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engineers achieved impressive fuel efficiency and output without dual-overhead camshafts or direct fuel injection, which add substantial cost, complexity, mass and package size.
Ward’s 10 Best Engines competition has recognized outstanding powertrains for 20 years. This installment of the 2014 Behind the 10 Best Engines series looks at the development of’s 3.5L SOHC V-6.
Previous versions of’s SOHC all-aluminum 60-degree V-6 were Ward’s 10 Best Engines winners in 2005, 2008 and 2009, and this new one already is a two-time awardee for 2013 and 2014. Tested by WardsAuto editors in a ’14 Accord sedan equipped with a 6-speed automatic, it pumps out 278 horsepower and 252 lb.-ft. (342 Nm) of torque while delivering segment-leading EPA-rated fuel economy of 21/34 mpg (11.2-6.9 L/100 km) city/highway.
The Ward's 10 Best Engines jury collectively averaged more than 28 mpg (8.4 L/100 km) over 837 miles (1,347 km) of driving, well better than the 25-mpg (9.4 L/100 km) combined EPA rating. "Turbocharged 4-cyl. engines, fast becoming the standard in this segment, struggle to post numbers like that," one WardsAuto juror wrote, “as did some naturally aspirated I-4s in this year's competition.”
The most significant difference between this V-6 and previous versions is the first-ever marriage of Honda’s intelligent variable-valve timing and lift electronic control (i-VTEC) to variable cylinder management (VCM), which is Honda's clever cylinder-deactivation system.and deactivate intake pushrods to shut down cylinders in their cam-in-block engines during light-load conditions, but Honda was first to use its (patented) zero-lift cam lobe technique to accomplish that in an overhead-cam layout.
Honda's i-VTEC hydraulically shifts the camshafts back and forth between two intake valve lobes. The first one optimizes valve timing and lift for low-rpm torque; the second is a high-lift, longer-duration profile for increased power above 5,150 rpm. Then this engine's VCM adds a third lobe with a zero-lift profile to the rear-bank cylinders only, which deactivates those three cylinders by keeping their intake valves closed.
While Honda's previous-generation VCM shut down two and sometimes three cylinders to save fuel, depending on driving conditions, this new system transitions between 6- and 3-cyl. modes only. And that simplification enables the addition of i-VTEC.
“We can only have three lobes and three oil circuits to control that,” Honda R&D Engine Design Group Manager Mike Dunn explained in a 2013 interview. “So taking away the 4-cyl. mode allowed us to add the high valve timing.”