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Wednesday, May 13, 2009

Toyota's 2010 Prius breaks cover

The third-generation Toyota Prius 50 MPG hybrid features a more aerodynamic shape, larger 1.8 litre 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 Litre to a larger and more powerful 1.8 litre Atkinson-cycle, four-cylinder engine should significantly improve the power to weight ratio and the performance of the Prius. The current 1.5Lt Prius has always scored well in city driving due to it’s regenerative braking but it has been noticeably lacking in highway performance due to it’s 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.

The remote air-conditioning system is the first system in the world to function on battery-power alone and that can be remotely operated, so the driver can adjust the interior temperature for comfort before getting in the car.
Reducing the vehicle's power consumption, potional LED (light emitting diode) lamps are used for low beams and also in the tail and stop lamps. Air conditioning, a major energy drain, has been re-engineered to increase efficiency and cool-down performance. In addition, an exhaust heat recirculation system reduces heat waste by warming engine coolant during cold startup, for improved performance. It also heats up the passenger cabin more efficiently.

Lighter chassis

The hood, rear hatch, front suspension axle and brake caliper are made from aluminium and the use of super high-tensile steel in the rocker inner, centre pillar, and roof reinforcement form a roll cage like safety cell for the occupants in the event of an accident. The 0-to-60 acceleration has been improved to 9.8 seconds, more than a second faster and disc brakes are now used on all four corners, replacing the front disc/rear drum brakes in the current model. Anti-lock Brake System (ABS), Electronic Brake Distribution (EBD), Brake Assist (BA), electronic traction control (TRAC) and Vehicle Stability Control (VSC) are included with Toyota's standard Star Safety System.

Dynamic Radar Cruise Control system, using advanced millimetre wave radar, is an available option. The system also enables Lane Keep Assist, which helps the driver stay safely within the lane, and the Pre-Collision System, which retracts seatbelts and applies the brakes in certain conditions when a crash is unavoidable.

Next-generation Intelligent Parking Assist features simplified settings to help guide the car into parking spaces. A back-up monitor, which provides a view of rear obstacles when reverse is engaged, is available with an optional voice-activated navigation system.


1.8-liter four-cylinder engine with VVT-i
Engine horsepower: 98 hp @ 5,200 rpm
Engine torque: 105 lb-ft @ 4,000 rpm
Electric motor: Permanent magnet synchronous motor
Electric motor power output: 80 hp/153 lb-ft torque
Hybrid system net horsepower: 134 hp
Emission rating: SULEV (with AT-PZEV)
Electronically controlled continuously variable transmission
Drive System: Front-wheel-drive
Hybrid battery pack: Nickel-metal hydride
Estimated fuel economy: 50 mpg (combined)*
Overall Length: 175.6
Overall Width: 68.7
Overall Height: 58.7
Wheelbase: 106.3
Ground clearance: 5.5
Coefficient of Drag: 0.25
Wheels: 15-inch alloy wheels
17-inch alloy wheels (optional)
Tire Size: 15-inch: 195/65R15
17-inch: 215/45R17 (optional)
Seating Capacity: 5
EPA class rating: Midsize
* Preliminary figure based on Toyota's internal testing. Actual mileage will vary.

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