Race Car Wiring: How to Handle It to Make Your Car Perfect

You expect nothing less than Allstar performance from your race car wiring.

That’s why you need the best automotive wiring adjustments. It’s a challenge the find the right setting. However, it enhances the safety and reliability of your ride.

Additionally, it makes it easier to maintain.

This guide focuses on race car wiring.

You’ll discover the right and wrong ways to hot rod wiring and discover the dos and don’ts of the process!

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What Are the Main Race Car Wiring Principles?

Multicolored wires in the engine control unit

Caption: Multicolored wires in the engine control unit

A reliable rod wiring harness applies several principles.

If you stick to them, you ensure everything works right.

Check out some main cautions and things to consider during the process!

Dropping Voltage

Have you heard about a “dead short?”

It should be the lowest resistance that still enables painless performance.

However, race cars are very demanding.

Therefore, there’s no room for mistakes in their electrical systems.

If you face even the smallest resistance, it can lead to major problems. 

You’ll have huge current potential if you mix ignition wire with solenoids.

It could exceed 30 Amps.

Therefore, the estimation of the voltage drop between cable ends is three volts.

That implies you could face many unpredictable situations.

While you can’t avoid some resistance, you want to find the best way to manage it.

Transient Voltage

If you say transient, that indicates a short-term event that occurred because something happened in the electronic system.

So, if you deactivate a solenoid, you generate a huge voltage for a microsecond.

Although that is a short time, it’s enough to cause problems with other components.

Your automotive wiring has many parts.

Therefore, it’s impossible to predict where the transient voltage will go.

You can manage it using a quality wiring harness and diodes throughout the coils.

Furthermore, install a diode in every relay or solenoid in the vehicle.


Bundle of wires for automotive wiring

Caption: Bundle of wires for automotive wiring

The first rule is that a control device shouldn’t share a connection with the power wire.

It’s smart to use separate wires for power connections. You won’t solve a problem by adding another ground.

Furthermore, that can cause more issues than resolve them.

The approach should be to create two separate buses.

So, the first one is “dirty” and handles large currents.

The other is a clean bus, which aims to reduce the risk of voltage dropping.

It’s imperative to have a quality wiring harness.

You might invest a bit more but minimize the risk of damaging the vehicle’s components.

Chassis Ground

The experts recommend minimizing reliance on chassis grounds.

It’s better not to connect grounding parts to the chassis harness.

The alternative is to find the grounding in the appropriate bus.

Furthermore, don’t connect the chassis to the clean bus.

You should only attach it to the negative battery terminal.

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Five Ways to Wire a Race Car

Serviceman working with auto cables

Caption: Serviceman working with auto cables

There are multiple ways to wire a racecar, so picking the right one is vital.

Extremely Wrong Way

Can you believe that most cars have this wiring?

It involves using both batteries’ sides – positive and negative – for various components.

Therefore, you connect noisier devices, fans, pumps, and electric motors to a single wire on both sides.

Furthermore, you apply the same approach to digital electronics.

The problem is that voltage drops are probable.

Additionally, what if you deactivate the current on a fan?

It can lead to a voltage spike in other components through common wires.

So, this could easily damage your car.

Therefore, you want to steer clear of this wiring diagram.

Wrong Way

You can add two wires to the positive battery ground.

That way, digital electronics have a separate wire from solenoids and other electrical connections.

On the other hand, these devices and digital electronics share the same negative wire.

That could lead to potential problems, such as voltage drops and spikes.

Another Wrong Way

What if you use an opposite approach to the previous one?

So, you add two wires to the negative battery but use a common cable for the positive charge.

Once again, the problem is sharing the same wire.

Therefore, you could face drops in voltage and electrical noise.

Furthermore, a voltage spike might occur if you deactivate the current for a specific component.

Good Way

A futuristic concept of a race car

Caption: A futuristic concept of a race car

Although you’ll use four cables, this will still be a simple wiring diagram.

So, the idea is the following:

  1. Connect two wires to the positive and the negative side.
  2. Attach your fans, pumps, noisy devices, and other components. Additionally, connect the cables to the digital electronics.

The electronics receive current from the wires differently than those used for solenoids and motors.

That implies there’s no shared path, meaning there’s no voltage drop risk.

A slight drop might occur if a large-load component draws power from the battery.

However, that’s insignificant compared to the methods described above. 

The Best Way

The best method is copying the previous diagram, which has a vital edition.

You add a diode across the power wires to absorb the transient voltage.

If you deactivate the current on a solenoid or another component, it generates a huge transient voltage.

It only lasts for a microsecond, but it’s enough to damage other components.

Therefore, you add the diode to prevent sensitive components.

Do’s and Don’ts for Race Car Wiring

A mechanic checking car wiring

Caption: A mechanic checking car wiring

Would you like to know how professionals handle that bundle of wires on a race car?

Here are some tips on how to handle a wiring harness on your vehicle:

  • Use zip ties. These will secure your wiring harness. Vibration is a frequent problem, so use zip ties as a solution. Additionally, your wiring harness will look better.
  • Don’t make wires longer than necessary. Unless you bought custom cables, their length is longer than you need. Therefore, you should shorten them. If you leave them too long, you make a mess. Furthermore, a longer cable loses voltage with every inch.
  • Solder your wiring. You might think about crimping the connections. However, it’s better to solder them. It ensures a better touch of the connector and the cable. Furthermore, it ensures vibrations won’t loosen the connection.
  • Don’t forget to set a master disconnect switch. It ensures a simple way to remove all electricity from the battery. It’s an emergency option but can protect your vehicle.
  • Apply grommets to protect the wiring harness. Do you need to pass a cable through a firewall opening? If yes, a grommet will ensure optimal protection.
  • Check if everything else works. That includes inspecting your steering column wiring harness and other parts. That ensures the vehicle will work well on the road.


If you want maximum performance from your car, the wiring should be optimal.

Ensuring your race car wiring harness is ideal takes a little time and effort.

If you need some tips regarding your cable assemblies, don’t hesitate to contact us!

Our wiring harnesses are the best choice for your car to achieve maximum performance. 

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