Intake

Current/Proposed Outline:

Basic theory

Intake system diagram

The intake system's purpose is to direct ambient air to your engine's air intake. On more traditional road cars and unrestricted race cars, the throttle is generally placed at the inlet of your intake runner (probably should have a source) to promote fast engine response. However, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction(citation). This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body. The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.

Restrictor power limit derivation

Should we put in separate page?

I think it is good information, but shouldn't be at the top because it isn't the most important aspect of the intake system. Probably put the limit in basic info and reference the calculation further down in the page.

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 energy 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.

Throttle control

The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between your turbocharger/supercharger and manifold. Common solutions include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).

Cabling

just copy/paste from old documentation, will clean up in another edit:

Foregoing a push pull cable, a bicycle brake cable will work perfectly fine. There is a lot of slack in the cable however, so a thicker gauge will stretch less. If the bike-cable is kept, proper, preferably swageless ends are to be usedswageless: https://www.electrolineusa.com/industrial/wire-rope-fittings/Swaged: <a href="https://www.nicopress.com/products/category/wire-rope?type=Stop">https://www.nicopress.com/products/category/wire-rope?type=Stop</a>

Dry lube like graphite or molybdenum disulfide are the best go to for high quality cable sheathing. However, if the cable is in a wet/humid environment or the sheathing is old or looks shady[word choice], a liberal dose of a high quality oil is desirable. Non-synthetic oils like mineral oil degrade the cable housing, so don’t use. WD-40 may also degrade the housing and will dissolve the lubricant applied to the cable by the manufacturer so be careful if used. Motor oil is a good default.Read for cabling how to’s: <a href="https://www.sheldonbrown.com/cables.html">https://www.sheldonbrown.com/cables.html</a> [change to "further reading" or smth]

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.

Intake 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 optimize 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. This phenomena can be seen in the video below.

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. Both ram tuning and Helmholtz resonators are simple methods to increase engine efficiency.