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Discussion and questions related to the course Motorsport Wiring Fundamentals
Hi HPA members and tutors
I'm doing a k20a swap to a lancer, ditching the original harness and making one from scratch, including charge harness. I removed most body electronics except for lights and wipers, and the battery is relocated to back row seats. the engine is stock except for intake and exhaust, ECU is a G4x Monsoon, and i'm using the link A loom as a starting point. it's my first time and my background in electicals is limited to HPA courses and car forums, so here are a few questions before I start building the wires.
1. My battery relocation and kill switch i referenced this article: https://adaptronicecu.com/blogs/articles/battery-isolators-kill-switches-and-voltage-spikes
The 2 pole emergency kill switch in my diagram seems a bit redundant since the main relay (using a tyco v23132 high current relay) essentially does the same job cutting off power to everything as well as killing the alternator field supply. it's definitely not the ideal setup but if you guys think it'll work I'm keeping it that way until I upgrade it to a cartek isolator or something similar.
2. in the diagram i use 1N4004 diode as surge suppressor, for ignition coil i'm fitting the diode in the fusebox, but is it necessary to have a diode for each relay coil?
3. Fan override switch - wiring them according to this article: http://www.wildweasel.ca/HowTo/Auto/J-Body/FanSwitch.aspx any problem with this method?
4. Link ecu manual suggests connecting both ECU ground wires separately to engine block, but i thought in my case it would be easier connected to negative busbar then through 1AWG wire to engine block. which one is better?
5. not exactly wiring related but the G4x monsoon has a barb port (built in map sensor) and I don't know what that is usually used for. Do i leave it open to get a reference atmospheric pressure reading or connect a silicone hose to manifold? is there any advantage of using this over wiring to the factory MAP sensor?
the diagram might take some time to read at so I really appreciate anyone putting in their precious time to help!
1. What's the intended usage for this car? Note that neither of those battery isolators are FIA compliant. if you don't need FIA, then you probably want both installed. Reason is the circuit breaker should be as close as possible to the battery. And the switch I assume you want within reach of the driver.
2. I've seen a capacitor used as ignition noise suppression. Diodes are more common for motors such as rad fan or fuel pump.
3. Is that resistor actually needed? The article doesn't say why it's there. I've wired override switches to a fan relay straight to ground without issue.
4. Ideally the grounds should run completely separately and ground at the same point on the block (your star point)
5. The factory map or the built-in MAP sensor will work equally well. Using the built-in one has the advantage of saving you having to figure out calibration. Downside is that a long vacuum line is vulnerable to cuts or getting pinched.
1- This is only a practice car that can also be driven to the race track so I don't have to tow. Not racing under any sanctioning body, just want to know whether it's going to cause damage to alternator or other electronics. If it's fine i'm keeping it this way.
1. Theoretically, if you shut off that type of master switch while the engine is running, it could damage something. The FIA-approved switches come with a high power resistor, and that's what lets you shut it off while running, and the energy from the alternator gets routed safely through the resistor.