In pursuit of better fuel economy, carmakers have created various forms of hybrids. In pursuit of a childhood dream, Chris Lentz created a wild hybrid.
The fifty-five-year-old electrical foreman from Jackson, Michigan, had longed for a jet-powered truck for decades. Two years ago, Lentz discovered a way to realize his dream when he met a pilot from New York who imported used turbojet engines. After watching an example run on a test stand, Lentz paid $10,000 for one. Obtaining a rolling platform for his new toy was a bit easier. Lentz bought a used STX on eBay for $12,000.
Lentz’s jet engine was designed in the mid-1950s by the Czechoslovakian company Motorlet to power the L-29 Delfin jet trainer. The Motorlet M-701 turbojet has a centrifugal compressor, seven combustion chambers, and a single-stage turbine. According to Jane’s All the World’s Aircraft, the powerplant weighs 728 pounds and produces 1962 pounds of thrust at 15,500 rpm.
To install the jet in the truck, Lentz fabricated a sturdy mounting stand, a twenty-gallon kerosene tank, and a control console from aluminum and stainless steel. His decorative touches include a red, white, and blue nose cone and a 2700 HP badge (not divulged is the 516-mph velocity needed to achieve that power level).
To light the burner, the pilot advances a red fuel lever and a blue throttle control while operating a two-stage electric starter. There are snapping sounds as ignitors fire in the combustion chambers followed by a muffled explosion and a whine not unlike a 737 taxiing past the lowered tailgate. Viewing the procedure from the rear of the truck reveals a bright orange ball of flame accompanying the muffled explosion upon ignition. With the jet idling at 3500 rpm and during full-throttle acceleration, there are waves of heat but no external flames.
Without jet assist, Lentz’s 231-hp V-8 accelerated its 6600-pound burden (truck, jet engine, two occupants) to 60 mph in a sluggish 14.5 seconds. We recorded a quarter-mile speed of 73 mph and a top speed of 85 mph.
The best of three runs in hybrid mode – exploiting both piston and jet propulsion – trimmed six seconds from the sprint to 60 mph. The quarter-mile speed jumped 30 mph and we achieved 140 mph after 45 seconds of acceleration. Feeding more ram air to the jet engine by moving it aft in the bed and shifting the F-150‘s transmission to neutral at 100 mph to cut the drag of its speed-limited driveline would likely improve performance.
Lentz occasionally fires his jet while cruising but mainly enjoys the reactions he experiences in parking lots and at car shows. His JET PWR vanity plate helps slow learners grasp the point of the bed apparatus.
Construction Cost: $25,000
Engines: 4.6L V-8 231 hp; turbojet with 1962 lb of thrust
Weight: 6221 lb
Weight Dist., F/R: 45.6/54.4%
Acceleration: 0-60 mph in 8.5 sec; 1/4 mile in 16.3 sec @ 103 mph
Top Speed: 140 mph