Fuel economy the focus for Honda Civic engineers

  • 10-Sep-2011 04:38 EDT
2012 Civic EX-L sedan.jpg

The 2012 Honda Civic is lighter than its previous generation. The EX-L sedan model shown, for example, is 58 lb (26 kg) lighter than before.

Illustrating the Civic’s significance to Honda, the compact car, if considered as a stand-alone brand, would rank no. 12 in U.S. sales, ahead of full-line brands such as Volkswagen, Mazda, and Chrysler, according to the re-engineered car’s Senior Product Planner Jay Guzowski.

The ninth-generation Civic has taken some hits, however, since its spring launch, most notably from Consumer Reports, which scored the Civic LX sedan too low to recommend it. Among the car’s faults, according to the automotive testing organization, are drop-offs in agility and interior quality, as well as a “choppy ride” and “pronounced road noise.” Redeeming qualities, again according to CR, include “decent rear-seat room” and its fuel economy.

Driving several Civic variants over the course of a day did not reveal any major deficiencies to this editor. What stood out was the result of the considerable effort expended by the car’s engineers and designers to improve fuel efficiency. All Civic models achieve higher U.S. EPA fuel-economy ratings compared to their 2011 versions, up by as much as 8% on the highway in sedans and coupes equipped with an automatic transmission.

Aerodynamics and lightweighting played a big part in this. Aero enhancements include plastic parts under the engine bay, fuel tank, and parts of the rear underbody to enhance airflow; front spoiler and strakes ahead of the front and rear tires to direct airflow around the wheel wells; and a new flat underfloor. The end result is a 3.4% lower coefficient of drag compared to the 2011 Civic.

A 10% more rigid unit-body structure is the result of enhanced structural design and increased use of high-strength steel (HSS) ranging from 340 to 980 MPa—55% on the new sedan compared to 50% on the previous model, contributing to a 7% reduction in body weight. The coupe structure consists of 56% HSS.

The attention paid to lighter-weight systems extended to the electric power steering (EPS) system, which is down by 1.3 kg (2.9 lb); a 1.7-kg (3.7-lb) lighter front subframe; a thinner-walled fuel tank, which saves 1.0 kg (2.2 lb); and a laser-welded exhaust silencer that is 0.5 kg (1.1 lb) lighter.

Curb mass for all sedan models is down compared to their previous generation. For example, the LX trim level with an automatic transmission is almost 50 lb (23 kg) lighter—2705 lb (1227 kg) vs. 2754 lb (1249 kg).

Interior packaging was another focus area for Civic engineers and designers. Passenger volume for the 2012 sedan is increased by 3.8 ft³ (108 L)—or 4.1%—to 94.7 ft³ (2682 L) through advancements in unit-body design and component integration. Gains have also been made in front shoulder room (+2.9 in/74 mm) and rear legroom (+1.6 in/41 mm).

The new coupe has slightly less passenger volume than the previous model—83.2 ft³ (2356 L) compared to 83.7 ft³ (2370 L) for the outgoing model.

Technology and features new to the Civic include an available “intelligent” Multi-Information Display (i-MID), a platform that integrates vehicle information and compatible personal electronics with a 5-in color LCD display and steering wheel controls; an available Eco Assist system (except on Civic Si), which provides visual feedback to promote or confirm efficient driving; and a new Motion Adaptive EPS system that works in conjunction with the standard Vehicle Stability Assist (VSA) to mitigate oversteer or understeer.

The Civic’s overall length, width, and height are the same as before, but the sedan’s wheelbase was reduced by 1.2 in (30 mm) to 105.1 in (2670 mm), and the coupe’s was shortened by 1.1 in (28 mm) to 103.2 in (2621 mm). The 2012 Civic sedan and coupe share nearly identical chassis construction: front MacPherson strut and rear multilink suspensions, with front and rear stabilizer bars and power-assisted, ventilated front disc brakes.

Both the sedan and coupe are powered by a 1.8-L inline four-cylinder engine with a 16-valve i-VTEC valvetrain and a dual-stage intake manifold, producing 140 hp (104 kW) at 6500 rpm and 128 lb·ft (174 N·m) at 4300 rpm. Both models receive an EPA-estimated 28/39/32 mpg (city/highway/combined) rating when equipped with the five-speed automatic transmission (AT).

An entirely new model, the Civic HF (high fuel-economy) sedan boasts the best highway fuel-economy rating (41 mpg) for a conventional, gasoline-only powered vehicle with an AT, according to Honda. The Civic HF is equipped with exclusive 15-in alloy wheels, low rolling-resistance tires that reduce rolling resistance by 20%, additional underbody covers, and a rear decklid spoiler. A 4% improvement in aerodynamic performance is the result.

The performance-oriented Civic Si coupe and sedan both feature a sport-tuned suspension and a 2.4-L engine (vs. 2.0 L in the previous generation), producing 201 hp (150 kW) at 7000 rpm and 170 lb·ft (230 N·m) at 4400 rpm—peak improvements of 4 hp (3 kW) and 31 lb·ft (42 N·m) compared to their predecessors. A six-speed manual transmission with a helical-type limited-slip differential (LSD) is standard. The i-MID on the Civic Si includes a new sequential rev-limit indicator and power monitor.

The new Civic Hybrid introduces the latest generation of the Integrated Motor Assist (IMA) parallel hybrid system, featuring lithium-ion batteries—a first for a Honda hybrid vehicle—instead of the previously used nickel-metal hydride type. Supplied by Blue Energy Co., a joint venture between Honda and GS Yuasa Corp., the 20-kW Li-ion battery, located behind the rear seatback, is 5 kW more powerful and 20 lb (9 kg) lighter (at 48.5 lb/22 kg) than the previous NiMH battery.

The 40 box-shaped Li-ion cells take up 36% less space than the previous 132 cylindrical NiMH cells. Battery capacity is increased by 285%, from 35 kAh to 100 kAh.

For the 2012 hybrid, a larger 1.5-L i-VTEC four-cylinder engine replaces the 1.3-L engine for improved mid-range torque. The dc brushless permanent magnet motor, positioned in between the engine and standard CVT, is 1.5 lb (0.7 kg) lighter (it weighs 42.5 lb/19.3 kg) and more powerful than before, providing up to 17 kW compared to 15 kW. Output was improved by reducing coil heat via an increased number of motor poles (8-pole pair/57 turn vs. 6-pole pair/56 turn) as well as by increasing magnetic flux density of the magnet.

Combined, the engine and IMA produce 110 hp (82 kW) at 5500 rpm and 127 lb·ft (172 N·m) at 1000-3500 rpm. According to Honda, the IMA system’s greater power and the battery’s 35% increase in efficiency enable more frequent electric-only operation in certain low-speed cruising situations. The Civic Hybrid achieves an estimated 44/44/44 mpg—up from 40/43/41 in the 2011 model.

(To view a more in-depth Civic Hybrid walk-around given to AEI by Yuuji Fujiki, the Assistant Large Project Leader–Hybrid, click here.)

Powered by a dedicated compressed natural gas (CNG) variant of the 1.8-L four-cylinder used in the sedan and coupe models, the Civic Natural Gas (previously named Civic GX) is the only vehicle certified by the EPA to meet both Federal Tier 2 Bin 2 and Inherently Low Emission Vehicle (ILEV) standards, according to Honda.

The Civic Natural Gas engine produces 110 hp (82 kW) and 106 lb·ft (144 N·m). Equipped with a standard automatic transmission, the alternative-fuel car gets an estimated 27/38/31 mpg. It is now available with a navigation system that shows public refueling stations for CNG.

Honda claims that the 2012 Civic Natural Gas will be much more widely available than in the current four states (California, New York, Nevada, and Utah) when it goes on sale this fall.

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