Fuel

Internal combustion engines can use a variety of fuels, the fuels available at US competitions are gasoline of octane ratings 93 and 100, and E85. No fuel additives can be used

Chemistry

Gasoline

Gasoline is typically approached chemically as pure octane.
$2{\text{C}}_{8}{\text{H}}_{18}(l)+25{\text{O}}_{2}(g)\rightarrow 16{\text{CO}}_{2}(g)+18{\text{H}}_{2}{\text{O}}(g)$

if we use atomic weights for carbon, hydrogen, and oxygen, we find that 2 mol of octane is 224 grams, 25 mol of oxygen is 800 grams which comes from 3809 grams of 21 percent air. This yields an air fuel ratio of 17.

Since gasoline is not pure octane and air is not exactly 21% oxygen. Experimentation yields the stoichiometric ratio of 14.7 grams of air per gram of fuel.

System Design

Fuel Storage

I.C.1.2 Packaging Restrictions

volume determination

• ways to pick factor of safety
  • competition strategy

Tank

mounting
material
form factor (exterior and interior)
sloshing is a meme

Bladder

just pour the gas in a kroger bag and let it flop in the wind /s

Fuel Lines

Material	Internal Diameter [in]	Pressure [psi]	Cost [per foot]	Minimum Bend Radius [in]	Supplier	Notes
Hard Lines
Aluminum	3/8-1/2 (OD)	250	2+		Russell	link pressure rating is wall thickness dependent
Aluminum (0.035 wall thickness)	1/4-5/8 (OD)	200	0.68		Summit	link pressure rating not specified formally, only mentioned in Q&A with conflicting answers, trust with caution
304 Steel (0.028 wall thickness)	.257-.319 (5.16-3/8 OD)	3500	2		JEGS	link
Soft Lines
Nitrile Rubber*	3/8	50	0.88		JEGS	link
Buna-N*	3/16+	50	1.1	1.25	McMaster	link yarn reinforced
Buna-N*	3/4+	150	7	3	McMaster	link steel wire reinforced
Braided Lines
Nitrile Rubber* and Steel	1/4+	50	3.50+		Spectre	link
Nitrile Rubber* and Stainless Steel	0.22+ (4AN+)	1000	6+	2	Pegasus	link
PTFE and Stainless Steel	0.27+ (4AN+)	1320	11.3+	0.75	Pegasus	link
PTFE and Aramid	0.27+ (4AN+)	1320	21.3+	0.92	Pegasus	link
PTFE and Polyester	0.38+	305+	15.8+	2	Pegasus	link

* not compatible with e85

Hard Lines

only legends do this [citation needed] +weight
- cost
-manufacturing
+pressure
- not as reusable year to year

Soft Lines

pressure and solvent rated
e85 sucks for this
+cost
+manufacturing
+reusable year to year / design to design
-pressure

Braided

you're gonna poke you're eye out kid
- cost
- mfg
- i hate
+ reusable
+ pressure rated

Pump and Pressures

depends on injectors, we ran 3 bar, not sure what other people did
low pressure if for tbi and pi, high pressure is for di
i think there are some comp rules on low pressure v high pressure systems talk about filters here? contribute to pressure loss...

Injectors

Throttle Body Injection

basically electornic carb

Port Fuel Injection

Fuel Injected into the ports just before entering the combustion chamber. Usually leads to well mixed charge [citation needed]

Direct Fuel Injection

big boys do this [citation needed]

Fuel Strategy

Efficiency

BSFC

link for calc citations[1]
copying from old school notes so i'll have to add context later -simon

this is for finding fuel consumption (mpg or equivalent) w bsfc chart

P_me (mean effective pressure)

n_mot (motor speed)

i_G (gear ratio for selected gear)

i_sec (FDR)

r_dyn (dynamic radius of tire)

V_d (displacement volume of engine)

i (constant for 4 stroke)

F_req (tractive force required)

p_me = (2pi*T_motor_required)/(V_d * i) = (2pi)/(V_d*i) * ((Freq * rdyn)/(i_G * i_sec) + T_low)

n_mot = (Velocity*i_g*i_sec)/(2*pi*r_dyn)

be (fuel consumption) usually experimentally determined

B_time = b_e*Pe/rho_fuel = b_e*p_me*V_d*n_mot*i/rho_fuel

B_distance = B_time/V

i = 0.5 for 4-stroke engine