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Discussion and questions related to the course Motorsport Wiring Fundamentals
I attached a photo of my wiring schematic that I came up with for my car. I believe I have satisfied all basic DC wiring requirements and followed all the rules. I am however not an electrician and this is my first project of this caliber.
Please have a look and point out possible pitfalls or bad practices.
I have the pinout for all electrical components prepared and ECU pinout finished. Engine bay schematic is pretty straightforward now.
Please delete, double post
Looks OK, except the starter related circuits seem 'strange'?
Normal practice would be to hve the switches, like the wiper and starter push button, wired between the fuse and the relays
It was an oversight while drawing. The final version will have that corrected.
I wire my switches between the pin 85 of the relay and the ground, the same like they would be if they would be connected to an ECU. There's nothing wrong with triggering the relay via pin 86 with +12v, but I like them to be wired all the same way.
But yeah, connecting the switch to pin 87 kinda remove the purpose of using a relay!
I can do that. Not a big deal. Other than fixing the location of the wiper and starter solenoid relay toggle switches I have had two other things suggested to me in a Facebook group.
One is to have the ECU on a relay. It's only 3A draw, which is why I was confident to go without one.
The other thing is to wire the alternator charge cable before the master switch. Basically the other pole.
Thoughts on that, any downsides to either way?
Putting the alt power wire to the battery would prevent load dumping, which is a good thing. At the moment I think your kill switch wont work, as the alternator still provides power to the ECU etc when the battery is disconnected.
I am a bit lost on MREL, where does 87 go? is that what feeds the engine (injectors/ignition coils etc?)
I'd recommend a relay that feeds the ECU and injectors together and a different one for the ignition coils. Possibly the relay for the ECU suggestion is to keep noisy loads off the ECU's (assuming Ecumaster looking at the pins #'s).
Having the injectors and the ECU on the same circuit usually ensures that they seem the same voltage, which ensures the injector dead time calibration is accurate.
In any case check your rule book. Drifting us usually pretty open but certain rule books (NHRA for example) require the battery cutoff to kill all electrical power in the vehicle, not just kill the engine.
Thank you for your reply. Don't want this to sound rude or ungrateful, but I think you should have another look at how the 6 pole master switches are wired and work.
Alt charge cable to the battery side of the master switch is something I contemplated, but all instructions and google results have it go to the fuse box side. Killswitch should work. When it's switched off the fat poles and circuit 2 lose connection. Only circuit 1 of the master switch ia connected.
Circuit 2 (I will update this to tie in much sooner on the logic circuit, before all relays) is the "ignition switched power" here. So once that diaconnects, the IG pin of the alternator disconnects and remaining charge dumps to ground through a resistor on circuit 1.
Mrel does in fact feed all Injectors, Coils, solenoids.
Currently Mrel (noisy stuff) and ECU (Ecumaster classic) share the fuse box, but no wiring.
You are not the first one to suggest having a relay for the Ecu. I didn't plan for one for a few reasons, but I am willing to take advice. Reasons were, rules/safety devices don't require one, it's very little amp draw and it's ignition switched since the master switch is essentially an ignition switch in my car.
I hear you about Injectors calibration times. I will look into adding another relay. Might have to look into adding micro relays because these 30A ones are a waste for 3A loads.