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Chris S Hackett
[quote=”nightflyr” post=204401]The unusual shifting nature of the sound is what really has me baffled. I sure wish someone could explain that to me.
That is fairly easy..
If it is a belt or drive accessory, it will shift speed along with engine rpm.
When your driving the engine rpm will change (lower) when going into higher gears.
It can sometimes disappear above a certain speed.[/quote]
I would understand and agree with this except that while the engine RPM is “linear” so to speak .. meaning that I steadily increase from idle to 2k RPM in a straight, smooth steady line, where as the sound “sifts gears” during this time. Meaning that the tone or pitch of the sound will increase to say .. 900 RPM, and then the sound will reset back to the low pitch and then climb back up to the high pitch at 11oo RPM, and then it will “shift” again and then begin climbing again to 1300 RPM and it cycles again. So while the engine RPM climbs slow and steach straight through from idle to 2k RPM, the mystery sound cycles through this low to high pitch several times throughout the RPM climb from idle to 2k RPM.