Best EFI System

[olddog]

Originally Posted by lvhdude

Most EFIs run same kind of fuel pressure? All use a return line?

Ford EFI pressure was 39 psi with vacuum line disconnected and the pressure drops 1 psi for every 2"Hg of vacuum. This makes the pressure from the inlet side of the injector to the outlet side constant. This is true with the older systems that had a return line.

The return line was done away with sometime after 1995. I read it was done to meet EPA requirements. I believe the fuel pump speed is modulated to control the fuel pressure on the newer cars. They may also run more fuel pressure.

The earliest systems used MAP sensor (measured manifold vacuum), throttle position, and engine rpm to estimate the amount of air entering the engine, via a complex calculation. You change anything that affected engine breathing and the calculation would be off.

Then they went to a Mass Air Flow meter to directly measure the air going into the engine. MAF is superior and can handle a lot of engine modifications. Few aftermarket EFI uses MAF. MassFlow is one company that does.

The throttle body injection systems basically mimic a carb. They are a little better than carb in accuracy. A lot of expense for little improvement in my opinion.