@Paul Kallus - My understanding is that 10 mph for one engine is not the same as 10 mph for an engine of a different type/scale in MTH land. I've seen this first hand and one of the local railroad clubs. However, speeds between the same engines (same release year) are supposed to be the same...which brings us back to your original issue. My understanding is that there is also settings in the eprom that determine the speed to engine translations. Mark D. might have some info on this as he's intimately familiar with the PS3.
Regarding Melgar's comments about friction, etc..., one would assume that with the tach system, MTH implemented some type of PID algorithm to give the "slower" engines more of a boost. Having said that, if the non tached motor is dragging, that would possibly account for the speed difference as basically the other motor would have to pull the slower motor. Lot to think about in terms of design issues.
As for lash-ups, I've been wondering (aka plan to ask), if anyone in MTH land has tried starting their lash-up to only discover than one engine doesn't start or one engine starts much later than the others. Your comments made me think about that again.
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