We already know the main selling point for racing with alcohol fuel (methanol) in classes where it is allowed: In an engine tuned correctly it can make more power than gasoline. That's all you need to know, right? But alcohol is also a tricky fuel that is notoriously hard on engines, especially wherever aluminum is involved.
The problem with alcohol is the fuel evaporates quickly, attacks aluminum, and offers virtually no lubrication, unlike gasoline. These drawbacks don't offset the fact that you can use alcohol to make gobs of power, but care must be taken with your weekly and off-season maintenance programs. Some of these precautions may seem a bit unusual if you are switching from a gasoline class to one that allows alcohol, but they really aren't major once they become part of your routine.
"The physical properties of the fuel are unique," explains Brad Cauzillo of Kinsler Fuel Injection, which manufactures some of the most respected mechanical fuel injection systems for Sprint Car racing. "Methanol dries relatively quickly, and it attracts moisture which can contaminate the fuel. When it dries it first turns to a gel. In the next phase it starts to clump up, and in the last phase it turns into something a lot like sand." In mechanical fuel pumps, the barrel valves, and other components used in alcohol systems, there are very tight metal-to-metal clearances, so getting sand into the system is detrimental.
Mechanical fuel injection...
Mechanical fuel injection systems such as this one from Kinsler Fuel Injection are common in Sprint Car racing and feature many moving pieces. If they aren't protected from the harmful effects of the alcohol in the racing fuel, performance can begin to suffer quite quickly. Courtesy of Kinsler Fuel Injection
"Another problem is methanol causes scaling," continues Cauzillo. "There is a chemical reaction that occurs between the aluminum and the methanol. That's why raw aluminum doesn't survive a long time if you don't maintain it. [Anodizing forms] a helpful protective coating, but the methanol will still eat through it."
Cauzillo recommends flushing the fuel system after every race. It should be done the next day if possible. Believe it or not, one of the best ways to do this is with race gas. With a mechanical injection system, you can plumb the fuel pump to an external fuel tank, install a very lean main jet, and crank the engine. It should crank, sputter, and die, but that will be enough to adequately flush the fuel pump, clean out the main jet, and wash down the combustion chamber and cylinder walls. But Cauzillo says the backside of the high-speed and secondary jets will not see enough fuel pressure to operate, so they still need to be removed and cleaned by hand. A lubricant/dispersant such as Marvel Mystery Oil seems to work well for this purpose. Drain the fuel tank and cap off any fuel lines that may have alcohol in them. Since moisture in the air contaminates the methanol, the system must be sealed off from the atmosphere as much as possible.
Of course, now that all the alcohol has been flushed out with gasoline (it needs to be race gas to avoid detonation problems), you need to have a way to get the gasoline out when the new season begins. It may take a little work to get the gasoline flushed out and the engine running on tune with the alcohol again, but it's worth it.
This is what you want to avoid...
This is what you want to avoid at all costs. This is a high-speed bypass valve that was in an engine where the methanol fuel wasn't properly flushed. It dried in the valve and created this deposit, which has the consistency of sand. Courtesy of Kinsler Fuel Injection
If you don't have that kind of time every week, Cauzillo says there is another option. A few fuel and oil manufacturers offer an alcohol additive that adds lubricity to the fuel. "Lubricants can help reduce corrosion," he explains. "There are a lot of products out there, and there are a handful we've tested that work well. The M2 brand that VP Racing Fuels manufactures is an upper-lube additive and works well. It's translucent and doesn't change the weight of the fuel. All you do is add it to the fuel and go race. A quart mixes with 35 to 55 gallons. It helps reduce the corrosion and adds lubricity to the methanol. That works really well for the guys who might lose a crew member for a week whose job was to flush the fuel system."
If you are running a carbureted engine, you can do the same thing. Many racers running carbureted alcohol systems keep a separate carburetor jetted for gasoline to flush the engine. Simply pull the alcohol carb, cap off the fuel feed lines that contain alcohol, bolt on the gasoline carburetor, and plumb a line from the fuel pump to an external fuel can. When you crank the engine and run it for a few seconds, it will flush everything from the fuel pump to the exhaust valves.
Next, the alcohol carburetor needs to be cleaned. This is as simple as draining the float bowls, pulling the metering blocks, and blowing out the jets, the float bowls, and the main block. Follow that up by giving everything a nice coat of Marvel Mystery Oil before reassembly.
After you have completed the final event of the race season and you are preparing your race car for winter storage, there are a few extra measures you should take. If you are racing a mechanically injected Sprint Car, Cauzillo recommends removing the mechanical pump and barrel valve, oiling them with Marvel, and capping them off. Next, disassemble your valves, clean them, and inspect for excessive wear on the poppet heads and on the diameter of the poppet. "Also," he says, "check the O-rings to see if they are swollen-maybe you have run some additives that have not worked well with that O-ring compound. If so, and you notice the O-rings are swollen, hard, or cracked, go ahead and replace them.
 At the end of the season,...  At the end of the season, pull the fuel cell from your race car and perform a complete disassembly and inspection. Begin by draining the cell and flushing out any remaining fuel and fumes with clean water. Here, the bolts holding the top of the cell's steel container are being removed. Courtesy of ATL |  Pull the bladder from the...  Pull the bladder from the container and check for cracks, which is a result of the bladder rubbing against a portion of the steel container. Courtesy of ATL |  Pull the foam out of the bladder,...  Pull the foam out of the bladder, dry the interior of the bladder with a clean cloth, and inspect the interior in the same manner the exterior was inspected. Courtesy of ATL |