Iridium Spark Plugs

Spark plugs get no respect! In fact, a lot of performance enthusiasts don't give them a second thought. They spend thousands of dollars building the ultimate performance engine then simply screw in whatever plugs the local auto parts store has in stock. The perception is that spark plugs are the lowest-tech components in the modern internal-combustion engine.

Change is Good
It's no wonder. Contemporary electronic ignition systems have made spark plug replacement in everyday passenger vehicles a thing of the past. And when a racer or high-performance engine builder has a misfire problem, the first thing he does is to add a more powerful ignition system. That's about to change. When the word gets out about the new Denso Iridium Power spark plugs that added 750-hp to Kenny Duttweiler's 450-cid twin-turbocharged Ford, engine builders and tuners will gain more respect for the lowly spark plug.


Kenny Duttweiler of Duttweiler Performance in Saticoy, California is no stranger to making horsepower, especially with turbochargers. After years of building little turbocharged V-6 Buicks that produce in excess of 1,500-hp, he found a lucrative market in NMCA's "World Fastest Street Car" classes building 1,700-hp small-block Chevy V-8s for winning racers such as Bob Rieger and Rod Saboury.


So when he bolted a customer's NHRA AA/Altered Turbo Ford engine on the dyno and had problems making the requisite 1,950-hp (out of 450 cubic inches on gasoline), he left no stone unturned. The engine had state-of-the-art everything—Motech engine management system, MSD Digital 7 ignition system and everything else you could think of. Kenny had isolated the problem to inadequate ignition performance. There was no audible misfire, but the engine made 1,700-hp at 17-psi of turbo boost and only 1,100-hp at 24-psi, indicating that the increased cylinder pressure was causing an undetected intermittent misfire. Reasoning that it was an engine-management or ignition-system problem, he replaced both. However, his Stuska dyno yielded the same results. Kenny replaced spark plugs several times with the best racing and platinum plugs he could find; still no improvement.


Kenny had correctly diagnosed the problem, but as far as he knew, there was no solution. He was already using the most powerful engine management and ignition systems on the planet, and he'd tried most of the "state of the art" spark plugs on the market. Kenny was running out of options and stated prophetically, "Some engines are spark-plug sensitive, especially Hemi-style engines. That's why Chrysler designed dual-plug cylinder heads for their Pro Stock motors in the early '70s. A turbocharged race engine is a variable-compression engine. At 25-30 psi of boost, the cylinder reaches an incredible 2,800-3,000 psi. The higher the cylinder pressure, the harder it is to fire the spark plug. This Ford engine we're developing is the worst of all circumstances. It has a hemispherical-shaped combustion chamber and a 4.670 cylinder bore that is a large area to light off at high rpm."