Gasoline doesn’t burn. The vapors of the liquid gasoline burns, and that’s extremely important to remember when you are thinking about controlling combustion in a gasoline engine. – Steve Burns, CEO of VP Racing Fuels
Attention to details wins races and Championships. Sure, it takes some skill in the driver’s seat, but no competitive racer can refute that it also takes some planning skill. Doing your homework. Figuring out how to maximize every little bit of horsepower and handling that your race car can make. Countless hours are spent getting your engine combination exactly correct so that it can make the most dependable power and be there at the end of the race.
One Size Does Not Fit All
It’s true, not all race fuels are the same. Not even fuels from the same manufacturer are identical. They are designed and formulated for specific applications. In that aspect, you can consider racing fuel another component of your race engine. It’s not a matter of simply gaining 2 or 3% more power by picking a higher octane fuel. It does go back to champions paying attention to details and selecting the right components to maximize their racing effort with consistency. Every racer and engine builder knows that there are differences in race components. There is no “one size fits all” for every crankshaft, camshaft, pistons or valves. These components are built for specific race or engine applications. For instance, a camshaft manufactured for a quarter mile drag race probably isn’t the best choice for a 3/8ths mile oval dirt track. What if we were to tell you that the same principal applies to fuels?
Let’s Get The Facts
We decided to get the straight facts about racing fuels from Steve Burns, CEO and founder of VP Racing Fuels. Along with Burns’ insider info as a research and development guru for premium racing fuels, we are drawing on information from Dr. Dean Hill, PhD Chemist that served as NHRA fuel inspector for National Meets for several years.
Remembering the fire triangle from our high school chemistry days, Dr. Hill added to the ongoing lesson by saying, “There must be fuel, Oxygen and spark or compression for combustion to take place. All three of these things can be controlled and adjusted.” VP’s Burns explained that an important concept to remember is that “gasoline doesn’t burn. The vapors of the liquid gasoline burns, and that’s extremely important to remember when you are thinking about controlling combustion in a gasoline engine.”
To illustrate this point, Burns said, “you have to have something that evaporates. You can take a piece of wood, and it will burn, but it doesn’t evaporate,” continuing his explanation of the vaporization of liquid fuel by saying, “what allows for combustion in the engine’s combustion chamber is the transition of liquid into a gas at temperatures below the boiling temperature at a given pressure.”
According to Burns, pressure, or heat, causes the cooler molecules in the fuel to get more excited and react with the air in the combustion chamber. The more heat that the molecule is exposed to, the more readily it becomes to react with the air.” The key to racing fuel, according to Burns, is “to control the reaction so that it is a smooth combustion.”
|Fraction||Boiling Range (oC)||Number of Carbon Atoms|
|natural gas||< 20||C1 to C4|
|petroleum ether||20 – 60||C5 to C6|
|gasoline||40 – 200||C5 to C12|
|kerosene||150 – 260||mostly C12 to C13|
|fuel oils||> 260||C14 and higher|
|lubricants||> 400||C20 and above|
So, let’s summarize what we have so far: The goal of an internal combustion engine is to take air, combine that air with a proper amount of fuel that will evaporate and burn in the combustion chamber to make power. Dr. Hill reminded us earlier that it takes fuel, oxygen and spark for combustion to happen, and that all three of these elements can be controlled and adjusted. Burn’s added to that by emphasizing a controlled reaction of fuel for smooth combustion.
Historically, fuel companies have dealt with the issue of controlling detonation by adding octane agents to preventing uncontrolled combustion. That has worked well for lower performance street vehicles. Race engines however, are a different subject.
Burns explained that manufacturing race fuel begins at the molecular level. “Pre-ignition is nothing more than the fuel igniting before I told it to go off. What typically happens is that the combustion chamber gets hotter and hotter as the engine is working, causing the reaction to happen quicker, at higher speeds.”
In the simplest terms, “Octane is the ability to resist detonation,” Burns said. “If the detonation happens during the compression stroke before the optimal position of the piston in the cylinder, you can have serious inefficiencies and many times in racing motors, severe engine damage.”
There’s A Lot More Involved
According to Dr. Hill, “There are two ways to ‘hop up’ gasoline. You can increase oxygen which enables more fuel to be burnt or increase the octane rating which enables higher compression ratios to be used.”
Burns agrees that increasing the octane rating can help with the self ignition and pre-detonation issue, especially in higher compression engines, “but resistance to detonation is more than just octane. There is a lot more involved.”
Octane rating is often misunderstood in pump gas usage. Although we all pull into gas stations and are offered the choice between several octane rated gasolines, the octane rating at the pump can be deceiving because of the ASTM standards on rating octane. You will typically see three acronyms to describe octane rating: RON, MON and PON.
- RON (Research Octane Number) is determined on a running test cell engine with a variable compression ratio under laboratory type controlled conditions. The results of fuel in the test engine are compared to known characteristics of fuel with different mixtures of iso-octane and n-heptane. For example, fuel with the same detonation characteristics as a mixture of 90% iso-octane and 10% n-heptane would have an octane rating of 90.
- MON (Motor Octane Number) is generally considered a better measurement of how fuel behaves under load. MON testing is similar to the RON testing procedure except the fuel mixture is preheated, higher engine speeds are used and ignition timing is varied to test the fuel’s knock resistance under stress. The MON of pump gas will normally be around 10 points lower that the RON number.
- PON (Pump Octane Number) is simply the average between the RON and MON and is most frequently seen displayed on gas station pumps as (R+M)/2. Don’t believe us? Go ahead and take a look on the gas pump next time you fill up at the local service station.
Hydrocarbon Octane Numbers
|Hydrocarbon||PON Octane Number|
What’s The Real Octane Rating?
As you can see, octane ratings mean different things depending on which ASTM standard you are measuring the resistance to detonation of a fuel. Burns’ statement concerning a fuel’s “resistance to detonation is more than just octane,” refers to the complete makeup and constituents of the fuel. As for octane ratings, most racers, and race fuel manufacturers consider the MON the most accurate rating of a gasoline’s octane rating.
Burns tells us that “you need a fuel that resists detonation, evaporates well with the air inside the combustion chamber and releases the most heat for the available oxygen.” The rapid expansion of air by heat is what makes power, therefore, what we are really looking at in fuel molecules is the energy potential.
Burns went on to say, “You can make fuel with a thousand different types of molecules. Wouldn’t you want to control the consistency by narrowing it down to the 500 or 600 best molecules?” To illustrate his point even further, he added, “It’s like having 1,000 players trying to make a team. You have them sitting there in the stands. To make a great team, you want to pick the players that you know are dependable under stress and are predictable performers.”
His analogy made a lot of sense to us. If you took the time to isolate the different players, discover what characteristics they had under game situations, you would pick the best role players to make a consistent winning team. “Putting together a winning team costs money. We see this with every dynasty type team put together in sports. But what you are rewarded with is the consistent “W” in the win column,” states Burns, adding, “Manufacturing fuel is no different. For racing fuels, we select the best molecules for a specific task.”
There IS a Lot More To The Equation
At the molecular level for example, the amount of carbon atoms in hydrocarbon fuel, can affect how quickly or how slowly the fuel burns. The more carbon atoms and bonds, the longer it takes to break the bonds and burn the carbon atoms. The way the atoms are bonded to each other also affects speed of the combustion and amount of energy released. When you’re talking about a couple of milli-seconds for an optimal energy window, dependable reaction is everything.
In essence, what Burns explained to us is that his engineers “hand pick” the constituents that make up the different types of fuel that VP Racing Fuels manufacture. Each type of fuel has a specific purpose and predictability by design. The cost of making a premium racing fuel is higher than a pump gas that operates in a wider operating range of variables and less energy potential, but it’s no different than paying a slightly higher price for an aftermarket engine component that is tailor made for high performance.
Final Thought: Let’s Put This All In Perspective.
A gallon of race gas can cost between $8 to $12 a gallon. The process of manufacturing that gallon of race gas goes way beyond the typical process of manufacturing pump gas. There is still the exploration, recovery of crude, fractional distillation, and refining, all done under the regulatory oversight of big brother. Then the selection of additives, the chemicals that make race gas a high performance product are selectively added. To cap it all off, there’s packaging, marketing, handling wastes and all the other costs of doing business.
Compare that to a bottle of filtered tap water that we put into our high performance bodies. We think nothing of paying $1.50 or more for a 9 ounce bottle of Evian water. Bottles of drinking water are as common in the pits as gallons of racing gasoline. Remarkably, bottled water has less regulatory oversight and taxes than gasoline. That water ends up costing the consumer over $21 a gallon. When it’s all said and done, it’s an amazing technical achievement to produce a gallon of high performance race gas at an affordable price.