Integrated Motor Assist (IMA)

Integrated Motor Assist (commonly abbreviated as IMA) is Honda's hybrid car technology, introduced in 1999 on the Insight. It uses an electric motor mounted between the engine and transmission to act as a starter motor, engine balancer, and assist traction motor. In its first generation, IMA could not power the car on electricity alone, and could only use the motor to assist or start the engine. The Insight and the 2003-2005 Civic Hybrid fall into the 'Mild Hybrid' category. In mild hybrids, the gas engine provides the main propulsion, and the electric motor provides assist whenever extra power is needed. In this arrangement, the electric motor cannot operate independently of the gas engine. The electric motor can generate electricity for the battery or consume electricity from the battery, but not both at the same time. In contrast, a 'Full Hybrid' integrates the electric motor, gas engine and battery, so that the electric motor can operate on its own when certain conditions are met. For some hybrids, it does this under low speed; once the vehicle reaches higher speeds, the gasoline engine starts up and takes over. Under hard acceleration, both the gas engine and the electric motor can work together to provide the needed power. Unlike mild hybrids, full hybrids are able to generate and consume electricity at the same time. In 2006, the Civic Hybrid moved into the full hybrid category, however, can activate the electric motor while the vehicle is coasting without turning the ICE on.It is different than the other full hybrid systems. While the Civic Hybrid cannot start from a stoplight under electric power alone, at certain light-load cruising conditions the electric can provide the sole means of propulsion.

The theory behind IMA is to use Regenerative Braking to recapture some of the energy lost through deceleration, and reuse that energy later on to help accelerate the vehicle. This has two effects: it increases the rate of acceleration, and it reduces the work required of the gasoline engine. The acceleration boost is important, as it allows the engine to be scaled down to a smaller but more fuel-efficient variant without rendering the vehicle overly slow or weak. This smaller engine is the primary reason cars equipped with IMA get better highway mileage than their more conventional counterparts.

Additionally, vehicles equipped with IMA can shut off their engine when the vehicle stops and use the electric motor to rapidly spin it back up when the driver releases the brake pedal. They also have a conventional starter as a backup, making it the only production hybrid system which can operate with its high voltage electric system disabled, using only its ICE like a traditional vehicle. However, since the IMA also acts as the vehicle's alternator, eventually the 12 V accessory battery would require an external charge.

Vehicles Using IMA:

• Honda Insight (1999-2006)
• Honda Civic Hybrid (2003-)
• Honda Accord Hybrid (2005-)

The 2005 Honda Accord Hybrid was the first V6-powered hybrid vehicle to market, powered by Honda's third generation IMA technology. Whereas the Insight and Civic Hybrid prioritized fuel economy over performance, the Accord Hybrid added more power to the equation, while still retaining Civic Hybrid-like gas mileage and low emissions. In fact, the Accord Hybrid combines its V6 and electric motor to generate a total of 253 horsepower - 9 more than the standard gas-only V6 engine.