That the 2006 H3 had engine problems, is a well known fact. There are 2006 H3s with over 100,000 miles on them and no engine problems, but many had the dreaded cylinder head problem. That the 2007 is a much better engine is not even a matter of debate, and year by year the I5 keeps improving. Problems with the original H3 I5 engine have depressed used car values for the 2006 models, although many have been fixed under warranty.
Daryl Ehrlich, Hummer's Development Engineer, summed up the improvements in the 2007 I5 engine over the 2006 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.
No comments:
Post a Comment