We took you through a battery of fuel pump testing last month, while including a showdown of real versus "fake" fuel pumps. Continuing where we left off, our second part focuses on testing a number of OEM fuel pumps including some of the newer high performance models available on the market today. Keep in mind that our documented pump dyno numbers don't necessarily reflect your unit's performance and, with any dynamometer, numbers can vary from one unit to another. The most important thing to take away from this story is to understand the capabilities of your OEM/aftermarket pump and the importance of maintaining proper fuel delivery.
Higher fuel pressure (PSI) = less fuel?
The fuel pump is one of the most important components in an internal combustion engine. Keep in mind that fuel pumps supply fuel volume; they do not produce nor create the necessary pressure in the fuel lines. Turbocharged cars using a boost dependent fuel pressure regulator will witness fuel spikes as high as 100 psi when initially stomping on the gas pedal at WOT. As the fuel supply line pressure increases to compensate for fuel, the pump literally begins to slow down as it tries to push the needed fuel from the tank to the injectors. As shown in all dyno figures for RC Engineering's testing, in relation to psi pressure and flow characteristics, the numbers (flow) begin to fall significantly when pressure and amperage increase due to load.
For boosted applications, because the numerical boost value is added on top of the base fuel pressure, it's vital that the pump delivers the necessary volume at the elevated fuel pressures. So while a pump puts out healthy numbers at 3 bar, if you're boosting 2 bar it needs to put out the necessary volume at 5 bar. This is something to consider for those who have upgraded to larger-sized injectors but refuse, or simply haven't had the time or money, to replace your OEM fuel pumps.
When testing our pumps on the RC Engineering fuel pump dynamometer, RC used a set voltage of 13.5 amps to display the flow characteristics associated with the increase in voltage. In side-by-side comparisons of flow characteristics in correlation to an increase in voltage, amperage ratings as well as flow capacities were significantly higher as psi levels were raised. With most vehicles today, 13.5 V is the normal operating voltage for a fuel pump. As fuel demands increase, however, and audio systems and various interior and exterior components are being used, it causes a draw in amperage in the car and fluctuation in power output, rendering the fuel pump to increase and decrease in flow. To remedy the problem and keep voltage consistent, or if looking to increase voltage, manufacturers such as Aeromotive (Billet Electric Fuel Pump Controller) offer fuel pump boosters with excellent proven results. At low fuel demand the FPSC slows the fuel pump's duty cycle and fuel rate, which in turn reduces the unnecessary pick up of residual heat from the engine compartment. As demand increases, the FPSC returns the fuel pump to 100 percent duty cycle for maximum flow using pulse modulation technology.
"Increasing the voltage is actually a great method of getting a bit more flow if you need it. The fuel pump is one of the few components that aren't designed to work at the traditional 12-13 V. As far as any decrease in longevity, RC doesn't have any long-term data to support voltage versus longevity, but we can assume if you're taxing your fuel pump with excessive voltage, it's going to experience a shorter life span," says RC Engineering representative John Park.
A large majority of owners sporting high horsepower vehicles, such as the R34 Skylines and Supra TT, have implemented a dual or triple fuel pump system with much success. Running two or three pumps inside the fuel tank enables dozens of RB26 or 2JZ engines to push the 1,000-plus horsepower marker with peace of mind that sufficient fuel is being adequately delivered to each injector at high rpm. When using a multiple pump setup, it is imperative to rewire each pump separately rather than splicing both pumps into the single wire factory circuit. Using the same wire inline causes an overload in amperage within the wires and significant loss in voltage, causing less fuel flow than using the typical single pump method.
"Using multiple pumps (assuming there is enough space) is another way of increasing volume and pressure handling capabilities. Although you don't necessarily get twice the amount of fuel, the increase in overall flow is substantial and works well for a variety of applications," Park says.
Drawbacks with using more multiple fuel pumps is the additional cost of purchasing two to three fuel pumps, placement of multiple pumps in the fuel tank, rewiring the factory fuel system, and, if necessary, adding additional voltage regulator units dedicated to each fuel pump. Of course there's always the issue of one or more pumps going faulty.
A general rule of thumb is that every gallon of gas is equivalent to 5.8-6.5 pounds (weight vary is dependent on temperature). Let's say you're at the track and we measured out the gasoline to be 6 pounds per gallon. If you filled your 14-gallon Evo IX tank (notorious for suffering from fuel starvation at 1/4 tank empty) to max capacity, the total weight would be 84 pounds. That's dead weight to consider in an event that doesn't require weight penalty or need to run more than three laps per session. So what's a simple yet effective solution for those weekend track warriors looking to enjoy a little quarter-mile run or apex carving session without running into dangerously lean conditions? It's simply called a surge tank.
The theory behind a surge tank is simple. Fuel is stored in an external unit while being placed between the factory in-tank pump and lines leading to the engine. Fed by the pump, the unit prevents fuel starvation due to hard cornering, braking, and acceleration by storing additional fuel into the aluminum surge tank. Fed through an inline pump, the surge tank supplies an ample amount of fuel into your engine, should the OEM tank ever experience a hiccup or starvation from its design. A fuel surge tank offers a little added insurance for the hard-core drag, road race, or autocross enthusiast who plans on racing his vehicle without the fear of damaging the engine.
Integrated Engineering recently released a new concept in surge tank design with a billet system using a single or dual Bosch 044 fuel pump(s). This ingenious design keeps the pump body submerged over 75 percent inside the tank. Using the fuel to submerge the pump muffles the noisy pump, provides cooler pump operating temperatures for longer life, and ensures it will have fuel even on steep turns or accelerations where the OEM pump could experience fuel starvation.