LAST week we tackled the importance of oil and oil filters. This week we’ll look at spark plugs and their importance in delivering a highly fuel-efficient, environmentally friendly engine that runs smoothly, helping generating the most power, torque and fuel economy.
A spark plug is a device that delivers a small electrical discharge or spark that ignites the air-fuel mixture inside your engine at a precise moment in the engine’s combustion cycle.
Unfortunately spark plugs don’t last forever. Idling in traffic, short drives, continuous starts and stops, poor fuel and extreme heat and humidity all wear out a spark plug’s service life. Tommy Teng, chief tuner, engine builder and shop owner of DTM Motorsports/Autotechnika, a high-performance independent shop located in Fort Bonifacio, Taguig City, states that while most manufacturers recommend changing the spark plugs anywhere from 10,000 to 30,000 kilometers in between, with some newer cars even boasting as high as 160,000 kilometers, the cold, hard reality is that performance drops significantly after only 5,000 kilometers, sometimes even less especially with older cars.
He has in fact seen a drop in performance after less than 1,000 kilometers if the engine it was installed in had other operating issues. Spark plugs that foul quickly are also a sign that there are other factors affecting your engine’s performance.
A spark plug’s ability to deliver a powerful electrical discharge is hampered when the two metal tips, called the central electrode and the lateral electrode starts to oxidize, wear away or becomes covered in carbon build-up. As these phenomena happen, the electrical charge delivered by the spark plug weakens, which causes poor combustion as it is unable to combust the entire air-fuel mixture.
The result is poor power and lots of unburned fuel spewing into the atmosphere and money thrown out of your exhaust pipe. In other cases, worn out spark plugs can cause pre-ignition or detonation, an even wherein the air-fuel mixture combusts before it is supposed to, which can cause severe engine damage or significantly shorten the life of your engine.
Other times, worn-out spark plugs can cause hard-starting, vehicle hesitation under acceleration and heavy load and a general lack of responsiveness.
As an example, my own car was suffering from hard starting and a very smelly exhaust pipe, signs that fuel was not being burned properly. A simple change of spark plugs and the results were surprising: one-click start and no more smelly exhaust pipe. All for the price of P900, about P150 for each spark plug.
The key to getting the most positive difference with your car’s spark plugs is choosing the right / proper spark plug for your car. The right spark plugs are the ones recommended by your car manufacturer with the right heat range (typically numbered 4-11 for NGK, and 16 to 29 for DENSO, the two most common spark plug brands in the country). These are categorized as HOT and COLD plugs. For NGK as an example, plugs 4-6 are considered HOT plugs, whereas plugs 7-11 are considered COLD plugs.
HOT spark plugs are able to retain more heat which helps clean itself from carbon build-up due to long idling periods and constant cold-start operations. But they are unable to shed off excess heat when subjected to extreme operating temperatures such as racing. COLD spark plugs are unable to retain as much heat, which makes them prone to fouling much more easily, but can shed off excess heat when subjected to extreme operations such as motorsports.
For most mass-market cars (your garden variety Toyota, Honda, Mitsubishi, Nissan, etc.) spark plugs are usually in the heat range of 5 as prescribed by NGK, or 16 by DENSO. Check the spark plug gaps as well; you can find some hidden horsepower and fuel efficiency if the plugs are gapped properly. The gap is the distance between the tips of the central electrode and the lateral electrode.
Advanced Engine Management (AEM Electronics) Systems, based in Hawthorne, California, USA, a leading aftermarket parts manufacturer specializing in stand-alone plug-and-play engine control systems for high-performance and motorsports vehicles, did an independent study to find out the ideal spark plug gap for a variety of cars and the results recommended a gap range of 0.044 inches/1.1mm to 0.032 inches/1.8mm for normally aspirated vehicles and a gap of 0.028 inches/0.7mm to 0.022 inches/0.6mm for turbocharged vehicles.
There are pros and cons so finding the right gap is crucial. A gap too small stresses the ignition coil over time particularly in starting the engine, whereas a gap too wide can have its spark snuffed out by the incoming air-fuel mixture. Hence, balance is key.
If you read your car owner’s manual, you’ll see that the manufacturer recommends switching to a spark plug one heat range colder if you live and drive your car in a very hot and humid country to better resist detonation/pre-ignition. I have done this on my car, and gapped properly, runs much better and resists detonation/pre-ignition better as my car, bought brand new a few years back, suffered from detonation/pre-ignition even when new, perhaps due to the heat and poor fuel quality at certain gas stations. My car, a Toyota Yaris came with the equivalent of an NGK 5 heat range. I switched to a 6 to improve performance. Check your owner’s handbook if there are such recommendations and instructions.
Check your spark plug every time you have your vehicle serviced, and if it looks remotely worn, have it cleaned or better yet replace it. A new set of plugs will be well-worth the added cost in as quickly as 2-3 full tanks of fuel.
Lastly, stray away from these supposed high-tech/fancy spark plugs that promise to increase power, efficiency and what-not. Whatever gains you might get in changing to these plugs is a result of changing to newer plugs, and nothing else. A new spark plug gapped properly and with the proper heat range for your engine will deliver all the performance and efficiency you’ll ever need and find in a spark plug.