Published on Sun, Dec 20, 2009
By: The LACar Editorial Staff
© All photos by Harvey Schwartz By Harvey Schwartz
The all-new 2010 Lexus HS250h hybrid will keep more of your money in your pockets as you pass gas stations, and will also have you seated in a Lexus with all of the luxury, convenience and safety that you expect from a Lexus. The Lexus HS250h is the first luxury hybrid to achieve an EPA Estimated Rating of 35mpg combined and is the first luxury car to come standard with a supplemental restraint system with 10 airbags. Hybrid efficiency is at the core of the new HS250h and Lexus's first four-cylinder gas engine and latest hybrid system take advantage of the company's continuous engineering advances to maximize fuel economy, minimize emissions and deliver driving pleasure. A highly efficient engine design, an exhaust heat recovery system, major efforts to reduce parasitic losses, a new evaporative emissions system and driver-selectable driving modes all make notable contributions. Significant efforts were also made to minimize engine noise. An Atkinsion-cycle engine design was chosen for its high efficiency and compatibility with hybrid operation in the new HS. The twin-cam engine uses four-valves per cylinder and Variable Valve Time with Intelligence on the intake side. The engine is undersquare, with an 88.5 mm bore diameter and 96 mm stroke, and has a relatively high compression ratio of 12.5:1. Peak output equals 147 horsepower and in combination with the hybrid drive motor, the HS generates 187 total system horsepower. That is the most of any other dedicated hybrid motor. Careful design of the intake system reduces engine pumping losses and its twin resonators minimize intake noise. The cooling system uses a modular construction that combines an aluminum engine radiator, hybrid system radiator, AC condenser and fan into a single assembly for minimal weight. Plus, the electric fan speed is controlled via Pulse Width Modulation to reduce energy consumption and noise. Careful ducting of the cooling system helps prevent hot engine air recirculation that tends to occur at low speeds and while idling, further enhancing efficiency.
One of the keys to lower fuel consumption involves heat. Similar to the Lexus RX 450h luxury SUV, the HS employs an Exhaust Heat Recovery system that captures the heat of spent exhaust gases to speed engine coolant warm-up and allow the hybrid system to stop the engine earlier, and more often in the driving cycle when it's not needed, for example in lower power demand conditions in city driving. Overall, the system can improve fuel efficiency by as much as seven percent in low ambient temperatures. Using a two-motor hybrid system, the new HS uses a 141 horsepower drive motor that combined with the 147 horsepower gas engine. A second motor in the hybrid system serves as both engine starter and generator to charge the hybrid battery pack. The efficient two-motor system also uses an electronically-controlled continuously variable transmission (CVT) that is a model of efficiency, simplicity and compact size with extremely smooth and quiet operation. A motor speed reduction planetary gear unit helps provide high power output in this small package. The HS also uses an easy-to-operate shift-by-wire system that eliminates the need for bulky shift cables, saving space and weight while allowing much more design freedom in placing the shift lever in the interior. An electric transmission oil pump eliminates another source of parasitic loss to further increase efficiency. Electronic operation allows a control strategy that invokes the oil pump only when needed, and since the oil also flows over the drive motor, overall efficiency of the motor and transmission are improved. I was truly impressed with the smooth and quiet operation of the motor and CVT. The HS also incorporates a drive-mode switch that allows you to select between four modes: Normal, Power Eco and EV. Each switch position changes the rate of throttle opening for a given throttle-pedal angle. Normal mode has an essentially linear throttle response that gives naturally progressive power. Power mode can be selected for a more responsive feel when desired, such as when merging onto fast moving freeways or when you want to quickly maneuver around slow city traffic. In Eco mode, AC settings are adjusted and the throttle response is reduced relative to the pedal angle to emphasize fuel economy, such as when you are in rush hour traffic or on short trips around town with little traffic. Under certain circumstances, the EV mode can allow the vehicle to be driven short distances using only the electric motors. 0-60 mph acceleration is surprisingly quick at 8.4 seconds. Responsive passing acceleration benefits from the instant torque of the electric motor and the CVT's ability to quickly find the optimal gear ratio to enhance your driving experience. The HS250h body design received considerable attention to aerodynamics. Ambitious goals were set requiring designers to work closely with aerodynamics from the outset to create a low-drag form in an attractive, spacious, yet compact package. Their work yielded a coefficient of drag of 0.27, among the best, enhancing fuel economy at highway speeds. The low nose encourages airflow while also helping enhance vehicle dynamics. Smooth transitions along the front fender and A-pillar avoid disturbance of the airflow. Subtle front-and-rear bumper spoilers and an available rear-lip spoiler contribute to low drag and minimize lift. The body sides taper from the center pillar to the rear where they meet the slightly kicked-out tail lamps, helping reduce drag-inducing wake turbulence. Also, a gull wing-shaped roof panel enabled designers to lower its profile to reduce air resistance and with a shape that is naturally stiffer than a conventional curved roof, engineers were able to reduce its thickness for further weight reduction. These improvements also lessen noise as the HS cuts through the air at speed.
Several measures were also taken under the car to promote airflow and reduce drag. Airflow resistance in the engine compartment was improved by optimizing the duct profiles around the radiator. Careful positioning of numerous underfloor covers plus added diffuser fins on the rear covers further reduce drag while enhancing straight-line control. Underlying the HS 250h's forward-think interior design is the implementation of bioplastic material. Known more formally as Ecological Plastic, the bioplastic uses plant sources as raw material and is used for parts of the interior upholstery in the car. Ecological Plastics are used in a number of injection-molded, foam and board components throughout the car, including trunk compartment trim, cowl side trim, door scuff plates, seat cushions and package tray. Overall, approximately 30 percent of the combined interior and trunk are covered in Ecological Plastic. From the driver's perspective, several important developments inside the HS250h transform the driving experience, making it easier and more enjoyable while also helping to enhance the driver's attention to the road ahead. The standard Lexus Premium Audio system offers a comprehensive suite that includes voice recognition, Bluetooth technology, an integrated satellite radio receiver, and USB/iPod connectivity operated via steering wheel controls or from the display screen. A multi-informational display situated in the instrument cluster keeps you informed of the numerous actions controlled by the steering wheel-mounted switches. The car's next-generation navigation system is optional and features Lexus's exclusive Remote Touch controller with user-adjustable haptic feedback. The innovative controller, similar to a computer mouse, eliminates the need for touch screen controls, allowing the pop-up navigation system to be mounted further up the center stack and away from the driver. The driver benefits with a clear, high-resolution screen, improved site lines and reduced eye movement. These advances combined with the physical feedback provided by the controller make the system extremely easy to use. Just point and click. Voice command, a casual-language-based voice recognition feature, is standard on navigation-equipped vehicles. This new technology allows you to give fewer and more flexible, conversational commands in a specific order for easier access to audio, climate, and navigation system functions to help you focus more on the road ahead. Another driver-inspired development is an optional Heads-Up Display (HUD). This system projects a miniature display on a small portion of the windshield in front of you, significantly reducing eye movement to see frequently viewed information such as vehicle speed. The display has been developed for maximum visibility, with crisp, high-contrast white lighting that makes it possible to see even in difficult lighting conditions such as driving on snow-covered roads. In addition to speed, the system also displays turn-by-turn navigation arrows and driver-assist warnings, as well as audio information and Touch Tracer (sensors on steering-wheel switches will show an image of switch layout in the HUD) both of which can be turned off separately from the rest of the display.
The high-visibility, electro-luminescent instrument cluster offers new ideas of keeping track of the various systems in the car and helps the driver to conserve fuel. A hybrid system indicator displays the hybrid system output and regenerative charging status, simultaneously indicating the efficiency of the system related to your driving style. An auxiliary Eco Drive Indicator light further assists you in maintaining the most economical use of system power. The multi-information display resides in the center of the hybrid system indicator. It uses high-contrast organic light-emitting diode (OLED) technology for maximum visibility and indicates various conditions such as fuel consumption, ambient temperature and cruising range. Also, several vehicle functions can be customized through use of the display with the multi-information switch. Like most Lexus vehicles the HS250h has an optional navigation system equipped with a back-up monitor. The new HS 250h also offers an available Wide-view Front Monitor to help enhance your ability to see in the traditionally blind areas around the front of the car. The front grille-mounted camera has a maximum 190-degree lateral field of view and allows you to see as close as 24 inches in front of the car within an 83-degree vertical field of view. Images from the two monitors feed into the available park assist ECU which processes and sends them to the navigation system display at separate times depending on whether the vehicle is moving forward or backward. The front monitor operates in either of two modes. Normal mode allows you to manually operate the camera with a switch on the lower left of the dashboard area. In auto mode, images from the front monitor automatically displays when the vehicle slows to about 6 mph or less and automatically shuts off when speed rises above 7.5 mph. You can also toggle from the front monitor on or off while in the auto mode. Other items related to visibility of your surroundings when driving is the slim A-pillar structure that helps improve visibility when pulling out of a parking space, inside or outside. HS250h engineers were able to create a relatively slim A-pillar structure to help improve visibility without degrading the structural integrity. Also, the HS250h uses side glass with a water-repellant coating that improves wet weather visibility and aids defrosting performance. As it is with ride, handling, noise and vibration, the body structure plays a key role in the fundamental safety characteristics of the new HS 250h. To help protect you and your passengers, the body is designed to be strong but strategically resilient to help absorb and distribute energy in the event of a crash. High tension steel components are carefully located in the body structure, doors, and other areas to help ensure strength in key areas. All HS 250h hybrids come with a class-leading 10-airbags with dual-stage and knee airbags up front, side curtain airbags and both front and rear seat-mounted side airbags to help protect front and rear passengers in certain types of severe frontal and side collisions. The front passenger is equipped with a twin-chamber airbag that further helps provide occupant protection. Additionally, front and outer rear seatbelts incorporate pretentioners with force-limiters to help further protect occupants in certain collisions. Active front head restraints are also standard.
An optional Pre-Collision system (PCS) with Dynamic Radar Cruise Control and Driver Monitor uses millimeter-wave radar to measure and maintain a pre-set following distance from a vehicle traveling ahead. The radar sensor is designed to detect certain obstacles in front of the car, and a PCS computer with vehicle speed, steering angle and yaw-rate inputs, helps to determine whether a collision is highly possible. In such a situation, PCS alerts you with an audible and visual warnings, preemptively retracts front seatbelts and pre-initializes Brake Assist (BA) so that increased braking will be applied the instant you depress the brake pedal. All of these safety systems only enhance the driving pleasure and enjoyment, never getting in the way of your regular or current driving style. The interior of the HS250h was designed to communicate the high level of innovation inherent in the car with the craftsmanship expected from Lexus products. Lexus's exclusive Remote Touch navigation system controller is a focal point of the interior design because of the many times that you will be using it. As a real Lexus luxury car, the HS 250h is comfortable with plenty of room for five people; as such the designers were intent on creating a fresh, appealing design befitting the brand that is also hybrid-distinct. Comfortable, supportive, 10-way power adjustable leather trimmed seats are standard (8-way power-adjustable front passenger seat), and special soft touch stitched details on the center stack and instrument hood provide an extra premium touch in the cabin. There are two levels of the new HS250h, standard and premium. Interior trim color include black leather, new light gray leather, parchment leather, and for the optional touring package, a distinctive black/light gray two-tone leather trim. A high-finish dark gray trim is featured on the standard model while the premium model has brown walnut wood trim. Front door trims also mimics the shape of the center stack and armrest providing a comfortable symmetry. The steering wheel center pad appears to float on the wheel, surround by control switches that also mimic the design and color of those on the center stack. The sporty leather-wrapped steering wheel also feature powered tilt/telescoping adjustments for the perfect placement in you hands. Comfort, quietness and convenience are a hallmark of all Lexus interiors so the HS250h comes with a host of each. When more than one driver uses the HS250h, an available new memory system allows individual driver settings to be recalled automatically by individual keys. There are three keys and each set the steering wheel position, seat position, exterior mirror positions and AC settings. The leather front bucket seats in the premium model get heated and ventilated seats that are trimmed with semi-aniline leather. Climate control in the HS250h is designed to provide comfort and clean air for all passengers. A dual temperature control system is used for front occupants and a dedicated rear blower is mounted in the center console promoting quick cool down in the rear. A plasma cluster ion generator, A/C clean air filter and a pollen removal mode help clean air inside the cabin. The interior gets a little extra help from the windshield, which has infrared-ray reduction properties that help keep the interior cool, allowing a smaller size A/C system than would be required. A 10-speaker, 137-watt Lexus Premium audio system features a six-disc CD changer, a subwoofer and center speaker standard. The system uses two-way woofer and tweeter systems in both front and rear for rich, clear sound quality. Real audiophiles will appreciate the optional Mark Levinson 5.1 channel Premium Surround Sound system that features 330-watts at only 0.1 percent total harmonic distortion and the system uses 15-strategically placed speakers for outstanding audio performance and sound quality. I loved the sounds coming from the speakers; it is one of the best factory installed systems.
Nimble handling, excellent body control, smooth ride and low noise in the HS250h are the best of any dedicated hybrid vehicle that I have tested, and they begin with a stiff body structure. The HS body is designed with superior stiffness overall with added focus in strategically-located areas that have the greatest effect on ride, handling and noise. Designed to balance handling, ride and NVH at high levels, the HS uses a rigid and compact MacPherson strut front suspension. The setup employs a 24mm stabilizer bar plus large diameter pistons and rebound springs in the shockv absorbers to help provide superior ride control at high speeds or when driving on curving roads getting off a freeway or in the mountains. The steering rack is directly mounted (no rubber bushings) to create an unfiltered connection between it and the suspension members to help accurately communicate what is happening where the rubber meets the pavement. Both setups reacted quickly to my inputs and I was surprised how easy it was to slice through the curving roads in the mountains. The double-wishbone rear suspension also balances performance and comfort and is important to its overall handling. Its compact design uses low-mount coil springs that also help improve cargo space. As in the front suspension, rebound springs are used to aid both handling and ride, and all mountings and bushings are optimized to help provide an excellent combination of ride, handling and low noise. I was amazed how well the HS250h handled during my test drive. Unlike other dedicated hybrids, I looked forward to driving the car as much as I could. The new HS rides on standard 17X7 alloy wheels and is wrapped with 215/55R17 all-season tires. The premium model comes with 18X8 alloy wheels wrapped with larger 225/45R18 all-season tires. All wheels feature the direct-type Tire Pressure Monitoring System. Getting back to the fun and pleasure of driving the new HS 250h is the improvement in the electric power steering (EPS) system. The vehicle-speed sensitive steering has been optimized to provide you with the ideal steering feel at any speed. Inertia compensation control, friction feedback and recovery control assist in tailoring the steering feel and effort that is most effective for a majority of drivers. I thought that the feedback and on center feel were superb. Like all Lexus vehicles, the new HS 250h braking system is comprehensive, and as a Lexus hybrid it is augmented by regenerative braking which also helps recharge the hybrid battery pack and improve fuel economy. The HS uses a newly developed electronic controlled brake (ECB) system actuator that is managed by the ECB computer and acts on the system's hydraulic brake components. The ECB computer also controls the interaction between the for-wheel disc friction brakes and the regenerative brake system. The new ECB actuator is smaller, lighter and consumes less electrical current than previous systems, making additional contributions to fuel economy. Enhancements in the system design also help improve brake feel and controllability. To my foot the feeling was always linear and always direct reacting to the force I applied. The HS features 10.8-inch vented discs up front and 11.1-inch solid discs in the rear. Braking control is enhanced with standard ABS and Brake Assist. Further enhancing of your control during braking is standard all-speed traction control and electronic stability control to help you maintain your desired direction under severe braking maneuvers over slick pavement. The all-new 2010 Lexus HS250h is on the cutting edge of hybrid energy driven automobiles and is injected with the Lexus knowhow of quality, workmanship, and engineering. It is the first purpose-built luxury hybrid and is perfect for the family that is used to the finer things in life that want to keep their driving footprint as small as possible. Prices start at just $28,000.00 for the standard model and up to $34,000.00 for the premium model. The new HS250h is another industry first for Lexus. © All words supra and pictures by Harvey Schwartz SIDEBAR COMMENT I don't get it. If I were building a Lexus version of the Prius, I'd want it to capitalize on what makes the Prius outstanding - i.e., have it get even better gas mileage, make it the first Toyota with lithium batteries, and the first to offer a plug-in hybrid system. Design-wise, I'd want it to look even more like something that George Jetson drives - like a cross between the LF-A and a UFO . Instead, with the HS 250h, we get a car that looks like a normal Lexus sedan and averages about 15 less miles per gallon of gas than the Prius. True, it still gets very good gas mileage, and the fit-and-finish is typical Lexus extraordinary. Well, I understand that Lexus dealers are selling every HS 250h they can get their hands on - which may explain why I'm not the head of any car company at the moment. - Roy Nakano SUMMARY JUDGMENT The Lexus of Priuses is more Lexus than Prius. For more information about Lexus products, go to www.lexus.com More photos from Harvey Schwartz can be found at www.autofotos.com
SPECIFICATIONS Name: 2010 Lexus HS 250h Price: $28,000.00 to $34,000.00 EPA mileage: 35mpg/city, 34mpg/highway Engine: Hybrid power system: Series/parallel system with 2.4 liter DOHC gas engine, 650 volt AC high-voltage battery and dual electric motors Horsepower: 147 at 6,000 rpm Torque: 138 pound-feet at 4,400 rpm Drive configuration: Front gas engine with hybrid transaxle and front electric drive motors Transmission: Electronically controlled continuously variable transmission (ECVT); planetary gear unit for gear reduction and power splitting, electronic front-wheel-drive control system Front suspension: MacPherson strut, coil springs, stabilizer bar Rear suspension: Double-wishbone with trailing arms, coil springs, gas-charged shocks, stabilizer bar Wheels/tires: 17X7 aluminum wheels/215/55R17 all-season tires standard 18X7.5 aluminum wheels/225/45R18 all-season tires optional Brakes: Front: electronically controlled brake system with regenerative control and incorporating ABS 11.1-inch vented disc up front/11.1-inch solid disc in the rear Overall length: 184.8 inches Overall width: 70.3 inches Overall height: 59.3 inches Curb weight: 3,682 pounds