Hi all, I would like to connect some custom circuitry to each line (coil and injectors) but am unsure if the ecu has enough juice to drive my electronics as well as perform its duty. Does any one know how many milliamps the ecu can provide to the coil packs and to the injectors. Or what the z32 coil requires to operate effectively (specifications), ditto for the injectors. any ways if any one has any info on the above it would be appreciated. thanks
OK each injector will draw under 2 amps at full saturation. The ECU pulls low (to ground) for *blah" Ms injector opening time and switches the injectors directly. The ignition system is in two parts. You have from ECU to ptu. Nissans typically employs a positive squarewave +5v waveform (circa) 3.5Ms and the ptu will trigger off the falling edge. The output side of the PTU, ptu to coil pulls the ignition coi -ive to ground, Typically (circa) 4 amps at full saturation. The issue you have here is dealing with high voltage back emf from the injector and coils. When you switch an injector, you set up and collapse a magnetic field around a coil which works similar to an ignition coil and induces a high voltage spike on both sides of the injector. This spike is dampened by the battery on one side and the injector drivers are heavily protected against back EMF spikes in the ECU Ignition coil primary side back EMF can be several hundred volts as the magnetic field collapses over the primary windings. Typically, the switching transistors in the PTU are rated to at least 400v back emf supression The vast majority of manufacturers use an ignition switching transistor (PTU) external to the engine ECU to help minimise induced RF noise which can severely affect touchy sensor circuitry such as knock sensors and crank angle triggers. So, direct electrical connections to both the injector and ignition power supplies will be heavily attenuated to guard against high voltage back emf spikes. E
I was aware of the emf on the coil lines, was hoping the injectors were going to be a bit cleaner to sample. I had assumed the coils would be noisy but low frequency, where as the injectors would be higher frequency but cleaner signal. So that assumption is wrong. I have isolated my circuits using an schmitt triggered opto coupler hoping this would remove the spikes. As it turns out it doesn't quite get them all, so now I am looking at introducing an rc debounce circuit after the coupler, but this is causing me grief so I was wondering if I could place it in front of the optocoupler. It was this that instigated my initial post as I am concerned the parasitic drain might cause the injectors/coils to not work to the requirments of the ecu tune. Having said all that I was unaware of how many amps the components have access to. Might mean I can get away with moving my debounce circuit forward. I was ignorant of the coil lines being hit with high voltage spikes, so that bit of information changes the requirements of my components some what. thanks for the info, very helpful.
