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IMA System 1.0-Liter VTEC Engine Specifications

Displacement: 995 cc
No. of Cylinders: 3
Bore and Stroke: in. (mm) 2.8 x 3.2 (72 x 81.5)
Weight: lbs. (kg) 124 lbs. (56.2)
Horsepower: 73 @ 5700 rpm

(67 @ 5700 rpm gasoline engine only)

Torque: 91 @ 2000 rpm

(66 @ 4800 rpm gasoline engine only)

Compression Ratio: 10.8:1
Valvetrain: 12-valve VTEC-E
Fuel Economy: tba
Emissions: ULEV


Offset Cylinder Bores

The IMA gasoline engine's 3-cylinder engine block is a highly compact, aluminum-alloy die casting. An unusual feature of the engine's design is that the crankshaft axis has been shifted, or offset, 14 mm, relative to the cylinder-bore axis. In other words, the crankshaft does not sit directly under the cylinder. This was done in the interest of minimizing friction caused by the side thrust of the pistons against the cylinder walls, just after top-dead-center, as each piston begins its descent on the firing stroke.

In a conventional engine, piston-side thrust and the friction it generates are the result of the crankshaft's resistance to turning at this point. This resistance is the result of the small angle formed by the crank throw relative to the centerline of the piston and cylinder. The IMA engine's cylinder bores are offset to be over the crank throw at this point, so the piston and connecting rod push straight down, thereby minimizing side force on the piston.

Cylinder-bore offset in the IMA engine accounts for as much as a three-percent reduction in internal friction.