FORMULA 500

WIRES FOR RACE CARS – PART ONE January 1, 2026

WIRES, they don’t make your car faster, but you need them to keep your car running or even getting it started.

HIGH POWER AND LOW POWER DEVICES
Devices installed in a race car should be divided into two categories: power devices and control devices.

Power devices are things that use a lot of current for brute-force operations like turning on solenoids and generating ignition sparks. They will generally have large-gauge, “fat” wires for power connections.

Control devices are things that make decisions and send and receive low-current signals like logged data and ignition timing triggers. They will generally have smaller-gauge wires for power connections.

Some devices will fall into both categories, like an ignition box that both generates sparks and receives a low-current signal to know when to generate said sparks. Often you will find that these devices have two sets of ground and/or power wires. There will be a large-gauge set for the power section and a small-gauge set for the control section.

TRANSIENTS
Transients are generated by power devices, such as solenoids, relays and coils, and are most harmful to control devices. Transients can be managed with the use of diodes across the coils, as well as proper wiring techniques. Every solenoid or relay in the car should have a suppression diode installed, some relays, or controllers, MAY have the diode built, others may not. Simply changing a relay, could cost you weekends of failed racing. We recommend, and there is no harm in, adding a diode as insurance, not to mention it may improve the performance of a coil-driven device. To this end, the best plan is to create a “Clean Bus” for the control devices and a “Dirty Bus” for the power devices. The goal of the clean bus is to minimize voltage drops, so it needs to be built with low-resistance cable and terminals. The goal of the dirty bus is to handle large currents, so it also needs to be built with low-resistance cables and terminals. In other words, use high-quality, low-resistance materials and methods for both.


Chassis Ground
Dependence on chassis ground should be minimized. The chassis may be grounded to the battery negative terminal, providing a definite ground path to the chassis, not accidentally grounded through the engine or other purposefully grounded part. Grounding devices to the chassis should be avoided. Instead, ground them to the appropriate bus. The Clean Bus ground should not connect to chassis, ONLY TO BATTERY NEGATIVE TERMINAL!


Battery Negative Cable Grounding to the Chassis
It is important to correctly connect the negative cable from the battery to the chassis. A poor connection there will cause a lot of problems. You can just put a bolt through a chassis member and bolt on the cable, but corrosion will eventually reduce the ground effectiveness.

Welding a bolt to the chassis and then put the ground cable connector on that bolt will be the most effective.

A small amount of this tune-up grease on the bolt and terminals will prevent corrosion.

DO NOT put a star washer between the ground stud and the battery cable. There are some opinions on this subject, but trust me, putting a star washer under the cable terminal is bad idea.
Silicone Dielectric Grease

File Name: WIRES FOR RACE CARS – PART TW0
January 1, 2026

Clean Bus and Dirty Bus *1
In race car wiring, a "clean bus" powers sensitive electronics like the ECU, while a "dirty bus" handles high-current components like the alternator and starter motor. This separation prevents electrical noise and voltage fluctuations from "dirty" components from interfering with the "clean" system, which is critical for performance and can prevent issues like engine misfires or sync loss. Both systems require quality wiring, separate power and ground sources, and are ideally fed directly from the battery to act as a filter.

EXAMPLE OF CLEAN BUS/DIRTY BUS
These devices should be connected to the Dirty Bus
Starter motors/starter solenoids
Solenoids
Relays
Pumps
Electric Blowers
Electric fans
Headlight bulbs

These devices should be connected to the Clean Bus.
Traction Control
Ignition On/Off
EFI On/Off
Boost Controllers
Shift Controller
Timers
Data Loggers
Dash
Sensors / Instruments

Here is a link to a PDF that explains a lot on how to wire your race car.
• https://moretraction.com/wp-content/upl ... To_Web.pdf
• When you get to this page, you have to click on the ” Wiring How To” to view the PDF.


THE WIRE
Due to its extra durability, the SXL wire is preferred for more intense conditions such as industrial or racing vehicles

The FAA's recommendation for aircraft may be applicable- wires less than AWG 20 should receive extra support (including terminations) and should not be subjected to 'excessive vibration', and wires with less than 19 strands should not be used.

While it is desirable to have the 19 strand 18 gauge wire, it is hard to find. So 16 strand 18 gauge SXL wire should be used.

Wire gauge less than 18 gauge should not be used as the pull strength of 20 or less gauge wire is significantly less.

High vibration applications, such as formula car racing require wire that will flex and not break. High strand count wire that is tin-plated is the best solution.


Voltage Drop
There will always be some voltage drop in a conductor due to current in the conductor.
• See the charts below.
An important consideration on the selection of wire gauge VS wire length VS current in the wire.

NOTE: Notice that the above chart mentions “round trip” Keep in mind that any current
that flows from the positive battery terminal must return to the negative terminal via the ground wire.
• So, when you calculate your wire length, remember to add in the length of the ground or return wire.

WIRES FOR RACE CARS – PART THREE
January 1, 2026


Wire Strippers
Klein Tools Automatic Wire Strippers Part Number: KLE-11063-W

If you don’t want to pop for this really nice Klein tool above, this one below will work. Very similar to the one I use:
Whatever wire striper you buy, make sure that it has a locking feature, you don’t want this open floating around in your toolbox. I found this at Lowes.


TERMINALS
In designs requiring high reliability, crimping is preferable to soldering but with the proviso that all crimped joints be inspected and pins be checked that they are fully latched (the latches can be seen on the correct side of the housing).

Soldering is just pouring a different metal in the gaps between the strands. Soldered joints are susceptible to fracturing especially on the surface of the pin where the different materials expand and contract at different rates and where mechanical stress has the largest leverage. In an application which has large temperature changes or high vibration, soldering is particularly unreliable.

Another issue with soldering stranded wires is that the solder wicks up the strands, turning the stranded wire into solid wires. That makes it susceptible to metal fatigue.

Understanding Ring Terminals
Ring terminals
Also referred to as ring connectors, serve as electrical connectors for attaching a wire to a stud or screw. They find extensive use in automotive, marine, and industrial settings because of their reliability and ease of use. Featuring a ring-shaped end that fits over a stud or screw, as well as a crimping end that attaches to the wire, these terminals facilitate secure electrical connections.

Ring terminals are used instead of fork terminals for more secure, permanent connections that resist vibration, while fork terminals are used for quick, easy connections where a connection needs to be made or broken frequently. Ring terminals are more secure because the closed loop provides a stronger connection to a screw or stud, making them ideal for high-vibration environments like industrial machinery or automotive applications

Choosing the right ring terminal involves considering factors such as the wire size, stud size, material, and insulation type. Each of these factors plays a critical role in the performance and safety of the electrical connection.



Locking Fork
Locking forks carry nubbed ends which snap onto the stud. That is why they are also known as “snap-on” fork terminals. The nubs create a space that is smaller than the diameter of the stud they are being attached to. This means you must push them past the point of resistance to get them to snap on. Don’t worry, they are designed for this, and as such the process causes no damage to the terminal or the stud. This locking action decreases the chances that they will fall off or come loose over time. Locking forks are a solid choice if you know you may be making changes to the electrical system in the future.

After you have finished attaching the terminals to your electronics, I recommend adding a small amount of clear RTV on the nut or screw terminal. This will keep the nut or screw from coming loose. You can easily remove the RTV if you need to remove the wire terminal.


Butt Connectors For inline wire splices, butt connectors (also called butt splices) join two wires end-to-end. They come in non-insulated or insulated versions, often heat-shrinkable.

Crimp each side of the splice onto one wire, then shrink-wrap the splice. This leaves a sealed, strain-relieved joint. Butt connectors are often used in automotive and marine applications. Watch out: use the correct AWG range – for example, don’t use a yellow AWG 12–10 butt on an AWG 18 wire, even if it “fits,” as the copper-to-copper contact area will be poor.

I have added the “Butt Connectors” in this description of connectors. However, I strongly recommend that you not use them unless it is a field repair. i.e. it’s race day and the damn wire broke. The more connectors in a circuit, the more chances of failure.


INSERTING THE WIRE INTO THE TERMINAL
• To twist or not
Here’s a non-obvious bit: the stronger you twist a bunch of strands, the shorter and fatter the bunch gets. So a manufactured wire’s final size is designed to be correct at the final twist.

So, why not twist by hand? Well, usually, people hand-twist far stronger than the factory twist. This means the strand bundle gets a bit fatter and shorter. But also, when we do it by hand, we usually use too much pressure and disturb the lay of the strands, introducing larger and more irregular air gaps. So, the end result is a bundle with the strands at uneven angles, with uneven gaps between them, and thus with uneven cross-section making the crimp less reliable.

A small amount of the wire should protrude past the metal part of the terminal as seen in the photos below.


CRIMPING
Crimping is the process of joining two conductors (wire or cable) by deforming a metal connector tightly around them. When done correctly, crimping creates a permanent, secure electrical connection that is more reliable than soldering. Proper crimps ensure a consistent current flow and can withstand vibrations and pulling in harsh environments.
The core of any good crimp job is the right crimping tool matched to the connector type and wire gauge.



I can’t recommend this crimper I recommend this tool for crimping both insulated and non-insulated terminals
• This tool has replaceable jaws for both insulated and non-insulated


Choose terminals for the wire AWG and application (e.g. heat-shrink insulated for moisture, marine-grade if needed)
Here is a fork terminal showing the wire gauge (18-16), that will work with this terminal.

Use the color-code chart below for heat-shrink butt/ferrule terminals:

Wire Gauge (AWG)...Connector Color.........Typical Use
22–18............................Red.......................Small wires (ground wires, signal)
16–14............................Blue......................Medium wires (12–14 AWG splices)
12–10............................Yellow....................Large wires (battery cables, high
......................................................................Current circuits)


Showing good crimp on insulated terminals
Showing good crimp on both sides of a fork terminal


Inspecting Crimps
A final check is crucial. Perform a pull test on each crimp: grip the wire near the connector and tug hard. The wire should not pull out. If it does, the crimp is unacceptable. Also inspect the die imprint: it should be full and even. A good crimp (like the rings in the photos above) shows a uniform pattern.



Warning!
Pliers are not crimpers! Neither are hammers, vises, needle nose pliers or flat rocks. A good crimper when used correctly will make a cold weld between the wire and the barrel of the connector. If you were to cut a well-executed crimp in half you would see a solid form of wire and connector. Using the wrong tool will not achieve a good crimp!

Shrink Tubing
Electrical connections can easily be protected with heat-shrinkable connectors, which in some cases have glue inside the terminal that when heated to shrink will also form a watertight seal. These are standard crimp connectors that shrink and seal with the use of a heat gun or small flame.

Standard Heat Shrink Tubing Sizes

Heat shrink tubing is available with sealing adhesive or not. I recommend using the sealing type shrink tubing on non-insulated terminals. It will give the wire some support to resist bending.

WRAP IT ALL UP
When you are finished up with making up your wires and are ready to put in the car, you should use some sort of bundling material. Not only does it make your wire installations look good, but it also offers protection for the wires.

TYPES OF WRAPS

Spiral Cable Wrap Tubing
Split Wire Loom


Spiral Cable Wrap Tubing
Spiral wrap tubing offers a unique solution for securing and protecting multiple cables or wires while allowing for easy access and adjustability. The spiral design enables cables to branch out at any point, making it ideal for complex wiring setups that require flexibility. It is particularly useful in applications where cables need to be bundled and protected from abrasion or harsh environments while still maintaining accessibility for maintenance and modifications. Spiral wrap tubing is versatile, whether used in industrial, automotive, or office environments, offering the perfect balance between protection and ease of use.


Split Wire loom tubing
Is a type of flexible convoluted tubing that is used for organizing and protecting wires and cables. It is commonly used in a variety of industries and applications, including automotive, electrical, and telecommunications.

One of the primary purposes of using wire loom tubing is to protect wires and cables from damage. The tubing provides a physical barrier that helps to prevent abrasion, bending, and other types of mechanical damage that can affect the integrity of the wires and cables. This can help to extend the lifespan of the wires and cables, and reduce the need for costly repairs and replacements. Another key benefit of using wire loom tubing is that it helps to organize and route wires and cables in a neat and orderly manner.

IMPORTANT: Never bundle wire to fuel or oil lines.

High Temperature Protection (Fiberglass)
Fiberglass High Temp Loom

A premium fiberglass high temp loom will withstand extreme temperatures,
capable of withstanding temperatures of up to 1200°F.

In environments where wires or cables are subjected to constant high heat conditions, such as in race cars or industrial machinery, high temperature protection is essential to ensure the longevity and reliability of your electrical components.


Environmentally Sealed Connectors

DEUTSCH DTM Connectors *2
The DTM series of environmentally sealed connectors was designed specifically to handle lower amperage needs. Each size 20 contact (24-20 AWG) is built to handle a 7.5 amp continuous capacity.
These connectors require special pins and crimping tools
NOTE: Deutsch is very proud of their crimpers, they are priced accordingly.


DTM Series Connectors Feature
Rectangular, Thermoplastic housing
Small "Mini" size
Accepts size 20 (7.5 amp) pins and sockets
Accommodates wire sizes 16-22 AWG
Available in 2, 3, 4, 6, 8, and 12 cavity arrangements

Deutsch 1062-20-0122 Socket used for 16-22 AWG wire

Deutsch 1060-20-0122 Pin used for 16-22 AWG wire
Weather Pack Connectors *3
Weather Pack is an environmentally sealed electrical connection system designed to withstand exposure to extreme temperatures, moisture, and harsh engine compartment fluids and chemicals. They are extensively used in severe duty applications including racing, construction, off-road, and industrial equipment. The connectors are made of a nylon material for the best combination of temperature resistance and flexibility. They have been tested to withstand temperatures of -40C to 125C. The terminals are tin-plated and utilize flex pin and lap lock designs to provide the highest reliability. Their dual locking tangs securely hold the terminal inside the connector cavity. Weather Pack self-lubricating seals feature multiple sealing ribs and will not stain, deteriorate or corrode other materials.


The Weather Pack connectors are available in 1 to 6 terminals.

Single Cavity Weather Packs


Six Cavity Weather Packs Weather Pack Terminals
Weather pack terminal crimping tool
JT&T (5000F) - Open Barrel Terminal Crimping Tool, 1 Pc. $28.45 The weather pack sealed connectors are a lower cost alternate to the Deutsch connectors.


About me:
I worked in the electronics field for over 30 years. My last job, before retiring, was a Control System Design Engineer at an over-the-road refrigeration manufacturing company located in Minneapolis, MN.

The units were powered by 3-cylinder Deisel engines, which vibrate a lot, plus the units were typically mounted on box trucks. If you ever drove one of the box trucks, you know that they ride, like, you know, a truck. The refrigeration units are exposed to the weather, so proper wiring and termination of the wires are important, just like they are in your race car.


References:
*1 https:__//moretraction__.com/__proper-wiring-principles/ (remove the underscore marks to see the correct link)

*2
https://www.deutschconnector.com/produc ... 1fcPKEbf6W

*3 https://www.wiringdepot.com/store/c/42- ... HivIiysw6f