0-Ohm vs. Factory Spark Plug Wires: How Much Resistance Is Really in Your Ignition Wires?

Most people never think about measuring the resistance inside their spark plug wires.

If the engine starts, runs and doesn't have a check-engine light, the ignition wires are usually assumed to be doing their job.

But there can be a major electrical difference between a traditional factory spark plug wire and a Granatelli 0-Ohm performance ignition wire.

And you can see that difference with a simple tool:

An ohmmeter.

What Does Resistance in a Spark Plug Wire Mean?

The ignition coil creates the electrical energy required to fire the spark plug.

That energy then has to travel through the ignition wire before reaching the spark plug.

Electrical resistance is measured in ohms.

The higher the resistance in the wire, the more the wire resists electrical current traveling through it.

Traditional suppression-style spark plug wires intentionally incorporate resistance to help control radio-frequency interference, or RFI.

That interference matters because ignition systems operate near sensitive electronics including:

• Engine control modules

• Sensors

• Radios

• Vehicle communication systems

• Modern OBD-II electronics

The problem is finding the right balance between controlling electrical interference and unnecessarily restricting the ignition circuit.

Even Traditional Ignition Manufacturers Recognize Resistance Matters

Granatelli isn't the only company that discusses the relationship between ignition-wire resistance and spark energy.

NGK explains in its technical information that resistance is used to suppress radio-frequency interference, but also states that too much resistance reduces sparking and ignition energy.

That is an important distinction.

Resistance has a purpose.

But excessive resistance isn't necessarily something you want between the ignition coil and spark plug.

Granatelli Motor Sports approached the problem differently.

Instead of depending on a conventional high-resistance conductor for suppression, Granatelli developed an extremely low-resistance ignition conductor combined with patented technology designed to suppress radio-frequency interference.

Factory Wire Tested at 1,737 Ohms

A great real-world example comes from an independent test performed on a C8 Corvette.

During an All Chevy Performance project involving a Corvette equipped with the LT2 engine, the factory spark plug wire was connected to an ohmmeter.

The factory wire measured:

1,737 ohms of resistance.

The Granatelli 0-Ohm wire was then tested using the same method.

The reading:

Essentially 0 ohms.

That is a dramatic difference in resistance between the two ignition leads.

The test gives enthusiasts a simple visual demonstration of what "0-Ohm" actually means.

You don't have to rely solely on advertising.

You can measure resistance yourself.

How Do You Test Spark Plug Wire Resistance?

Testing a conventional spark plug wire is relatively simple.

You need a digital multimeter capable of measuring resistance.

Step 1: Remove the Spark Plug Wire

Remove the wire from the vehicle according to the proper service procedure for your application.

Always pull from the boot or connector rather than pulling directly on the cable.

Step 2: Set the Multimeter to Ohms

Set your digital multimeter to measure electrical resistance.

Depending on the meter, it may automatically select the correct resistance range.

Step 3: Touch One Probe to Each Terminal

Place one meter probe against the conductive terminal at one end of the wire.

Place the second probe against the conductive terminal at the opposite end.

Step 4: Read the Resistance

The number displayed is the electrical resistance through that ignition lead.

Traditional suppression wires may show substantial resistance.

Granatelli 0-Ohm technology is engineered to provide an extremely low-resistance electrical path.

Why Doesn't Granatelli Just Use Old-School Solid-Core Wire?

Because modern vehicles are very different from old race cars.

Traditional solid-core racing wires can have very low electrical resistance, but they can also generate significant RFI and EMI.

That can interfere with modern electronics.

Granatelli's technology addresses this problem through a patented low-resistance design incorporating radio-frequency suppression.

The technology is covered by U.S. Patent No. 7,185,622.

The patent describes ignition-wire designs with resistance levels below several ohms, including designs providing substantially no resistance, while also incorporating methods for suppressing radio-frequency emissions.

That combination is what makes the technology different.

Extremely low resistance without simply ignoring RFI suppression.

Why Does Lower Resistance Matter?

Think of the ignition system as an electrical path:

Ignition Coil → Ignition Wire → Spark Plug

The coil generates the energy.

The wire transfers it.

The spark plug uses the available voltage to create the spark that initiates combustion.

Every component in that chain matters.

Granatelli's goal is to reduce unnecessary resistance in the path between the coil and spark plug.

The concept is straightforward:

Let the ignition coil's available energy reach the spark plug through the lowest practical resistance path.

Does 0 Ohms Automatically Mean More Horsepower?

Not automatically.

This is important.

Simply measuring less resistance does not guarantee that every engine will produce a specific horsepower increase.

Actual results depend on the entire vehicle combination, including:

• Existing ignition-wire condition

• Ignition coil output

• Spark plug condition

• Plug gap

• Fuel

• Engine compression

• Boost pressure

• Tuning

• Vehicle mileage

• Engine modifications

A vehicle replacing worn, damaged or extremely high-resistance wires may respond differently than a new vehicle with a perfectly functioning factory ignition system.

But reducing resistance removes one potential restriction from the ignition circuit.

What Happens as Spark Plug Wires Age?

This is another reason resistance testing can be useful.

Spark plug wires operate in one of the harshest environments on the vehicle.

They are exposed to:

• Extreme engine heat

• Exhaust heat

• Vibration

• Oil and chemicals

• Thousands of heat cycles

• Constant high-voltage electrical pulses

Some traditional resistance-style wire designs can also increase in resistance as they age.

That means a wire that still looks acceptable externally may not necessarily perform the same electrically as it did when it was new.

Checking resistance can provide another way to evaluate the condition of an older ignition system.

Why Performance Engines Put More Demand on Ignition Systems

As engine performance increases, ignition demands can increase as well.

This becomes especially important with:

Turbocharged Engines

Higher boost generally means increased cylinder pressure.

Supercharged Engines

Just like turbocharging, increased cylinder pressure makes the spark environment more demanding.

Nitrous Applications

Nitrous dramatically increases the amount of oxygen available during combustion, increasing ignition-system demands.

High-Compression Engines

Higher compression creates more cylinder pressure that the spark must overcome.

E85 Performance Applications

High-output E85 combinations can place significant demands on ignition components.

High-RPM Engines

The ignition system has less time to charge and fire as engine speed increases.

This is why serious performance builds pay attention to coils, plugs, plug gaps and ignition wires rather than treating them as simple maintenance parts.

Ignition Wires Should Be Treated as Part of the Performance System

Enthusiasts regularly spend money reducing restrictions elsewhere in the engine.

We install larger throttle bodies to reduce airflow restrictions.

We install performance exhaust systems to improve exhaust flow.

We install larger fuel systems to support additional horsepower.

So why ignore the electrical path responsible for initiating combustion?

Granatelli's 0-Ohm technology approaches ignition wiring with the same performance philosophy:

Remove unnecessary resistance wherever practical.

More Than Just the Resistance Reading

A performance ignition wire also has to survive the engine compartment.

Depending on the application, Granatelli ignition wires can feature:

• Extremely low-resistance conductor technology

• Patented RFI/EMI suppression

• Stainless-steel conductor construction

• High-temperature silicone boots

• Fiberglass-reinforced jackets

• Direct-fit vehicle-specific lengths

• High-temperature boot options

• Ceramic boot options for extreme exhaust heat

• Compatibility with modern OBD-II vehicles

For vehicles running headers, turbo systems or other high-temperature exhaust configurations, Granatelli also offers ceramic boot wire sets designed to handle extreme heat near the spark plugs.

Measure It Yourself

One of the most interesting things about ignition-wire resistance is that enthusiasts don't have to take anyone's word for it.

Grab a multimeter.

Remove a factory spark plug wire.

Measure the resistance from terminal to terminal.

Then compare that reading to a Granatelli 0-Ohm wire.

The numbers tell the story.

An independent All Chevy Performance test measured approximately 1,737 ohms through the factory C8 Corvette wire, while the Granatelli replacement measured essentially 0 ohms.

That is exactly why Granatelli calls them 0-Ohm ignition wires.

The Bottom Line

Spark plug wires may look like simple pieces of cable, but they are a critical electrical connection between the ignition coil and spark plug.

Traditional ignition wires commonly use electrical resistance as part of their RFI suppression strategy.

Granatelli took another approach.

Using patented technology, Granatelli 0-Ohm ignition wires are engineered to deliver an extremely low-resistance electrical path while still addressing the RFI and EMI concerns that are important on modern vehicles.

Less unnecessary resistance.

More efficient ignition-energy transfer.

And an electrical difference you can actually measure with an ohmmeter.

If you're upgrading the ignition system on a naturally aspirated, supercharged, turbocharged or nitrous-powered vehicle, don't overlook the few inches of wire connecting your coil to the spark plug.

Every combustion event has to pass through it.

Learn More

Read more about Granatelli's patented 0-Ohm ignition technology, browse the Granatelli ignition-wire lineup, and compare the technology with independent testing from All Chevy Performance.