So I finally drove enough to get down to about 1/8 tank of the 87 octane ethanol... Filled it up with the 91 premium (best available in my area, no 93), and still drove carefully for about 30 miles. It STILL makes the noise when the supercharger kicks in.
The "rate" or speed of the sound seems to be what I would consider consistent with one of the cylinders of the v6 firing. As RPMs rise and fall, so does the speed of the "flutter" but again, ONLY when the supercharger starts measuring boost on the DIC. If I play with the throttle just right I can get high RPMs going without boost and hear no sound vs. lower RPMs with boost and then the sound is there. Of course, high RPM and boost the sound is there too. Just trying to note that RPM isn't the factor, but the boost from the supercharger is, whether it is higher or lower RPM.
Temped to put the whole front end up on jack stands this weekend, having my wife get in the car, have her put it in drive and with the hood popped put it into drive and hit the gas enough for the supercharger to kick in and then see if I can localize the sound under the hood. The problem is that this idea seems fairly dangerous. I could do it in the driveway to prevent the car from possibly coming off of the jack stands and driving through the back of the garage, but nothing would prevent me from getting run over if something like that happened, even in the driveway. I guess some thick, long, and wide wood blocks could be more stable than the jack stands, but still, there is always a risk.
The reason for needing to so something like that is just because the supercharger does not kick in when the car is in neutral and thus the sound never happens.
Can't imagine the cost of a time slot at a dyno machine just to diagnose a noise under the hood, plus I don't know where I would find that here in the middle of Iowa. At that point, I would just take it to a mechanic that can lift the whole car off the ground with a car lift.
