Main wiring harness from scrath... a few questions

[unfrgivn]

This car is gutted and used 95% for road racing, it will see little to no street time, but I want to wire up signals, headlights, and stuff to pass inspection because I don't have a trailer 100% of the time to get the car to the track. The car is a '93 Hatch with a redtop SR. I know the ECU is not from a stock 240, but the power hookups should be the same for both so all my questions pertain to the stock s13 wiring harness.

I know a decent amount about electronics and wiring in general, but haven't done much with car electrical systems, so this will be fun.

Questions Begin-------------------------Instead of the stock system where you have several different stages of powered devices CONSTANT 12v, ACC, IGN, START... I plan on having a master kill switch off the battery which then gives power to a momentary switch and a relay to power the starter solenoid, as well as power to a main fuse block which runs all the circuits for headlamps, brake lights, wipers, signals, ecu, gauges, etc...

1. Charging System: If I ground the alternator to the engine and run the other large bolt to +12v on the battery through a 100A fuse is that good enough, to charge the battery? Do I need to worry about the 2-wire plug if everything is just runing off the battery? It looks like in the FSM that on the alternator plug the white wire joins the wire running to battery+ before the fusible link, and the white/red wire runs through the SMJ to the charge light on the dash and is powered from the 10A ignition on fuse. I don't care about the charging light or anything, but if I need it then I can just wire up an incandescent light at the end of the white/red wire and connect the other end to ignition on power?

2. ECU Power: Since I have no main engine harness anymore and the plugs for ECU power over by the battery tray are gone, I need to re-think this. I've looked at the FSM many times, but I get very lost in the huge mass of stuff that I'm no longer using. I assume ECU-Backup power is a constant 12v for when the car is off so the ECU doesn't loose anything stored in memory, Then there are 2 large power wires which can just be on when my master kill switch is on, and the last wire is the orange (ignition start wire) that plugs into the ecu along with the speedo/tach/consult plug that goes over to the driver's side. Is this wire also on when ignition is on or what? Does it normally get power from the alternator at the fuse box and can therefore just get power as well when my ignition kill switch is on? In short what exactly does the Ignition Start Signal wire do?

3. Headlights: Once again I have read the FSM EL section so many times my head hurts, because some of the wiring diagrams are crazy with all the different options, high-beams, running ligths, headlights, motors, dimmer, etc... I want to run a simple switch that pops up the motors and turn the lights on, lowers the motors and kills the lights when off. I could use a DPST switch and hook up a timed-relays to each pole for sending the popup motors a 2-second singal because when constant power is applied to the motors they start to short after they fully open/close. I know stock there is a timer box that controls this, but I think using a timed relay will work just the same. There will be a 3rd relay that powers the lights off the same pole as the lights up relay. I am sorry this is so confusing, because I am very confused myself. Does what I'm saying make any sense at all or has anyone created a custom headlight wiring harness without the use of the stock timer assembly or stock headlamp relays?

I have everything laid out on paper and it's starting to make sense, but any insight into the above 3 systems would be greatly appreciated!

[slipnfall]

sorry i don't have time to give a more verbose answer, but about the starting system. If that orange wire is the one I think it is, yes you will need that. It gets power when the ignition key is in the 'start' position(cranking). This is considered a 'cold start' signal wire. It basically tells the ECU you are starting, so it sets up non-sequential firing and provides extra priming to the fuel pump(IIRC). Anyways, the engine will start without this signal going to the ECU, but it will be much harder to start: you'll have to crank and be on the gas.

Please excuse my ignorance, but why exactly are you worrying with removing all this wiring? I mean, I'm all for simplifying things, but is it worth the effort? You're retaining exterior lights, ECU, stock gauges... seems to me like you're just going to be pulling single wires out of harnesses...

[s13sr20chris]

1) i would try to mimic the stock setup as much as possible. you can go with big ground wirebig + wirelittle + wire from plugwarning wire i would try to use all of them

2) you need to make sure the orange wire at the ecm sees 12v during cranking. believe me, the sr wont start without it!

3)the headlamp circuit is a big pain in the bum. if i were you i would do one of two things. keep it stock. or have the lamp up/down be a manual operation. by this i mean wire up the lights so they work. when you are on the street or at the inspection station go out and turn the manual knobs untill the lights are up. when you race, turn them down. you could have the setup you mentioned above but its pretty complicated.

[unfrgivn]

Thanks guys...

The car is already gutted of every wire because in the process of stripping wires out of the harness one at a time, it all of a sudden became a huge mess by the SMJ, and I said screw it, the car's electrical system is not that complex to start from scratch. Plus then I will know for sure where every wire is running in the event of diagnosing or short or whatever. I also will not be using the stock dash, headlights or gauges for too much longer so it's nice to have everything done by hand.

I will connect the orange ignition start wire off the same momentary switch that signals the starter solenoid (turn key replaced with momentary push button) and that should work.

I was thinking about the whole turn lights on with a switch, crank them up manually in the rare event i drive at night or need inspection, but figured since i was custom wiring everything there had to be an easy way to rig them up. I will just re-configure some relays and start testing different things. Eventually I should be able to get it all working.

Thanks for all the replies, I appreciate you guys taking the time!

[s13sr20chris]

no prob. the relays are really the ideal way of doing this. i hope it works out without messing up your headlamp motors. it think this will reap some small benifit of weight and complexity savings.