More muscle for the '07 Hummer H3
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Zipping around in the Hummer H3 just got even more fun thanks to the introduction of a new, more powerful 3.7L five-cylinder engine. This new powerplant boasts a welcome 22 more horsepower and 17 lb-ft of torque than the engine it replaces. This translates to 242 hp and 242 lb-ft of torque.
How They Did It
Hummer's Daryl Ehrlich, Development Engineer, Energy and Drive Quality, summed up the goals of the project by saying: "Our goal was to improve acceleration performance and driveability with the new 3.7L engine, yet minimize impact to fuel economy by implementing new technologies like Regulated Voltage Control and a high-efficiency alternator." With goals set, the team increased the cylinder bore from 3.66 inches to 3.76 inches. Of course, this increase in diameter necessitated bigger intake and exhaust valves, so larger 1.52-inch intake valves replace the previous 1.45-inch intake valves, and larger 1.32-inch exhaust valves replace the previous 1.18-inch exhaust valves. Engineers also revised the profile of the dual overhead camshafts to optimize valve lift and duration in accordance with the larger valves. Naturally, these modifications require more airflow, so engineers increased cylinder head airflow to match the demand of the larger valves and revised camshaft. Major attention was paid to creating a quieter engine too. The list of noise-reducing changes includes a connecting-rod oiling system, aluminum camshaft cover, and tighter-clearance balance shaft bushings. Finally, as stated earlier, fuel economy was also a major concern. With that said, the team integrated Regulated Voltage Control into the mix. Quite simply, this system shuts down the alternator when voltage isn't needed, thus elimin-ating drag on the engine. The result is a larger engine that makes more power than its predecessor but suffers no decrease in overall fuel economy.