The center electrode ends in a gold or palladi⦠As the ground strap length increases, this adds more mass and can slow the growth of the initial flame kernel. So a small intense spark is much better than a big, weak spark, especially when dealing with richer fuel mixtures and more volumes of fuel being burned. Surface gap plugs present the flame kernel to the piston (or rotor) more directly, reducing the travel time from the spark to the combustion gases. (Right) This melted plug was destroyed when the nitrous system went lean. The boot didn't fit the new plugs as snug as the old AC Delco's, and the internal plug resistance may have been different. Any weakness in materials or construction the spark will find an easier path to ground than the plugs. If you pay close attention, you’ll notice that most racing plugs do not employ extended-nose center electrodes. It is important not to exceed the installation torque, however it is a good idea to torque the spa⦠The plug on the left is a cold plug with a shallow ceramic depth. Torquing the plugs to the published spec with anti-seize overtorques the plug which potentially could break the internal seal between the insulator and the shell, creating a leak path. You are still running the same coil, cap, rotor and wires designed to provide spark to a .035 gap. Why is this plot drawn so poorly? Cut back ground straps are also useful in applications where a standard strap may interfere with the piston dome. This can occur as a result of high cylinder temperature and/or pressure that causes the air and fuel to self-ignite. We'll send you raw engine tech articles, news, features, and videos every week from EngineLabs. (Left) Often, a projected-nose plug (shown on left) with a long ground strap can build excessive heat and cause pre-ignition issues. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. From there, the heat is dissipated into the cylinder head and eventually into the cooling system. The 1978 plug gap spec was reduced to .040" and we gapped all future plugs to that spec with no more issues. As is stated at the end of the excerpt, you'd need to run your car on a dynamometer to find the best spark plug gap. Spark plug gap refers to the gap between the spark plug center electrode and the grounding electrode. So you might look around for a shorter plug to create more clearance for the spark plug boot. This keeps the ground electrode short, minimizing its path to the cylinder head where the heat can be dissipated. The wider gap is to promote a bigger spark to the fuel/air mixture in the combustion chamber for a better burn. Pischinger and Heywood [10] found that the cyclic variation of flame propagation near the spark plug influences the amount of heat release at the spark plug gap and this greatly influences the so-called rapid burn angle. Reeves points out that the facts support the exact opposite conclusion. Most competition engine builders commonly choose a colder heat range plug to prevent possible engine damage. Another idea that can offer potential advantages is a cut-back ground electrode where the ground strap is cut or filed to uncover the center electrode. So thecombination of increasing the heat range, and the platinum center electrode contributed to making the engine idle better, cleaner, and more efficiently. We removed the threads on these two plugs to illustrate heat range. Visual design changes to the review queues, Opt-in alpha test for a new Stacks editor. Why do my mobile phone images have a ghostly glow? I have documented dyno sheet where we lowered a spark plug gap from .045 to .032 and picked up 35 hp. We will safeguard your e-mail and only send content you request. The two main ways to reduce quenching are by reducing the mass of metal around the flame kernel, or widening the gap ( which I guess also effectively reduces the amount of metal in contact with the flame kernel ). Thus, to check the spark plug gap at high engine speeds, you'd need to run at full throttle and immediately turn the ignition off without allowing the engine to idle. How does ambient temperature affect engine efficiency and fuel consumption? Changing the electrode gap is called a spark plug gapping. There may be something about utilizing different heat ranges on a plug to help with combustion, but don't know for sure either. However, if you drive at full throttle most of the time, you should reduce the gap by about 0.010" for better performance. A common question with performance engines is selecting a spark plug heat range. The copper core does transfer a significant amount of heat. Perhaps this is due to the much wider gap on the surface gap spark plugs they use. Platinum spark plugs come in two varieties - single and double platinum. For tuning these engines, it’s best to start with a very cold plug with a short ground electrode. An iridium plug uses an extremely fine wire (0.5 to 0.6mm or 0.019-0.023-inch) that, because of its small size, can reduce the required coil voltage by as much as 20-percent. Some manufacturers may have the optimal gap set, while others will be a lot more conservative. Other than tectonic activity, what can reshape a world's surface? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. A precise air and fuel mixture requires a precise and timely spark to burn it. The heat range is established by the distance the heat in the center electrode and insulator ceramic must travel before it contacts the steel body of the spark plug. MSD’s Spark Guard is dielectric grease used to protect the boot from sticking to the spark plug and minimize errant spark leakage. On the other hand, it was believed that less amount of material near the gap is a major contributing factor for more rapid growth of the flame kernels. This is also incorrect and relates back to our earlier point that a fine-wire electrode has no impact on heat range. A spark plug gap is the distance between the end of the electrode and the base of the spark plug. Reeves says the single- and double-platinum were employed strictly as a measure to increase the durability of the spark plugs. The plug melted because of excessive heat in the chamber. While spark plug gap does not have a direct effect on timing, excessive gap in a power adder application can easily cause engine misfire. This often is a result of dyno test data where the colder plug appears to work just fine. This grease is an insulator not a conductor. The center electrode’s precious-metal material does not contribute to the heat range, nor is it a factor with regard to pre-ignition. Longevity is a key advantage of platinum spark plugs. This makes it hard to come to a strict conclusion. This is an Autolite race plug that is also configured with a side gap. We’ll start with detonation, which is an uncontrolled combustion pressure spike that can occur at any time, even before the spark plug fires. The plug on the left is a hotter heat range than the plug on the right. How much can sub-optimal octane affect efficiency or power? Copper is used as the core material for nearly all spark plugs. The new plugs were a different brand (Champion) and the spark was arcing from the plug boot down to the plug base. The results presented in [3] and [7] showed that a spark plug with fine center and ground electrodes produced lower combustion variation with a reduction of approximately 3.1% in COV and 2.4% in the fuel consumption compared to regular spark plugs. It was reported by Hori et al. This process occurs thousands of times per minute, but for it all to work, the source of the spar⦠That’s walking a very fine line. I recommend them for older vehicles that don't need platinum plugs. Your ignition system will thank you for your attention to detail. So we decided to talk to Director of Engineering for Autolite, Jerry Reeves, who not only knows this subject really well, but is a car guy, too. For street engines, the extended-nose is good for part-throttle efficiency. Fine-wire plugs like this Denso Iridium (left) requires much less voltage to fire the same spark plug gap versus a standard copper-core plug (right). The move to iridium plugs could potentially be a performance advantage.
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