|Ti-VCT components. Click to enlarge.|
Ford is introducing its 2011 Mustang with a new 3.7-liter, dual-overhead-camshaft (DOHC) 24-valve V-6 using Twin Independent Variable Camshaft Timing (Ti-VCT), also featured in the 2.0L EcoBoost engine announced in July (earlier post). The new V6 can produce 305 hp (227 kW) of power and 280 lb-ft (380 N·m) of torque.
Coupled with a six-speed automatic transmission, the 3.7L engine delivers 19 mpg US city/30 highway—a 19% improvement on city fuel economy and a 25% improvement on highway fuel economy compared to the 2010 model (16 mpg city/24 highway). With a six-speed manual, the 2011 Mustang delivers 18 mpg city/29 highway, up from 18 mpg city/26 highway on the 2010 model with manual. Ti-VCT can account for up to a 4.5% fuel economy improvement over non-VCT-equipped engines, according to Ford.
|Twin Independent Variable Camshaft Timing (Ti-VCT) uses electronic solenoid valves to direct high-pressure oil to control vanes in each of the camshaft sprocket housings. Click to enlarge.|
The high output is due largely to Ti-VCT, which allows variable control of valve operation across the rev range. The variable cams operate on a Direct Acting Mechanical Bucket (DAMB) valvetrain using polished buckets and roller finger followers to reduce friction. The end result is as much as a 3% improvement in fuel economy and a 10% improvement in power output versus traditional engines without these advanced features.
Ti-VCT enables extremely precise variable control of valve overlap—the window of time in which both the intake and exhaust valves in the engine are open simultaneously. By adjusting overlap continuously, an engine can operate at optimum settings for peak fuel economy or peak power output as conditions demand. Ti-VCT also facilitates an “internal EGR” effect, reducing NOx and hydrocarbon emissions throughout the engine’s operating range.
This overlap control via Ti-VCT helps us eliminate compromises in the induction and exhaust systems. Drivers are going to notice improved low-speed torque and increased fuel economy and peak horsepower. Plus, there are benefits they won’t notice, too, such as reduced emissions overall, especially at part-throttle.
—Jim Mazuchowski, Ford manager of V-6 powertrain operations
As a DOHC design, the 3.7-liter V-6 uses two camshafts per cylinder bank—one to open the intake valves and one to open the exhaust valves. Traditionally, camshafts only have been able to open the valves at a fixed point defined during engine design and manufacturing. But with modern variable cam timing systems, the camshafts can be rotated slightly relative to their initial position, allowing the cam timing to be advanced or retarded.
Ti-VCT takes this technology and applies it to both the intake and exhaust camshafts of its DOHC design, using electronic solenoid valves to direct high-pressure oil to control vanes in each of the camshaft sprocket housings. By using one valve per camshaft, controlled by the Electronic Control Module (ECM), each intake and exhaust cam can be advanced or retarded independently of the other as engine operating conditions change, providing an exceptional degree of valve timing control.
Ti-VCT is complemented by special-tuned composite upper and lower intake manifolds for efficient air delivery and lighter weight. Ignition power is delivered by a high-energy coil-on-plug design, while piston-cooling jets and a lightweight die-cast aluminum cylinder block improve the durability and efficiency of the 3.7-liter V-6 design.
In addition to the six-speed transmissions, other system improvements enhancing fuel economy include:
A new Electric Power Assist Steering (EPAS) system which eliminates the drag of an engine-operated hydraulic power steering pump.
Aerodynamic improvements such as a new front fascia, tire spats on the rear wheels, modified underbody shields, a taller air dam and an added rear decklid seal.