[37147]

I really like jnissen's reply. Just use OEM parts. However, I'd like to offer a couple of conceptual insights as to what MIGHT be happening. It could be great to use an app on a phone or iPad (SPLnFFT) that can show pictures of sound frequencies and levels before and after the repair. The belt/pulley system is quite complex dynamically, with the belt sections acting as springs and the effective masses of the pulleys and tensioner acting as masses. The tensioner is a Mass-Spring-Damper (MSD) system on its own. In addition, the teeth of the belt on the pulleys deflect, modifying the effective spring. The resonant frequency of a system is approximately f(hz) = 2pi*sqrt(AE/L/M). A is the cross sectional area of the belt. E is Young's modulus "stiffness of the belt", L is belt equivalent length, and M is the "effective mass" of the pulleys & loads referred to the belt. So... at a first level, the area of the after market belt is lower. The belt is softer so E is lower. These tend to drop the natural frequency of the belt. However, the square root in the above equation tends to reduce these effects and is probably not enough by itself to make your noise. The tensioner has its own natural frequency. So if the natural frequency of the tensioner connected with the belt is close to the lower frequency of the belt and pulleys you can get an audible beat frequency that is the difference between the two frequencies. This is the effect of two people whisling high notes that are just a bit different from each other. You hear the difference between them. You mentioned a "rattling" sound". That can also be bearings that are shot in the pulleys (did you check the bearings in the pulleys?). You mentioned: "weird vibration there that causes the belt to slap a bit and vibrate the tensioner". They can make rattling sounds by again interacting with the belt. In this case the resonant frequencies could be higher since the pulleys and belt are creating their own resonance with lower effective masses involved. Belt slapping is yet another dynamic similar to vibrations in the string in a musical instrument - resonances love to absorb energy at their natural frequency. I hope no one tries to go down the theoretical path, as you may never return. Let the Honda engineers agonize over this... So.... I'm glad you found that replacing with OEM parts and with a new tensioner worked out.