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

by Tim Fulton on February 17, 2014


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:


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:


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.


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.


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.


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

Popularity: 6% [?]

Comments on this entry are closed.