Overheating
Big external fuel pumps are notorious for overheating, so how do you avoid it? Assuming the application has the proper fuel pump installed, the most effective methods of reducing fuel temperatures are as follows. "First, if not already in place, install a return line to the fuel tank to keep the fuel moving," says BG. "Second, to avoid overworking the fuel pump, use correctly sized fuel lines and a vent hose. Third, by installing a heat sink, high fuel temperatures can effectively be dissipated. Routing fuel lines through the chassis rails of hot rods is currently fashionable, but this practice causes increased fuel-line temperatures and should be avoided."
Wet Flow Bench
Although it's still a relatively new R&D tool, Barry Grant recognizes the virtues of the wet flow bench and uses it to improve its product line. "Carburetors are precise instruments that contain almost 200 components, so it is essential they are tested before shipping," says BG. "Using the wet flow bench-powered by two 60hp electric motors and capable of generating 2,000 cfm at 20.4 inches of water-we check all carburetors before shipping. A nonflammable liquid with a specific gravity similar to that of gasoline is drawn into the carburetors. Then, float levels, accelerator pump circuits, fuel flow at wide-open throttle, and fuel flow through the idle-metering circuits are performed in addition to general checks for leaks." BG's fuel pumps and regulators are also wet-tested on separate flow benches. These tests check for leaks and fuel flow as well its amperage draw.
Regulator Placement
"Place the fuel pressure regulator at the end of the fuel rails instead of in front of them in EFI applications. Mounting the regulator before the rails will not allow it to adequately sense fuel pressure changes, hindering its ability to react. The two most common plumbing configurations for high-performance EFI applications are parallel plumbing and series plumbing. Parallel plumbing involves pumping fuel from the tank into a Y-block in front of the fuel rails, then distributing the fuel to both cylinder banks. At the back of the engine, a crossover hose connects the rear ends of the fuel rails. A fuel pressure regulator is situated in the middle of the crossover hose, which discharges excess fuel to the tank through the return line. Unlike parallel plumbing, series plumbing involves feeding fuel to all eight cylinders via one continuous circuit instead of two with the regulator positioned at the end of the fuel circuit. The main disadvantage of series plumbing in high-powered engines is an inconsistent supply of fuel to the last two cylinders in the series."
Fuel Volume
Be wary of blanket statements that outline specific fuel volume requirements for a given amount of horsepower. It's best to follow the manufacturer's recommendations for both fuel pump size and usage, as two different engine configurations can have vastly different fuel demands even though they make the same horsepower. "Methanol-powered engines have vastly different requirements than gasoline engines, as do race engines when compared with street applications," BG explains. Blown and nitrous'd engines require increased fuel volume as well in comparison to naturally aspirated motors. "A fuel pump operating in, say, a 650hp naturally aspirated application may be inadequate in a 400hp motor running a 250hp shot of nitrous, as pressure drops when nitrous is activated. Also, forced-induction applications require a fuel pressure regulator that is boost-referenced, which feeds additional fuel for every pound of boost measured."