Discrepancy Between Engine Hour Meter and Reality

[lorenzo123]

Correction: Sorry, I meant to say the key was not on during engine shutdown.

[Tom1340]

Originally Posted by Tellie

I got the joke and thought it funny.
But in all seriousness if the OP ran the motor twice as hard at twice the rpms that could account for double the hours. Geesh, it's simple math.

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Yes, it's quite obvious that this is an hour value meter. It doesn't matter how long the engine ran, but how much work it thought it did compared to what a normal engine would do. These meters are also used by Lawyers to calculate billable hours.

[S/V Antares]

The VDO Tach unit shown has a digital readout for calibration and eng. hr functions. The engine hours will only post when there is rpm inpunt. Not with the key on and not running. I think the clock is wrong.

VDO once made Tachs that the hour meters were based on fixed rpm. Example: 1800 rpm for 1 hour showed 1 hr. At 900 rpm for 1 hr it would show 1/2 hr. This was used to get a better picture engine ware which is not based on time but piston travel. The normal running RPM (ie. 1800) was determined by the manufacturer. This practice was dropped in the early 80's.