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Ford’s “new” Twin Independent Variable Camshaft Timing is the jewel in the 2011 lineup; 30 miles per gallon and 305 horsepower in the V-6, 25 miles and 412 horses in the V-8. But if the much-touted Ti-VCT isn’t really new, it sure is improved.
The little engine that could - Duratec 1.6 Ti-VCT.
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Introduced in late 2004, the first Ti-VCT engine was the 1.6-liter Duratec tucked under the skin of the Focus and Focus C-Max. It offered 115 horsepower, 15 more than the Duratec that had hauled the little car around since 1998, and claimed a more responsive throttle and better gas mileage.
For those who don’t know, valves in the engine open to let in the fuel and air mixture, close to contain the power-producing explosion, and another set of valves open to let free the leftover gases — the exhaust. It is the engine’s camshaft that opens these valves, and the timing must be precise, or the engine will not operate properly, if at all.
The tough part is designing the camshaft’s profile, the position and shape of the cam lobes on the shaft, to work across the band of revolutions an engine goes through. It’s a tradeoff that can limit low-end torque or high-end power.
Bumps in the road
Variable timing allows the cam profile to change, which results in greater efficiency and power.
At high engine speeds, an engine requires large amounts of air, which means keeping the intake valves open as long as possible. However, this can cause problems at the lower engine speeds as unburned fuel exit the engine while the valves are still open. This leads to lower engine performance and increased emissions.
If the cam is designed with a shorter duration, the intake valves may close before all the air has been given a chance to flow in at higher rpm, reducing performance. This is why pure racing engines cannot idle at the low speeds (around 800 rpm) expected of a road car, and idle speeds of 2,000 rpm are not unusual.
Variable timing is meant to offer the best of both worlds. After its success with the four-cylinder Duratec, Ford gave the V-6 the treatment with the single-cam Duratec 30 in the 2006 Fusion, Mercury Milan and Lincoln Zephyr, again with promising power results: 221 horsepower, but just 10 miles per gallon. The new energy crunch made that mileage figure unacceptable.
The Mustang GT 5.0 will use Ti-VCT to pull 412 horsepower and 25 miles per gallon out of the V-8.
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Enter the twin-cam era. Ti-VCT provides extremely precise variable – yet independent – control of timing for intake and exhaust valves. Drivers of the 2011 Mustang GT will notice abundant torque and class-leading fuel economy. An additional benefit of Ti-VCT is a reduction of emissions, especially in situations when the throttle is partially open.
How the technology works
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 oil control solenoid 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.
The new 3.7-liter engine for the 2011 Mustang V-6 will be built at Ford’s recently retooled Cleveland Engine Plant No. 1.
More ponies for the pony
The new 5.0-liter V-8 in the 2011 Mustang GT is also a double-overhead-camshaft configuration that employs two camshafts per cylinder bank. 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 the pressurized oil. Using camshaft torque energy provides faster throttle response and maximizes use of existing energy, to aid fuel economy. Camshaft torque energy Ti-VCT actuation is a Ford innovation, introduced first on the 3.0-liter V-6.
Can you wait for 2011?
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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. “Ti-VCT is a win-win-win technology,” said Barb Samardzich, vice-president of Global Powertrain Development. “It helps our new range of engines to deliver high performance with unsurpassed projected highway fuel economy of 25 miles per gallon and reduced emissions.
“Ti-VCT technology will continue to proliferate across the Ford powertrain portfolio. By 2013, you can expect to see this advancement available on 90 percent of our nameplates.”
— Ken Simmons
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