Lexus HS 250h luxury hybrid sedan conceals high-tech gear
Bob Plunkett, Sun, 13 Dec 2009 06:43:33 PST
LAGUNA BEACH, Calif. -- The slinky sedan we're steering along California 1, the Pacific Coast Highway, in Laguna Beach looks cutting-edge cool with a sweeping profile featuring a racked-back windshield and arching roofline which descends to the high-decked tail.
Its tapered V-angled prow carries a thin grille scored with chrome-coated fins and a low intake valence gaping wide, plus canted lamp clusters of an irregular format mounted at the top of front corners with projector-type low-beam lamps drilling round points in shimmering acrylic caps.
Flanks are taut and the silhouette is edgy yet so smooth it scores a coefficient of drag figure for aerodynamic efficiency of only 0.27.
Stylish lines etched into the package of what appears to be a conventional four-door sedan actually conceal complex mechanisms which make this vehicle quite special -- and totally high-tech savvy.
Lexus labels it as the HS 250h, a high-mileage luxury hybrid electric vehicle (HEV) equipped with a gas-electric powertrain and a carload of sophisticated hardware and computerized electronic controls.
First, there's the aerodynamically-smooth body and lavishly appointed five-seat passenger compartment of a mid-size luxury sedan.
Second, there's the high-voltage and high-torque Hybrid Synergy Drive (HSD) system developed by Lexus/Toyota.
It teams a thrifty but conventional 2.4-liter four-cylinder Atkinson-cycle engine which operates on gasoline with a pair of high-torque electric motors -- one to turn the front wheels and the second to work so many power accessories as well as crank up the gasoline engine and recharge on-board batteries.
All energy produced by the on-board motors is directed to the front wheels in infinitely variable measures through an electronically controlled continuously variable transmission (ECVT).
Summation of all powertrains in HS 250h is the equivalent of 187 hp and fuel economy numbers climb to 35 mpg for city driving and 34 mpg on the road.
The gas-sipping four-cylinder engine, with dual overhead cams and Toyota's smart variable valve-timing (VVT-i) system, makes 147 hp at 6000 rpm and torque of 138 lb-ft at 4400 rpm.
The first electric motor-generator (dubbed MG1) has a maximum voltage capacity of AC 650 v.
The second electric motor-generator (MG2) nets 105 kW (141 hp).
Supplying electrical juice to all of the motors in the Lexus hybrid system is a 244.8-volt direct-current nickel metal hydride (Ni-MH) battery tucked between the cabin's rear seat and the trunk.
Internal recharging occurs either during braking, when the gas engine operates as a generator, or when the electric generator does the recharging job. Thus, the HS 250h never needs to be plugged in for recharging as would a purely electric vehicle.
HS 250h can run on the gasoline engine alone or on the MG2 electric motor, or in a mode with both plants contributing power simultaneously.
* NORMAL -- HS 250h performs like a conventional sedan with linear throttle response for progressive power.
* ECO -- the economy mode to trim fuel consumption with acceleration slightly more gradual as the HSD computer meters the fuel flow and also adjusts output of the air conditioning system.
* POWER -- the throttle increases sensitivity for quicker accelerations and sporty moves.
* EV -- HS 250h moves solely on battery power at low speed for about a mile.
Lexus acceleration tests for the HS 250h indicate the vehicle can move from 0-to-60 mph in 8.4 seconds and reach the quarter-mile mark in 16.6 seconds.
Acronyms in car safety for HS 250h include VGRS (variable gear ratio steering) and EPS (electric power steering), ECB (electronically controlled brakes), ABS (anti-lock brake system) with EBD (electronic brake-force distribution) and VSC (vehicle stability control) plus ETC (electronic traction control).
The passenger compartment in HS 250h is a luxurious space filled with comfortable seats and useful instruments and controls plus lots of standard equipment.
The layout includes a pair of buckets up front flanking a center console and a rear bench built for three but scooped for two.
The area is surrounded by hidden air bags -- up-front inflators for front seats plus seat-mounted side air bags and more to shield the knees, then curtain-style air bags tucked above side windows front and back.
A highly visible electro-luminescent instrument cluster houses a graphic display which illustrates operation of the HSD energy system with icons providing feedback so a driver can learn how to consume less fuel through efficient driving techniques.
HS 250h Standard edition stocks seats trimmed in leather with ten-way power controls for the driver's seat and eight-way power controls for the front right seat, power windows and power door locks, automatic dual-zone climate controls, SmartAccess key system with pushbutton starter, tilt-and-telescopic steering column, the 137-watt Lexus Premium Audio with 10 speakers and AM/FM/XM/6XCD/MP3/WMA/USB, a moonroof, heated exterior mirrors with integrated puddle lamps and turn signals, front foglamps and 17-inch aluminum wheels with 215/55R17 V-rated all-season tires.
HS 250h Premium edition adds heated/ventilated front seats with driver's seat memory, wood cabin trim, rain-sensing windshield wipers, electrochromic side-view mirrors and 18-inch aluminum alloy wheels with all-season tires.
Optional gear includes a Touring Package, Navigation Package, Technology Package, Park Assist Package, Mark Levinson Premium Surround System, LED headlamps with AFS (adaptive front-lighting system), even a tail spoiler.
Lexus marks the MSRP for new HS 250h at $34,200 (Standard) and $36,970 (Premium).