total extra weight would be about 2-2 1/2 lbs and one more shaft and an over running clutch on the input saft and the magnetic clutch to cycle the system and the belt is already there dirving the water pump like the Classic. This is what the Honda Accord uses. Actually you wouldn't need the over running clutch as the shaft is free to rotate when the clutch is released. This is even simpler than I envisioned no wonder Honda uses it.
I'm confused. Clearly there is no belt 'already there' in the 04+. The water pump is electric also. Are you talking about the belt in the Hondas or the Classic? What does that have to do with adding a whole new assembly to the 04+? Even if you could, and wanted to add some sort of contraption to the 04+ to do this. (Which would entail taking up space and rearranging the engine compartment anyway, remember, once you don't have a belt you are free to locate pumps and compressors anywhere, not just where they are in line with a belt), you would still be putting a drag on the ICE 100% of the time for something even you propose using only a miniscule portion of the time. I just don't get it. I still see absolutely no benefit, and the benefits of doing it the new way are overwhelming.
In Dallas I see no net change in summer versus winter MPG. The A/C hit seems to be compensated by the increased efficiency of the engine in warmer ambient. I would advise getting a custom front window Sunshade and then of course park facing the Sun (south, for an all day park), as much to keep UV off the dashboard as to keep the cabin cooler.
Tempus brings up a good point about belts and water pumps. However, I was under the impression that there are multiple water pumps on the Prius and that one of them is belt driven. I do see a belt on the passenger side of the engine compartment. If that isn't for a water pump, what is it for?
Actually, the 2G does have a belt and one mechanical water pump to circulate coolant in the ICE. Stupid idea if you ask me. That could have been one more wear maintenance part eliminated if they had gone all electric on that one. They could have made the heater core electric pump do double duty to circulate coolant exclusively for the ICE by using another bypass valve or re-arranging the existing one. When I first got the car, and found out the power steering and A/C were electric, and it had 2 coolant motors, I had assumed NO BELTS!!!! Boy was I disappointed when I found out I was wrong.
I hate to be a cynic, but perhaps the reason the belt was left in there was for the miniscule cost savings and possible servicing revenue Other than that, it sounds like all electric would be the way to go hands down. In general, the less moving parts you have the better(at least more reliable). EDIT: A small cost savings does add up when mass producing however...
the problem is the small electric water pump is prone to failure, I do believe Rick (htmlspinner) has had one pack it in on his 2004 Prius, more so than the mechanical on the ICE. The reason most mechanical water pumps fail is over tightening of the drive belt. If the belt is properly adjusted they are long life units. Not uncommon to have them go 20,000 hours without problems. From a manufacturing viewpoint to have the shaft exit the front of the compressor and add the clutch assy is not much of a chore and would only add about $30 to the cost of manufacture. The location of the 2k4 Prius compressor is virtually in line with the belt and pulleys used to drive the water pump.
Possible servicing revenue? Is this a Prius or a Pontiac? :wink: Mechanical pumps are both common and reliable in general. If the pump would always be running when the engine does it is probably slightly more efficient than the electrical, thou must be very slight for such a small pump. Given the amazing engineering of this car, I generally assume the engineers had some reason for everything they did. To be this efficient every little detail must have been discussed at length.
