Basic race car wiring: quick and dirty

Hi Folks. So the budget RX7 racer is looking less like a budget and more like a pit

Time to step back and start from square one. The electrical is a mess, want to rip it all out and start from scratch. Looking for real simple, ignition, fuel pump, front lights (no turn signals needed), rear lights, fuel pump, wipers, instrument panel (going to run the stock gauges for now), am I missing anything? I'm running a carb.

Any help, diagrams, pictures, parts lists, just about anything you could help with would be great. I'd like to have this ready ASAP, racing season is here and I'm not getting any younger.

Thanks,

J

tractor stores carry cheap basic headlight switches, ignition switches, and rocker switches.

i'd get a good fuse block and some good non chinese wire and start there. get switches for your needs and a scrap of aluminum and a label maker or sharpie to sub for one of those expensive switch panels.

They used to wire choppers with three wires. That's probably all you need, plus one for the starter (choppers were kick start only). I suggest starting with a large sheet of paper or a white board and drawing out what you have/need. Or buying one of those Painless sets, which people seem to like.

I'd look into solutions for tractor, dune buggy, and hot-rod wiring harnesses - either pre-made harnesses or diagrams. Nothing will be exactly what you need. You'll need to modify it to suit the wipers and turnsignal delete.

The Painless system is nice but pricey. I agree on making your own switch panels from sheet aluminum. On switches, I like toggles over rockers and Pegasus carries the best I've ever used. I use those Radio Shack mini LED's for on/off indicators.

For splicing wires, those insulated butt connectors blow chunks. Get the non insulated ones and cover them with shrink wrap. On the push on connectors, again I like the non insulated ones covered with shrink wrap, helps keep the wire from flexing and breaking.

For fuses, the parts stores carry the 4 position ATO (plug in) type fuse blocks. Like this:

Those work very well and are 'keyed' so you can lock them together.

Plan ahead. If you think you might need to remove a sub assembly such as the instrument cluster, run all the wires through a plug to allow quick removal without cutting. The Radio Shack 'Molex' connectors work good on low draw circuits, like under 15 amps, that are not exposed to weather. Anything high draw need a heavy duty connector and wet locations need Weatherpacks or similar.

Can'r find a good image of a Molex. Go to radioshack.com and search 274-242 for an example.

Weatherpack:

My advance is simple, do it right the first time. Doing a proper wiring job isn't hard and doesn't take a lot of time but finding electrical bugs is a pain in the ass. Take your time plan things out and document the work so if you do have to debug the electrical you don't end up wanting to pull your hair out.

word ^

Oh, I need to add: if you don't know how to solder, learn how. Soldered joints on stuff like the fuse block will go a long way toward making the whole thing bug free later. Radio Shack carries a decent 40 watt 'pencil' iron which does a good job for $8.99 or so. And no I don't own Radio Shack stock.

Thanks for the help guys, I was feeling pretty bummed about the car. Now I think I can actually make it work.

Now does anyone know where I can get a Weber 48 IDA for cheap ?

When I did my parts hauler truck I made it as simple as possible.

I used the above ATO fuse blocks and good quality auto wire.

The painless harnesses are great for hotrods but they're really too complex for a simple job.

I run five harnesses from the panel when I wire my cars. It's simpler than it sounds.

1 harness runs down the driver's side of the engine bay to power headlights, front turn signals and marker lights. I use Bosch relays to power the headlights directly from the battery rather than runing all the current through the switch. Makes the headlights brighter too.

1 harness down the pass side for heater, wipers, electric fan and accessories.

1 harness down the middle to run the engine.

1 harness inside for interior stuff.

1 harness to the back for lights.

The rear light harness is made from industrial 12/3 extension cord. 1 length per side give you stop, running and turn signal lights.

If anything goes wrong in an individual system I know what wire to look for in under a minute.

Good luck.

Shawn

I really like my painless kit. It is a bit expensive, but worth it in my opinion.

I started ripping out the old wiring and dash. It was very cathartic. At first I was trying to save some of the dash because it was in reasonable shape. However, 25 +year old plastic is not happy about being pulled and it soon became a rip fest! I should have the rest out some time tomorrow and then I can start wiring.

Two more questions:

Anyone here know how to wire the distributor for the 12a? I'm trying to follow the wiring from to the coil to the dizzy, I think it makes sense but if someone has done that, I'd appreciate your input.

I've decided to chuck the instrument cluster. Any suggestions on low buck but good quailty tach, oil pressure, voltage, and temp guages? I'd like individual so I can set them with the needles all pointing the same direction as good.

Thanks.

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Use those 20% off coupons from GRM.

Missed this thread a couple of days ago- I did the re-wire on my '74 race GTV from scratch. Made measurements, laid that onto a sheet of large plywood, and started running wire.

I used 10 circuit breakers I got from a Marine supply place, one for each head light + high beam, aux lighting, fuel, ignition, wipers, and some other things. The breaker were put in place of the glove box door.

The spade connecters were fun- I actually went to Moldex, found the correct plug that fit in the OEM connectors, and then asked who sold them. Their reply was- ask for an engineering sample, and we will send you them. I still have 50 of them left.

I did need a very good quality crimping tool- one that does a double crimp- one for the wire, and one for the insulation. So far, so good.

You'll be fine.

Oh, as for drawing- I started with an electronic version of the original harness, and then erased what I didn't need. I also did my best to use the same colors, but finding two color wire is a pain.

And remember- strain relief.

Eric

Ok, I'm kind of confused.

Here's a written description of what I want to do, I got this from the rx7 forum:

Quick and sleazy job. This is just ignition and start for an electronic dist.

Battery ground to chassis ground. "Welding Cable" Engine ground strap to chassis. "Welding Cable"

Battery positive to big lug on the starter. "Welding cable"

Battery positive to a toggle switch. 16-gauge From Toggle to positive of both coils. 16-gauge

Battery positive to a push button switch. From push button to the spade terminal on starter.

Battery positive to a toggle switch. 16-gauge From Toggle to positive of fuel pump. 16-gauge

Battery positive to a toggle switch. 16-gauge From Toggle to positive of elec. fan. 16-gauge

Negative of the leading coil to tack pick up wire. Wire tack like instructed in manual.

Wire distributor to coils like in the link above.

Flip your switches; you should have fan, fuel and spark. Push the button to start.

You of course should add fuses in line and relays.

I'm confused about where the fuse panel, switches, and relays go in relationship to the power off the battery terminal. And where does the alternator wire in? Sorry to be so clueless

Hokay. A fuse is meant to protect the wiring, switches and the load (motor, etc) in the event of a short. That means it should be as close as possible to the power source. So for each circuit you go batt> main kill switch> short wire> fuse> long wire> control switch> load> ground.

You can simplify that by using terminal strips, like this:

Avoid the cheapie white terminal strips with the little set screws in them, those just pinch the wire and can often create high resistance.

On a real simple race car, I'd keep the number of switches to a bare minimum: ignition, lights, wipers. I have found with rotaries that being able to turn the fuel pump off is A Good Thing. So I'd have a toggle for that but run the ignition directly off the kill switch (also see below).

Relays are for high draw items like lights, heater blower motors etc. On a gutted 1st gen RX7, there's not a whole lot which will need relays. Even the fuel pump only draws about 3-5 amps, meaning a toggle switch will work fine. The ignition coils draw a lot of power, but instead of a separate toggle switch or relays I'd suggest wiring them directly to the big output terminal on your kill switch. If you want to fuse them, then I'd look into those big maxi fuses. I'd go 40 amps and put them where you can get to them easily, plus carry some spares. You might even consider circuit breakers for that particular use, again mount them where you can get to them easily.

I'm going to start a E36 M3storm but welding cable, while nice, is not really necessary for battery cables. Those premade battery cables from the parts house will work just ducky.

On alternators: for an RX7 to make it work all you need is a wire directly from the alternator + terminal to the battery +, then there are two small wires going to the alternator. One of those needs to have power when the ignition is switched on. Unfortunately, i do not remember the color so you probably need to grab a wiring diagram to find out for sure which one it is. The second small wire is, on 1st gens, a power output. This goes to a relay which does all kinds of crazy stuff and also runs the charge indicator light. The problem: just about every car out there uses that wire as a ground instead of a power wire. There is a way to make it work which involves a relay and some other funky stuff. I can post a diagram if you want to wire in a light, or you can leave that wire disconnected (insulate the tip of it!) and use an ammeter in the dash.

A word on grounds.

Many people think a ground is unimportant because 'it doesn't carry power'. Nothing could be further from the truth. Grounds are more important than the power side of things! If they are crappy, weird things will happen, I have seen melted heater control cables, for instance.

Be sure the engine is correctly grounded to the body, use a decent 'switch to starter' battery cable and clean the paint off of the mount points. Then be certain the battery is grounded properly as well.

I don't know what automotive electrical engineers think about this but the story I got from fellow aircraft electrical engineers was that a circuit breaker is designed to save the wiring, the device is already considered gone if there's an issue in the circuit. So size the fuse for the wiring, size the wiring for the job + one step up from absolute minimum, that's the idea.

Something else; heavy jumper cables may be cheaper per foot than pre-finished battery cables. Buy the proper lugs and learn how to install them on freshly stripped cable (a bench vice & a large Allen key is a great pair of tools for the job) and this might be a good way to go for cabling large amperage items like your battery or chassis grounds, etc. (I've got 16ga zip cord for speaker cables because it was 1/2 the cost at Wal-Mart vs. 18ga stranded "speaker wire").

Jensenman wrote: A word on grounds. Many people think a ground is unimportant because 'it doesn't carry power'. Nothing could be further from the truth. Grounds are more important than the power side of things! If they are crappy, weird things will happen, I have seen melted heater control cables, for instance. Be sure the engine is correctly grounded to the body, use a decent 'switch to starter' battery cable and clean the paint off of the mount points. Then be certain the battery is grounded properly as well.

Relatable story- working on a prototype vehcile, where the front subframe was where the engine was grounded. The car used braided brake lines, and since someone forgot to ground the subframe to the car (used rubber isolators for NVH), the brake lines ended up being the engine ground.

Sparks where you never expected to see them.....

Yea, grounds are a LOT more important than most people think, so a major +++1111 on this post.

Eric

Strangest ground story I have heard: Omni/Horizon car with A/T issues, the transmission shifted weird. On disassembly the inside of the tranny case had an oddball goldish color. Due to a missing ground cable, everything in hte car was grounding through the struts and CV axles. This caused the inside of the tranny to act like a primitive plating tank. When the front wheel bearings were removed, the races and balls were covered with black pockmarks where the power arced as the car was rolling.