The TPC, short for Two Passenger Car (also referred to as the Two Passenger Commuter), was an experimental two-seat car developed by General Motors and shown to specialists at the end of 1982. It was built by GM's Advanced Product and Manufacturing Engineering Staff, under Robert J. Eaton, GM vice president in charge of that staff, to explore the practical limits of fuel economy compared with other small cars around the world. Because it was intended as a worldwide-competitive design study rather than a regular production vehicle, some minor emission and safety standards specific to the United States were excluded from its engineering. GM never put the TPC into production; the company's smallest models sold later through Chevrolet dealers were instead built by Japanese partner companies.
Despite being conceived mainly for commuter and urban use, the TPC received unusually thorough aerodynamic development. Extensive wind tunnel testing at the GM Aerodynamics Laboratory produced a drag coefficient of 0.31 and an aerodynamic drag force of 4.9 square feet, helped by a minimal frontal area. Contributing design details included flush glass, rear-view mirrors mounted inside the passenger compartment instead of outside, tires and wheels kept flush with the wheelhouses, tapered front fenders, a sloped hood, a rear roof extension with ventilation air flow beneath it, an air dam integrated into the front end panel, and large radii on the front panels and windshield pillars. The rounded front end flowed into a steeply raked windshield and curved roof, while the beltline dipped in an arc to allow generous side glass area; strongly curved side windows permitted the mirrors to be relocated inward. Only a small section of each door glass could be opened, and door cutouts extending up into the roof made entry and exit easier. The tail was short, high, and rounded, concealing a luggage compartment described as spacious relative to the car's overall size.
The TPC measured 128.4 inches (3261 mm) long, 46.3 inches (1176 mm) high and 56.3 inches (1430 mm) wide, on an 80.2-inch (2037 mm) wheelbase — almost identical in wheelbase to the Austin Mini, only about 2 cm wider than the Mini, yet some 20 cm longer and 16.5 cm lower. Unlike the four-seat Mini, the two-seat TPC was not designed around maximum space efficiency but around the most rational possible transport for two occupants; even so, its cabin offered 32.4 inches of shoulder room, 37.2 inches of head room and 42.5 inches of leg room. Construction relied on light-weight steel for the main structure, with the entire front end, doors and rear fenders made of aluminum. The result was a curb weight of just 1,070 lbs (485 kg), including the air conditioning system made necessary by the large glazed area — far below the 2,200 lbs of the Chevrolet Chevette, then GM's lightest production model.
Power came from an 0.8-liter three-cylinder engine of aluminum construction weighing about 120 lb (roughly 55 kg in other figures), with an aluminum block, head, ram-tuned intake manifold and valve cover. Ram tuning delivered ambient air under natural pressure to each cylinder, working alongside sequential port fuel injection to maximize output from the low-friction engine. It produced 40 hp, driving the front wheels through a transversely mounted, long-geared five-speed manual gearbox. With a power-to-weight ratio of about 12 kg/hp (against 15 kg/hp for the contemporary Mini 1000, which made 41 hp), the TPC was said to offer lively performance for its size: 0-30 mph took 5.3 seconds, 30-60 mph took under 13 seconds, and 0-100 km/h was estimated at around 20 seconds. Other economy-oriented features included zero-drag drum brakes on all four wheels, low rolling resistance tires, and transverse composite plastic beams in the front and rear suspension combining the roles of spring, control arm and roll bar.
Fuel economy was the TPC's most notable achievement, returning 68 mpg on the EPA city cycle and 95 mpg on the EPA highway cycle while still meeting EPA emissions requirements; European-style testing recorded 3.5 l/100 km in city driving and 2.5 l/100 km on a highway cycle limited to 96 km/h. With a four-gallon fuel tank, GM estimated a driving range of 270 miles in typical commuter use and
