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By: Jason Giacchino
Email: offthepegs @ atvsource.com

December 2008 - Off The Pegs

The Two-Stroke Resurfaces

Just when you thought the two-stroke engine has breathed its last breath, British automaker Lotus announces a high performance car prototype equipped with a direct-injection two-stroke engine! Before we get optimistic about an industry-wide rejuvenation of what have been affectionately labeled “2-smokes” throughout the years, let’s keep in mind that the Omnivore, as Lotus has named it, is yet just a prototype. Not only that but even if somehow the car were to be put into production, EPA restrictions coupled with decibel-limitations would pretty much guarantee it would never be free to rip around the tarmac of the United States.

Even still, it’s a pretty wild concept considering that our industry (as well as most other power-sports) has all but issued the kiss of death to the two-stroke mill by and large. To trace the turning point we would have to head back to late 1997 when Yamaha tried its hand at a 400cc thumper to campaign against the then-exclusive 250cc two-stroke supercross class. Of course, we can now state with utter confidence that the effort paid off and essentially laid the framework for what has become the 450cc class. However,  at the time it was quite a gamble. Worse still was that the writing was on the wall for some time that the days of the two-stroke were numbered. Restrictions that began on the West Coast began to spread across the country until all that remained of the 2-stroke were units sold for closed-course competition use only. ATVs, of course, fall into the jurisdiction of off-highway recreational vehicles for much of the country, hence placing additional pressures on an industry already riddled with manufacturer reluctance (thanks to lawsuits and legalities left lingering from a decade earlier).

This essentially left the OEMs at a crossroads. Their choices were either to develop a more environmental-friendly two-stroke (something Honda began developing) or to abandon the whole idea and focus on competitive four-strokes. Keep in mind that at the time of these negations, four-stroke engines were limited to play-equipment at best. Models like the Kawasaki Mojave, Honda 300EX, and Yamaha Warrior would have had a long way to go to be competitive against the highly modified 250Rs and Banshees that ruled the roost at the time.

Yamaha rolled the dice and silenced all of the naysayers, pit pundits, and skeptics when Doug Henry proved that this new 400 (which took advantage of AMA rules that allowed a massive displacement advantage to encourage the manufacturers to allocate R&D into four-stroke technology) could not only keep up with the 250 two-stroke, but actually outperform it.

In the generations that followed, displacements bounced around a bit before settling into the unanimously accepted 450cc configuration. It wasn’t long after that these engines began to be considered for their performance potential in an ATV chassis. A decade after the four-stroke revolution began and we have competitive 450cc entries from all four of the Japanese manufacturers (a unification never before seen in the ATV industry) in addition to entries from the likes of Austria’s KTM, Canada’s Can-Am, and America’s own Polaris.

But I digress, the news that inspired this entire rant came from the simple announcement that Lotus has decided to buck the trend and put some of their R&D budget into not just a two-stroke (which is unique enough in a car as it is) but one in which the compression ratio is variable. This would allow the sports car to run on a wide range of fuels without detonation or pinging. With unstable oil costs and international efforts on hybrids and gasoline/ ethanol blends, the finicky two-strokes of yesteryear would certainly be impractical in today’s market.

The bottom line is even though odds are very high that the Omnivore production will never see the light of day, it’s refreshing just to know that the world hasn’t swept all knowledge of the two-stroke under the proverbial rug. I know I, for one, would love to hear the scream of a well tuned two-stroke on the racetrack once more, even if it’s in a form of racing I have little to do with.


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