An aero-engined car is an automobile fitted with an engine that was originally designed for aircraft. The endeavor began when war surplus hardware triggered builders to fit these robust, liquid-cooled units. Front-engined installations usually employ in-line V12 motors, and some individuals continue to create road or track cars that carry the unmistakable stamp of a plane engine between the fenders.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
Can an airplane engine be used in a car?
Yes, an airplane engine can be used in a car. An aero-engined car is an automobile powered by an engine designed for aircraft use. Military-surplus aircraft engines were readily available in the interwar period and were used to power numerous high-performance racing cars. Some individuals have produced cars with plane or helicopter engines, since 1924 every outright land speed record-breaking car has been propelled by aircraft engines. The Beast, a 19 ft (5.79 m) car, uses a 27-liter (7.13 gal) Rolls-Royce Merlin aeroplane engine, while the Vampire jet car is powered by a Rolls-Royce Orpheus jet engine that generated 4,500 lbs (2041.2 kg) of thrust.
Turbine engines have been utilized in concept and prototype road cars; the Chrysler Turbine Car and Fiat Turbina are examples, and General Motors Firebirds are turbine-powered road cars. Liquid-cooled aircraft engines are more adaptable for automotive use, yet few swaps can top a car containing an engine that was never even designed to drive wheels. A 1939 Plymouth uses a Jacobs R-755 radial engine mounted in place of the hood, driving through a belt-driven automatic transmission to deliver 300 hp. Brutus is powered by a 47-liter BMW aircraft engine generating 550 hp, and early piston-engined adaptations produced some of the fastest and most successful land speed record attempts.
I understand that a jet motor is intended for high-altitude operations, not for ground operations. At short rates it would probably run inefficiently, and fuel expenditure would be big. Huge heavy and physical magnitude of such a power plant would involve a redesign of an automobile's frame, turning the endeavor into more of a custom-built land-speed car than a functional conveyance. Functional necessaries are varied: an airplane motor undergoes stringent regular service, whereas I regard that it would be a perpetual source of worry and cost. Upkeep and dependability worries are substantial, and its malfunction in aviation is ruinous. Therefore my view is that this is an unrealistic undertaking, even if absolute HP and force images are enticing.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
What are the differences between an airplane engine and a car engine?
Differences between an airplane engine and a car engine are given in the table below.
| Airplane Engine | Car Engine |
|---|---|
| Optimized for a much narrower RPM range | Optimized for a wider RPM range |
| Has thrust bearing to handle forces involved | Does not have a big thrust bearing |
| Typically runs at full power for a few minutes during takeoff and climb | Operates at a small fraction of full power for freeway cruise speeds |
| Designed to operate at or above 75% maximum continuous power for its lifecycle | Only operates at full power for a few seconds |
| Runs at a large fraction of max during level flight which may last for hours | Throttled back to produce the small fraction of full power needed to maintain freeway cruise speeds |
| Promotes additional stress and wear | Does not promote as much stress and wear |
| Generates thrust | Does not generate thrust |
| Cooling system is more adequate for continuous operation at full power | Cooling system is too small for continuous operation at full power |
| Horsepower and torque value run almost parallel lines | Horsepower peaks in the high RPM range; Torque peaks in the low RPM range |
Aircraft engines are optimized for a much narrower RPM range than an automobile, and they are expected to operate at or above 75% maximum continuous power for the entire lifecycle without electronic controls. A modern car engine throttles back to a small fraction of full power to maintain freeway cruise and only sees full output for a few seconds during hard acceleration. Its horsepower peaks in the high-RPM range and torque peaks low, producing a steep power curve very different from the near-parallel horsepower-and-torque lines of an aircraft engine.
An airplane engine typically runs at full power for a few minutes during takeoff and climb, then settles into flying for hours at a large fraction of maximum. Automotive engines, tested against more severe temperature extremes, must respond instantly to every traffic light and hill while coping with rapid density changes from sea level to mountain passes. Because car engines are expected to work at all elevations, they carry a cooling system sized for stop-and-go heat rejection. That same system is too small for continuous operation at full power, whereas an aviation cooling system is deliberately over-built for exactly that condition.
Mechanically, reciprocating aircraft engines carry a big thrust bearing to absorb gyroscopic and propeller loads, and they are designed for part swaps to speed field servicing. Automotive engines, redesigned with expenses amortized over hundreds of thousands of units, achieve reliability through dual independent ignition systems and tighter production tolerances. If automotive engines are operated like aviation piston engines, higher-octane fuel is required to prevent detonation under constant high load. While an airplane engine failure forces an immediate landing, a car-engine failure merely obliges the driver to pull over - proof that the operating environments are different in every sense.
