Quote:
Originally posted by Peryn
I haven't heard it, but i've got a theory. Before you shift, you would normally be working in the higher RPM ranges. Thus, you will be putting out a higher volume of exhaust gasses than you would at a lower engine speed. Well, when you shift, the engine speed drops significantly. So the amount of exhaust you put out drops dramatically. You have this large flow "pulse" moveing through the exhaust before you shift, and a very lower pressure "pulse" after you shift. Between the two i imagine there is a sort of vacuum. Not a lot, but there is a vacuum between exhaust pulses. When that high pressure pulse clears the exhaust, air is now free to move from the outside to inside your exhaust pipes to fill that vacuum and meet up with the lower pressure pulse. That air moving in could be what your hearing.
Again, i haven't heard the sound, and really have no idea what causes it. This is merely speculation, that seems to make some degree of sense to me.
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Seems like it would be reasonable, but although the exhaust gas volume may be reduced, there is still no vaccum, as it's still a positive displacement of exhaust gas coming behind it. Also, that wouldn't be a v8 or ford-exclusive sound.
Can't say I'm familiar with the sound you speak of, but then again, you won't see me behind too many Fords.