The IMA electric motor operates in parallel with the system's gasoline engine, supplying an additional 25 lb.-ft. of torque in assist mode. This eliminates the need for a separate, heavy electric drive motor. The high-efficiency, permanent-magnet motor has a maximum output of 10 kilowatts. The motor's ultra-thin design - only 2.3 inches wide - allows it to be mounted directly between the engine and transmission. The IMA electric motor's high torque characteristics at low speeds makes it ideal for assisting the IMA engine during low-rpm acceleration, thereby increasing overall efficiency during normal driving.
The motor also functions as the generator for the IMA system, thereby saving the additional weight of a separate unit, and as a high-rpm starter, quickly spinning the engine up to its idle speed. If the IMA system battery charge is low, a separate 12-volt battery and starter motor will start the engine.
Another innovative feature of the IMA system is the use of the electric motor to damp engine-idle vibration by application of reverse torque to the crankshaft. The reverse torque pulses are exactly in phase and opposite the 60-degree torque fluctuations of the gasoline engine. As a result, the Insight's IMA gasoline engine is remarkably smooth throughout its operating range.
The IMA system's idle-stop feature saves fuel and minimizes emissions when the Insight is stopped by temporarily shutting off the gasoline engine. The system is automatically engaged when the driver places the gear selector in neutral and takes his or her foot off the clutch. A green "Auto Stop" light indicates when the feature is operating. When the driver pushes the clutch pedal and engages the transmission, the IMA motor immediately restarts the gasoline engine.
The IMA feature will not operate if the battery state of charge is low, or the engine has not warmed up, or if the air conditioning is operating. When the economy mode is selected, the idle-stop feature will work; however, it will periodically keep the engine idling so that the air conditioning can maintain a comfortable cabin temperature.
Also, if the transmission has not been shifted out of first gear, for example in slow-moving traffic, then the idle-stop feature will be ready to accelerate, and to conserve electrical energy.