I think I'd try something simpler (in my mind) first... I'd find the sound file for the engine in question on the MTH website. I'd take the ADPCM program from Mark DiVecchio, chop out the sounds of interest and turn them with perhaps Audacity or something similar to MP3 clips say ... load these onto the phone or similar blue tooth device -- and then put a small blue tooth speaker in the dummy, etc...
The big issue: sounds under manual control. Another is the clips will never be spot on to what you really want ... but if you get tired of this approach, then it wouldn't be too much to add more computer control to the sounds.
(for example it would not be too hard to play the start up-->idle engine clips in sequence and have the idle clip loop until further notice from a computer)
