Quote:
Originally Posted by cmouta
Is that a fair comparison? good mileage from highway driving comes from overdrive gearing that brings the RPM of the engine down for a long time. Less effort to move a moving car, less throttle, less air, less fuel used over time.
In stop and go, the engine is probably seeing higher revving through gears working harder to get you to get you moving, which is where the worse fuel economy comes from.
So when I think of comparing a car to WOT on my tractor, I imagine max RPM, max air, max fuel being burnt hence my thoughts about bringing throttle down when not loading.
But admittedly I really don't know anything about tractor engine design. Maybe its more efficient at WOT? I picture the engine sitting there pegged from being WOT, waiting to have that energy used for working my Hydro pump or for PTO and its being wasted if not doing either. Again, I don't know if that is right. That's just how I imagine it.
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It's a difficult explanation, and I'm not going to put it very eloquently but here goes. Yes, at WOT, the engine is going as fast as it has been designed to go but the real fuel usage comes from load. The engine will use more fuel at WOT under full load than it will at WOT with no load because it takes less fuel and air to make that piston go up and down when there is no load on the motor. Plus like I believe J-Mech said, revving up and down uses more fuel as the motor has to work harder to get back up to 3600rpm thereby negating any fuel savings offered by lowering rpm's while backing up and/or disengaging the PTO. Hope this helps!
Oh, and these single cylinder engines, imho, literally sip gas like a fine wine. By comparison, the 2 cylinder KT-17 in my 682 chugs the stuff like a ravenous beast that's been starved in the desert for a week. Moral of the story; don't worry about the gas usage.
