Originally Posted by
wfchobby
Hi,
as the others said injectors appear to be commonly driven by the switching of a negative to the injector. Taking that signal can be done, ive done it on my Audi from all 6 injectors for the purpose of driving a separate injector into the manofold directly after the butterfly, injecting h20 thru that injector on each injector cycle, length and speed. So i simply made a 6 input "or" gate using pnp transistors and combined the output to switch the output stage.
So because the negative is switched, i required a positive trigger pulse for the duration of the injector signal, see attached diagram. R1 and r2 setup base resistor current bias for the 557, D1 protects any spike from the injector from overvolting the base emitter junction, on the output side at the collector, the led and resistor are optional. This will give you a means to obtain an injector signal that should not interfere with the output stage of the ecu driving the injectors..but do at your own risk.