I was going to speculate as to how they could go wrong with so many engine sounds, like guessing that they didn't check the audio until they got back to the studio, then realized it was garbage and un useable so they had to improvise...but thats just speculation. Instead I'll just ramble based on my experience in sound design and audio production.
First they should identify where things go wrong during the recording process, or where things go wrong in the sampling / manipulation process. The sounds guys need to go back to the drawing board on this issue.
Perhaps they should take a page from the Need for Speed series approach to audio, in which they record an entire RPM range of a car (under full load), then half throttle through the rpm's, then light, and then mix between the layers on the fly depending on how much you apply the throttle. I'd volunteer to program this myself. Its NOT a hard concept to put in action. They just need to get over the fact that they CANNOT replicate engines based on synthesis, which sounds like they are trying to do, and failing miserably at it. In other words, they need to use longer audio samples, and rely less on adding synthesis techniques to compensate for their poor recordings / samplings of any given engine.
Most of the cars in the game sound like a generic / muffled mid rpm sample, which is then getting pitch shifted up or down based on the users input, hence the vacume cleaner effect. What they STILL FAIL TO REALIZE is that engines are much more dynamic. They don't simply increase pitch. They scream, roar, sputter, click, bang, choke, vibrate based on surface movement, and their character evolves often through the rpm range, like awakening monsters only at specific RPM's. The sound guys need to be recording every car under different loads, both On and OFF the track, and implement the sounds properly. No shortcuts. No BS. If GT7 doesn't deliver epic engine noises later this year / next year, I'll begin to lose faith in the series.
