|The 400hp naturally-aspirated 5.0L is the current high-end application of Ti-VCT in the Ford lineup. Click to enlarge.|
Ford has officially announced the 2011 Ford Mustang with an all-new advanced naturally-aspirated 5.0-liter V-8 engine. The 5.0-liter four-valve Twin Independent Variable Camshaft Timing (Ti-VCT) V-8 engine in the new Mustang GT will deliver 412 hp (307 kW) and 390 lb-ft (529 N·m) of torque.
The Ti-VCT technology (earlier post) is a key element in helping the new 5.0-liter V-8 Mustang GT deliver projected fuel economy of up to 25 mpg US on the highway cycle—better than the pervious model—despite its performance. The gasoline (91 octane recommended, 87 octane minimum) engine offers a specific output of 82.4 hp/L. An additional benefit of Ti-VCT is a reduction of emissions, especially in situations when the throttle is partially open.
Ti-VCT provides extremely precise variable—yet independent—control of timing for intake and exhaust valves. Independent adjustment of intake and exhaust valve timing allows maximum fuel economy at part-throttle, while delivering optimized power in full-throttle situations. An added benefit is improved drivability and responsiveness across the torque curve.
Ford intends to make Ti-VCT—which now ranges in announced applications from the 1.6L on the Ford Fiesta up to this 5.0L in the Mustang—available on 90% of its nameplates by 2013, according to Barb Samardzich, vice president, Powertrain Development. (Earlier post.)
|The 2011 Mustang GT. Click to enlarge.|
The new 5.0-liter V-8 in the 2011 Mustang GT is a double-overhead-camshaft configuration that employs two camshafts per cylinder bank—one camshaft to operate the intake valves and one camshaft to operate the exhaust valves. Ti-VCT rotates the camshafts to advance or retard the cam timing, based on several measures including throttle opening.
Working like a ratchet, the one-way valves allow precise timing of camshaft events, continually optimizing timing to provide maximum thrust or fuel economy, based on driver input.
An element unique to the Mustang GT 5.0-liter V-8 application is that Ti-VCT is actuated by camshaft torque, with assistance from pressurized oil. This meant that minimal upgrades to the oil pump were required, resulting in less parasitic drag. Increased volumetric and thermal efficiency gives faster Ti-VCT response at all engine speeds. Camshaft torque energy Ti-VCT actuation is a Ford innovation, introduced first on the 3.0-liter V-6.
During the development phase, camshaft lift profile and port optimization started with higher-lift Ford Racing aftermarket units, modified for compatibility with various four-valve-per-cylinder heads. Extensive CAE and dynamometer testing was performed to fine-tune camshaft events and port flow for performance and fuel efficiency in conjunction with the variable camshaft timing.
The resulting all-new aluminum four-valve-per-cylinder heads feature a compact roller finger follower valvetrain layout leaving more room for high-flow ports for free-breathing performance. Head structure was designed to support higher cylinder head pressures and cross-flow cooling for sustained high-rpm use. Head bolt size was increased from 11 to 12 millimeters to contain the higher combustion pressures.
The aluminum block was developed for optimized windage and oil drainback under lateral conditions and high rpm, such as a track-day outing for an enthusiastic owner and driver. Increased main bearing bulkhead widths and nodular iron cross-bolted main bearing caps with upsized bolts were also employed to accommodate the significant performance increase.
An additional element is the increased capacity and baffling of the deep-sump stamped steel oil pan to enable sustained high-rpm use and offer the convenience of 10,000-mile oil change intervals. Piston-cooling jets also were incorporated for performance-minded customers and for faster oil warm-up on cold start.
Specially designed tubular exhaust headers were developed to maximize exhaust pulse separation and improve flow.
The six-speed automatic transmission on the 2011 Mustang GT will deliver up to an estimated 25 mpg US highway and 17 in the city. This is up from 23 mpg US highway and 17 city for the 2010 model. Six-speed manual transmission Mustang GT models for 2011 are projected to deliver 24 mpg highway and 16 city, matching the 2010 model but delivering significantly more horsepower and performance feel.
Other contributors to the 2011 Mustang GT fuel economy are, EPAS (electric power assist steering) and an additional rear decklid seal to enhance aerodynamics.
Fuel economy also is aided by engineering a lightweight powertrain. The engine, as shipped, weighs 430 pounds (105 kg). This represents a weight savings of more than 20% versus the previous 5.0-liter offering. Lower mass can be attributed to the aluminum block and heads, the lightweight composite intake manifold, composite cam covers and hollow camshafts.