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Don't look now but 2012 is just around the corner.
Why should snowmobilers care? That's the year new emission limits take effect, and so far the Big 4 claim they can meet today's 2010 standards with their current intake manifold EFI and semi-direct injection systems.
Ski-Doo engineers claim to meet the new 2012 standards with their E-TEC Direct Injection System, and Yamaha has thrown all its cards into the 4-stroke hat. Arctic Cat, Polaris and Ski-Doo all have 4-strokes in place that could replace their 2-strokes, but they all seem confident that they will meet 2012 standards with their popular, light and powerful 2-stroke engines.
While Ski-Doo is promoting its E-TEC system, even expanding it to a new 800cc engine, things are eerily quiet on the Minnesota factory front. Arctic Cat and Polaris assure us that they have direct-injection systems under development, but when you ask for details everyone clams up like you were probing into some highly classified government defense secrets.
An Arctic engineer hinted at diesel injector technology, and rumors are connecting Polaris with Orbital systems as used by Mercury Outboards. Orbital is an Australian company that promoted its patented "Air Assist" system in the late 1970s. Injecting fuel into the cylinder in a combustible form is complicated, and Orbital therefore uses a small compressor to inject an airstream with fuel premixed into it.
This system has been in development for a long time, and is available. Outboard engines had to meet emission rules long ago, and the industry is dependent on light weight, so obviously it was important to keep a 2-stroke power head, particularly on higher horsepower units.
Evinrude bought up the Ficht system from its German inventor and started a long development process.
George Miller had been head of Evinrude's Wankel engine department, but when that program was discontinued, he resurfaced as director of OMC research in Milwaukee. OMC's research department had, up until then, been busy with a number of projects, but Miller put all the department's resources behind the direct injection program, resulting in a number of advances.
The major improvement was in the control of fuel quantity for all load conditions by using a "voice coil" system to drive the injection piston-plunger. When Bombardier added the Evinrude brand to its line of recreational products, it placed considerable resources behind the now re-named E-TEC system, both to perfect it for the outboards, and later for 2-stroke snowmobile engines. With its investment in E-TEC direct injection, the always progressive Bombardier Recreational Products now has a jump on the competitors.
Will others catch up?Can the Minnesota manufacturers catch up in time to meet 2012 emission standards with their 2-strokes?
Developing a proprietary direct injection system will take a lot of resources and a long time, as it did for Evinrude and Ski-Doo. One imagines both Cat and Polaris are well along that road.
Fortunately there also are a number of new technologies available in the automotive market, as the automakers have been developing direct injection systems since the 1970s. The auto industry believes that direct injection will replace manifold electronic fuel injection, just as the EFI systems replaced carburetors. It's just a matter of critical hardware being available at production level costs.
Direct fuel injected 2-strokes are nothing new, they have been around for 100 years in the form of diesel engines in ships, trains, trucks, and stationary power units. During the 1980s and '90s, all the Detroit car makers had active 2-stroke development programs using gasoline direct injection systems to meet emissions goals.
While attending an automotive conference (Society of Automotive Engineers) I talked to an engineer involved in one such program. He claimed they had been successful in developing a gasoline direct injection 2-stroke system that meets emission standards, but the 2-stroke program was discontinued because they did not feel a 2-stroke crank with its needle and ball bearings would last the required 200,000 miles in a car. But, he said they had learned so much about direct injection that "we took the knowledge and transferred it over to the regular 4-stroke gasoline engine research division."
The result? Today there's an emergence of direct injection in autos with several cars now using it. Cars using gasoline direct injection also have been successfully run in endurance races.
The most promising technology is the high pressure "common rail" system using piezoelectric injectors. To inject the fuel and make sure it is atomized into a combustible mixture in something like one-thousandth of a second, you need extremely high pressure, quick-reacting injectors. The common rail system operates at 1400 bar, which translates to 20,000 psi. Compare this to an E-TEC system that operates at 600 psi, or an EFI system that only needs 35-50 psi to function, and you get the idea that some really strong hardware is required in the common rail system. Its pump also needs to be strong to supply the high fuel pressure.
Piezoelectric injectors use a sophisticated material that is able to react quickly to electrical input, but they're also very expensive compared to regular injectors, and require higher electrical charges. On the other hand, they are so fast that they can accomplish several injection cycles during the combustion expansion stroke in a diesel engine, and this has improved both fuel economy and produced smoother running diesel engines.
Attaining high injection pressure had previously only been possible with larger mechanical piston pumps where the fuel quantities were controlled by the piston stroke. The common rail system is fed by a single pump, pressurizing the rail, and fuel is delivered to separate piezoelectric injectors placed in the cylinder heads.
Ski-Doo's E-TEC system delivers fuel through the stroke of a piston plunger, but in its case, the piston movement is controlled by the voice coil. So the E-TEC uses proven piston plungers controlled electronically; and since it's all combined in one unit there are no high-pressure fuel lines to worry about.
High-pressure common rail systems are now operating in truck diesel engines and there are several cars now available with comparable technology.
Demand to lower the cost of components for mass production is now showing results. Delphi just announced a new range of GDI (Gasoline Direct Injection) injectors. Delphi's new injectors have been designed to match the performance capability of a piezoelectric injector, but with what the company terms a significant cost advantage and less current draw requirements.
Will it work on a sled?Can this technology be transferred directly to a 2-stroke snowmobile engine?
There will probably be some changes to combustion chambers and pistons to make it work. Pistons may have pockets to receive and atomize the spray, and combustion chambers may be shaped to interact with the injectors and their placement in proximity to the sparkplug.
So how sophisticated does the system need to be on a snowmobile engine?
"We could probably meet 2012 standard using an old diesel piston pump" was the comment from an engineer in northern Minnesota. He did not seem overly concerned, since the snowmobile standards are not yet as strict as the new auto limits.
Perhaps the result will be available automotive GDI systems adapted to our snowmobile 2-strokes, without a major expense in developing unique hardware. That would certainly be welcome in an industry that has already invested heavily in new models and engine technology the past 10 years.