Auto Tech: Honda’s CR-Z Hybrid

By Jim Kerr

Photo Gallery:
2011 Honda CR-Z

See a hybrid vehicle and you probably automatically think of fuel economy. The hybrids currently on the market do enhance fuel economy by using a combination of gasoline engines and electric motors, but hybrids can also be built for performance. Electric motors produce strong torque at low speeds, while gasoline engines typically need higher rpm to reach maximum torque. Combine these two characteristics in the right proportions and you can have a vehicle that can put performance sports cars to shame. Unfortunately, for the enthusiast, hybrids have had limited transmission choices, and although efficient, they have been more utilitarian than sporty. That has now changed with the introduction of Honda’s CR-Z.

The CR-Z is a compact two-seater sports coupe. The curb weight of only 1,205 kilograms definitely helps performance, as it is the power-to-weight ratio that makes a vehicle quick rather than just brute horsepower. But there is more to making a sporty car than just acceleration. Shifting is one of those factors, and to make the CR-Z fun, Honda has made this hybrid vehicle available with a manual transmission.

There are two types of hybrid drives now on the market. The first type, pioneered by Toyota in the Prius and with similar designs used by other manufacturers, has a gasoline engine combined with an “automatic transmission” that uses two electric motors in the transmission. By varying the speeds and direction of the electric motors, the transmission can provide variable gear ratios as the vehicle accelerates. This type of transmission is also capable of propelling the vehicle on electric power alone with the gas engine turned off.

The other type of hybrid drive on the market is used by Honda, and called IMA or Integrated Motor Assist. This system has a thin, powerful electric motor that uses the gasoline engine flywheel as the rotor for the electric motor, with computer-controlled electro-magnetic windings around the circumference. Theoretically, this type of hybrid electric motor could propel the car by itself, but because the gasoline engine flywheel is part of the electric motor, the gas engine crankshaft has to turn all the time. Instead, Honda uses the electric motor to assist the gas engine as required. During deceleration, the computer controls can deactivate the gas engine valve train so the electric motor can operate as a generator with minimal drag from the gas engine.

Honda’s IMA system is the one that best offers the versatility of adding a manual transmission to the mix. Because the electric motor is built around the engine flywheel, any type of transmission could be bolted up to the engine. Honda has used a CVT automatic transmission on other hybrid models because the continuously variable gear ratios aid fuel economy. Now the CR-Z hybrid has a six-speed manual transmission as standard equipment, although the CVT is optional too.

The hybrid system and manual transmission work well together. Because electric motors produce great low-speed torque, it makes pulling away from a stop sign a breeze. The clutch is easy to modulate and it never feels like the gas engine is about to stall. With maximum torque between 1,000 and 1,500 rpm, the transmission can be shifted into a higher gear than you normally would if the car had just a gasoline engine. An upshift arrow on the dash indicates when you should shift up for maximum fuel economy and the car will drive smoothly in sixth gear at only 50 km/h!

The manual transmission still has AutoStop just like the automatic transmission models. As the car comes to a stop, if operating parameters are met, the engine will stop. The electric motor instantly restarts the motor as soon as the transmission is shifted through neutral into another gear. It takes a change in driving habits to make the Autostop feature work. Instead of shifting to first gear when sitting at a traffic light, leave the transmission in a higher gear and only shift to first when you want to go. The engine restarts as soon as first gear is selected.

Press the CR-Z Sport mode button on the dash and the computer operates the hybrid system for sporty performance. The six-speed manual gearbox really adds to the sporty feel and performance of the car and it would feel right at home on a twisty road cutting a few apexes. Honda has proven that hybrids can be economical and provide sporty, fun performance too.
Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automobile Journalists Association of Canada (AJAC).

Source;
http://www.canadiandriver.com/2010/10/06/auto-tech-honda%E2%80%99s-cr-z-hybrid.htm