DETROIT – With the SS moniker on its front doors and liftgate, GM Performance Division (GMPD) engineers made sure the ’08 Chevrolet HHR SS lived up to the heritage of those badges. The HHR SS is not the first production SS model developed by GMPD, with such standouts as the TrailBlazer SS and Cobalt SS Supercharged under its belt, but it is certainly the most important since the group is now responsible for the “go, stop and turn” credibility of all future SS models.
The HHR SS is powered by a turbocharged and intercooled 2.0-liter Ecotec DI engine that delivers 260 horsepower (194 kW) and 260 lb.-ft. of torque (353 Nm) with the standard five-speed manual transmission. It is rated at 235 horsepower (175 kW) with the available automatic transmission.
Features such as “no-lift shift” and other driver-selectable performance modes help the HHR SS achieve 0-60 mph performance in 6.3 seconds and cover the quarter-mile in 14.8 seconds at 98.5 mph. The top speed is more than 150 mph, with the manual transmission.
“The HHR SS offers drivers a totally integrated performance driving experience,” said John Heinricy, GM Performance Division executive. “It was developed on some of the most challenging tracks in North America and Europe, and has been tuned to deliver confident handling and road manners, while also maintaining overall ride comfort.”
As with other GM Performance Division-developed vehicles, the HHR SS was validated on Germany’s famed Nürburgring racing circuit, where it set a new lap record of 8:43.52 minutes for its class, besting the previous record of 8:54.38 held by the Opel Zafira OPC.
“It’s not often that you see a vehicle like the HHR at Nürburgring – and you certainly don’t see one lapping the track as quickly,” said Heinricy. “Frankly, the HHR SS is going to surprise a lot of enthusiasts with its improved control and feel on both the street and the track.”
2.0L Ecotec DI turbo engine details
The Ecotec 2.0-liter turbo engine produces 2.1 horsepower per cubic inch of displacement (130 hp / 97 kW per liter) and is the most powerful engine in the Ecotec family. Gasoline direct-injection technology helps the Ecotec engine produce more power while maintaining the lower fuel consumption of a small displacement port-injected engine.
With direct injection, fuel is delivered directly to the combustion chamber to create a more complete burn of the air/fuel mixture. Less fuel is required to produce the equivalent horsepower, especially at normal cruising speeds, of a conventional port-injection combustion system. Direct-injection technology works well with turbocharging and helps deliver a great balance of power and economy.
Highlights of the HHR SS’s Ecotec 2.0L DI turbo engine include:
Components including the steel crankshaft and forged connecting rods are high-strength items that provide strength and enhance durability. Oil-spray piston cooling helps reduce cylinder temperatures and promotes longevity by delivering pressurized oil that continuously lubricates the pistons, which reduces friction. To enhance combustion, the piston tops feature a dish shape that deflects incoming fuel toward the spark plugs.
To accommodate the direct-injection system, the Ecotec 2.0L DI turbo has a unique cylinder head and intake manifold. The cylinder head incorporates mounting locations for the fuel injectors – items that are typically mounted in the intake manifold on port-injection engines. Specialized and extremely precise multi-hole fuel injectors are used to meter fuel and deliver it in a finely atomized manner. They are supported by an engine-mounted high-pressure fuel pump.
Apart from the mounting positions of the fuel injectors, the cylinder head has conventional port and combustion chamber designs. Large stainless steel intake valves and sodium-filled exhaust valves are durable components designed to stand up to the high-performance capability of the engine.
The unique cylinder head, fuel system, pistons and intake manifold are the major components that differentiate the 2.0L DI turbo from other members of the Ecotec engine family. Mobil 1 synthetic engine oil is installed at the factory. Synthetic oil was selected for its friction-reducing capabilities and high-temperature performance.
Turbocharger and charge air cooler
Pumping up the HHR SS’s 2.0L Ecotec engine is an intercooled turbocharger system. The turbo blows pressurized air into the combustion chambers to enhance horsepower and torque, while the system’s intercooler circuit cools the turbocharged air charge to maximize its effect. The turbocharger is sized to deliver a significant horsepower boost and almost no spool-up lag. Maximum pressure is almost 20 psi.
Because the pressurized air pushed by a turbocharger becomes heated, the HHR SS’s system employs an air-to-air intercooling system. With it, the pressurized air passes through a heat exchanger mounted behind the grille in the lower front fascia, where it is cooled before it enters the engine. Cooler air is denser, enabling the combustion chambers to draw in more air for maximum power. The cooler air also staves off the possibility of detonation at higher temperature, which allowed engineers to tune the engine for maximum power and ensure consistent performance in all driving conditions.
Backing the turbocharged engine is a standard GM Powertrain Sweden F35 five-speed manual transmission; the optional automatic is GM Powertrain’s 4T45 electronically controlled four-speed. Semi-synthetic transmission fluid is used for its capability of absorbing heat and resisting breakdown during high-performance driving.
A performance-oriented feature referred to as “no-lift shift” allows maximum performance with the manual transmission – upshifts can be performed very quickly without lifting the throttle. An algorithm in the engine’s controller enables this high-performance feature, which helps maximize acceleration and gear changes.
A short-throw shifter with stiffened shifter bushings and modified cables and attachments enhances confidence behind the wheel, giving the driver a firmer, more direct and quicker shift feel. The manual shifter also is located higher than other HHR models, placing it in a more intuitive position for performance driving. An SS-specific center console is wrapped around the short-throw shifter.
A limited-slip differential is available with the manual transmission.
Chassis tuning and brakes
Conveying the HHR SS’s turbocharged horsepower to the pavement is an FE5 sport suspension that includes a host of other chassis, steering and braking revisions – and a set of gorgeous 18-inch forged aluminum wheels. The elements pull together to give the vehicle surprisingly agile ride and handling characteristics, as well as an enviable maximum lateral acceleration rate of 0.86 g (with the manual transmission) – grip comparable to many sports cars on the market.
The MacPherson strut independent front suspension uses SS-specific gas-charged twin-tube struts, unique steering knuckles with optimized geometry, 28 N/mm linear coil springs with specific damper tuning, stiffer control arm handling and stabilizer bar bushings, and a direct-acting, 23-mm solid stabilizer bar. At the rear, the SS’s semi-trailing twist beam axle uses monotube gas-charged shocks with specific damper tuning, a 24-mm solid stabilizer bar, stiffer axle bushings and multi-rate coil springs (30-40 N/mm). StabiliTrak electronic stability control and traction control are standard.
A unique electric power steering (EPS) system is tuned to match the SS’s handling prowess. The rack-and-pinion gear has a quick 14.8:1 ratio, which is 20 percent quicker than other HHR models, and the new EPS provides improved precision and a more viscous feel. A smaller-diameter steering wheel enhances the quick, sporty steering capability.
Four-wheel disc brakes with ABS are standard. They consist of 11.65-inch-diameter (296 mm) front vented rotors with 54-mm single-piston calipers in the front and 9.84-inch-diameter (270 mm) rear solid discs with 38-mm single-piston calipers. The standard anti-lock brakes are connected to the StabiliTrak electronic stability control system to enhance stopping and handling in emergency driving situations.
The disc brakes are visible behind one of the HHR SS’s most distinguishing features: a set of 18-inch polished forged aluminum wheels. The wheels have a Corvette-inspired split-spoke design and ride on SS-specific Michelin Pilot Sport performance tires that are rated for all-season driving.