PederJonsson wrote: ↑20 Dec 2019, 16:24There is no high pressure pump on earth that can change its displacement so fast as it would require for this application. Without a pressure regulating valve after the high pressure fuel pump the fuel parts after the high pressure pump would explode when you suddenly let go of the throttle at high rpm and there is zero demand for fuel.saviour stivala wrote: ↑20 Dec 2019, 13:41The fuel flow to engine as used in 2019. Between 3 and 4 low pressure electrically driven fuel pick-up pumps picks-up fuel from tank comartments and supply fuel at low pressure true a one-way valve to the fuel collector-pot. Fuel collector-pot vents air and access fuel supplied back to tank through a one-way pressur/vent regulator. Fuel from pressurised collector pot flows through fuel flow meter to feed intake of high pressure mechanically driven pump (normally driven by an intake camshaft) through a one-way valve incorporated in intake of high pressure pump. The high pressure pump delivers fuel flow to the injectors fundamentally proportional to engine RPM. The fuel cobsumed by the engine is also approximately proportional to RPM at full throttle. But at closed throttle, the engine uses no fuel. To match the fuel supplied to RPM at full throttle, the pump has a variable displacement mechanism actuated by a sophisticated pressure regulating device. The injectors fuel flow is controlled by SECU (standard electronic control unit) The SECU hardware and control software is common to all F1 engines, but the calibrations are free withen range permitted by FIA. All fuel that passes through the fuel flow meter must end-up in combustion chambers. There is no fuel return to the fuel tank and neither fuel 'backflow' through the fuel flow meter. The presurised fuel collector pot eleminates airation from the fuel supplied to the engine.
However the high pressure fuel pump is matched to the regulations so it cannot supply more fuel than the allowed amount below a certain rpm, above this rpm the excess fuel must be bled off by a fuel pressure regulating valve.
That’s the most stable way of controlling your fuel supply to the injectors. Now you have a constant pressure and flow(regulated) and only need to work with the timing of the injectors to match your demand from the engine.
F1 engineers can surely tweak and maximize this to better fit their demands but the basics will be the same.
So when you don’t measure the fuel flow that is dumped away you need to measure the fuel amount in the tank before and after the race to see if it corresponds to what you measured with the sensor. With a second fuel flow sensor you would have control over all fuel that passed the high pressure pump in every scenario.
So the potential to “cheat” in my opinion is to harvest/collect the fuel that is bled off from the pressure regulating valve and then introduce the fuel into the high pressure fuel pump when you have the demand for more power. Now you have more fuel available for the injectors than the fuel flow sensor can measure. As the engines are very “detuned” when it comes to fuel I believe even a smaller amount of fuel could make a big difference.
A likely scenario could also be that the term pressure regulating valve is just named as a safety valve. In one or another way the maximum pressure must be regulated as the high pressure pump is mechanical and works in relation to the rpm of the engine. The maximum fuel rail pressure is also regulated. On a DI engine you want as high fuel rail pressure as possible, this gives you a better consistency of your spray pattern related to the cylinder pressure.
No need for a regulator if the pump has a means of reducing or cutting its output to achieve the same.
For example you could use a variable speed drive or an internal relief mechanism in the pump.