Inner working of an ELF/PC/voodoo

[Banshee]

If it wouldn't give away too many industry secrets, how does these unit work?

I understand that it detect boost and lengthen the time that the injectors remain open, but how does it tell what rpm the engine is at?

Since most of these superchargers will remain at one boost pressure for most of the rpm range, wouldn't it need more fuel at higher rpm then lower rpm given the same boost?

[99mx5]

These piggybacks basically work based on boost pressure. They sense boost and have a lookup table (map) to determine how long a signal is applied to a wire for an injector to extend the factory signal to hold the injector open to add more fuel. Some piggybacks (ELF, Voodoo) have potentiometors to tweak the map and adjust the injector signal.

Other devices such as the SS have 3D maps that use RPM and boost and software that allows the user to assign the value in the map for the amount of signal to be applied to the injector(s).

The new powercard uses injector load as a determining factor for adding fuel.

[Tom @ Fast Forward]

Actually, even the old/current JRPC uses RPM to help determine fuel required.

[99mx5]

Really?
The PC only has a pwr, gnd, 12v, and 4 injector wires and a boost sensor. Unless it detects RPM through ECU pulses of the injectors which could be determined by injector pulses which is activated by CAS sensor or crank sensor. I can understand that.

[Tom @ Fast Forward]

:) Simple huh. Why go look for a tach signal when you have injectors pulsing.