The stock Honda fuel pump will be used to provide required fuel pressure. As installed in the Lupo 3L, the 1.2L engine did not require a fuel pump to provide head pressure to the engine driven fuel pump. However, the fuel pump will be retained to preserve the original Honda fuel system in order to reduce system development headaches. We don't want to make too much work for ourselves.
Just because we're maintaining the old Honda fuel pump doesn't mean we can't make it a bit more efficient. Because the 1.2L engine doesn't require positive pressure we can reduce the output pressure of the fuel pump. We'll start by targeting approximately 7 psi and see how that works. Traditionally a mechanical pressure regulator would be used to regulate pressure. But to conserve energy we'll use Pulse Width Modulation (PWM) and a few cheap electronic bits to control the speed of the fuel pump by rapidly switching the fuel pump on and off. The result will be the fuel pressure we desire.
Of course the whole shooting match will be controlled with an Arduino microcontroller. Using a potentiometer as our input to the Arduino, we'll be able to set fuel pressure from 0 psi to the maximum operating pressure of the pump. Depending on our emissions solution implementation, we may need to set a specific fuel pressure for a diesel dosing injector. In that case we'll be able to dial up exactly what we need in the future as the emissions system takes shape.
