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RedDevil · 08-31-2013, 03:15 PM

Within certain limits only.

A conventional CVT can couple any number of revs to any kind of speed, within the limits of the CVT. So on the highway I'm always on the far end of the scale ('top gear') and my RPM rise in tandem with speed.

The Prius has a HSD drive, which is a planetary gear set with additional electric motors and generators that simulate CVT behaviour. It has 3 gear ratios where the electrics don't have to do anything (the gearbox is switched to one of its 3 gears matching the ratio needed) and then it will be at its best, probably more efficient than any other gearbox.
In between the motors and generators compensate for the unmatched ratio and cause a slight loss of efficiency. On the whole, still better than my CVT.

Best of all, you can have a HSD gearbox in any brand of car, as long as that is Toyota.
Patent laws...

Because of the workings of the HSD there is no strict limit to the ratio, it can be 'infinite' (engine stalled, electric motors running).
The art is to make the gearbox work at its most efficient ratios for your regular use. Changing the tire size may help a bit. But as the transitions in the gearbox are seamlessso is the effect on efficiency; there are no sharp cliffs.

08-31-2013, 03:15 PM	#33 (permalink)
RedDevil Master EcoWalker Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 3,999 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 52.82 mpg (US) Thanks: 1,714 Thanked 2,247 Times in 1,455 Posts	Within certain limits only. A conventional CVT can couple any number of revs to any kind of speed, within the limits of the CVT. So on the highway I'm always on the far end of the scale ('top gear') and my RPM rise in tandem with speed. The Prius has a HSD drive, which is a planetary gear set with additional electric motors and generators that simulate CVT behaviour. It has 3 gear ratios where the electrics don't have to do anything (the gearbox is switched to one of its 3 gears matching the ratio needed) and then it will be at its best, probably more efficient than any other gearbox. In between the motors and generators compensate for the unmatched ratio and cause a slight loss of efficiency. On the whole, still better than my CVT. Best of all, you can have a HSD gearbox in any brand of car, as long as that is Toyota. Patent laws... Because of the workings of the HSD there is no strict limit to the ratio, it can be 'infinite' (engine stalled, electric motors running). The art is to make the gearbox work at its most efficient ratios for your regular use. Changing the tire size may help a bit. But as the transitions in the gearbox are seamlessso is the effect on efficiency; there are no sharp cliffs. __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.2 Gmeter or 0.13 Mmile. For confirmation go to people just like you. For education go to people unlike yourself.