DETROIT - Ask a performance enthusiast the best way to make a car go faster, and he'll probably say there's no replacement for displacement. A bigger engine is how you get more power to the wheels.
But as automotive engineers continually improve the internal combustion engine in an era of high fuel prices, that truism is changing. Indeed, technology is making higher performance available from smaller engines.
Consider the Pontiac Solstice GXP roadster that is due in August.
The Solstice GXP's engine is one of the most powerful GM has ever made - based on its size. It's a 2.0-liter Ecotec engine rated at 260 hp. By comparison, the 2.4-liter, four-cylinder Ecotec on the base Solstice puts out 177 hp. And GM says the added performance of the GXP does not affect fuel economy or emissions.
GM has engineered many engines over the years that develop more than 260 hp - but they were all V-6 or V-8 engines of more than 2.0-liter displacement. The Solstice GXP's 130-hp per liter is the highest output per liter of any engine GM has ever made for a production car.
GM tried making four-cylinder performance engines before but did not have much success. Two notable engineering failures were the Chevrolet Cosworth Vega of 1974-76, which ushered in 16 valves and electronic fuel injection on GM four-cylinder engines. In the 1980s and 1990s it made the Oldsmobile Quad 4. Both engines had reliability problems and had little impact in the marketplace.
Pocket rocket fighter
The Solstice GXP just may give Pontiac street cred with fans of exclusive, expensive, four-cylinder pocket rockets. Two cars of that ilk are the Subaru WRX STi, which has a 300-hp 2.5-liter engine, and the Mitsubishi Lancer Evolution, with its 286-hp 2.0-liter powerplant. Those cars are priced around $35,000. The Solstice GXP will start at about $26,000.
The GXP option is about $6,000 and includes a few other performance and safety items. Referred to internally as the Ecotec LNF, the GXP engine is loaded with new technology.
Some features of the LNF engine include:
- Gasoline direct injection, a first for a GM engine in North America
- A twin-scroll turbocharger with an intercooler that boosts power and eliminates turbo lag
- Variable valve timing on both camshafts and lightweight sodium-filled valves
- Unique oil-cooled, low-friction cast aluminum pistons.
Where does the power come from? Ed Groff, the engineer who oversaw development of the LNF engine, points to two things - the large amount of air the engine sucks into the combustion chambers and the engine's 14.7:1 air-fuel ratio. That mixture is called stoichiometric, and it helps the engine run at its most efficient.
Direct injection of gasoline also adds power, says Groff. Fuel is shot into the combustion chamber and onto a specific machined portion of the piston.
The LNF engine - it also will be optional in the 2007 Saturn Sky - is one example of how GM might approach high performance if cheap gasoline is gone for good.
"I think you'll see the direct injection go to other engines, for sure," says Groff, who has been working on engine technology for most of his almost 30 years at GM. "I think you will see the power going up. We won't sit still with 260. There is turbocharger technology out there designed to help you increase top-end power."
Groff said what separates the LNF from other turbocharged small-displacement four-cylinder engines is that you don't have to rev the daylights out of it to get the car to go fast. That's not true with all sports cars. The Honda S2000, for example, must be revved to about 6,000 rpm before it comes alive.
"There are a lot of competitor engines that don't have much on the bottom end," says Groff. "They are designed for cars that don't need the bottom end and for drivers who like to maintain high speeds. We wanted the Solstice GXP to be fun to drive for a broader spectrum of customers. We wanted the low-end torque. You don't need to downshift as often because you have all this low-end torque."
GM Vice Chairman Robert Lutz - the father of the Solstice - says the GXP reminded him of driving the current-generation Chevrolet Cor-vette. Lutz says the Solstice GXP he tested has immense power that comes on smooth and strong. GM says the Solstice GXP will reach 60 mph in 5.5 seconds.
While most of the development work on the LNF engine was carried out at GM Powertrain headquarters in Pontiac, Mich., Groff says engineers from GM's European operations also helped develop certain parts and test the engine.
The LNF will be built at GM's Saturn plant in Spring Hill, Tenn. It also will be used in the Opel GT roadster, which is based on the Solstice.
Other automakers are planning small but powerful engines, too. Ford Motor Co.'s current 4.0-liter V-6 is rated at 210 hp, but there's a 3.5-liter on the way that develops 250 hp. And Ford spokesman Nick Twork points out that when the overhead-cam 4.6-liter V-8 replaced the old pushrod 5.0-liter engine, power increased.
Says Twork: "With any new engine we do want to make it more powerful than the outgoing engine.
"And if we can do it with less displacement, it's a good thing because displacement has a relationship to fuel economy."
You may e-mail Richard Truett at [email protected]