Intake

Current/Proposed Outline:

restrictor implications

we don't have the math extension yet, so this is gonna look wack until we do
general equation
for ideal compressible gas flow:

A	Area
R	Gas Constant
$T_{t}$	Total Temperature
$\gamma$	Specific Heat Ratio
M	Mach number
$P_{t}$	Total Pressure

$mdot={\frac {A*p_{t}}{\sqrt {T_{t}}}}*{\sqrt {\frac {\gamma }{R}}}*M*(1+{\frac {\gamma -1}{2}}*M^{2})^{-{\frac {\gamma +1}{2(\gamma -1)}}}$
when M becomes 1, the flow is considered choked. The equation becomes:
$mdot={\frac {A*p_{t}}{\sqrt {T_{t}}}}{\sqrt {\frac {\gamma }{R}}}(1+{\frac {\gamma -1}{2}})^{-{\frac {\gamma +1}{2(\gamma -1)}}}$
With some basic assumed values at sea level, the maximum mass air flow through the restrictor can be found:

A	3.14 e-4	m^2
R	0.286	kJ/kg-K
$T_{t}$	300	K
$\gamma$	1.4
M	1
$P_{t}$	101.325	kPa

[citation needed for above values?]

Plugging these into the equation above yields a steady state mass flow rate of 0.074 kg air per second
If we assume an AFR of 13.1 (typical lambda for high torque for NA engines[citation needed]), and a Q_LHV of 46 MJ/kg [citation needed], the mass air flow yields a power limit of 265.5 kW or 356 hp total energey output. If the thermal efficiency of the engine is assumed to be a nominal 33%, the maximum available mechanical power is 88.5 kW or 118 horsepower with 100% volumetric efficiency.

Manifold design

The intake manifold typically runs from the plenum to the cylinder heads / air intake ports on the engine. It's design can be adjusted to increase performance using the tuning methods below. The manifold also contains ports for the fuel injectors.

Form fact

Not sure if an extra section is needed for plenum or if that is included in 'manifold'? Always thought that manifold was just the intake runners leaving the plenum...

I definitely think plenum and plenum tuning should get its own bit! good catch. i had form factor here as just a place to put all the different ways to lay runners: 4x1, 2x2, angles, lengths (i know some teams run two cyl w very short runners ans 2 with long runners even) ,plenum shapes etc, but maybe its not needed as a section here?

tuning (ram, helmholtz)

Tuning takes two forms for the intake manifold: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold (including Helmholtz resonators).

The basic principle behind ram tuning is that a cylinder intakes air at a particular frequency, i.e. a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence ram tuning is done to optimise performance at a selected rpm. The way in which it is implemented is to modify the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next lot of air. This means that the pressure at the inlet will be higher whenever the engine needs air, giving better volumetric efficiency for the engine.

Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine.