My old Corolla automatic transmission used to have Drive D followed by several lower:rockon: gears. I used to shift to lower gears while going up or down a mountain. This helped in braking through engine RPM change. So why Prius 2010 changed all this to only ONE drive D? This has nothing to do with ABS fixes.
Um... There is a lot of good information on this site if you search for it. It seems to me that "CVT transaxle" and "regenerative braking" would be a good place to start.
That would be the whole infinitely variable transmission thang. "B" is used only for coming down mountains because it invokes/allows more engine braking to avoid riding the brakes. Using it anywhere else will harmlessly but pointlessly reduce MPGs. It in no way changes the effective transmission ratio.
Because Prius has only *one gear*. If you are interested in how the Prius transmission works, read this: Whats Going On As I Drive?
I want to include this web page also, it has a cool interactive diagram between the mph and electric motors and engine. Toyota Prius - Power Split Device
It would also make sense to post this question in the Gen III forum since you are asking about a 2010 Prius. Tom
because there are not real gears like in your corolla. Honda in their insight created 7 pseudo gears, and I like this solution better. Although I have no idea why they chose 7 or what the best number should be. The prius has a B gear that is quite like a 2 on traditional automatics. Since there is no completely right answer, you can decide if you like toyota's 2 or honda's 7, or even if you like the implementation. I'd really like speed racer style buttons.
As everyone pointed out this is by design. However, I would suggest that future incarnations try to capture on the "traditional" feel of gears as they did (I believe unfortunately w/accelerator pedal at neutral = slight decel). There have been issues with the joystick transmission setup especially with the separate button 'P'. I would suggest instead, a more intuitive approach using a standard shift controller with the positions: "P, R, N, D(Eco), D(Nml), D(Pwr), B". Although debatable, I feel this parallels better the traditional concept of "shifting down" in an automatic (although I still prefer manual, lol) D(Eco) would be the "default" akin to D3 on traditional cars and would put the car into "Eco" mode. This would get you weaker acceleration (not really true on automatics, but if you imagined a manual transmission, keeping a car at high gear makes it go fast but very weak acceleration). D(Nml) would then improve on that acceleration, and finally, of course D(Pwr) representing "Power" giving you maximum acceleration similar to being in low gear. I had trouble fitting "B" because it can be invoked in Eco, Nml, or Power modes, but I think it most fits at the end because there it simulates gearing down to a really low gear to use engine/compression braking. This should remove the thought of "B"="Battery". Heck, they should probably rename "Eco", "Normal" and "Power" to just D3, D2, and D1 anyway to remove any misnomers (as if Power is not eco-friendly when it can probably be more fuel efficient than Eco or Normal if the car is driven in an aggressive manner). Then just rename "B" mode as "D0" eliminating further confusion with "Battery" mode. The only disadvantage is that you'd have to be in "Power" mode by the time you engage "B" meaning either you're going to be shifting rapidly between B and your desired drive mode or stuck with using Power (not a bad idea if you consider steep downgrades are usually followed by upgrades and that you'd probably get better mileage when climbing back up to shift away from B mode instead of leaving it engaged). I say bring back the simple shift selector with button interlock to avoid the 3-second delay but keep it electronic. One final advantage of this method? You could continue to emulate "old automatic" style behavior of flashing the reverse lights (as you pass through R) when engaging Park. I've used this trick sometimes to identify a car ahead has just engaged Park or has just shifted out of Park.
Pretty sure the best number is zero (CVT). This may be why the Insight is less efficient, particularly off the highway.
I had a 3 Diamond Outlander SUV with a 'fake' computer generated 6 spd. CVT that you could lock into any speed, otherwise it shifted from gear to gear like any other auto/tranny. Liked it, but what I miss more than that with my '10 'V', is that when I put it into 'B' for engine braking, the cruise control cuts out- why? Very frustrating as I have to reset it from scratch every time. Getting use to the CVT 'rubber-band-drive' is not happening, the engine changes speeds, and sounds, but not much else speedwise happens in a direct relationship via the foot and ear inputs one expects in controlling one's forward movement in a car (regaredless of a car's use or gas, or electric, or both for acceleration.)
So you remember you are in a power robbing state and shift back out of B, when you get to the bottom of the hill. I am surprised that anywhere in PA needs B. You only want to use B if you have over a 600 foot drop in a hill. No place in PA is over 3300 feet tall, but I suppose 700 ft of it could be in one incline. An example of where you do want B: http://www.oregon.gov/ODOT/MCT/docs/EmigrantHill.pdf
I like B for the 'feely control' of going faster and slower by using one pedal on curvey roads and hills, like driving a manual tranny in a lower gear. It is not power robbing when you give the car gas (it acts the same as if it was in D), and it only hurts gas milage a little during braking. I shift to D during braking if I am going to do a complete stop so the battery won't be turning the engine over (it consumes no gas while it acts as a brake, or idles- being rotated by the electric motor.)
