It seems everyone has a story about a racing friend who had a racing friend that somehow got away with hiding a nitrous bottle or an extra fuel container with nitromethane-laced fuel that helped them win races they wouldn't have otherwise. You've maybe even heard a few yourself. Odds are that many of these old stories are fabrications like the old "alligators in the New York sewers" urban legend, but more than a few are also likely true.
There are lots of other popular cheating stories that follow various themes in racing, but the illegal fuel stories are among the most popular because it actually is one of the easiest ways to squeeze more power out of your engine.
Of course, there are also lots of situations where your choice of racing fuel doesn't have to be shrouded in secrecy because it isn't prohibited by the rules. In fact, your fuel choice can be critical to the success of your racing program. We've already done research in Circle Track proving that a quality race gas can provide quite a bit better performance over standard pump gas even in low-compression engines because the companies that blend the pump gas are more concerned with protecting OEM vehicle's exhaust sensors, limiting hydrocarbons and cutting costs than they are the power potential of the fuel. Plus, pump gasoline blends will vary quite a bit from summer to winter, making tuning your carburetor that much more tricky.
But not all race fuels are created equally, either. In fact, because manufacturers of racing fuels do not have to take the "one size fits all" mentality, they can blend fuels specifically for certain engines or racing classes. One of the subcategories when it comes to different types of racing fuel is what's known as an oxygenated fuel. Oxygenated fuels can be either leaded or unleaded, have a wide variety of octane levels, and have many other characteristics. But almost all oxygenated fuels have some type of additives in the gasoline that have the right mix of ingredients in the chemical compound to create oxygen molecules when that compound is broken down.
This is the key to making extra power: The extra oxygen in the combustion chamber means you can add even more fuel, and when the two are burned the result should be additional energy pushing down on the piston. When done correctly, the extra oxygen molecules also help burn the existing fuel more completely. For years a compound known as MTBE was a common additive oxygenated fuels, but MTBE has been proven to be quite dangerous to both the environment and ourselves so it's rarely found in fuels anymore. Since the demise of MTBE, ethanol and a chemical called propylene oxide have become two of the more popular attitudes to create oxygenated fuels. But since there is no requirement to print an ingredients label on the side of your fuel can like you would find on a pack of Twinkies, it can be difficult to learn precisely what is in the fuel you are burning. Understandably, fuel manufacturers like to keep the exact recipe for the blends used in their racing fuels private.
Regardless, most of us are more interested in improving our results on the racetrack than we are retaking that high school chemistry class we slept through anyway. The truth of the matter is that in the right situations, and oxygenated race fuel can help a race engine produced significantly more power than the same engine own standard race gas.
Everett Bradham is the shop foreman for Willy's Carburetor and Dyno Shop in Mt. Carmel, Illinois. Willy's is one of the top carb tuners in stock car racing and is constantly improving its carburetors through rigorous research and development. Willy's offers its customers carburetors tuned specifically for racing with oxygenated fuel, so we asked Bradham about the benefits of racing with the stuff.
"We've tested with oxygenated fuels several times," he says. "And just recently we did a test with some of VP's fuels. We tested the VP113, which is an oxygenated fuel, against the VP-110, which is a very high quality standard race fuel. The VP113 is considered a 5-percent oxygenated gas, and we were running it on what you might consider a standard Street Stock motor with a two-barrel carburetor. We had to go up two jet sizes with the VP113 compared to the standard fuel and we saw a gain of around 10 horsepower.
"Then we tested VP's CHP race fuel, which is a 10 percent oxygenated fuel. We ran it on the same engine as the VP-110 and the VP113 and had to go up another two jet sizes, but we also saw a gain of around another 10 horsepower. So the stuff really does work. You won't see gains that good in a better engine with more efficient cylinder heads, but for that application with the Street Stock level engine that's pretty good power to be made."
VP's Freddy Turza explains that oxygenated fuels are most effective in stock-style or low compression engines because the oxygenated fuel blend helps the engine work more efficiently. "A lot of times when people hear 'oxygenated fuel' they think about cheating with nitromethane in the fuel. And that's not the case. There is a power-enhancing chemical blend that goes into the fuel but the purpose of it is to achieve better vaporization to equalize all of the runners in the intake manifold.
"Whenever you have to work with an inefficient combustion chamber, that's where this fuel is typically going to be the most helpful," he continues. "Like the CHP fuel we designed specifically for applications racing crate engines like the Chevrolet 602 or 604 engines. Those are typically lower compression engines and its efficiency is low because of restrictions in the carburetor, intake manifold, or the intake runners themselves. By increasing the efficiency of the fuel, you are able to help these types of engines generate more power."
The key with oxygenated fuels is that the performance gain isn't necessarily with the peak power numbers. Hendren Racing Engines in Rutherfordton, North Carolina, is a certified crate engine rebuilder for several series. Steve Hendren says that one of the biggest benefits of oxygenated fuels when it comes to crate racing is lower in the rpm range. "We've done extensive testing on oxygenated fuels versus standard race gas," he says. "On average, depending on the engine and the weather, you are looking at a gain of 7 to 10 horsepower versus standard race gas. And that's a big deal with a 602 or a 604 crate because they are all the same, so even a seven horsepower advantage is going to be significant on the racetrack.
"But the gains you can make with a fuel like this isn't simply a peak power number. Really, the main difference you will see is the low-end torque and the horsepower through the midrange. And that's pretty much where you want it anyway, because you don't pass too many guys going into the corner. Most of your passing is coming out of the corner, and that's where that extra low end torque is going to come into play."
One issue with oxygenated fuels is that you can't simply pour it into your fuel cell and expect an instant bump in both horsepower and torque. As Bradham mentioned, on the dyno the oxygenated fuel required bigger jets. The reason is simple: to make more power you have to burn more fuel. Simply increasing the jet size may work on the dyno, but we're racing cars, not engine dynamometers.
"You've got to get more fuel in there," Bradham says of running oxygenated fuel versus standard race gas, "so the first thing a lot of guys will think of is just to go up on the jet sizes until you get what you need. You can do that, but as you go up on the jet sizes you start losing a little bit of driveability--the carburetor won't operate as cleanly. That's because the bigger the jet, the 'dirtier' the car drives, so to speak. When you start rolling onto the throttle on turn exit, the jets start moving more fuel, and the fuel isn't atomized as well because of the bigger holes in the jets.
"You can increase fuel in more ways than just increasing the jet size," he continues. "One way that you can keep the drivability nicer is by increasing the power valve size. That's a delayed fuel enrichment circuit that doesn't initially come in as soon as you roll on the throttle but adds fuel a bit later depending on the power valve you have in the carburetor. That way you can adjust it to add fuel when you are at wide-open-throttle but no part throttle. So that's one way to help the carburetor give the engine more fuel while still maintaining a good, crisp throttle response."
As a professional carb tuner, Bradham knows all the tricks, and he says that Willy's applies several to its carbs built for racing oxygenated fuels, but he was willing to share one more example. "Sometimes you may also need to richen the idle circuit up too," he says. "The idle circuit isn't just for idling around in the pits. It also affects the car when you roll off the throttle on turn entry and through the turns. When you go into the corner and get off the gas, those throttle plates shut and the only thing fueling your motor is the idle circuit. Remember, when those throttle plates are shut, that cuts off the fuel from the main circuit that you've worked so hard to tune. So if you have had to richen up the main circuit for the oxygenated fuel, then you probably will have to richen up the idle circuit too. If you don't, you will heat up the motor on deceleration because it's running too lean. And then because it is too lean, when you get back on the throttle it's going to stumble and fall on its face. And it's going to struggle to pull until you get over that delay when the carburetor is able to get fuel back into the engine through the main circuit."
Besides your carburetor, making the switch to an oxygenated fuel means you may also have to take a close look at the rest of your fuel system. Typically, an oxygenated fuel means 4 to 5 percent more fuel consumption. Typically, that's not enough to require running a larger fuel cell, but Turza says he has seen situations where a racer needed to upgrade their plumbing from the fuel cell to the fuel pump.
"I can't say you have to run at least a -10 AN line or something like that," he says. "And really it's never the fuel line that's the problem. But sometimes your AN fittings can be a problem and limit fuel flow. It's never the quality name brand stuff like Earl's, Brown and Miller, Goodridge, or guys like that, but the private label or import stuff that's really cheap. Sometimes the inner diameter (id) on those fittings isn't as large as the name-brand stuff and it can cause a restriction in the fuel flow from the cell to the pump. You may not notice it with standard race gas, but when you move to oxygenated fuel and are trying to move more through there, you may wind up with a restriction you didn't realize you had before."
Oxygenated fuels can also be harder on components in your fuel system. It's probably because oxygenated fuels typically contain greater amounts of methanol in the blend, but you will need to keep an eye on rubber components like the power valve plunger, carburetor gaskets, and your fuel pump and pressure regulator. Oxygenated fuels aren't as corrosive as alcohol fuels, but they certainly are more aggressive than standard race gas. And if you are racing an older fuel cell, you may need to consider replacing the foam. Newer foams are unaffected by new fuel blends, but older foam can be dissolved by oxygenated fuels. If you start running an oxygenated fuel and notice your engine stumbling or trash in the carburetor, make sure to check your fuel cell.
Besides needing to burn more of it compared to a standard race fuel, oxygenated fuels are also a bit more volatile. That doesn't mean that it's going to blow up in your face or anything like that. It simply means that it contains more "stuff" in the blend that will evaporate into the air more quickly than a standard gasoline.
"The shelf life of an oxygenated fuel is going to be less than a standard race fuel," Turza says. "One thing that we highly recommend at VP is it's OK to put the fuel in those plastic jugs going to and from the racetrack. They make life a lot easier when trying to fuel the car at the racetrack. But when you get back home, you want to get any leftover fuel back into that steel drum and get the bung back on nice and tight. The light ends of the fuel will evaporate into the atmosphere. And you may not realize it, but those plastic jugs are porous to that stuff, and over time the light ends of the fuel will evaporate right out. When that happens the fuel will still burn, but it has lost some of what gives it its power enhancement. So make sure to keep it in the steel container we package it in for storage."
If you aren't already, Turza also recommends running a return line from your fuel regulator. That's because oxygenated fuels are more susceptible to heat. "These fuels sometimes have a tendency to go into vapor lock because of the increased under hood temps on these race cars," he explains. "I have seen guys run a deadhead regulator where the fuel is stuck in the carburetor and fuel pump when the car is under caution and the engine is barely running above idle. The fuel isn't getting used as fast so it has more time to pick up heat, and that's what leads to vapor lock. The oxygenated fuels are more sensitive to this, so I definitely recommend insulating your fuel lines and running the extra fuel back to the fuel cell by using a return line. That keeps the fuel circulating under caution so it won't heat up as badly."
Thankfully, Hendren says that after many hundreds of rebuilds, he hasn't seen any signs that running a good quality oxygenated fuel is any harder on a race engine than standard race gas. So if your racing class allows it, you are willing to make a few changes to your race car (and can stomach the higher fuel bill), an oxygenated race fuel may be an easy way to help squeeze a few more horsepower out of your racing engine and give you an edge over the competition.
