The carburetor alone is not...
The carburetor alone is not the fuel system. Instead, the carb is a component within the whole fuel system. It's no more important from a systemic perspective than the fuel lines. The system has to work in complete harmony as a whole or the performance of the car suffers.
The Saturday night racer faces some very real issues with the fuel systems in their cars. The demands on the fuel system can make or break a racing program depending on the level of preparation that the racer places on the system.
From a systemic perspective, the fuel system isn't that complex. The whole system will usually include a fuel cell, some fuel line, a filter or two, either a mechanical or electric pump, and the fuel delivery device, either a carburetor or possibly fuel injection. Depending on the complexity of the fuel delivery device there may also be a fuel pressure regulator, a fuel pressure gauge, and a return line to the fuel tank or fuel cell. The higher the power level of the engine, the more complex and involved the system requirements will be.
It's a simple equation: As the power levels climb, the fuel system will get more and more complex.
For Saturday night racer applications, the fuel system doesn't start in the car, but at the point we as racers start to control the fuel. In this case, that's the point of sale for the fuel. Racers may bring their own fuel to the track or they may purchase fuel from a vendor at the track.
While it doesn't look like...
While it doesn't look like the filter is easy to work on, in reality it's fairly accessible and in a location that protects the fuel lines and the filter from damage due to an errant rock or dirt clod.
The fuel may be transferred several times prior to it ever reaching the fuel cell or tank in the car. It's in this manner that we can introduce variation into the fuel system through contamination by dirt, water or by mixing different grades or ages of fuel. Any way you look at it, we have the opportunity to maintain or degrade the quality of the fuel. So for the Saturday night racer to more precisely control the fuel system, we need to really understand the process of how we move and use the fuel.
Once the fuel is in the tank or the fuel cell, we still need to be concerned about the cleanliness of the fuel. Fuel cells don't last forever and the foam inside the bladder can break down over the course of a season or sooner, depending on the fuel you are running. If this happens, the fuel will be contaminated by the foam and can cause system problems. The foam should be replaced at the intervals suggested by the fuel cell manufacturer. Racing fuels can be very caustic depending on the chemicals used as additives in the manufacturing process.
By the same token, if you're still using the OEM tank, you're not home free just yet. It's entirely possible that the tank has seen a good number of over-the-road miles and is possibly or more than likely contaminated with rust and scale after many years of use as a grocery getter. You may want to remove the tank and have it cleaned. The truth of the matter is that once the OEM tank is removed, you might as well think about installing a fuel cell just for the safety that this type of tank offers.
This Dwarf Car has a very...
This Dwarf Car has a very clean setup for the fuel cell. It's mounted solidly to the chassis and is fairly well protected. This isn't a brand new car but one that is very well maintained.
Some gasoline blended for the racing industry is very hard on the rubber components of the fuel system. This can be the lines, gaskets and any diaphragms. These "rubber goods" are especially sensitive. They're synthetic rubber and plastics, but they're not completely impervious to the chemicals in fuel. Depending on the type of fuel you run, it can cause some rubber goods to degrade and the performance of the car will suffer.
You also need to be concerned if you're running alcohol, as alcohol is hydroscopic, meaning that the alcohol will absorb water out of the air. So if you live in an area that has high-ambient humidity and you're not exercising great care to prevent your fuel from undergoing exposure to the air, you will get water in your fuel. Alcohol is also very corrosive to aluminum parts. If you allow fuel to sit in the lines or in the carburetor for extended periods, you will get corrosion. Even the steel portions of the fuel system are subject to rusting from alcohol fuels due to the higher instances of water in this fuel. The use of alcohol fuels will require greater fuel system maintenance just to keep the system clean.
The fuel line started out...
The fuel line started out as a flexible neoprene line, then it was joined to a hard line as it passed through the driver's compartment. At the engine, the hard line was replaced with another neoprene fuel line. Hose clamps were used to secure the line joint and to secure the fuel line to the chassis to keep it from moving and becoming damaged.
A big funnel with a filter...
A big funnel with a filter in it and a translucent fuel jug. This Modified uses alcohol so the translucent fuel can is not a problem. Notice the dirt near the filler neck on the fuel cell. Take care that no dirt is allowed to enter the fuel cell during the fueling process.
In this installation, the...
In this installation, the line exited the tank and was routed to a fuel filter, then to an electric fuel pump, then a fuel pressure regulator was installed. This is a fairly typical installation. All that is missing is a fuel pressure gauge in the dashboard.
This Street Stock racer has removed the metal OEM fuel lines and replaced them with synthetic rubber line. Notice the exit point on the firewall where the fuel line passes through. The fuel line is run through the tube in the driver's compartment. You'll find this type of fuel line arrangement in NASCAR Cup racing. The only thing this racer could improve is the routing of the fuel line in the engine compartment. The fuel line is on top of the upper control arm.
The fuel is routed from the tank to the fuel pump through fuel lines. If you're still utilizing the OEM fuel lines, they're usually made up of a combination of hard lines, usually made of steel or flexible steel lines, and rubber or neoprene hoses. Steel lines are usually very durable. The only caution is that in the original OEM applications, they weren't designed for frequent disassembly, which can lead to premature wear at the fittings and threaded joints. Make sure the fuel lines are routed in such a way that they won't move excessively. A fuel line can become damaged by suspension components traveling through their range of motion, causing leaks. If you're running the fuel lines through the passenger compartment, most racing organizations require that the line be run through a section of steel tubing to protect the driver from potential leaks.
The majority of cars at the track will have an engine-mounted mechanical fuel pump. These pumps usually run off of an eccentric on the camshaft or possibly a belt-driven pump. These pumps are diaphragm, piston, or gear-type pumps for engines requiring a higher volume of fuel. These types of high-volume pumps are usually found on engines running alcohol or very high horsepower gasoline engines. Some racers have opted to remove the mechanical fuel pumps and use electric pumps. But there are issues with electric pumps. Some racing organizations don't allow them due to the fire hazard when a fuel line is damaged and the pump continues to run on a car involved in a crash. That said, there are a good number of racecars using electric fuel pumps with no problem.
The location and the type of fuel filter is an area of concern that could take up a great deal of text. There are two schools of thought on this issue: one, place the filter between the tank and the pump; and two, place the filter between the pump and the carburetor. I haven't seen any data showing an advantage to either method. But placing the filter between the tank and the pump has advantages. It keeps the pump from dealing with any debris that could plug or damage it.
Notice the fuel pressure gauge...
Notice the fuel pressure gauge on the far right. Fuel pressure is a good addition to any instrument cluster. This gauge is instrumental in monitoring the performance of the fuel system.
Placing a filter between the pump and the carburetor offers some positives, with the biggest being that it is usually easier to change or service the filter. Experience has revealed that the easier any part of the car is to work on, the more frequently it will get serviced. This point about maintenance often leads to many Saturday night racers installing a fairly large high-flow filter in the line from the tank to the pump and a finer filter between the pump and the carburetor. This gives the racer some operating margin.
Depending on the sensitivity of a carburetor, many racers may require the addition of a fuel pressure regulator. The regulator is mounted between the fuel pump and the carburetor. If you're going to run a regulator, you should also run a fuel pressure gauge. The pressure gauge is one tool that you can't do without. Granted, some pressure regulators have a type of gauge built into the regulator face in the form of pre-set figures that are supposed to equate to a given or indicated pressure. You still need a gauge to monitor the system to see what you're getting at the carburetor.
The fuel system isn't a mystery, nor is it overly complex. The premise is quite simple-route fuel from the tank to the engine. The execution can be quite elegant and very simple. Using care, common sense, and good sound engineering practices, a trouble-free fuel system is something that will serve the racer well and be a key contributor to winning. Next month, we take a look at fuel transportation.
A high-volume fuel filter...
A high-volume fuel filter with a replaceable paper filter element. These filters are also available with a stainless steel filter element that is washable and reusable. This is the type of filter that you will need for high-horsepower applications.
A disposable canister filter....
A disposable canister filter. This type of filter can be purchased at most auto part and racing supply stores and is made by a number of different manufacturers.