Why Modern Hemi Engines Have 16 Spark Plugs Instead of 8 – Jalopnik

Back when carburetors and cigarette lighters were common in dashboards, a Gen-II Hemi didn’t need many spark plugs to prove its point. Eight cylinders, eight spark plugs – simple, loud and unashamed. But when Chrysler rolled out the Gen-III Hemi in the Dodge Ram in 2003, things got a little rosier. Suddenly, each cylinder had two spark plugs, bringing the number to 16 for engines like the 5.7-liter, 6.2-liter and 6.4-liter Hemi offerings.

The original Chrysler FirePower (331 cubic inch V8) of the 1950s was a pioneering Hemi engine. It had large hemispherical combustion domes that allowed air and fuel to mix freely and explode efficiently – which is where the name Hemi came from. But that dome also caused a problem: one spark plug could not ignite the entire charge evenly. The result was that some parts of the turret were left with some unburned fuel.

After a number of years, Chrysler engineers resolved this by adding a second spark plug. Two ignition points mean faster, more complete combustion, better power and performance, fewer emissions and a small difference in fuel efficiency. It wasn’t about doubling the horsepower, it was about cleaning up the ignition. Still, old-school Hemi fans can’t help but grin. The modern Hemi may burn cleaner, but it certainly doesn’t feel or smell like the old one.

So yes, two plugs per cylinder makes sense – from an engineering point of view. But from a car owner’s wallet? That’s another story. Sixteen spark plugs mean double the parts, double the labor and double the swearing, especially if you’re on the lookout for a broken one. In addition, these engines produce more heat because two spark plugs spark together. Finally, the choice of fuel is important. The more expensive high octane is more suitable for Hemi engines to maximize performance.

However, the extra plugs help by improving ignition control, smoothing out combustion timing and making the engine just a little bit cleaner. By ensuring stable ignition, they also help reduce knocking and provide drivers with better throttle response. It’s smart technology, but not particularly idealistic. When a Hemi coughed raw fuel out of the exhaust pipes in the 1960s, no one cared. Nowadays you can’t even start without the computer nodding approvingly. Progress, right?

Frankly, dual plugs make the Hemi surprisingly refined for a 400-horsepower powerhouse. They improve cold starting, increase power, reduce engine load and make operation smoother. But for purists, it feels like trading whiskey for green tea. Sure, it’s better for you, but it doesn’t quite have the same kick. So, is it worth it? Technically yes. Maybe not financially. Spiritual? Let’s just say the classic eight-plug Hemi still wins in the garage of nostalgia, where a little inefficiency was part of the fun.