Austin Healey Sprite: aerodynamically & mechanically modified to get 65 MPG

by Tim Fulton on February 17, 2014

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EcoModder presents another streamlined, high efficiency blast from the past.

Beneath these extensive modifications lies a 1960 Austin Healey “Bug Eye” Sprite.  It was built by EcoModder member Tom Shrimplin as a high-efficiency commuter to take him to work at the Institute for Environmental Research at Kansas State U in the 1970’s.

Tom explains, “I was driving 110 miles per day so I began modifying the Sprite and doubled its mileage over a period of years to a consistent 65 MPG (unheard of in those days).  This was a 1960 “Bug Eye” with an 850cc engine. It turned close to 3000 at 60 mph and gave 33 mpg on average, originally.”

Here’s the same Sprite in “33 mpg” form:

aero-austin-healey-sprite

Mechanical modificiations were extensive:

  • Engine: the original engine was replaced with a 1600cc engine from a Ford Pinto
  • Engine modifications: the camshaft was retarded 2 notches (making a poor man’s Atkinson cycle); electronic ignition was substituted for the original system (in combination with a wider spark plug gap this permitted running a slightly leaner air/fuel ratio); adjustable on-the-fly carburetor from a Briggs & Stratton lawnmower; belt driven cooling fan removed.  Tom says it never overheated, even in summer.  He could run cabin heater fan if the coolant temperature started to climb.
  • Tires: new for the time radial tires with lower rolling resistance
  • Transmission(s):  a big portion of the mpg improvement came from adding a manual 3-speed Buick transmission inline (but reversed) with the Pinto 4-speed manual, providing 12 forward gears and up to a 2.5 overdrive.  The engine ticked over at just 1100 rpm @ 55 MPH (Nixon speed limit days). Excellent for economy, but requiring more from the driver: “a slight incline required downshifting.”

Here’s the car part-way through its transformation:

aero-austin-healey-sprite

Of course, the most obvious mods were of the aerodynamic variety.

Tom checked all the important boxes:

  • Frontal area reduction courtesy of a raked windshield
  • “Boat-tailing” at the rear
  • Re-sizing the cooling opening to suit the reduced engine load
  • A set of four fender skirts
  • Smooth(ish) hubcaps.

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Tom doesn’t apologize for the function-over-form aesthetics: “It was made of junk yard body pieces, pop rivets and bondo.” He painted it bright yellow for safety, because somehow drivers failed to notice the low-slung car streamliner on the road.

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Ultimately (after 250,000 miles), the modified car was taken off the road & dismantled. A student got the chassis in exchange for destroying the body. He had a Midget and could use the parts.

Today at 87 years old, Tom is still ecomodding.

A few months ago he added a short aerodynamic extension to his recently acquired 2000 Honda Insight that improved its fuel economy by 5% on a familiar route.  He says he prefers driving the Insight to the old Sprite.

insight-xpedro

For more information and discussion about Tom’s projects, check out the forum thread on his AeroSprite, or the thread about his Honda Insight.

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