AmSnow.com is now SnoWest.com
¦ Better temperature control
Looking at the engine components that Dallas and Darren had displayed on the desk in the DTR control room, the most obvious difference compared to the previous Polaris twins is the now-diminutive coolant passages in the crankcase, cylinder block and heads. Shrinkwrapped! The large capacity, lazy flowing coolant passages in the early cylinders and heads are gone—replaced by modern, low-volume, extremely narrow coolant passages that promote higher velocity, more turbulent coolant flow that does a much better job of scouring heat from the cylinder bores and combustion chamber surfaces. Both the 850’s head and cylinder have 1/3 the coolant capacity of the 800s! Google a photo of a modern NASCAR engine block. Gone are the flat V8 block sides, replaced by shrinkwrap-appearing outer castings that mirror the four round cylinder bores closely on each side of the V. On the 850 Patriot, improved cylinder and head cooling can result in reduced likelihood of detonation and will help cool pistons and exhaust valves better than before. Add to that, a new lower temp thermostat begins opening at 92F then is wide open at 100F. Good!
¦ The good news
The new single ring pistons still require heavy loading break-in to create optimal sealing and maximum horsepower. On this zero-hour engine, we picked up 5 to 6HP over 35 to 40 dyno sweep tests on Polaris VES synthetic injector oil.
The dyno session was done on a warm, humid day. Water in the air saps horsepower by displacing oxygen, and the ECU doesn’t compensate for it. After the engine break-in was complete, we fed 30F refrigerated dry air to the engine intake, and put four gallons of 30F (chilled in the 1,000 cubic foot refrigeration room) 91.4 R+M/2 octane pump gas with 3.8 percent ethanol in the tank. The ECU was taken out of break-in and left in max performance non-ethanol mode, which probably should be referred to as a “high octane mode” since due to its cooling effect and added O2, ethanol added to premium fuel is a good thing when it comes to making HP. Probably the only time to switch to “ethanol mode” is when you can only buy low octane ethanol fuel and experience detonation.