Yes, there are engines with three spark plugs in one cylinder – Jalopnik

Oh, your Gen-III Hemi has two spark plugs per cylinder? Cool, cool, but let’s raise the bar, okay? Oh yes, three spark plugs per cylinder, now we have it! Three-plug engines are to two-plug engines what $10,000 bills are to $100 bills. You’ve probably handled a $100 bill, but you probably don’t know anyone who has even seen a $10,000 bill in person.

Before we get to an actual example, let’s discuss why three plugs would be desirable. We will use the known advantages of twin-plug engines – that is, engines with two plugs per cylinder – as a launching pad.

On two-valve heads, those valves are usually next to each other, pushing the plug to one side or the other (unless you have that half-grapefruit Hemi chamber). This causes slow, uneven combustion, which can be solved by placing symmetrical plugs on either side. You can better tune the ignition advance with two plugs and also ensure more complete combustion of the fuel in the chamber. Moreover, a little redundancy in the system won’t hurt if a plug fails.

Theoretically, triple plugs would be even more effective. Drag racing legend Dale Armstrong thought so, so he tried to develop a three-plug head (in addition to a two-speed supercharger). The National Hot Rod Association (NHRA) feared that these inventions would be too expensive to implement or that the cars would be made too quickly, and they were banned before Armstrong could even try them. A patent for a three-valve, three-plug head was granted in 1996 to inventor and engine designer Jim Fueling, a man who took nominative determinism to its logical extreme. Now, if there is a three-plug version included in Meatspace, I can’t find one, so unlike nouns that are people, places, or things, this seems to be just an idea.

To explain why an overcrowded three-spark-plug, four-valve cylinder head is worth the engineering agony, Bajaj claims that tripling the number of spark plugs allows 27% faster flame propagation than a dual-spark plug design, and 50% faster than a single-spark plug design. Engine power is listed as 24.5 hp or 24.16 hp. Bajaj is also apparently using Triple Spark for its Dominar 400, which puts out 40 PS (39 PS).

If 24 horsepower doesn’t sound like much, note that the goal of Triple Spark was not just more horsepower, but also lower emissions, smoother operation at high rpm, easier starting, and less fouling of the spark plugs. Bajaj also claims that the three-plug design eliminates knocking, but that seems to conflict with one of the biggest drawbacks of cramming three devices that create electrical arcs into a confined space: heat. It’s no surprise then that the Pulsar NS200 uses liquid cooling, and Bajaj admits that a cooling failure can lead to serious engine damage.

But hey, it’s all about the results, right? And 24.16 horsepower from a 200cc single-cylinder engine isn’t bad. Except that KTM gets 25 hp or 24.66 hp in its 200 Duke with just one plug. And users report that both the Pulsar NS200 and 200 Duke have similar fuel economy of around 76 or 78 mpg, as tracked by users on Fuelly, although someone with a 2015 Pulsar NS200 hovers at 83.6 mpg. Bajaj says that while the two bikes perform about the same at high speeds, the Pulsar NS200 is much more efficient at low speeds. Anyway, Bajaj bought KTM last year, so it would now just be a power struggle to pit the bikes against each other.

Frankly, it seems like three-plug designs are overkill and dual plugs are fine. After all, the NHRA didn’t send Dale Armstrong’s three-plug heads out the door, and it’s not like two-plug dragsters hurt horsepower. Dual spark plugs were perfectly sufficient for Kenny Bernstein to reach 300 mph in 1992, the first driver to do so (btw, Dale Armstrong was Bernstein’s crew chief at the time). And after Scott Kalitta’s death, the NHRA shortened drag racing distances by 1,000 feet, so the organization probably isn’t eager to approve changes that will add even more power.