Design Steps for Intake & Exhaust Systems P M V Subbarao Professor Mechanical Engineering Department Acoustic Theory to maximize Volumetric Efficeincy ….

Geometrical Details of Intake System

Primary & Secondary Induction Systems The prime system responsible for flow of air is called as primary system. The remaining part of the system, which is not actively feed the cylinder is called as secondary system.

Effective Inductance The EFFECTIVE INDUCTANCE for a pipe with different cross-sections may be defined as the sum of inductances of each section.

Relative Dynamic Responses of Primary & Secondary Systems The INDUCTANCE RATIO (a) is defined as the ratio of the secondary inductance to the primary inductance. INDUCTANCE RATIO (a) The CAPACITANCE RATIO (b) is defined as the ratio of the Secondary Volume to the Primary Volume. V2 = Secondary Volume = Volume of Intake Runners that are ineffective (n-1)

Inductance ratio for Intake System Calculate the Separate Inductances: Determine the Inductance Ratio (a)

Determine the Capacitance Ratio (b) Determine the Induction system Resonances (IND)1 = Inductance of the primary length (IND)1 = Iport + Irunner

Helmholtz Tuning of Complete System Determine the Primary Resonance: Determine the Frequency Ratios: Determine the Tuning Peak:

Intake Tuning Peaks become:

A combined equation is possible indicating it’s 2nd order

David Visard’s “Rule of thumb” Equations Using Visard's Equation for Runner Length 1. Starting point of 7 inches for 10,000 RPM 2. Add length of 1.7 inches for each 1000 RPM less Using Visard's Equation for Runner Diameter

More Ideas for Enhancing the Flow

Selection of Valve Timing for Better Flow

Stages of Valve Lifting when the inlet valve opens, a rarefaction wave is sent upstream from the valve. When this wave encounters a change in area such as the intake manifold, a compression wave is generated and sent downstream back to the inlet valve. This compression wave increases the local density of the inlet flow, a process called the "ram effect".

Valve Lift Curves

Pseudo Flow Velocity Pseudo Flow Velocity is a parameter to study the effect of valve geometry and the rate change of cylinder volume on air flow into cylinder. PFV is the ratio of rate of change of cylinder volume to instantaneous minimum valve flow area.

Flow Kinematics through Valves

Exhaust Gas Flow Through VALVES

Measurements during Exhaust Stroke

Stream Tube formed by Flow Through Valves Equivalent Converging-Diverging Nozzle Configurations: Mild Separation. Severe Separation

Strategies to Maximize Intake Air Quantity Most decent heads will have an equivalent flow through the valve area as a unrestricted port of about 80% of the valve area, this is if the camshaft it matched to the heads.  Some well ported race heads may have an actual flow of an area up to 85%, but for the most part it is around 78-80%. To further help fill the cylinder, it helps to have a high velocity at the back of the valve.  To do this the intake port can be tapered.  To be effective, there should be between 1.7 and 2.5% increase in intake runner area per inch of runner, which represents a 1-1.5 degree taper. 

Effect of Sonic Conditions and Irreversibilities Isentropic Quasi steady Flow Flow Losses Mass of Fresh air :Intake Process Choking