TALLER DE LA UNIDAD 1 Y 2

A. Categorías léxicas y uso del diccionario.

VTEC (Variable Valve Timing and Lift Electronic Control)

Is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles. It was invented by Honda R&D engineer Ikuo Kajitani, and was the first system of its kind. Different types of variable valve timing and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, AVCS from Subaru, VVTL-i from Toyota, VarioCam Plus from Porsche, VVC from Rover Group, VVEL from Nissan, etc.).

VTEC was initially designed to increase the power output of an engine to 100 PS/liter or more while maintaining practicality for use in mass production vehicles. Some later variations of the system were designed solely to provide improvements in fuel efficiency, or increased power output. In practice, a fully variable valve timing engine is difficult to design and implement.

Additionally, Japan has a tax on engine displacement, requiring Japanese auto manufacturers to make higher-performing engines with lower displacement. In cars such as the Toyota Supra and Nissan 300ZX, this was accomplished with a turbocharger. In the case of the Mazda RX-7 and RX-8, a rotary engine was used. VTEC serves as yet another method to derive very high specific output (power/unit displacement) from smaller-displacement engines.

The VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of one cam lobe actuating each valve, there are two: one optimized for low-RPM stability & fuel efficiency; the other designed to maximize high-RPM power output. Switching between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low RPM ones. From this point on, the poppet valve opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load. The switch back from high to low RPM cams is set to occur at a lower engine speed than the up-switch (hysteresis) to avoid a situation in which the engine is asked to operate continuously at or around the switch-over point.

IDEA PRINCIPAL DEL TEXTO

Se esta hablan de VTEC el cual es no mas que un sistema de distribución desarrollado por Honda para mejorar el rendimiento volumétrico de un motor de combustión interna de cuatro tiempos. Este sistema utiliza dos perfiles del árbol de levas y selecciona electrónicamente entre los perfiles. Fue el primer sistema de este tipo.

Abreviaciones:

timing [ˈtaɪmɪŋ] noun : the time when something happens

improvement [ɪmˈpruːvmənt] noun : a change for the better; progress in development

• Palabras de contenido: valvetrain, camshaft
• Palabra de funcion: of, in, and, by
• Verbos: was, is.
• Adverbio: practicality, Additionally
• Articulo: the power,
• Preposiciones:
• Conjunción: and, or
• Cognados verdaderos:displacement, combustion
• Cognados falsos: maintaining, actuated
• Sufijos: practicality, Additionally
• Prefijos:output, inputs

B. Estructura de la oración:

The VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations.

Frase nominal

1. Nucleo de la frase nominal: The VTEC system
2. Pre modificadores:The VTEC
3. Post modificadores: of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations.

Frase verbal

1. Nucleo de la frase verbal: is a simple method
2. Tiempo verbal: simple present

The switch-over point is variable, between a minimum and maximum point, and is determined by engine load

Frase nominal

1. Nucleo de la frase nominal: The switch-over point
2. Pre modificadores:The switch-over
3. Post modificadores: between a minimum and maximum point, and is determined by engine load

Frase verbal

1. Nucleo de la frase verbal: is variable,
2. Tiempo verbal: simple present