Tach reading HIGHER than Hobbs

[prhutson]

I installed a used D-10 EMS into my Glastar with 4cyl Lyc O-320 last fall. At annual, I noticed that the tach, which I had been logging, read 80 hours since installed, while the Hobbs read 24 hours. The Hobbs is the more accurate record of my engine & flight time. My cruise tach setting is at 2600, and since much of my winter flying is IFR drilling, the tach should read less, not almost 3x higher than the Hobbs. The RPM reading is correct. Thoughts, or just ignore the tach time?
Thanks
Paul

 

[Dynon]

That shouldn't be possible, obviously, but there's nothing immediate that comes to mind. You're not seeing RPM spikes or anything? You have a lycoming/continental it sounds like?. One thing that could cause this is if tach and hobbs started from different numbers. Ie, hobbs started at 0 but tach was erroneously or mistakenly set to something higher? Over the next flight or two, keep an eye on the two times to see how they increment.