Variable-cam timing (VCT) allows the opening and closing of intake and exhaust valves be fine-tuned to varying demands. The VCT mechanism uses oil pressure to rotate the cam in relation to the sprocket. An electric solenoid, governed by the engine's computer, controls oil pressure within the VCT mechanism.
The 5.4-liter V8 features three valves per cylinder with a central spark plug. The pistons have longer skirt sides for quiet operation.
A slide-out air filter gives easy access for maintenance.
Using two intake valves helps fuel-air mixing prior to combustion, improving power delivery and fuel efficiency. Multiple valves move more air through the engine, which means more power. Ford engineers were able to get the same benefits of four-valve engine designs, such as a central spark plug and symmetrical combustion chamber, by using the two intake/one exhaust valve scheme. Additionally, eliminating the two-camshafts per cylinder head of four-valve designs saves weight, cost, and is less complex. The two 33.8-mm intake valves allow peak airflow of 350 ft3/min, compared to the 250 ft3/min of the 5.4-liter V8 which uses a single intake cylinder. A larger 37.5-mm exhaust valve forces gases out.
A single-overhead cam is used for each cylinder bank. Traditionally, camshafts are permanently synchronized with the crankshaft so they operate valves at a specific point during combustion. However, the new powerplant uses variable-cam timing (VCT) that lets valves operate at different points during combustion. The result is performance tailored to the engine's instantaneous speed and load. The VCT mechanism uses oil pressure to rotate the cam in relation to the cam sprocket. An electric solenoid, directed by the powertrain-control module (PCM), controls oil pressure in the VCT mechanism.
Additional benefits of variable-cam timing include a reduction in pumping losses and more torque at low speeds without diminishing high-end power.
When the engine operates at lower speeds and lighter loads, eight electronically controlled metal flaps at the end of each intake runner close, thanks to an electric motor, leaving only a small opening. Air jets through this gap, creating a tumble effect in the combustion cylinder and forcing fuel to mix more thoroughly and burn quickly and evenly. The flaps, called charge motion-control valves (CMCV), open at predetermined points as the engine revs up. At higher speeds, the valves do not affect the intake, letting maximum flow into the combustion chamber at wide-open throttle.
An electronic-throttle control (ETC) uses input from the accelerator to actively modulate torque at the drive wheels. Replacing a mechanical throttle linkage is an acceleration-position sensor in the cabin, electronic controls, and an actuator at the throttle valve in the engine. Software algorithms note how the engine is running, as well as ambient conditions, and adjust the throttle as necessary. Throttle control curves are tuned to remain consistent over a wide range of operating conditions, including temperature and altitude, which affect engine response and power.
ETC has a number of safety features, including redundant sensors and double return springs at the accelerator pedal, dual sensors at the throttle valve, a closed throttle-default actuator, redundant microprocessors, and self-diagnostic software. There are multiple fail-safe mechanisms in the software and hardware. In the event of a minor fault, the truck will still operate in "limp mode." If there's a failure, the PCM shuts off the fuel injectors.
To keep all this power reigned in, Ford engineers took special measures to muffle the engine. For example, intake and exhaust manifolds are quieter, thanks to NVH engineers adding vibration-resistant ribbing and reinforcement. Also, a three-part tuned mass absorber in the valley beneath the intake runners keeps sound in. A sound-absorbing engine cover wraps around the edges of sound-absorbing blankets at the front and rear of the engine. The pistons are also shaped with noise reduction in mind. Longer side skirts help control piston movement and minimize slap. The three-valve design itself reduces operating noise, as engineers balanced forces from valve and spring movement against each other, aiming the resultant force vectors toward the engine's center of gravity. This cuts total engine vibration. At the top of the engine, magnesium cam covers are vibration resistant, but weigh less than traditional aluminum covers. The cam covers are further isolated from vibration by rubber mounts. The engine block is stiffer than in past V8 designs by adding computer-designed reinforcements cast into the block sidewalls and thicker metal along the gasket surfaces. This, in conjunction with a new oil pan made of metal sandwiched around a plastic core, helps quiet sound coming from the bottom of the engine.
The 5.4-liter three-valve V8 and 2004 F-150 will go into production early this summer.