I recently purchased a Bachmann 3 truck shay loco with the tsunami DCC decoder.  This is my first experience with a shay.  When it runs at low speeds the synchronized chuffs sound like they are running at a high RPM.  Is this normal for a Shay?  I realize that the RPM's would naturally be faster than a normal engine due to the mechanics of the Engine and the smaller diameter of the wheel.  I just did not think that it would be that much faster.  Does anyone here have one of these Shays? and if so, is this normal. 

Is there any harm in leaving a digital engine on track idling while running other engines?  If so, how long is it safe to allow engine to idle?  I am currently running 3 Bachmann Spectrum DCC engines with Tsunami sound.