SDI or DI?

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Dear Motorhead,

I’m in the process of snow checking a polaris 2009 600 IQ. In Supertrax I read about the new technology Ski-Doo has with E-tec engine.

My Question is will the Polaris engine be somewhat close on fuel mileage as the Ski-Doo?



Thanks for your email!

Your question is very interesting. The CFI system used on the Polaris Liberty 600 engine is closely comparable to the SDI system used by BRP on Ski-Doo’s the past four years. They both inject fuel just outside the cylinder wall (and in the CF into the crankcase as well). 

The E-Tec is the first direct injection snowmobile engine. This means no fuel is injected until the last 20 degrees or so of crank rotation – this means the injector has to be located on the cylinder head and fuel only enters the cylinder after the exhaust port is closed. This is a significant difference and allows for very lean mixtures from idle to mid range.

If you compare a CFI to a DI (which we have done this winter) at trail speeds the DI engine will get better mileage – about 20 percent or slightly more. However, at full throttle or when riding hard the difference is much less, maybe 5%. This would be comparing on any given day – please do not ask for actual mileage numbers as they change – dramatically – with snow conditions and are mostly meaningless as a comparison.

I believe these percentages are pretty close to real world activity.

Hope this helps.

Motorhead Mark

Supertrax Online
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