Valvematic represents a positive evolution of Toyota’s patented variable valve timing with intelligence technology (VVT-i ), allowing for throttle-free control of engine speed.
This may seem confusing – if more air isn’t allowed into the intake manifold, either manually or by computer, how does fuel delivery and RPM increase? But this is precisely the advantage of Valvematic.
With VVT-i, engines can move air in-and-out at the same rate as the flow of traffic and actual driving conditions, while also reflecting engine load and rotation. In addition to VVT-i’s current valve timing control, Valvematic’s new variable valve technology provides continuous valve lift control. This is new, and great for both drivers and engines.
You might wonder how engine speed can be controlled if the throttle valve is gone or inactive. Jettisoning the standard throttle ensures atmospheric pressure air is accessible right up to the intake valves. Prior to Valvematic, the throttle typically limited the quantity of air available, creating a vacuum; engine pumping losses resulted as air entered the cylinders.
With Valvematic, pumping losses are significantly reduced. The volume of intake-air is now controlled solely by valve lift; therefore, yesterday’s reliance on the throttle valve has been eliminated.
Throttle plates remain an engine component and are functional, but are generally inactive. Their primary use is to provide a back-up system for safety purposes. They remain entirely open when the car is in use, preventing the troublesome intake manifold air-restriction and consequent pumping losses.
The result is obvious. Improvement of both fuel efficiency (5% – 10%) and acceleration (10% – 12%) is generated by Toyota’s enhanced speed ratio of 6.3. In addition, emission of CO2 is reduced because of better fuel-use and acceleration response, generating optimal performance.
More than that, Valvematic engines are also equipped with fluctuating intake manifold length. The resultant lift-height ranges from one millimeter (about 1/16th inch) to 11 millimeters (about 7/16th inch). Operation of the variable valve lift control is improved because the diversity of lift-height is more responsive to real-time conditions within the engine.
One way Valvematic achieves these cool developments is by working in conjunction with VVT-i to maximize the size-difference between the system’s pulleys. VVT-i does this without causing an increase in the size of their exterior case.
In function, Valvematic resembles BMW’s Valvetronic-operation but, as this description shows, is far simpler, and thus less likely to require mechanical attention or overhaul.
The basis of variable valve lift is the position of the oscillating arm, each of which has a ramp-profile dependent on its position to the rocker arm’s point-of-contact. The total quantity of lift changes in relation to the distance of the oscillating arm to the rocker arm. Helical gears on the additional shaft are (1) provided for each valve mechanism, and (2) designed to move the oscillating arm.
Computer-generated commands in the motor move the add-shaft’s internal plunger, initiating the appropriate degree of helical gear rotation, which changes the fulcrum point of the oscillating arm. The resulting pivot compels the various parts of the arm’s ramp-profile to contact the rocker arms. Motion of the intake camshaft powers the oscillating arm, causing the rocker arm to open the valve and change the lift without needing oil pressure to operate.
In closing, the Valvematic method is simpler than its competitors, and provides three essential advantages:
(1) better operating performance; as the engine runs more efficiently
(2) good mileage; the latest technologies generate economical driving
(3) cleaner, greener operation; lower levels of harmful substances are released as exhaust omissions
Valvematic, Toyota’s latest gadget, represents another step in the evolution of automotive engineering and performance.
Want to learn more about how car technology is evolving? Check out our ebook, Apple iCar: Apple’s Auto Industry Experiment.