Tweet
Use a torque wrench and tighten to the factory torque spec when installing spark plugs on your Ultras.
Not only the properly torqued plugs would come out easier later, but also they ensure the peak performance of your Ultra's engine. Over-torqued plugs are more likely to develop an internal crack causing intermittent "no-spark" condition. Have you ever heard or experienced Ultra 250/260/300 suddenly running poorly, and then runs better right after replacing the plugs? And then, you wonder, ÔÇ£Why does Ultra go through plugs like 2-strokes?ÔÇØ That's because one or more of your spark plugs have the internal crack and they are not firing.
Through the crack in the spark plugs center core ceramic insulator, the current will find an easier route (with less resistance) to find the ground, instead of trying to jump the ground electrode gap. When that happens, you are running on either 3 cylinders only or less.
Supercharged engine's peak combustion pressure is approximately 56% higher than that of the same N/A engine. More fuel/air in the same volume combustion chamber (1498 cc, same as 15F) means higher combustion pressure even though compression ratio is substantially less, Ultras 7.8 (250/260), 8.4 (300) vs. 15F's N/A 10.6. The NGK PMR9B spark plug for Ultras is specifically designed for such high combustion pressure engines against the possible internal cracking. That's when the proper plug installation torque becomes critical - you don't want to induce any unnecessary stress on the plugs by over-tightening them. According to NGK, only 2 vehicle manufacturers use the PRB9B plugs. Kawi (on their Ultras) and Maserati's first gen supercharged 405 HP 4.2L V8 Gran Turismo in 2007 (now 4.7L making 440 HP) , Quattroporte, etc. Do yourself a favor and use a torque wrench on plugs next time. After all, it's your ski.
Not only the properly torqued plugs would come out easier later, but also they ensure the peak performance of your Ultra's engine. Over-torqued plugs are more likely to develop an internal crack causing intermittent "no-spark" condition. Have you ever heard or experienced Ultra 250/260/300 suddenly running poorly, and then runs better right after replacing the plugs? And then, you wonder, ÔÇ£Why does Ultra go through plugs like 2-strokes?ÔÇØ That's because one or more of your spark plugs have the internal crack and they are not firing.
Through the crack in the spark plugs center core ceramic insulator, the current will find an easier route (with less resistance) to find the ground, instead of trying to jump the ground electrode gap. When that happens, you are running on either 3 cylinders only or less.
Supercharged engine's peak combustion pressure is approximately 56% higher than that of the same N/A engine. More fuel/air in the same volume combustion chamber (1498 cc, same as 15F) means higher combustion pressure even though compression ratio is substantially less, Ultras 7.8 (250/260), 8.4 (300) vs. 15F's N/A 10.6. The NGK PMR9B spark plug for Ultras is specifically designed for such high combustion pressure engines against the possible internal cracking. That's when the proper plug installation torque becomes critical - you don't want to induce any unnecessary stress on the plugs by over-tightening them. According to NGK, only 2 vehicle manufacturers use the PRB9B plugs. Kawi (on their Ultras) and Maserati's first gen supercharged 405 HP 4.2L V8 Gran Turismo in 2007 (now 4.7L making 440 HP) , Quattroporte, etc. Do yourself a favor and use a torque wrench on plugs next time. After all, it's your ski.
310R
Current Ski's; 2013 Utra 300x & 2013 Yamaha VXR ; Previous Skis
Comment