It’s common knowledge that big horse power engines need a big fuel pump (or pumps) to support that power. With most EFI fuel systems, the fuel pump works flat out to pump fuel up to the fuel rail where the fuel pressure regulator does what its name suggests – it regulates fuel pressure. Any unused fuel is then bled off by the regulator and returned back to the fuel tank via the return line. Selecting a correctly sized fuel pump for a high performance EFI engine is almost exclusively based on the maximum engine power output that is desired – this is an obvious fact which can’t be avoided.
However, while the focus usually surrounds reaching maximum power goals, what is often overlooked is how an EFI fuel system functions when an engine is not operating at maximum power (idle, cruise, part throttle operation or while on a low boost setting). In this case, a smaller amount of fuel is required by the engine and often a vast majority is returned back to the tank. The system still works, but there a number of drawbacks that need to be considered:
- Heating of fuel – When fuel is being constantly circulated to the engine and then back to the tank, it absorbs heat from the pump as well as from the engine itself as it passes through the fuel lines and fuel rail in a hot engine bay. Elevated fuel temperatures reduces fuel pump life/performance and also reduces fuel density, which can affect the tune.
- Fuel pressure regulator capacity – As most of the fuel is passed through the regulator at low engine loads, the regulator must be large enough to allow the entire fuel volume that the pump can produce through it. This means that a much higher flowing fuel pressure regulator is often required when fitting a larger pump and a larger diameter return line to the tank can also be required.
- High fuel pump and electrical load – With the pump running at full current and high speed constantly, the pump temperature is elevated and the fuel pump lifespan is reduced. Furthermore, the high current draw from the fuel pump increases the electrical burden which increases the alternator load and hence engine load without any benefit. Many high performance EFI pumps draw in excess of 15A when at full speed. It seems pointless to draw over 15A continuously when cruising around at low load if 1-2A will do.
- Fuel pump noise – While this is not such an issue on dedicated race vehicles, owners of road registered vehicles with a high performance EFI fuel pump often find the hum of their pump running constantly at full speed to be irritatingly loud during idle or cruise conditions.
An elegant solution to these four problems is to control the speed of the fuel pump relative to the engine’s fuel requirements so that the pump runs slowly at idle and progressively increases as engine load/speed increases. When done correctly, fuel pump speed control results in significantly reduced fuel heating, much lower noise and current draw at low loads and accurate control of fuel pressure using a either a stock low flowing fuel pressure regulator or even no regulator at all (in the case of closed-loop fuel pump speed control).
This fuel pump speed controller does exactly that and works by receiving a pulse width modulated (PWM) signal from an ECU. It is suitable for use with various devices containing brushed DC motors such as fuel pumps, cooling fans, and electric water pumps. Successful sustained testing has been completed with loads drawing up to 18A continuously.
The controller requires a constant low frequency (100Hz) pulse width modulated (PWM) input signal from an ECU or another similar device with a PWM capable low-side driver. Unlike many cheaper speed controllers on the market and despite the low input frequency, this controller will modulate the fuel pump at an ideal fixed high frequency of 20kHz which is above the audible range of a human ear as well as allowing for very consistent speed control. An output duty cycle of between 8% and 100% can be commanded, although our testing has revealed that most fuel pumps will not operate below 20% duty cycle.
While most aftermarket ECU’s that features a configurable general purpose PWM output table can be used with this controller, any Link G4+ ECU with firmware version 5.6.1 or later features a convenient open loop speed control function that allows the fuel pump speed to be defined versus fuel injector duty cycle. By taking the known size of the fuel injectors being used and fuel pump flow vs duty cycle & pressure data that we have collected for some of the most common fuel pumps that we sell it is easy to come up with a reasonable set of values to use for open loop speed control. We recommend using values that result in approx 20% more fuel flow than what the engine actually requires and letting a small (typically stock) fuel pressure regulator take care of the small excess. We provide instructions for setting up fuel pump speed control this way on a Link G4+ ECU that makes setting up this controller a breeze.
Available in either brand new or refurbished condition. Refurbished units are individually tested and cleaned.
- Fuel pump speed controller unit
- Connector kit with connector housing, terminals and seals
- Billet alloy mounting bracket