Variable intake control, variable intake pipe length and harmonic booster

Category:Brake system foundation - Date:2015-10-17

modern engine intake pipe design technology content is higher and higher.

1 variable intake pipe length Technology:

When the engine is in the middle and low speed, a fine and long intake passage is chosen, because the long inlet can make full use of the air flow inertia of the intake air, and the valve is equipped with a variable valve timing mechanism to improve the air charging efficiency at low and medium speed. At high speed, the choice of coarse and short intake passages is beneficial to reduce the intake resistance and improve the charging efficiency at high speed.

The principle diagram of variable intake pipe length

most of the main pipes can be controlled by vacuum.

The working process diagram of variable intake pipe length

In the Mazda and the variable intake pipe length is known as the VIS variable intake system inertia

VIS variable intake inertial system is actually variable intake pipe length.

The length technology of the new BMW 7 system variable intake pipe

2 Intake harmonic supercharging

about harmonic supercharging technology, on some pages, variable intake pipe length is called harmonic supercharging, and harmonic supercharging is variable intake pipe length. I think this is a question of progress and concept.

For the principle of harmonic supercharging, we can understand that in the engine's intake stroke, the gas flows to the inlet valve at a high speed. If the intake door is closed suddenly, the gas flow near the intake valve is stopped suddenly, but the intake pipe is still in the intake air because of the inertia effect. So the gas near the intake valve is compressed and the pressure rises. After the inertia of the gas, the compressed gas begins to expand and flows in the opposite direction to the air flow, and the pressure drops. The expansion gas is reflected back when it passes to the inlet of the intake pipe to form a pressure wave. If this pulsating pressure wave is compatible with the opening / closing of the intake valve, the reflected pressure wave is concentrated near the inlet valve to be opened. When the inlet valve is opened, the effect of the pressurized intake air will be formed. Thus, the aerating efficiency and power of the engine are improved.

The technical diagram of the TOYOTA ACIS harmonic supercharging

Similar to the variable intake pipe length, the harmonic supercharging is also a vacuum controlled conversion valve designed in the intake pipe, and the air chamber (also known as a harmonic chamber) is designed. When the engine works in the low speed zone, the control valve piece is closed, and the transmission line of the compression wave in the intake pipe (wavelength). When the engine is running at high speed, the control valve is opened. At this time, the air chamber is involved in the gas supply. Because of the air flow at the outlet of the air chamber, the inlet pressure contraction wave can only be transmitted between the air chamber outlet and the intake valve, and the transmission line (wavelength) of the compressed wave. So that the engine can use the compression wave to improve the charging efficiency in the full speed range. It is probably TOYOTA's ACIS system that first used harmonic supercharging. In the early TOYOTA 6 cylinder engine, ACIS system was adopted.

ACIS is the compression wave instead of the expansion wave.

it is important to note that, unlike the present design of the long intake pipe, the intake pipe design was very short, so it could be called the harmonic pressurization at that time, and now it can be called variable intake pipe length.

3 variable intake pipe throttling technology

when the engine is at high speed, the throttle valve opens and gets a large flow of mixed gas. When the engine is at low speed, the throttle valve has a small opening, and a better intake negative pressure and mixed gas eddy current can be obtained. The efficiency of the engine is improved at high speed and low speed.

Schematic diagram of variable intake pipe throttling technology

Real Fawkes variable intake valve cut-off valve

the state diagram of Fawkes's shut-off valve with variable intake valve.

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