Nissan 370Z Forum - View Single Post - What is "bottle" beneath intake duct on passenger side?

Mandingo · 12-22-2012, 02:05 PM

The intake tumor is there to silence intake noise and to (theoretically) increase efficiency.

Quote:

How the Resonator can improve Volumetric Efficiency

-In an IC engine, air or the air-fuel mixture is sucked inside the cylinder while the piston is moving toward bottom dead centre (BDC).

-As the filling process progresses, the charge air gains more and more momentum, so the speed of the charge air increases gradually.

-As soon as the piston reaches BDC, suddenly the inlet valve closes. But, the air in the intake manifold still has a substantial amount of velocity (or dynamic pressure).

-Eventually, the flowing charge air hits the closed valve, and the pressure of the charge air at the vicinity of the valve increases. The pressure wave bounces back and starts moving toward the opposite direction.

-If a resonator is attached with the inlet manifold, then it will act like a spring to the just-created pressure wave.

-The frequency of the resonator determines the speed at which the pressure wave will proceed again toward the inlet valve.

-If the frequency of the resonator and the speed of the engine (which determines the interval between the opening and closing of the inlet valve) are properly tuned, the pressure wave will hit the inlet valve again at the time when the inlet valve is open. This phenomenon will cause a rush of charge air into the cylinder. The charge air will be forced into the cylinder, causing the increase in volumetric efficiency.

-The point to be noted here is that you will get maximum benefits of increased volumetric efficiency only if the engine running frequency and the resonator frequency are properly tuned. That means you can get maximum benefit only for a particular engine operating speed with a fixed frequency resonator.

-For selecting a resonator, the engine operating speed, intake manifold design, and volume of the intake manifold need to be considered. Roughly, the resonator frequency is kept around double the engine frequency in order to get the benefit of the volumetric efficiency increment.