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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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