On 30/07/13 21:02, Andrei Alexandrescu wrote: > On 7/30/13 11:35 AM, Walter Bright wrote: >> On 7/30/2013 11:18 AM, Andrei Alexandrescu wrote: >>> Thanks for this anecdote. It's at the very best circumstantial. (With >>> the engine >>> off, the oil pump wasn't even started!) >> >> The oil pump is driven by the crankshaft, so if the engine is turning, >> the oil pump is. (There are some highly specialized race engines with an >> electric oil pump, but that is highly unlikely here.) >> >> I was told by U-Haul that when towing a car long distance, you couldn't >> just put the manual transmission in neutral. You had to take the >> driveshaft out, because the transmission was designed to circulate the >> oil based on the front shaft turning, not the back shaft. It would sieze >> after a while if you only turned the back shaft. > > So that invalidates the anecdote.
I feel guilty... > >> I also pointed out the "hammering" effect of alternately forward driving >> then back driving the rotating parts, as the parts forcefully take up >> the slack of hysteresis. > > I guess any brisk adjustment of throttle would be unadvisable, one direction > or another (i.e. releasing the clutch with a large difference in rotation). > Back driving, however, happens as soon as one just lifts the foot off the > pedal - the inertia of the car pushes on the engine. > >> I also pointed out the effect of unburned gas from backdriving washing >> oil off of the cylinder walls causing undue wear. This definitely >> happens with carbureted cars, but with modern fuel injection the fuel is >> shut off when backdriving. > > That's my understanding as well. With fuel injection, essentially backdriving > is rolling on zero gas consumption while preserving some mechanical energy - > aweee-sooome. > > > Andrei > -- Jordi Sayol