Quote:
Originally Posted by bcfromfl
So...now I'm trying to learn more about all this, and I find the following at a link I Googled:
Problem with just adding larger injectors: The higher the fuel pressure, the harder the fuel pump has to work, and more electrical energy is required to open the fuel injectors.
What can go wrong with larger fuel injector upgrades? I often see builds with goals of 500hp and more using 1000cc fuel injectors because of the price jump to a larger injector. They assume they can simply turn the fuel pressure up to increase the flow of the injectors if they run out. While it may be true that 1000cc injectors flow over 1500cc at 100psi base pressure, it is simply not feasible to run that high of a base pressure on a regularly driven vehicle. Remember that a 100psi base pressure is 120psi at 20psi of boost.
At these high pressures, fuel flow is actually reduced in the rest of the fuel system. The resistance to flow in the fuel lines increases as the pressure increases, restricting flow.
Fuel pumps are rated at 43psi of pressure. Your 320lph fuel pump only flows 200lph at 100psi. Most in-tank fuel pumps have a built-in pressure relief valves that open at 100psi, making it impossible for fuel pressure to raise with boost using a 100psi base pressure. Even using a base pressure of 60psi will put serious strain on the fuel pump, causing potentially lean conditions and premature pump failures.
This invites the question...will a larger injector flow correctly at conservative supercharger pressures?
|
Not sure I am following you... can you clarify your question?
I don't think anyone here is cranking up their fuel pressure to add more fuel... I think most people stick with the OEM ~52psi and just upsize their pump and injectors. With a return setup and boost referenced regulator you could easily see 60+psi of actual fuel pressure at full boost with a modest setup, but the base pressure is still much lower in the 50's. Even the lower pressure model of the Walbro 450 has a working pressure into the 80's which would allow you to run 30psi of boost and still keep proper fuel pressure.
edit: I think I see what you are asking now... that link might be geared towards fuel systems with very few injectors... It's misleading to say "Its a bad idea to try to have 500hp with 1000cc injectors" without specifying if they mean 2 injectors or 200 injectors. 6 1000cc injectors is EASILY capable of 500whp on pump or E85. I ran out of injector at 538whp with only 600cc injectors on pump, and I am only running the stock 52psi regulator with no boost reference at all.