Turbo surge sounds more like a rattle snake, IMO.
If you hear the constant whistle as you are applying load/throttle, then after TQ lockup and 4th gear (OD) you hear a slight whistle but more of a "shhhhhh" constant sound, that's normal. You're in OD, less RPMs, less load, less whatever it takes to maintain the same MPH. The noise when letting out of the throttle under load is normal, air will find the least resistance way out, and the only way out for some of it is back through the intake. The compressor wheel cannot physically turn the other way unless you have a big time mechanical failure, how could it? It's constantly spining in one direction with the exhaust gas being the driving force.
PSDs don't have anything to necessitate a blow off valve for the turbo, ie throttle plates. I also don't think you can hear our wastegates in our PSDs, not sure how accurate that is though. Mine makes the same amount of sounds with or without the red wastegate hose connected.
Without knowing how fast you're driving;
Leave overdrive off at the speeds you think are weird, you'll still have the converter locking up but you will have more RPMs at the same MPH, and more of a "load" obviously.. plus the turbo will be spooled a little higher.
Dont know how correct all this was, but I usually leave OD off when I'm under 50MPH, the turbo is always spooled around 4-5PSI, plus all you hear is whistle coming at you whereas if I was cruising around in OD, you wouldn't hear the turbo as much incab as explained why. Plus with the straight pipe, it's cool to leave it in 3rd with those higher RPMs, noise! I usually race the PSD with Overdrive off as well.
So what you are hearing IMO has always been there, you have just eliminated the sound dampening. You haven't created any new sounds, you can just hear them better now with less restriction.
Last edited by Lord Tauk : 10-24-2007 at 03:15 PM.