HYPERSLED ENGINES: POLARIS CLEANFIRE 800
Cleanfire is the Polaris nomenclature for its Semi-Direct Injection (SDI) technology used on both its 600 and 800cc USA-built 2-stroke twins.
Semi-Direct technology has been around in the snowmobile biz since the early two-thousands and was initially offered by Ski-Doo prior to the introduction of the company's trademark E-TEC Direct Injection.
In a 2-stroke, Direct Injection effectively seals off the bottom end from inducted oil and fuel and places the fuel injectors right in the combustion chamber, usually at the top of the piston. This is not the case with SDI. The principle behind SDI is to allow the engine to run as lean as possibly safe to deliver clean exhaust.
In a Semi-Direct Injected engine like Cleanfire, the fuel injectors are located in the boost ports and deliver gasoline to the top of the piston as crankcase pressure moves the charge up through the boost ports.
Meanwhile, oil in minimal mounts, metered by an electronic oil pump, is injected into the crankcase. Residual oil is transferred to the top of the pistons as the engine cycles so there is adequate lube for the cylinder walls and piston rings.
In order to meet EPA standards, it's really important with an SDI engine to use a "knock" or detonation sensor. This electronic device, usually mounted on the cylinder head, "senses" an overly lean situation with the fuel-air mixture and alters engine timing to keep heat to a minimum. Today, you can drive a Cleanfire with a knock sensor and it's so subtle you may not even know it's working.
Cleanfire has really perfected SDI technology so it is transparent and both the 600 and 800 deliver extremely good bottom end power with incredibly crisp throttle tip-in and response. It's no surprise they do; these engines are designed to run really lean all the time and that's exactly what you get with a race engine.
At the same time, the crankcase is getting sufficient lubrication and is kept cool without the need for liquid-cooled cases.
More Like This
LATEST VIDEOS View All
2020 Crossover Snowmobile Shootout!
January 21, 2020
Luke takes a closer look at the 50/50 crossover snowmobile market addressing its appeal to ...
SNOWTRAX TV 2020 - Episode 4 Sneak Peek
January 19, 2020
Coming up on the next episode of SNOWTRAX TV...
2020 Backcountry XRS 850 vs 2020 Switchback Assault 800
January 16, 2020
AJ's got two of the top off-trail sleds parked side by side giving you a full overview and ...
Full Test Ride of The 2020 Polaris Indy XC 137
January 15, 2020
AJ evaluates the 2020 Polaris Indy XC 137 powered by the 850 Patriot engine to see how well ...
Ski-Doo Summit 850 Turbo First Ride Impressions
January 14, 2020
AJ breaks down his impressions of the brand new 2020 Summit 850 ETEC Turbo after riding it ...
The Most Insane Mountain Riding Experience at CKMP!
January 14, 2020
After being crowned North America's Top Snowmobiler for 2019, Dustin Boyd is treated to a ...
Top Gear View All
January 19, 2020
MBRP QUIET SERIES TRAIL EXHAUST
Finally! An aftermarket exhaust company has answered the call trail riders have been begging for.
Ask Motorhead View All
April 3, 2019
NOT HAPPY WITH SHOOTOUT RESULTS
Luke responds to a viewer's disappointment about the results of our 600-class, 129-inch shootout.
Press Releases View All
Tourism View All
December 18, 2019
THE ULTIMATE SNOWMOBILE BUCKET LIST FOR QUÉBEC THIS WINTER
Take a moment, close your eyes and think of the most beautiful winter landscapes you could possibly imagine!