A number of the most popular, most beloved 2-stroke engines in snowmobile history were actually grossly inefficient and EPA dirty.
They simply had to go in an effort by the OEMs to clean up their total corporate average emissions.
I call these engines “rotten” because that’s what they’re doing – rotting – in older sleds while the pricey tooling used to cast their myriad pieces literally rots away.
PART 2: The Ski-Doo Series III SDI
This engine doesn’t fit the description of dirty at all! As a matter of fact, when it first appeared in the early 2000s it was the cleanest 2-stroke ever built and gave snowmobilers mega-hope the 2-stroke would always be viable.
This, despite the EPA’s graduated system of gauging air pollution emitted from snowmobiles, culminating in a final and very tight CO2 and hydrocarbon goal line by 2010!
Ski-Doo’s SDI twin had an illustrious career powering a legion of ‘Doos including the ZX platform and the original REV. These engines were – in their day – the envy of the industry.
Rotax actually was the first to deliver “in-port” fuel injection rendering the crankcase completely dry.
The SDI was way ahead of other 2-stroke engines in the biz and, frankly, the industry reeled when Ski-Doo put the SDI 600 out to pasture in favor of the all-new Rotax E-TEC Direct Injection 600 powerplant.
Using two injectors running sequentially above and below one another in the transfer port, the SDI was exceptionally fuel-efficient and delivered smooth response without gurgling or sneezing when cold.
Truly an iconic mill is now rotting. So sad – but I regularly control my emotions with a quick pull up Kevlar Lake on an E-TEC 850.