Q: How important is hybrid propulsion vs. other technologies to the Insight's efficiency?

A: One of the ways in which the Insight is most misunderstood is in thinking of it simply as a hybrid gas-electric car. Hybrid propulsion is only one of a number of significant technological advancements incorporated into this remarkable car.

Compared to a similarly sized 1.6L 3-door Civic, the Insight consumes only 54% as much fuel over the same distance, and so also produces only 54% as much greenhouse gas.

This is the amount that Honda tellus us each technology contributes to this improvement over the 3-door Civic:

Important points to properly understand this chart:

• This doesn't show the importance of the indirect contribution from motor assist: While power regeneration & idle stop are directly responsible for nearly 1/3 of the Insight's improved efficiency, this ignores the second and equally important role of the electric portion of the powertrain:

  The electric motor indirectly allows for much more efficiency gain by allowing a smaller gasoline engine to be used without compromising performance. While the Insight would still offer about 70% of its efficiency gains without the electric motor & batteries, performance would be much worse. So, not only does the electric motor & batteries directly improve efficiency, but they also make other efficiency improving measures acceptable to the driver who doesn't want to give up good performance for the sake of efficiency.

• The technologies are intertwined; you can't remove any piece of the puzzle without affecting other areas: Breaking down the amount contributed by each technology, as is done here, can be a very misleading. The real genius of the Insight his how all its technologies are tied together and work in harmony to achieve so much. For example, without the weight and drag reducing body technologies, the Insight would have needed a significantly larger engine to achieve the same performance, and as a result efficiency would be reduced much more than the 35% direct contribution to efficiency made by body technologies.

  In other words, each of these technologies are much more important to the overall package than the 30%-35%-35% breakdown might suggest.

• These numbers are based on an average of city & highway driving: In the city motor assist plays a bigger role than indicated here. On the other hand, on the highway aerodynamics and low rolling-resistance tires play a much greater role.

Q: What does it mean that the Insight is a hybrid car? What kind of hybrid is it? Is the Insight an electric car?

A: The term electric car generally refers to a vehicle that is propelled solely by an electric motor. In this case the electricity may be stored in batteries, or generated on-board, perhaps by using a fuel cell. This is not the case for the Insight. Rather, the Insight uses both an electric motor and an advanced gasoline engine to propel the car. For this reason, the Insight is classified as a "hybrid" gasoline-electric vehicle.

Part of the confusion that arises is that there are many ways in which a gasoline engine could be combined with an electric motor to create a "hybrid" car, so just saying that the Insight is a "hybrid" doesn't tell the whole story.

In the case of the Insight, a "parallel hybrid" system is used, where both the electric motor and gasoline engine directly contribute to turning the wheels of the car. With the Insight, the gasoline engine is the primary source of power, just like most cars on the road today. The electric motor is then used to add extra boost when needed. Up to 50% more torque is supplied by the electric motor above what is supplied by the gasoline engine alone. This setup has a number of implications:

• Most cars have a significantly larger, less efficient engine than is needed to maintain highway speed. This extra capacity is only used when accelerating or climbing hills, but impacts the efficiency and "cleanliness" of the engine all the time. Using an electric motor to assist the gasoline engine for acceleration or climbing grades allows Insight's gasoline engine to be optimized for maintaining cruising speed.
• All the energy used by the Insight ultimately comes from burning gasoline. This means that you just refill the Insight as you would any other car, but it means that the Insight cannot be charged from an outside source and run on electric power alone. This gives the Insight a range of over 700 miles (1150 km) before refueling, which is much more than a typical pure-electric car's range of 100 miles (160 km) before recharging. For some people this matters, for others it does not. Much debate has centered over which is preferable from an environmental standpoint. Because the Insight's gasoline engine is so clean burning, many see it as preferable to electric power that originates from nuclear and some other sources. It is certainly much cleaner in areas where coal electric generation is used.
• In normal stop-and-go city traffic, a lot of energy is wasted each time you come to a stop, in the form of heat generated by the brakes. With its electric motor/generator, the Insight is able to take advantage of regenerative braking technology seen in pure-electric cars, to reclaim some of this energy that would otherwise be lost.

Honda has also taken advantage of the electric motor / generator for the following purposes:

• There is no conventional alternator - all the normal electric components are supplied power from the electric motor/generator, converted from 144v to 12v by a DC-to-DC converter.
• The IMA electric motor is normally used to start the car, though the Insight also has a conventional starter motor for backup purposes.
• The electric motor is timed to smooth the gasoline engine. At idle speed, the electric motor actually operates in generation mode at the moment of ignition, when the gasoline engine is producing the most power. A moment later when the gasoline engine's crankshaft then begins to slow down, the electric motor operates in assist mode, reapplying the energy it absorbed, greatly smoothing the engine's idle.

Q: What is the IMA system?

A: IMA is Honda's name for the hybrid gasoline/electric system employed in the Insight. The IMA system incorporates the electric motor/generator, the battery pack, and a lot of control circuitry that controls when power is supplied to or taken from the electric motor, controls charging of the high-voltage battery pack, and converts the electricity from one form to another.

Q: What is regenerative braking? How does it work on the Insight?

A: When you drive your car in city traffic, a lot of energy is wasted each time you brake to come to a stop at an intersection, make a turn, etc. In effect, the energy of your forward momentum is lost in the form of heat in your car's brakes. More energy is then needed to reaccelerate you back to your previous speed.

The idea behind regenerative braking is to recapture some of the energy that would otherwise be wasted by braking, store that energy in batteries, so that that energy can later be used when you reaccelerate. This idea is widely used in both pure electric and hybrid electric vehicles.

How does it work? Because many electric motors can also operate as generators, the same electric motor that helps to propel the Insight is also used to generate electricity and recharge the batteries. The more electricity that is drawn from the motor/generator to charge the batteries, the more drag the motor/generator creates, effectively slowing down the car.

In the Insight, when you press the brake pedal lightly, the electric motor operates in regeneration mode, and the car begins to slow just as it would with normal brakes. If you press the brake pedal further, the normal brakes then also come into play, slowing you down even more.

Honda has done an excellent job of making this work very naturally and transparently; there is a good chance that you won't even realize that the regenerative braking is happening until you get to know the Insight.

One side effect of having the IMA motor positioned between the engine and the clutch is that the regenerative braking only takes place when the car is in gear and the clutch is engaged. This means that if your IMA battery state of charge is becoming depleted, you may want to downshift into lower gears as you decelerate to help recharge the battery.

Q: The Insight has "low rolling resistance tires". What does this mean?

A: One of the ways in which overall energy efficiency is improved in the Insight is by using a low-rolling-resistance tire design.

The Insight's tires are designed to reduce rolling resistance by 40% compared to conventional tires, while also reducing weight by 5%.

While tire material and tread design are an important part of the low rolling resistance equation, one of the biggest factors is reducing the amount that the tire deforms as it rotates. While you may think of tires as being round, when loaded with the weight of a car, they are no longer a circle. Rather, they deform so that the bottom of the tire is "squeezed". To the right you'll see an exaggerated illustration of this effect.

The result of this deformation is that as the tire rolls down the road, it is constantly changing shape. This continual deformation wastes a significant amount of energy. In order to reduce the amount of this deformation, the Insight's tires are inflated to fairly high pressure (38 psi front, 35 psi rear, by Honda's specs). Disadvantages of higher pressure are that it decreases ride softness, and increases tire noise. The Insight's tire design is also relatively low profile, meaning that there is less sidewall to flex, further reducing energy lost to this rolling resistance.

In terms of tire tread design and material, the Insight's original equipment tire is the Bridgestone Potenza RE92. This is what Bridgestone says about the Potenza RE92:

• High performance tire designed to complement today's sporty coupes, sedans.
• Circumferential tread grooves provide efficient channeling of water to help resist hydroplaning.
• Bridgestone's variable pitch technology "effectively limits" road noise.