Fuel Sytem Tune - Fueling The Equation

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.

Filters
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.

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.