Fuel Injection

[kwklein]

I'm a newbie here so go easy on me...

My question is this:

without any change in duty cycle or duration can I increase the amount of fuel going into the engine by increasing the pressure?

This question/answer will help me on my path to answering the big picture questions...

 

[Greenlight]

Absolutely, the equation is:


New Flow Rate = Original Flow Rate x (New Pressure/Original Pressure)^.5


Of course at some point the system becomes "choked" and an increase in pressure will not increase flow.

 

[kwklein]

thanks! so increasing the pressure will increase the flow more than the negative effect pressure would have on volume?

 

[dgallup]

Static flow rate will go up with the square root of the pressure. This effect will continue to go up as long as the injector is strong enough to ovecome the system pressure. However, duration of injection will decrease slightly with increasing pressure because the start of injection is delayed while the electomagnetic force that opens the injector continues to build up enough to overcome the higher pressure. The injector will also close a tiny bit faster. As you keep increasing pressure at some point the rate of decreasing duration of injection will equal the rate of increasing flow rate, beyond that point dynamic flow will go down and shortly after that the injector will cease to open at all. All of the dynamic effects are also a function of dynamic pulse width, system voltage and the injector hydraulic and magnetic circuit design. If you keep the pressure increase small (1 bar or so) you won't have problems.