Specific Gravity: primarily an indicator of how fast a fuel will burn; lighter fuels burn faster
False. SpG has no relation to flame speed. Flame speed is a function of chamber turbulence and laminar flame speed. The differences in laminar flame speed are small and dependent on type of fuel and mixture; not Specific Gravity.
Good race fuels are usually lighter and therefore often burn faster,
False. See above.
despite the popular misconception that higher octane fuels burn slower
Octane has no contribution to flame speed, either faster or slower. It all depends on the composition of the fuel, not octane.
Faster burning fuel will require less timing for max power (lower SG fuels can make older chamber designs burn faster, and modern chamber designs faster still/ fuel SG is a "hack" / control point by which you can increase the speed of combustion to get more VE & torque -if you appropriately retard timing to account for it)
False. Fuel laminar flame speed is a minor contributor to total flame speed. Mixture ratio does contribute slightly to flame speed. A change in SpG could cause a change in mixture ratio however minor.
Most pump gas ranges between an SG of 0.720 - 0.770
True but incomplete. Since fuels are metered by volume, the fuel ratio is determined by the stoich value of the fuel and the SpG. Fuel stoich values can range from 14.2 to 15.2.
Specific Gravity can affect fuel metering in carbureted engines (unclear whether there are issues with port or direct injected engines)
True. Whenever fuel is metered by volume, SpG does affect mixture as does stoich value.
Vapor Pressure: primarily an indicator of how stable a fuel / a fuel's octane content is under storage (the higher the vapor pressure the faster the fuel's oxygen content will degrade)
Reid Vapor Pressure is an indication of the evaporative properties of a fuel. It has nothing to do with fuel oxygen nor octane.
The rating system is based upon how much pressure will build up in a sealed container @ 100F
Partially true. RVP is the rise in pressure of fuel vapor when the fuel temp is raised from 32F to 100F.
Butane is normally the primary fuel constituent/additive responsible for the vapor pressure (more butane blended in for winter grade gas)
Sometimes true. Butane is a gas at normal temperatures and therefore difficult to retain in solution in the fuel. Some high quality race fuels do use butane to raise RVP.
Winter grades of gas, especially in cold climates, normally have higher vapor pressures (up to 12 PSI) to help with cold weather startup and idling
True. The actual RVP value will depend on the state and month of the year.
Summer grades of gas have lower vapor pressures in the 7.8-9 PSI range
True.
Lower grades of gas generally have higher vapor pressures and are more volatile;
False. RVP is mandated by area and season, not by type of fuel.
87 octane can see octane degradation after only 3 months;
False. While an open fuel container can lose certain components due to evaporative losses, the light fractions are not the primary octane improvers.
93 octane is usually stable when well stored to 9 months;
False. 93 octane is no different than 87 octane.
race gas 1-2 years in ideal storage situations
True. Properly stored, fuel has a long shelf life. The military stores fuel for dozens of years.
Does fuel with a higher vapor pressure atomize better/faster than fuel with a lower vapor pressure or should we not conflate vapor pressure and atomization?
A fuel with a high RVP does indeed evaporate quickly; a property that helps with poor carburation but is subject to vapor lock.
Fuel components' / octane enhancers' ability to "add energy" / "energy density": If I remember correctly, a discussion on octane boosters that actually increase power / "energy density" of fuel stated that Toulene was an example of an octane booster that increases a fuel's energy / makes more power,
"Octane enhancers" do not add energy or energy density; they raise the fuels ability to resist detonation. Some fuel components such as Toluene, do add a small amount of fuel energy. By adding 15% Toluene to isooctane we will raise the fuel energy from 1270 BTU/lb air to 1274 BTU/lb air.
while ethanol fell in the opposite category as an octane-boosting additive that actually decreases the final fuel's energy capacity.
Ethanol does have a slightly higher specific energy than isooctane (1270 to 1278) but its main advantage is its evaporative cooling property which increases inlet air density.
-When I looked up the SG of Toulene, I expected to see a fairly low SG, expecting that the increase in energy was from the Toulene percentage causing the fuel to burn faster, but Toulene has a relatively high SG of 0.867 so I realize I'm thinking about this all wrong...
You were right, you are wrong.
-What is the indicator / metric that a fuel component will add vs. subtract energy from the final fuel blend?
The heat of combustion of a fuel determines its energy. The amount of fuel that can be burned is limited by the amount of available air. The heat of combustion divided by the stoich value gives us the BTU per lb of air, which we call specific energy.
Cooling Fuel: Does this actually make more power? If so, how?
Does chilled fuel just chill the incoming air charge and make more power via making denser air and allowing more ignition timing because the air fuel mixture and ultimate combustion temps are slightly lower?
Are there negative power effects from chilling fuel? -Does it make the fuel atomize worse? Make the fuel burn slower? (I just can't see chilling fuel to be anywhere near as beneficial to producing power as chilling the incoming air charge.)
Chilling fuel is a complete waste of time. It could be useful when using a very volatile fuel to avoid vapor lock.
Anyone know of a good website/ database containing common pump and race fuel RON, MON, SG, & Vapor Pressure numerical range targets? (otherwise how the heck is a normal person supposed to apply any of this?)
Take a course in Organic Chemistry.
Pump gas should be ignored for any competitive purpose. It is totally inconsistent and unpredictable.
VP Racing fuels has a master fuel database available on line that lists some useful fuel parameters. But not
how to select or use them.
Does SG impact fuel metering in EFI engines? -Do you need to make any EFI changes when switching from a higher SG to a lower SG fuel?
As long a fuel is metered by volume, SpG and the stoich value are necessary to control mixture properly.
Chasing SpG and stoich values becomes an hassle and time sink. Much better to find a good consistent fuel and stay with it. Chasing weather is hard enough.
What are the other major fuel attributes and items that should be understood and factored in?
There are only about 25 more fuel parameters that should be considered and have not been raised. Fuels and combustion remain a black art augmented by folklore and misinformation. Consider that every Formula One team has a team chemist and technical partnership with a major oil company. Yet, most racers simply seek cheaper fuel or gifted sponsorship instead of knowledge and technical insight.
Every serious racer should establish a connection with someone with a chemistry background, an analysis lab, or university chemistry dept. Unfortunately, many sanctioning bodies mandate spec fuels and in the process destroy any hope of increasing technical understanding of our very interesting and intellectual challenging sport.
