Wiring and relays ?

[coup in australia]

Hey all,
Coupe arrives end of Feb and trying to educate myself as much as possible and one thing is wiring and relays so can can you suggest what on the car should use a relay ?

Any other newbies want a crash course on relays watch this. https://www.youtube.com/watch?v=UAeKTlieYhw

Thanks again to all you contributors

[Big Blocker]

check out the12volt.com for a ton of info about relays, diodes and switches. It's a car stereo site but the info is universal in regards to electrical components and their usage.

As far as relay usage beyond what comes in the wiring harness; horn(s) and fan(s), I [personally] added fuel pump, headlights (Hi-Lo switching), special relays for my custom turn signal system, start circuit, charging control.

Doc

[NAZ]

Besides using relays to switch higher current, they can be useful for other things as well. Before we had PLCs and computers controlling electrical circuits, we had relay logic.



I designed the electrical system in my race car as there was no commercially available wiring “kit” that fit my needs. I have a lot of relays controlling circuits, some because of high current and some as an interlock that requires one or two variables to be in range before allowing a component to power up. Here’s few of the things I use relays for:


· Switching my nitrous oxide tank heater from the starting battery / alternator to a Milwaukee lithium battery. When the car is running the heater is powered by the starting battery and when the ignition is off it runs on a rechargeable power tool battery. Keeps the bottle warm in the staging lanes without draining the starting battery. The Milwaukee battery is mounted in a docking station making it easy to swap out just like on a power tool.



· Switching off my nitrous solenoid when the fuel pressure drops below a pre-set point. Using an adjustable pressure switch to control the relay ground and the power from the nitrous controller to complete the relay coil circuit. Two variables must be met – the need for nitrous injection and sufficient fuel pressure.


· Switching off my ignition when the oil pressure is low. An adjustable oil pressure switch controls the coil ground on the ignition box relay. The ignition switch provides the 12VDC + to the relay coil. A one-shot timer relay acts as a bypass allowing the engine to start and run for several seconds before arming the ignition relay.


· My radiator electric fan is controlled by a relay and wired so it can’t back-feed the system and keep the engine running when the ignition switch is off. The typical brush type fans will act as a generator when they spool down and can keep the ignition powered up depending on how you wire the system.


· I have a master relay (150A solenoid) that cuts power to my power distribution system. It’s operated by a switch near my fire system pull handle. This is in addition to the master switch mounted at the back of the car required by NHRA. A simple swipe of the switch as I reach for the fire handle will kill all power.

There are maybe a dozen more but this gives you some ideas of ways to use relays.