Toyota's 2010 Prius breaks cover

The third-generation Toyota Prius 50 MPG hybrid was revealed today at the 2009 North American International Auto show. The new Prius features a more aerodynamic shape, larger 1.8 liter petrol engine with optional roof-mounted solar panels and intelligent park assist. Unfortunately the 2010 Prius is not yet a plug in hybrid and still comes with a relatively small Nickel-metal hydride battery so EV only mode will not exceed approx 5 miles. While the current model Prius is EPA rated at 46 mpg, the third-generation Prius has increased fuel economy to an estimated 50 miles per gallon for the new Prius (it has not been EPA rated as yet).

90% new Drive System

The move from 1.5 liter to a larger and more powerful 1.8 liter Atkinson-cycle, four-cylinder engine should significantly improve the power to weight ratio and the performance of the Prius. The current 1.5l Prius has always scored well in city driving due to its regenerative braking but it has been noticeably lacking in highway performance due to its small engine capacity and the additional weight of a battery pack compared to vehicles with similar engine capacity. Contrary to conventional wisdom, the larger engine actually helps improve highway mileage. By making more torque, the new engine can run at lower average rpm on the highway. When operating at lower rpm, the new engine uses less fuel.

Toyota has used an electric water pump for the first time that increases engine’s efficiency by removing auxiliary loads from the engine’s crankshaft. These loads, such as the power steering and the air conditioning compressor, are powered directly from the 500v battery at achieve much higher energy efficiency. The 1.8-liter Prius engine is the first Toyota engine with no belts under the hood. The 4 cyl VVT-I puts out 98 hp (72 Kw) @ 5,200 rpm with 105 lb/ft (142 Nm) @ 4,000 rpm compared to 76hp (57 Kw) and 82 ft/lb (111 Nm) in the current model.

The Hybrid Synergy Drive system in the 2010 Prius is 90 percent newly developed with significant improvements over previous models. These include a lighter continuously variable transmission (CVT), an improved inverter cooling system and improved control logic to enhance brake regeneration.

The electric motor is still a permanent magnet AC synchronous motor (BLDC). Power has been increased from 50kw (67hp) to 59kw (80hp) while the Electric only torque figure provided in this press release says 153 ft/lb but the current model Prius has 295ft/lb (400Nm) so we’ll take that as a Toyota typo. Toyota say net hybrid systems power has increased from 110 hp (82 Kw) to 134 hp (98.5 Kw).

Worlds lowest Cd

The aerodynamic design of the new 2010 Prius was an important factor. The goal was to create a wedge shape with steeply raked windscreen and square rear end corners to reduce aerodynamic drag. The overall height of the Prius is the same, but moving the top of the roof 3.9 inches to the rear alters the roof profile. This also allows for enhanced rear headroom and improved aerodynamics. The new Prius received more hours of wind tunnel testing than any other Toyota in history, resulting in the cleanest aerodynamic profile of any mass-produced vehicle in the world. By focusing on the shape of the body, underfloor, wheelhouse liner and shape of the wheels, the designers of the new Prius were able to reduce the coefficient of drag (Cd) value to 0.25, compared to 0.26 for the previous model. The airflow under the car was studied extensively. Engineers made changes to the shape of the fender liner, front surface of the underfloor, and added a fin at the rear floor cover to increase linear stability.

An optional sliding glass roof is packaged with solar panels, located over the rear seating area, that powers a new ventilation system. This solar powered ventilation system uses an electrically powered air circulation fan that does not require engine assist. The system prevents the interior air temperature from rising while the vehicle is parked, making the cool-down time shorter when the driver returns to the vehicle, thus reducing the use of air conditioning. As it is usually hottest inside a vehicle when the sun is shinning rightest this should prove an efficient way to power a cooling system.

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