 FUEL SYSTEM SETUP
The first thing you should read and recognize from this article is one word; "System". The fuel system on your vehicle is just that by definition:
SYSTEM
-noun: "an assemblage or combination of things or parts forming a complex or unitary whole"
When you begin to plan your fuel system there is a short list of things to consider before you open up your wallet and start buying parts. Choosing the correct combination of 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. Mistakes in component selection could cause component failure, power loss, inconsistencies at the race track, or engine damage.
- How large is your engine?
- How much horsepower does the engine provide?
- Is this a street, off-road, or racing application?
- Is the engine fuel injected or carbureted?
- What fuel pressure is required?
- Is the engine supercharged, turbocharged, or are you using nitrous?
- Is the fuel being used gasoline or alcohol?
- If class racing, what do the rules allow?
- Do you have the budget to do this right the first time?
FUEL DEMAND
When you calculate fuel demand you need to look at engine size, horsepower, the fuel being used, and whether the engine is fuel injected or carbureted. It is useless to add too large pump to an underpowered engine, and the detrimental opposite if you use too small a pump. You can use 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. Too small of a pump 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 you have to take into account additional fuel demand. When your engine goes into boost or the nitrous system is activated, your fuel system must be capable to meet the added fuel requirements. On nitrous systems it is best to have a separate fuel system specifically for the nitrous.
FILTERING
Just because you have some clear glass $5.00 inline filter before your carburetor, does NOT mean you have adequately filtered the fuel system. There is so much crap in commercial underground fuel tanks, and your car's fuel tank, why take a chance? You should have filtering before your fuel pump(s) and also before the final destination (carburetor or fuel injectors). A good canister-style (Mallory #3140 or #3160) 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 is the minimum. Any dirt that enters the system could damage the fuel pump, regulator, or other components.
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 to be able to make it to the cruise and street racing that evening. The install was quick and sloppy. Not many days later he parked the car at his home that evening, not realizing the nitrous bottle valve was left open. That was not too serious of a problem, but 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 that the solenoid did not fully close.
Overnight the nearly full nitrous bottle slowly emptied into the engine. Though nitrous does not ignite by itself, when he went to start the car the next morning, 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 spark plugs
- Nitrous plate was broken in half
- Carburetor base plate cracked and throttle blades bent
- One mounting boss on the intake for the carburetor broken off
- One muffler launched right off the exhaust tubing
- Various broken bolts
I was working in a machine shop at the time and it was a fewq days later when 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 during installation, and did not follow required safety precautions. A simple filter screen on the nitrous line would have saved that engine and a costly hit to his wallet.
INTENDED USE OF VEHICLE
Different uses require slight changes to the fuel system. If you have a drag race application, you will want a system 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 can operate at full delivery for hours at a time. Off-road applications are subject to extreme shock abuse, and street applications have to operate a wider operating range, dealing with heat, emissions, and other handicaps.
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 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 economical, emission-compliant, and operate through a wide RPM range.
PRESSURE REGULATION
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 your engine. Too little or too much fuel pressure can cause air/fuel mixture problems, component damages 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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