Designing the Optimum Fuel System
The first and most important term to focus upon comes from the title of this article. That word is “System”. The fuel system is just that, by definition—a system. Understanding what defines a system and the planning involved for a specific vehicle is the first priority.
- How large is the engine?
- How much horsepower does the engine produce?
- Is this a street, street/strip, off-road, marine, RV/Towing, or race-only application?
- Is the engine fuel injected or carbureted?
- What fuel pressure is required (this is determined by many factors)?
- Is the engine supercharged, turbocharged, or using nitrous?
- Does the application use gasoline or alcohol for fuel?
- If class racing, what do the rules allow regarding component selection?
- Is the available budget adequate to create the proper fuel system for the application?
Fuel Demand
Filtering
Many years ago an acquaintance installed a plate nitrous system on a pristine, original 1968 Camaro RS. He and another friend hastily installed the kit one afternoon so they could show it off at a cruising event and possible street racing later that evening. The install was quick and sloppy. A few days later, after repeatedly activating the nitrous during a few more test runs on a road outside of town, he parked the car at a friend’s home for a visit. It sat there for a few hours and later that evening when he returned to his vehicle—not realizing or really caring that he had left the nitrous bottle valve open—he went to start the car and go home.
To be clear, leaving the bottle valve open is not too serious of a problem—if a system was installed correctly. However, the fact that they did not install a filter (screen fitting) in the nitrous feed line before the nitrous solenoids was a problem. Days later, the excuse was that the person helping, A) did not feel it was necessary, and B) what they had was not the proper size. Debris accumulated in the nitrous feed line during installation and entered the nitrous solenoid enough to prevent the solenoid from fully closing.
– (2) broken pistons
– (1) bent connecting rod that partially exited the cylinder wall
– (1) pushrod through a valve cover (this was one of the most interesting to see)
– Various broken rocker arms
– A few bent valves
– Camshaft broken in two
– (2) destroyed (shattered) spark plugs
– The nitrous plate was broken in half
– Carburetor base plate cracked and throttle blades bent upward around the cross shaft
– One mounting boss on the intake for the carburetor broken off
– One muffler launched right off the exhaust piping
– Various broken bolts
– And, a dented hood and inner fender on an otherwise pristine Camaro RS
Proper filtering of the fuel itself is just as important. If an engine goes lean (lack of adequate fuel pressure or volume), engine damage can and will occur. The more powerful or modified the engine, the more important this becomes, and greater the chance of catastrophic failure.
Intended Use of Vehicle
Fuel Pressure Regulation
Proper fuel pressure is important for a variety of reasons. We detail the differences between dead head (blocking) style versus return (bypass) style regulators in our Fuelish Tendencies article. Maintaining correct fuel pressure is important to the consistent and efficient operation of every engine. Too little or too much fuel pressure can cause air/fuel mixture problems, component damage from lean conditions, lost power, lowered efficiency, higher emissions, and shorter engine life. Example:
POOR System — (one large system with two regulators in series “not recommended” … and no filters after regulators)
Good Street and Street/Strip System … Return regulator system on carbureted applications. Note however that it is missing a filter after the regulator. Oops!
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Please review other Fuel System related tech articles