Top 100: More Valves = More Power

John Deere Power Systems redesigned its four-cylinder, 4.5-liter and 6.8-liter diesels with four valves per cylinder to span horsepower ranges from 160 to 275. The new head and electronically controlled fuel injection from a high-pressure common rail boosted power 25 percent over their two-valved predecessors. The 4045H and 6068H are also tuned for higher peak torque and 30 percent greater low-speed torque. Deere says fuel economy is improved by at least 5 percent.