The G10 (sometimes referred to as the "G10A" to set it apart from the later G10B) is an inline 1.0 liter three-cylinder, four-stroke cycle gasoline engine utilizing aluminum alloy for the block, cylinder head and pistons. It is equipped with either a carburetor or electronic fuel injection and was also offered as the G10T with an IHI RHB31/32 turbocharger and either MPFI or a carburator. It has a single overhead camshaft driving six valves. Cylinder spacing is 84 mm (3.3 in), as for the four-cylinder G13/G15/G16 engines.
A 73.9 mm (2.91 in) bore and 77 mm (3.03 in) stroke give the engine a total of 1.0 L (993 cc/61 cuin) of displacement. It produces 48 hp (36 kW) at 5100 rpm and 77 N·m (57 lb·ft) at 3200 rpm with 9.5:1 compression in the carburated model, 55 hp (41 kW) at 5700 rpm and 79 N·m (58 lb·ft) at 3300 rpm in the fuel injected model. The original home market version originally offered a carburated 60 PS (44 kW) JIS at 5500 rpm, later power output fluctuated around 52-55 PS.
From 1984 to 1988 the standard G10 engine used a hemispherical head carbureted design with mechanical lifters. From 1989 to 2001 the engine received updates in the form of throttle body injection and hydraulic lifters. A detuned 49 hp (37 kW) unit, with a slightly different camshaft, two-ring pistons and differently tuned engine control unit, was used in the ultra-fuel-efficient Geo Metro XFi model, which delivered as much as 58 miles per gallon. In the US, the G10 in the 2000 Chevrolet Metro became the last engine available on an American-sold vehicle to use throttle body injection for fuel delivery.
Through the 1985-1991 model years a turbocharged MPFI version of the G10 was offered in some markets. This engine delivered 70 hp (52 kW) at 5500 rpm and 79 lb-ft (107 N m) at 3500 rpm. This turbocharged engine, with mechanical lifters, was available in both the US and Canadian Firefly/Sprint/Forsa from 1987-88. Only the Canadian Firefly/Sprint had this option, with hydraulic lifters, in the 1989-1991 model years. In the domestic Japanese market, the car was originally carburated (80 PS JIS at 5500 rpm, 118 N·m (87 lb·ft) at 3500 rpm) and went on sale in June 1984. In October 1987, along with a facelift, the home market Turbo received fuel injection and power output went up to 82 PS (60 kW) JIS, torque to 120 N·m (89 lb·ft). It was a short-lived version, however, as by September 1988 the car was no longer on sale in Japan.
As is inherent in the physics of the inline-triple engine, the G10 tends not to idle as smoothly as other engines such as a straight-six engine. This engine has a non-interference valvetrain design.[WIKI]
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