We’ve alluded to the idea an ideal solution for snowmobile companies looking to feature DI on their 2-strokes would be to license Yamaha’s marine outboard technology called HPDI (High Pressure Direct Injection).
We’re not sure whether this tech is even on the block for licensing agreements to other manufacturers but it sure would be an effective strategy for companies looking to gain an edge in the 2-stroke market.
The best part is, Yamaha has long ago made the decision to be an exclusively 4-stroke snowmobile company and will likely never use HPDI on 2-stroke engines in our sport. Kind of a waste, really.
Here’s how HPDI works. It is primarily a computer-electronic system that uses a very high-speed processor to monitor engine timing and the sequence of introducing a finely atomized, high pressure spray of fuel at very precise intervals during the combustion cycle.
There are actually two fuel pumps in the system. The first takes the fuel from the gas tank, via various filters, into a vapor separator which then directs liquid gasoline into a second high pressure pump that jacks fuel pressure to about 700 psi.
The highly pressurized fuel is pumped into a fuel rail (or rails, depending on the engine layout) where individual electronically controlled fuel injectors (one for each cylinder) squirt the atomized charge at precisely the correct window of time to optimize the burn.
Although HPDI is slightly more complex than Ski-Doo’s E-TEC system and employs more parts, it works really well and has been in use for a long time.
The benefits are smooth idling, easy start-up and extremely good emissions stats.