All,
I was mixing up oil changes with fuel burn when I said I used tach
time - I use clock time for fuel burn, since tach time is linked to
engine RPM. So my 4.5 to 5 GPH is based on elapsed time, not tach
time. I do oil changes between 25 and 30 hours tach time (I have a
filter).
Larry Snyder
N99340t
On Jan 31, 2008, at 9:50 AM, John Cooper wrote:
> I never get better than 6 gph. If we're doing touch and goes,
etc. I may get 7 gph. I'm using tach time, is that right?
No. The tach “time” passes slower when the engine is running slowly
and faster when the engine is running fast. A typical C85 tach
should record one hour in one hour (i.e. be accurate) at 2500 RPM.
Basically, if you go by tach time your fuel consumption will be
almost the same regardless of engine speed. It will take a very
long hour to burn all that fuel at 1800 rpm, however.
Bottom line, measure gallons used verses actual elapsed time.
John Cooper
Skyport Services
518 797-3064
www.skyportservices.net
