We don't have synonyms for tachs yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are tach, tachy and tachi.
(n) :
(informal) Clipping of tachometer. [A device for measuring the revolutions per minute (RPMs) of a revolving shaft, as with the driveshaft of an automobile.]
(n) :
(informal) Clipping of tachometer. [A device for measuring the revolutions per minute (RPMs) of a revolving shaft, as with the driveshaft of an automobile.]