[F500] 2-Stroke Death may be premature

[Chuck McAbee]

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   The Two-Stroke Lives (cleanly, too)

   Evinrude's  E-TEC  engines  have done the seemingly impossible: saving
   the air-cooled two-stroke from oblivion
   By Christopher A. Sawyer, Executive Editor Chris's Bio-[icon_inf.gif]
   Write Christopher-[icon_env.gif] 

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   About  10 years ago, Chrysler's Joe Goulart was singing the praises of
   the two-stroke engine as an automotive powerplant. His dream, however,
   couldn't  pass  muster  with  the  EPA.  As  a  result, the automotive
   two-stroke engine died. Environmental concerns dogged the recreational
   two-stroke,  as well. After years of doing nothing, the EPA set strict
   pollution  limits  for  recreational  vehicles  (personal water craft,
   snowmobiles,  etc.),  which  called  into  question  the  two-stroke's
   continued  viability.  Fortunately,  no  one  told  George  Broughton,
   director   of   Engineering,  Boats  and  Outboard  Engines  Div.  for
   Bombardier  Recreational  Products  (Sturtevant,  WI). He and his team
   created  the  Evinrude  E-TEC  family of two-strokes; engines that are
   clean and darn-near worry free.

   Fuel Injection That Sings
   "The trick was to make an engine that would idle at 500 rpm and make 1
   hp,  and  run  6,000  rpm  and  make 250 hp while meeting the emission
   standards,"  says  Broughton.  Part  of  the solution involved using a
   Lorentz coil. Better known as the voice coil that drives loudspeakers,
   a  Lorentz coil is made up of a permanent magnet and coil winding, and
   produces  a  force  proportional  to  the current applied to the coil.
   Which  makes  it perfect for devices requiring high acceleration, high
   frequency  application,  and  a  flat  force  vs. displacement output.
   Another  big advantage is that it can push or pull, so it can be reset
   between injection events very quickly.

   "The  strength  and  duration  of  the  injection pulse determine fuel
   droplet  size," says Broughton, "which varies to meet the unique needs
   of  an  air-cooled  two-stroke."  At low engine speeds, small droplets
   offer  the greatest atomization, and the most homogenous mixture. This
   is sprayed over the spark plug, and ignited as a stratified charge. At
   high  speed,  larger  droplets are used to cool the top of the piston.
   (Cooling  also  is helped by use of a NASA-developed alloy three times
   stronger  than  conventional  alloys  at temperature. Broughton's team
   found it while searching the Internet.)

   A  swirl-nozzle  fuel  injector  with  0.046-in.  tangential  slots is
   another  key  to  clean combustion. "It's made through metal injection
   molding,"  says  Broughton, "and starts as a piece about three or four
   times  bigger  than  the final product. Then it's shrunk to size in an
   oven  like  a  new  pair of blue jeans in the dryer." The fuel rail is
   pressurized  to 30 psi, and the Lorentz coil amplifies this to 600 psi
   (1,000  psi  is  possible,  but  as  yet  unnecessary) under wide-open
   throttle conditions.

   No Battery, Plenty of Spark
   The E-TEC's electrical system is based around a magneto - like a Model
   T - for a simple reason: recreational vehicles are put into storage at
   the  end  of  each  season,  then  pulled  out  when the weather turns
   favorable.  Batteries  die  in storage, so relying on one to drive the
   fuel  injection  system  and  engine  controller only adds to customer
   frustration.  "The  magneto  produces  from  150  to  300 volts," says
   Broughton,  "but that is reduced to 55 volts to drive the oil and fuel
   pumps  and  the  fuel injectors. It's further reduced to 14.7 volts to
   charge the battery, if the boat has one."

   Evinrude  promises  an  E-TEC engine will start within one revolution,
   something most two-stroke owners will find hard to believe, especially
   for  an engine that's been in storage. The key is the sealed injection
   system.  Though the fuel in the gas tank may oxidize over time, no air
   can enter the fuel system itself. The gas stays fresh. As the flywheel
   starts  to  turn,  the magneto sends current to the engine controller,
   which determines where the piston is, when to inject the fuel and fire
   the  spark  plug  -  all inside of one revolution. At the end of three
   year's  use,  and  except for greasing the lower drive unit because of
   its  constant immersion in water, Broughton insists the only item that
   may need service is the spark plug. "The E-TEC is designed to go three
   years without any dealer interaction," he says.

   Oil and Catalysts
   But  what  if  the  regulations get tighter, won't two-strokes be at a
   disadvantage because of their propensity to burn oil? "Oil isn't a big
   player," says Broughton, "because the amount burned is about 1% of the
   total  intake  charge,  and  it  never  mixes with the gasoline." (The
   average  user  of  a 50-hp E-TEC will go through two quarts of oil per
   year.)  Hydrocarbons are the predominant pollutant, a portion of which
   are  scavenged  and burned in the next combustion cycle. When emission
   standards  tighten,  Broughton  will  be ready with a simple reduction
   catalyst he terms, "1970's technology." Right now, the engine is clean
   enough to pass California's 2008 standards.

   Broughton   doesn't  claim  E-TEC  technology  might  have  saved  the
   automotive  two-stroke,  but  he does suggest Detroit's obsession with
   preventing  the  lubricating  oil  from being burned during combustion
   sent  them  down  the wrong path. "Their concentration on retaining an
   oil  sump, oil scraper rings, and relying on plain bearings instead of
   roller  bearings,"  he theorizes, "increased the amount of oil burned,
   which  harmed emissions performance." And it may be another reason why
   automotive  two-stroke  emission  performance degraded over time. "The
   E-Tec actually gets cleaner as it progresses through the EPA test," he
   says.  "And  we  never have to worry about the potential for secondary
   pollution  when  changing the oil." Maybe not, but try selling that to
   the EPA when discussing emission tradeoffs.

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   Tighter emission standards were supposed to mean the end of two-stroke
    engines for recreational use. Apparently, Evinrude wasn't listening.
      It uses a Lorentz coil to drive the fuel injection system, which
      allows it to produce a stratified mist at low speeds, and larger
   droplets to cool the piston at high rpms. A NASA-developed alloy that
         is three times stronger than current piston alloys at high
    temperatures eliminates a weak spot found in conventional two-stroke
    designs. Evinrude claims the new design will start in less than one
     revolution of the engine, and be across its full engine line by MY
                                   2005.

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   --- Chuck McAbee

   SEDIV #16

   --- sedivf500 at earthlink.net

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