Last year (2020) I installed a new digital hour meter, the Isspro R8865 from Moyer. It replaced the old mechanical hour meter, part of the ancient mechanical tachometer that runs off the accessory drive. After decades of running well it stopped turning over the hours and started clicking. The little plastic worm drive finally gave up the ghost. I didn't realize until I took it apart that I was supposed to oil it. There was a tiny cup on the back to drop oil into. The tachometer still works. It took me a while to realize I was now counting the hours the ignition was on, not the hours the engine had been running. I try to not leave the ignition on, but occasionally it happens, sometimes overnight. I know this is supposed to fry the coil, but I have seen no evidence of that. The coil I have now was bought from Moyer in 2018.
Anyway, since the new hour meter my fuel economy has improved about 100%. I used to average about a gallon an hour, now it is two gallons an hour. I have put 75.6 gal in the tank to fill in 4 fill-ups, while the new hour meter has elapsed 172.3 hours. That's 2.28 hours per gallon. I do spend a lot of time in forward at low rpms, maybe that's it, but that's nothing new. Unless I have been leaving the ignition on with the engine off as much as when it's running, which I doubt, I have no explanation for this phenomenon. The good old A4 is running like a champ; starts easily with choke, a little rough until it warms up in a few minutes. I have an Indigo thermostat which warms it up quickly. The idle adjustment screw is out from the seat 1 turn, adjustable main jet is out 2 turns. It may be a little rich, but I see no soot on the plugs. No smoke in the exhaust. I have put 3000 hours on the beast since the rebuild in 2001. I did retard the timing a bit this spring (turning distributor counter clockwise) while running at 1500 rpm in forward, to make it sound better. in 2019 the vacuum at 1500 rpm was 10, now it is 12, so the engine isn't working as hard. I get about 5.5 knots at 1750 rpm. Is it possible that a slight timing adjustment could decrease fuel usage by a factor of 2?
Anyway, since the new hour meter my fuel economy has improved about 100%. I used to average about a gallon an hour, now it is two gallons an hour. I have put 75.6 gal in the tank to fill in 4 fill-ups, while the new hour meter has elapsed 172.3 hours. That's 2.28 hours per gallon. I do spend a lot of time in forward at low rpms, maybe that's it, but that's nothing new. Unless I have been leaving the ignition on with the engine off as much as when it's running, which I doubt, I have no explanation for this phenomenon. The good old A4 is running like a champ; starts easily with choke, a little rough until it warms up in a few minutes. I have an Indigo thermostat which warms it up quickly. The idle adjustment screw is out from the seat 1 turn, adjustable main jet is out 2 turns. It may be a little rich, but I see no soot on the plugs. No smoke in the exhaust. I have put 3000 hours on the beast since the rebuild in 2001. I did retard the timing a bit this spring (turning distributor counter clockwise) while running at 1500 rpm in forward, to make it sound better. in 2019 the vacuum at 1500 rpm was 10, now it is 12, so the engine isn't working as hard. I get about 5.5 knots at 1750 rpm. Is it possible that a slight timing adjustment could decrease fuel usage by a factor of 2?
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