Toyota Variable Induction System, or T-VIS, is a

variable intake In internal combustion engines, a variable-length intake manifold (VLIM),variable intake manifold (VIM), or variable intake system (VIS) is an automobile internal combustion engine manifold technology. As the name implies, VLIM/VIM/VIS can vary ...

system designed by

Toyota is a Japanese multinational automotive manufacturer headquartered in Toyota City, Aichi, Japan. It was founded by Kiichiro Toyoda and incorporated on . Toyota is one of the largest automobile manufacturers in the world, producing about 10 ...

to improve the low-end performance of multi-valve engines. T-VIS is intended to improve the low-end

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of t ...

of high-performance, four-stroke

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal com ...

s - by changing the

geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...

of the

intake manifold In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/ air mixture to the cylinders. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the ...

according to the engine rotation speed. The system uses two separate intake runners per

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infi ...

, one being equipped with a

butterfly valve A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates. Principle of operation Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valve ...

that can either open or close the runner. All valves are attached to a common shaft which is rotated by a

vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or " void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often di ...

actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) an ...

outside the manifold. T-VIS does not actually keep one of the intake valves from opening or seal off the port for one valve.''Toyota Twin Cam''
p. 11 The engine control unit (ECU) allows vacuum into the actuator by powering a

solenoid valve A solenoid valve is an electromechanically operated valve. Solenoid valves differ in the characteristics of the electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the ...

when the engine rotation speed is low. At higher engine speeds (e.g. 4,200 rpm), vacuum is cut off and a spring inside the actuator causes the butterfly valve to fully open. The idea behind the system is that in the lower engine speed band, the speed of the intake air will be increased because the intake runner

cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...

per cylinder is smaller. However, when engine speed increases, the second runner is opened, decreasing airflow speed, but increasing the airflow volume, better matching the engine's airflow needs at higher revolutions and improving top end power. With modified engines it may be desirable to have the T-VIS open earlier than stock, because modifications that improve an engine's power output may do so by increasing airflow per engine revolution, resulting in a high airflow at a lower rpm. In addition to providing more air at higher engine speeds, the system also creates a swirl in the combustion chamber at lower rpms. The swirl makes for more efficient combustion, and is due to the asymmetric nature of the airflow with one intake runner closed. Applications: * 1982.08-1990 1G-GEU/ 1G-GE * 1983-1989 4A-GE * 1986-1989 3S-GE (Both Rev 1 and Rev 2 of the 1st Generation 3S-GE) * 1986-1993/95 3S-GTE (through 1995 in US market, 1993 everywhere else; 1st & 2nd generation motors only)

References

See also