Toyota Prius Forum banner

1 - 15 of 15 Posts
G

·
Guest
Joined
·
0 Posts
Discussion Starter #1
I was wondering if you generate the same amount of power back to the battery by applying the brake pedal as you do by shifting into the breaking gear? Intuitively, it seems to me that you want to do as much of your stopping as possible using the B gear since this doesn't use friction to stop your car the way brakes do, but I don't really understand how the system works.
 

·
Registered
Joined
·
928 Posts
B mode uses one electric motor as a generator to slow the car and the other electric motor to use the generated electricity to spin the unfueled engine. Some of the generated electricity also goes to the battery.

Since B mode is often more agressive than you would be with the brake pedal, typically more energy is wasted spinning the engine than you would waste heating the brake pads. Anyway, the consensus seems to be that B mode will keep your battery fuller, but will also reduce overall gas mileage. The Prius User Manual also suggests that use of B mode will often lower gas mileage.

My advice is to only use B mode on those long downhill stretches that you would normally go down in 2 in a traditional automatic transmission car.
 
G

·
Guest
Joined
·
0 Posts
Discussion Starter #3
Thanks

Thank you for this info. The dealer who sold me the car was suggesting that using B gear was the key to getting the best milage from the car. I'll try making more use of the brake and see what happens to my milage. I'm only on my second tank of gas.

I've been noticing a couple of other interesting phenomena. The first is the fact that cruise control seems to do a much better job of getting good milage than I do, regardless of speed. The second is that when I'm just getting rolling out of a parking lot or something, the milage seems to be in the single digit. Perhaps the engine is just spinning fast until the car warms up, just like in a regular car.

Jon
 

·
Registered
Joined
·
115 Posts
My wife and I both have new Prius and tested two different strategies. She used the B whenever possible instead of using breaks and I used my break as normal and never used the B. I get about 57.8 MPG (according to the computer) and she gets 50 MPG. We travel the same route and generally use cruise control whenever possible. Granted this is ancedotal observation but now that she has gone to just driving regularly and only using B on very very steep hills her mileage has jumped up to 54 MPG and hopefully higher.
 

·
Premium Member
Joined
·
2,820 Posts
One thing to remember: using the brakes will illuminate your rear brake lights (safety first!), while use of the B gear will simulate engine braking (with no brake lights lighting up).

Except for a few rare occurances, you'll recharge more with regular driving in D with braking than using B.

The owner's manual also cautions against heavy B usage as it'll lead to lower fuel economy.
 

·
Registered
Joined
·
2,285 Posts
B-mode is great for slow-n-go freeway creeping. No moving from pedal to pedal, just use the throttle to modulate your speed, just like with a stick shift. No brake lights? Again, just like a stick shift, and they DO come on if you come to a near stop, since B mode doesn't do much at walking speed. It's a great calf muscle saver in traffic!
 

·
Registered
Joined
·
4,878 Posts
Reading my owners manual I determined that Toyota put in the "B" shift to be used where engine braking would take some of the load off the normal brakes and should be used in circumstances like steep and prolonged down hills where there were for instance warning signs for eighteen wheelers to shift into lower gears. I've read nothing to change my mind about this.
 

·
Registered
Joined
·
363 Posts
Tadashi said:
My wife and I both have new Prius and tested two different strategies. She used the B whenever possible instead of using breaks and I used my break as normal and never used the B. I get about 57.8 MPG (according to the computer) and she gets 50 MPG. We travel the same route and generally use cruise control whenever possible. Granted this is ancedotal observation but now that she has gone to just driving regularly and only using B on very very steep hills her mileage has jumped up to 54 MPG and hopefully higher.
Have you tried switching strategies to see if the mileage follows the strategy rather than the driver?
 

·
Registered
Joined
·
115 Posts
Yes, I initiallly started out doing the same thing for my first tank and only got 50 MPG (ven though that computer said 55 MPG). The second tank of gas I avoided using except for this really steep hill (transmountain highway in El Paso) and got 57.5 MPG (58 MPG computer). I also noticed I get more regen icons now that I used to and my battery is generally at 60-70% whereas it use to be at 40-50%.

Something else that is hard to account for is the learning curve. With experience the wife and I have learned to drive more efficiently thus higher MPG. maybe we have just not figured out the most efficient use of yet.
 
G

·
Guest
Joined
·
0 Posts
Discussion Starter #10
I've seen my milage go from a pretty consistent 42 mpg up to 48 since I started following the advice here and using B only on the steep downgrades (I drive one every day on my way to work). If any of you folks getting 54 and 57 mpg would like to share additional tips I would be most appreciative

Jon
 

·
Registered
Joined
·
115 Posts
Not sure what to tell you that has not been said already on the other posts. I avoid using the brakes as much as possible (coasting to stops), use cruise control on freeway, use downhills to accelerate, avoid using heat or A/C (usually have vents open in Spring), stay at posted speed limit or slower, check tires, keep junk out of car (excess weight), and learned to feather the petal for driving under 25 mph to primarily use the electric motor instead of the ICE.
 
G

·
Guest
Joined
·
0 Posts
Discussion Starter #12
I think you're last bit of advice, "feather the pedal under 25 MPH" is my biggest challenge. I try to go light on the pedal, but it always seems that whenever the gas engine engages under the speed of 25 my instantaneous milage reading drops into the low teens.
 

·
Registered
Joined
·
111 Posts
B in snow

Back in the days, we had the clutch and downshifted in snow when the traction became iffy. I wonder if they same applies to B mode in snow. MRV, as much snow as you have seen this winter, what are your experiences?
 

·
Registered
Joined
·
363 Posts
Re: B in snow

leebek said:
Back in the days, we had the clutch and downshifted in snow when the traction became iffy. I wonder if they same applies to B mode in snow. MRV, as much snow as you have seen this winter, what are your experiences?
There is no need to downshift an electric motor for power. Torque is at maximum when RPMs are very low.
 
1 - 15 of 15 Posts
Top