Planning A Fuel System


The first and most important word in to recognize comes from the title of this article. That word is "System". The fuel system is just that, by definition---a system.

-noun: "an assemblage or combination of things or parts forming a complex or unitary whole"
When planning a vehicle's fuel system, first consider a short list of important factors before opening the wallet and randomly purchasing parts based upon advertising, friend recommendations, or some online article---including this one!. Choosing the correct combination of fuel system components is imperative to optimum output, consistency, and reliability. Quality fuel system components are not inexpensive, and installing the wrong parts make the costs that much higher in the long run. Mistakes in component selection can cause component failure, power loss, inconsistencies at the race track, or permanent engine damage. Here are are few questions to consider;
  • How large is the engine?
  • How much horsepower does the engine produce?
  • Is this a street, street/strip, off-road, 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?
  • Is the fuel type gasoline or alcohol?
  • If class racing, what do the rules allow?
  • Is the fuel system budget enough to do this right the first time?

When calcuilating fuel demand, the engine size, horsepower, fuel type used, and whether the engine is fuel injected or carbureted are the first considerations. It is useless to add a fuel pump that is too large to an underpowered engine, and detrimental to the opposite, when too small a pump is used. Please read our Fuelish Tendencies article to help determine fuel pump size for a gasoline engine.
Fuel supply is based upon two parameters; pressure and volume. The volume of fuel must be matched to the requirements of the engine throughout the RPM range. A pump that is too small will starve the engine for fuel. The delivery pressure much meet component requirements so as to maintain correct air/fuel ratio, fuel atomization, and instant fuel availability (carburetor float bowls or fuel injector requirements).
On forced induction (supercharged or turbocharged) or nitrous applications, taking into account additional fuel demand is imperitive for engine survival. When an engine enters a boosted state or the nitrous system is activated, the fuel system must be capable of meeting the addiotional fuel demand instantly, efficiently, and repeatedly without fail. On nitrous systems it is best to have a separate fuel system specifically for the nitrous.
Just because someone installed a clear, viewable $5.00 inline filter before the carburetor does NOT mean the fuel system is adequately filtered! There is so much crap in common commercial underground fuel tanks that we never see, and also inside of a vehicle's fuel tank, why take a chance with a basic filter? Proper filtering should begine before the fuel pump(s) on the vehicle and also before the final destination (carburetor or fuel injectors). The bare minimum includes a high quality canister-style or inline filter on each line before the fuel pump, then a cleanable screen inline filter before the carburetor, injectors, or nitrous system fuel solenoids. Any small particle contaminant that enters the fuel system could easily damage the fuel pump, regulator, or other components---and that does not include possible engine damage as a result.
Many years ago an acquaintance of mine installed a plate nitrous system on a pristine original 1968 Camaro RS. He and another friend installed the kit one afternoon in haste so they could make it to a cruising event and possible street racing that evening. The install was quick and sloppy. A few days later, after horsing around most of the morning and activating the nitrous while making trial runs on a road outside of town, he parked the car at a friend's home for a visit. Later that evening when he returned to his vehicle, not realizing the nitrous bottle valve was left open, he went to start the car and go home. Actually, leaving the bottle valve open is not too serious of a problem. However, the fact that they did not install a filter (screen fitting) in the nitrous feed line before the solenoids was a problem. Debris had accumulated in the nitrous feed line during installation and entered the nitrous solenoid enough to prevent the solenoid from fully closing.

Over the many hours he was there, the nearly full nitrous bottle slowly emptied into the engine. Although nitrous does not ignite by itself, when he went to start the car it did not want to start as smoothly as it had in the past. Thinking it was starving for fuel he pumped the throttle a few times and he experienced the best ignition of his life. When the engine fired, the residual nitrous and cold-start fuel ignited, or should I say exploded. The short list of damages included:

- (2) broken pistons
- (1) bent connecting rod that partially exited the cylinder wall
- (1) pushrod through a valve cover
- Various broken rocker arms
- A few bent valves
- Camshaft broken in two
- (2) destroyed (shattered) spark plugs
- 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 tubing
- Various broken bolts
- A dented hood and innner fender on an otherwise pristine Camaro RS

I was working at a local automotive machine shop at the time and although I had heard about this eent immediately, it took him a few days before he brought in the various parts of what was left of his engine to see if we could salvage anything. All that damage because he and a friend were not cautious and responsible during installation, and did not follow necessary safety precautions. A simple filter screen on the nitrous line could have saved that engine and a costly hit to his wallet.

Different uses require slight changes to the fuel system. On a drag race application, design a system that is optimized for drag racing. The same holds true for circle track or road racing, street, or off-road. Drag race applications operate for seconds at a time, while circle track applications can operate at full fuel delivery for hours at a time. Off-road applications are subject to extreme shock abuse, and street applications have to function efficiently over a wider operating range, dealing with heat, emissions, and other concerns. All demand safety and reliability.
For most circle track applications the rules mandate mechanical style pumps. For these applications a belt-driven pump is more efficient because of the run time. Drag racing applications must fight G-forces at launch and save as much weight as possible. Plus, a drag race engine is not operating at near steady-state RPM as a circle track car. The acceleration of a drag car mandates larger output pumps, and higher instant demand. Off-road applications need to survive jumps and odd travel angles from the terrain, causing various delivery concerns. Street applications are abused by heat, road debris, the dirtiest fuel, and have to be relatively economical, emission-compliant, and operate through a wide RPM range.

Proper fuel pressure is very 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.

POOR System --- (one large system with two regulators in series "not recommended")
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