Discussion and questions related to the course EFI Tuning Fundamentals
my question about the dead time is when the engine operate at idle at 3bar fuel pressure set on fuel regulator then we get into the boost level to 1.5bar what makes the fuel pressure encrease greather then 3bar pretty much add 1.5bar on top of the 3bar that i have the fuel regulator its set up to operate at idle should i use the high number dead time or just set it with the 3bar dead time provide from the manufacture?
example on the injectors sheat we have 43.5psi up to 70psi dead time
wich one its the right number to chose?
The differential fuel pressure (ie absolute pressure in the fuel rail minus manifold absolute pressure) is what the injector data sheets refer to. So if you have your fuel pressure regulator plumbed to the manifold pressure as the air pressure reference, then the differential pressure remains constant probably 3 bar if you set the fuel pressure to 43.5 psig with the engine stopped, or with it running, but the pressure reference disconnected.
example with the engine stop and igsw on the fuel pressure its set to 3bar then with engine running at idle it will drop to consistance 2.7bar then running the engine the from 2000rpm and above the fuel pump speed will encrease and fuel pressure going up to around 4bar within zero boost then at full throttle open it will rich 4.5bar of pressure and stay for the longs as i'm boosting...would that change anything on dead time previous settings or it will be compansated by the injectors pulsewith?
So is the ECU controlling the fuel pressure by adjusting the fuel pump speed, or do you have a fuel pressure regulator?
The reason for asking is: with the engine off, fuel pump on, the fuel pressure of 3 bar and a fuel pressure regulator plumbed correctly should be the exact same as engine running at 0 boost (ie, ambient manifold pressure), but you say that it's 4 bar.
That doesn't make sense, the fuel pressure shouldn't go up unless the fuel pressure regulator is seeing an increase in pressure. Are you sure your boost pressure is calibrated relative to ambient?
If you were using a gauge sensor (ie, relative to ambient), and treating it as absolute, it would be off by one atmosphere of pressure (1 bar), so it would indicate 0 bar when you really had 1 bar of boost.