Pony Cars Stampede To Greener Gas Ratings

Ever since Chevrolet met the challenge of Ford’s Mustang with the debut of the 1967 Camaro in the fall of 1966, the two “pony cars” have relentlessly battled for class supremacy. Historically, the battle has been one of horsepower. Today, rising gas prices and government fuel efficiency mandates are giving their power duel a green tinge.

Ford threw down the fuel economy gauntlet when the EPA certified the 305-hp, 3.7-liter V6-powered 2011 Mustang at 31 miles per gallon in highway driving, setting a new benchmark for fuel efficiency in the performance-centric segment. The previous 4.0L V6 automatic Mustang had a 24-mpg highway rating.

The 2011 Camaro’s horsepower rating was only negligibly lower (304 hp), but one-upmanship rules the pony car segment. Internet flame-warring fanboys snipe at one another on web forums and in burger shop parking lots.

So, GM quickly re-certified the 2011 Camaro’s 3.6-liter V6 engine to a higher 312 horsepower rating, saying the initial certification was excessively conservative and that the true horsepower number was higher than the Mustang’s. However, the Camaro’s 29-mpg EPA highway gas mileage number was stubbornly resistant to such a rapid re-do, so Chevy has a thoroughly revised version of the V6 in the works for the 2012 Camaro. Whether the new engine can match the Mustang’s 31-mpg remains to be seen, but Chevy is so far saying that it will definitely get 30 mpg, getting Camaro over an important threshold.

This fuel economy target doesn’t mean that performance is forgotten — this is a pony car, after all. Camaro’s horsepower is up to 323-hp for model year 2012. This new engine, code-named LFX, also sheds 20 pounds of pork, helping the Camaro on the scales where it is at a significant disadvantage to Mustang.

Most of the weight savings comes from new aluminum cylinder heads that have integrated exhaust manifolds cast in. Much of the rest of the weight savings is due to substitution of a plastic intake manifold for the aluminum one used before. The heads feature improved intake port design for better airflow into the cylinder, while the intake valves are enlarged to 38.3 mm diameter to let more air in.

Additionally, the camshafts have longer intake duration, so the intake valves are not only larger, but they remain open longer, also contributing to increased airflow.

The 2012 Chevy Camaro engine is direct injected, so no gasoline comes mixed with that air through the intake port. Instead, it is squirted directly into the combustion chamber by a fuel injector mounted next to the spark plug. These are the latest-generation injector technology, providing improved vaporization of the injected fuel for reduced pollution and improved efficiency.

These new injectors have improved control of the fuel spray into the cylinder at low fuel flow rates, so they don’t waste gas or make excess pollution at part throttle, reports Ameer Halder, GM’s assistant chief engineer for V6 engines. And through extensive computer modeling, the injectors’ spray pattern is redesigned to avoid squirting gas onto the valves, which also contributes to increased efficiency and cleaner emissions, he said.

While they were at it, GM engineers made a slew of other changes to help quiet the engine, because direct injection can be noisy, producing a clattering sound that not even engine enthusiasts appreciate.

For enthusiast drivers who want to balance their performance with fuel efficiency, the Camaro-Mustang battle will continue forcing both auto manufacturer camps to improve, so customers win whichever car model they choose.

Surely the Ford guys are already hard at work on their response to Chevrolet. Maybe we’ll see a 35-mpg Mustang in the not-too-distant future. — Dan Carney, Motor Matters

Manufacturer photo: The 2011 Ford Mustang achieves 31-mpg highway. The upcoming 2012 Camaro V6 will have Direct Injection, improving its EPA ratings from the current 29-mpg.
Copyright, AutoWriters Associates Inc., 2011

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