible EPA cleanliness, astonishing fuel economy and impressive power.
When it comes to 2-strokes, no one is on the same game board as Ski-Doo and likely won’t get there anytime soon.
The keynote technology with E-TEC is direct injection. DI uses similar engine mapping principles to EFI or SDI systems and even a series of sensors to report pertinent data on throttle position, engine load and temperature back to a common computer processor.
The difference is that E-TEC has its injectors positioned at the very top of the combustion chamber on the cylinder head. These unique voice coil activated injectors are programmed to inject fuel within a 15-degree window of the 2-stroke cycle, at the precise, optimum millisecond of scavenging.
The results are threefold: A very strong power stroke, a very clean and thorough burn and the lowest fuel-to-oxygen-ratio possible. The last benefit means you use less fuel to get the same pop you would with a higher ratio of fuel-to- air.
The 600 E-TEC also features a liquid cooled crankcase. This is important technology when you’re dealing with extremely lean burning 2-strokes (Remember, all the fuel is being injected at the top of the engine – 2-strokes normally scavenge their fuel from the crankcase upward, via transfer ports).
On a DI engine, because there’s no gasoline getting into the bottom end to cool it, crankcase temperatures skyrocket. By liquid cooling the engine’s bottom half as well as the top, temperatures are kept at acceptable levels and the engine’s lifespan is much more secure.
As mentioned, we’ve had about 20 months of real world testing with E-TEC and, despite it’s impressive beginnings, it continues to get better and better. Fuel economy is absolutely amazing – our E-TEC 600s have all reset the dial on mileage figures we originally thought snowmobiles should be able to get to.
2009 E- TECs were remapped from the original prototypes we rode and, with a very slight compromise in gas mileage, delivered class leading performance. This engine already exceeds 2012 EPA standards and is raising the bar very high for the competition.
We’re waiting impatiently for more E-TEC engines to arrive on Ski-Doo’s roster – especially an 800 E-TEC.