The “B” setting allows the drive motor to continue to produce reverse torque by being used as a generator, and the electricity generated is used to drive the engine via the motor alternator. This effectively allows the engine to be used as a brake and regulate vehicle speed. The engine is spun at high speed with no fuel being injected, using it as an air pump to dissipate the momentum of the vehicle. It will also charge the battery but when you run out of capacity to charge because the battery is full, it will use the engine to dissipate energy. The engine kept running and didn’t go into EV mode right away because it cooled down by processing air without combustion. If you were driving down a long steep grade in “D” the car will fill the batteries up to 100% and then you will be using friction brakes which can overheat if the grade is long and steep.
@@ibeatmycatandmydog9322 Not normally. Most braking is still done by recharging your batteries in the normal driving mode. If you are in the mountains or a long very steep hill then it would be useful, just like using low gear to descend a steep grade on a conventional car. In B mode the generators charge the batteries but also “waste” energy by spinning the engine with the fuel turned off and using it as an air pump for “compression braking” to save wear and more importantly heat buildup in your brakes. This is not necessary in normal conditions.
@Andrew H No, your battery will recharge faster with regular regenerative braking. However, as stated previously, if you are descending a long steep grade, the B mode will consume extra energy by spinning the engine in order to slow your descent down a long hill. If you use this function in normal driving, some of the energy that could go to your batteries will instead go to turning the engine when turning the engine is not needed. The only time this would be advantageous is on a long hill descent where the battery will recharge to over 80% before you reach the bottom of the hill. In this case turning the engine as a dynamic braking load instead of engaging the friction brakes will allow you to control your descent speed without overheating the brakes.
@@thatcarguy1UZ so how does “b mode” work in full EVs? (Not hybrids). I have this exact shifter in a 2014 RAV4 EV, and have accidentally driven miles with B mode engaged not knowing anything other than the fact that the cruise control won’t work. Took me several months to connect the two. It doesn’t seem to brake much. After discovering what it really was, I tried to use it like I would with the Chevy Volt, and apply it when stopping.
A lot of manufactures have a CVT transmission but the transmission in the Prius is a completely different design. There is no belts, it's a variable transmission based on planetary gears with the ratio being changed by the difference in speed of the Prius' separate electric motors which drive different parts of the gearset. It's a fascinating piece of technology.
You are correct. Calling it a CVT is a bit misleading, because it is an entirely different design. One gasoline engine, and two electric motors are connected to the drive wheels, through a planetary gear-train which functions like a differential in reverse; When they are pulling in unison, full power is transferred to the wheels, but when the electric motor is running at a different speed to the gas engine, a gearing ratio is achieved, to allow the gas engine to run at more efficient speeds. In fact, "neutral" is never actually neutral, because the motors and engine are never disconnected from the drive-train; the electric motor compensates for the gas engine in whichever direction it needs to turn, to allow no torque to go to the wheels, allowing it to roll.
Thanks for explaining the "B" mode. Bought my 2007 Prius new and never used it before. Still on original brakes, Four new tires, couple change outs of wiper blades, three headlamps, and one new battery. Most reliable vehicle (besides my '97 Chevy S 10) I've ever owned.
MG1 actually spins the engine up during B mode to create drag on the drive train. The engine is not actually producing power, the injectors are off. The main reason not to use B mode during normal driving is it causes the engine to spin and places a electrical load on the system. The hybrid ECU also normally tries to prevent 100% charge as the batteries last longer if not charged all the way to full.
B" mode is also fantastic for snowy downhill driving. It just slowly grips it's way down the road without having to use foot braking which is where most skids start. Getting some good winter tires and using the prius technology to your advantage can make this car VERY good in the winter.
Thanks for the clarification of the "B" mode. I have a 2007 and always wondered. Bought it new and currently have about 125k on the odometer. Just wondering if the lower glove compartment lamp is normally ON whenever the headlights are on.
Great to know! The Prius is also quite good on ice in general, even without B mode. My 2016 Prius had its first test on ice last winter when I had to drive on a back road that was a complete sheet of ice. Normally, I would have just glided over it and not turned the wheel, but this road was downhill and curved so I had no choice but to brake and pray. The Prius performed amazingly. Basically the anti-lock braking system kicked in right away when I gently hit the brakes, and it pumped them the whole time we went over the ice. It was nice and smooth (just sounded scary) and I was even able to turn without skidding once. I think the Prius knew to do this because it could sense the tires losing traction and so it pumped the brakes to help regain traction. And I didn't even know I could use B mode to help in snow so I might try that next time!
Was a passenger in a Prius on a road freshly covered with snow. Had hard time explaining "B" mode to the driver. I suggested using the "B" mode to trim off excess speed rather than braking, especially while turning. At low speed was all too easy to slide into another vehicle while negotiating through a neighbourhood with narrow roads, random parked cars and changing gradients. Got earfull for being too technical.
B-mode is an option to waste energy in the form of using the gasengine to compress air. This does helps to slow down the car. The passive regeneration is about 2x as strong in B then in D (no foot on break). So you are charging your battery 2x as much. Problem is that the car is loosing speed from compressing air as it is enginebreaking. This will make you get less total energy into your battery compared to just keeping shifter in D-mode and apply a little pressure on the breakpedal. This way you are only using the rechargegenerator to slow down your car and are able to get maximum charge from the downhill. Note that you should not go to close to maximum on the charge bar. As the bar gets closer to maximum it starts to softly apply frictionbrakes wich lead to heat instead of battery charge. So in ECO standpoint B-mode should be avoided. As others said B-mode is usefull when battery is fully charged and still going downhill and in winter to get some free engineheat from enginebreaking friction to reducing the engine ON-times at redlights and slow speed driving that in summer normally is done in EV mode. Forced engine running is due to heatsettings. Turning heat off will allso turn gasengine off (if engine is 60+ degres celcius). So dont waste kinetic energy with enginebreaking when you have regenerative breakes. Non hybride cars can save brakepads by using enginebreaking.
Depending on the vehicle's speed and the battery SOC (state of charge), the Prius will do this using regenerative braking and/or high-RPM zero-fuel-flow engine braking. ... Just as you might downshift into 2nd gear when going down a long, steep hill to prevent brake damage, you can "downshift" into "B" mode on a Prius.
I enjoyed the video! I used B mode on a very steep hill in Portland, Maine. It does grab very well, and it did bring me below the speed limit. Great feature!
Thank you! I am an Uber Driver. I just picked up a 2014 Prius 2. The money, that I am saving in gas, pays my note. I had rider today ask me about the B drive.; I had no idea! Thanks so much! Best, Matt
Oh man, good stuff brother. I'm the opposite - I drive 99% of the time in PWR Mode. I love how much more fast it can accelerate and I it goes immediately without me having to push down too hard on the pedal.
"B" mode is also fantastic for snowy downhill driving. It just slowly grips it's way down the road without having to use foot braking which is where most skids start. Getting some good winter tires and using the prius technology to your advantage can make this car VERY good in the winter.
This was great explanation and demonstration of B-mode on the Toyota Prius. I am in hopes that you will do more video explanations and demonstrations on the Toyota Prius... Especially the Gen-4 Prius for me :) Very informative!
Awesome explanation! I have a 2014 Prius V 5 on the way from LA (Carmax) so I'm learning all I can about these. I'm a techie person so I already know this will be fun to drive.
I am an uber driver in Seattle bought prius at 0 miles maintaining it since then properly now it's at 170k one problem windshield wiper motor, other than that no problem no engine check light. same engine as yours 1.8l. I use b made going down the hill it charges your battery plus helps you with good mileage. car had plenty of power it can top out 125mph easy. awesome car. The b mode is actually engine braking I don't recommend on very steep hill. With b mode you can always charge your battery 100%. I have been doing it since I have owned it. I still get between 45 to 50 mpg
When the battery is full and you say the engine is still running, it's because it can't regen any more energy to the battery so the engine has to take over the braking instead. It's a clever system and has its uses, but I've not had to use B mode myself as my area is fairly flat.
@@cutflow2 It's not desirable, but you can if you want to. Instead you should use regen to slow down and recapture as much energy into the battery as possible for best fuel economy. B mode is for long hill descents not for general stopping.
its not only the transmission that is breaking the car but also the high compression ratio of the prius engine (13:1 rather than 10:1 in a regular otto engine) witch produces a "bigger" vacuum in the cylinders as the pistons are moving downwards.
My Prius 3 was able to charge the whole battery (all lines) in the French mountains. I drove 4000 km in Europe from the Netherlands to the French Pyrenees and back again. Average usage 5.1 liters per 100km, this is not bad in my opinion if you know that on the Highways was the speed was 130km per hour and a lot of steep hills. In the hill's B mode worked perfect but sometimes the engine made a lot of RPM's when it was very steep.
Hi JL. Got my own Prius now and really enjoying it, thanks for all the useful advice you've passed around. BTW, in B Mode going downhill the engine turns over to provide mechanical friction braking without burning any fuel. This is like a typical has engine coasting downhill doesn't use fuel, but the Prius in B Mode will not overcharge the battery from regeneration. I hope this helps you and your many followers to understand the Synergy motor better. Happy Thanksgiving to our American cousins from UK with best wishes for the Holidays.
I wonder what happens if you're going down a steep hill using the brake pedal only to slow the car down and the battery is becoming full, does the control system just gradually use only the friction brake pads to slow the car (it doesn't automatically select `B' mode and spin the ICE faster)?
You have 3 means of braking - regen, friction and engine braking. When you use B mode, it not necessarily means that you are regenerating better. Most of time its better to use D-mode and apply brake pedal slightly, as long as the CHG range is not exceeded. B-mode is OK for really steep hills and loaded car. It also automatically uses the B mode, when the battery is full. Tested yesterday when driving downhill from large hill. Of course its stupid to worry about high rpms, its made to do this!
How did you get that mpg gauge near your speedometer? Is it something w/ split screen mode? I have something similar but does not show the mpg gauge; but instead shows the eco/power mode.
I normally never use the B mode. Unless it's very steep. You can just press the brake pedal gentle and it will regen as much as it can. If the battery should get full, the car automaticaly activates the "B" mode, even when you are in drive mode. Because the battery is full it needs the engine to simulate braking.
Hi, from the Caribbean Puerto Rico... thanks for info. I need maintenance for my 2016 Prius you recommend "sintectic oils or convencional oil??? thanks
Thanks for a great video. I use B mode frequently on my 2004 Prius. (I'm the original owner.) Thanks to that and other practices (like trying to coast to a stop at traffic lights) I will be having the brake pads & shoes replaced for the FIRST TIME at the 200,000 mile service interval in a couple of months. * The engine may sound like it's running, but it is not. The vehicle is using the engine compression, without fuel, to help control the speed. It's the same as downshifting in a conventional transmission but keeping your foot off the gas. * My car manual says not to use B mode above 40 mph. Later models may be different. * My father-in-law had a small Farmall tractor from the early 1950s with a CVT transmission. So does my wife's 2003 Saturn Vue.
2020 manual..."When the vehicle is driven at high speeds, compared to ordinary gasoline fueled vehicles, the engine braking deceleration is felt less than that of other vehicles. p. 345
B-mode is really for continuous hilly terrain like how you find in Europe in mountainous areas. Typically just before reaching the bottom of the hill you gas the car and remove your foot off the gas pedal around half way to allow the momentum and battery power to move you to the top; once at the top of the hill you place the car in B-mode to allow the brakes to charge the batteries much faster in order to repeat the process again at the upcoming hill. Doing so decreases fuel consumption quite a bit in such terrain.
Unclear. So it ships out of B-mode automatically when exactly? Is it possible to forget to take it out of the mode because I don’t see you using your hand actually shift anything it just automatically went out of the mode because you accelerated or stepped on the break?
I've noticed as well when driving my 2016 that if you have cruise control set & start going down hill it seems to automatically kick in Engine braking although the indicator doesn't show it in "B" mode trying not to go past the set speed & man i can imagine how quickly you would have gained speed going down the hill in neutral because mine definitely gains speed even quicker in neutral going down hill =p
I love the energy graph but I prefer seeing the tachometer. The graph actually shows your gas pedal position and you could gauge it at the ECO line: the gas engine kicks in when that much acceleration is needed. When the battery is 8 bars full, the engine basically runs off the electric motor/battery to make room for more braking transfer.
Yes, and when the battery is full and therefore no regenerating is engaged anymore. Regenerative braking power is about at least 20 kW (differs because of the variance in HSD models) when you touch the brake pedal and in B-Mode engine braking comes on top which are about 35 kW. Engine braking power in Toyota hybrids is not as high as in conventional gear-driven cars at low gears with high engine rpms because the HSD although it is continous variable in gear ratios with the help of the Engine-Generator 1 it is more limited. Therefore engine rpm is lower than in conventional gear-driven cars and so is engine braking power. But you get the regenerating power on top and you are even or better. Only on long hills and especially the non plugin Toyota version with the small batteries which are charged full in a small time and from then on no regenerating power. Therefore it makes sense to put the car in B-Mode on steep hills or long desecendings to give the mechanical brakes a longer time to dissiapate the heat.
Is that an aftermarket cover on the lower portion of the steering wheel ? I thought the stock version was white. If it is aftermarket, where did you buy it? Thanks
I think the cruise control is unavailable? priuschat.com/threads/ev-b-rake-mode.179453 2020 manual p. 406 ■Situations unsuitable for dynamic radar cruise control with full-speed range. ●On steep downhills, or where there are sudden changes between sharp up and down gradients Vehicle speed may exceed the set speed when driving down a steep hill. p. 415 : ■Dynamic radar cruise control with full-speed range can be set when ●The shift position is in D."
I hardly steps on the break, I've always use the Break mode, to exit a highway or slow down from the traffic or slide down from a hill, 50,000+ odo now and the breakers condition are still excellent!
The best for long transmission durability is changing from Eco to B when speed is constant. To prevent a jerk which happens because mode change when slowing down.
Instead of B-mode, what would happen if you stay in D-mode and partially depress the brake pedal (enough for regen, but not enough to engage the physical brake) as you are travelling down the hill? In other words, you are regen-braking all the way down. Is regenerative braking alone enough to keep the downhill speed under control?
The B mode doesn't affect the charge, like many people seem to think. In fact, the engine is charging better in D mode, because the combustion engine does not brake the car by using part of the driving force. Moreover, this is perfectly visible in this video. In D the load bar fills up completely, while in B it only goes up to a third. Moral: in B, you brake more and better, but you don't charge the electrics better or faster. I don't even know if we're really saving fuel anyway. But I do know that it avoids the need for brake discs. So good point for the mechanics.
An interesting thing to note with priuses is that even though they have a lot of engine braking, you need to use the brakes every once in a while because depending on humidity, they can inflate just enough so that the pads rub against the rotors, slowing the car down and eating up a lot of battery and fuel. Happened to my grandpa because he lives near the sea, he started breaking more often and now the problem is gone.
Driving down a slight gradient in B mode as a Prius driver, then seeing your battery charge is one of the best things. Happens all the time. Every time I press on the brakes it feels like I'm making money. Love this car.
Except the B mode doesn't affect the charge. In fact, it's charging better in D mode, because the combustion engine does not brake the car by using part of the driving force. Moreover, this is perfectly visible in this video. In D the load bar fills up completely, while in B it only goes up to a third. Moral: in B, you brake more and better, but you don't charge the electrics better or faster.
@@HilljoonaCorrect, D is the main. I was just expressing my love for driving downhill in B mode, on top of the typical charging gained from rolling around. Also should replace the word "brake" in your moral so people don't get confused, as B as you stated uses the engine to slow the car and not the brakes. :}
Yeah! :) For May 12th 2017 I explore my first hybrid, little Prius sister, used Yaris HSD (EU). The first, non-dual highway trip to home gave 55 mpg / 37 mph.
I have a 2020 Prius prime and b mode disabled my cruise control and keeps the engine running while in hybrid mode. The engine never turns off when coasting or when stopped.
@@jettlash1000 love mine, though dealer does not use W16 as requested by manual. If W20 oil used change every 5k otherwise 10k. some say heavy acceleration not available w/out engine in EV mode but I have never had that problem when tested... nice electric torque now we have insurance discount for safe driving...
The effects you see are not unexpected. Usually, the B-mode is interpreted as "extra regenerative mode", but this is wrong. The Toyota manual states that the B-mode "applies engine braking", not "regenerative braking". After some digging, I found that in B-mode the gas engine is coupled to the wheels, like in a regular engine brake, but without being fed with gas; internal friction and air compression act as brake, wasting the energy that can not be regenerated (need more braking than can by applied by regeneration, battery is full, etc.). I don't remember where I read that, but it makes perfect sense with what you observed: 1. Around 5:30, before you shift into B, regenerative braking is quite strong, as seen in multi-info display; dropping in B-mode, while barely gaining any speed, the regeneration gets rather low. 2. You hear the engine being on, but the hybrid display shows that it does not generate energy -- consistent with engine in motion, but not consuming gas (instant MPG is over 100). The B-mode is useful in two cases: 1. You need more braking than can be provided by regenerative braking 2. Your battery is full, but you still need braking; regenerative braking can't store any more electricity. Short version, in B-mode, braking energy is wasted, not regenerated, which is why you are advised not to use it. The guys using it all the time will get worse overall mileage because of this.
That's not true, B mode turns the regen on full blast. If you have an app thats monitors your battery you will see how quickly the amperage jumps up and the voltage reaches full charge after just a short time on B mode.
I also have a Prius (2016). when in B mode and it's strictly charging the drive battery, if you change your MID to display the electrical layout it shows that the wheels are charging the battery but the ICE is not engaged/active. So it is in a sense in EV mode, but not showing the green ev icon
I have a question about your Prius. Just two days ago I noticed when I’m stopped on hill (front of car facing up the hill), the energy flow screen shows there’s power going from the battery to the wheels even when I’m not moving. On flat ground it doesn’t do that. Did I just not notice it before or is something broken? Does yours do that? I have my routine service coming up on Monday and will have them take a look at that as well.
jettlash1000 No my foot is completely on the brake and it still sends power from the battery to motor. Only happens on hills tho. Getting it looked at on Monday.
@@alansach8437 Nvm, found this online somewhere way back. It doesn't change the gear ratio while accelerating, only when off the accelerator. Therefore it changes nothing except that it gear brakes when off the accelerator.
I just bought a new Prius and was wondering if it's ok to shift from D to B mode while on the move without damaging the gearbox or only select B mode before any acceleration?
Prius isn't using a CVT transmission as used in other vehicles. The Electric Motors (2 of them in non-awd versions) are used as generators when not in use. B-Mode forces the Electric Motor into Generator mode increasing induction to the drive-shaft and slows down the wheels/car. The generated energy gets stored in the battery pack. The fact that this car is not using a conventional transmission or CVT and the inline configuration of all 3 motors - petrol engine and 2 E-motors make it possible to use this car even when the battery will go bad. The Prius drive system uses e motors to keep the petrol engine in a sweet-spot for rpm and drive-shaft load using advanced electronics resulting in good fuel economy. Watch as reference "Niels Blaauw - Prius Hybrid Drive Explained". One reason why the Prius is mechanically a reliable car: simpler "transmission", no conventional starter motor, engine running at ideal load and rpm. Keep fluids right and you will enjoy a great car for a very long time (ps don't forget to change the air intake filter for the batteries)
I have noticed in B mode, with the battery fully charged, the engine makes much more noise when running. I am not sure if that is because the battery is fully charged? It is a little worrisome. Do you notice this too? Is it a problem?
Very interesting seeing the way this Prius works. Probably going for my first Hybrid soon. Do you think I will miss my Camry’s comfort and 2.5 + 8 speed transmission kick?
@@tractorguy1994 I mean it gets great gas mileage, 2016 doesn’t have horrid control like 2015 and lower. Yeah if u want a fast car then this isn’t for u but u want cheap driving then yea
First. Thank God for you. I watched so many videos that just wasted my time until you showed up. Second. So you just shift on the fly right? Does it stay in B until you pop it back up? Do you have to shift back to drive from B? That's cool. So basically find a hill. Charge it and your Gucci. I'm gonna read the manual. But this helped a lot for a 2013 Prius Persona
Thanks for the info, so it works like all the other Toyota hybrid. Anyway in B mode the petrol engine runs continuously in order to slow down the car, it's like as you said at the beginning putting a low gear in order to save the brakes. Since on the Toyota hybrid when the battery is full the regenerative brake drops (otherwise you'll overheat the battery), the only way to avoid the brakes is to kick in the petrol engine and let it "absorb" the energy. Unfortunately to do this the ecvt has to burn some petrol, instead of the "standard" car that doesn't burn at all when the engine is drag. Maybe in USA is not so useful, but try to come in Italian appennini's roads whitout using the B and you'll burn your brakes after the first hill :)
I've had my 2012 Prius now for a month and I've been using the B whenever I want to slow &stopfrom around 70 mph. Will this cause the engine to over reve,and possibly damage the engine?
Let me help by putting this in simpler terms; Normally when a Prius going downhill, coasting and braking are regenerating kinetic energy into electricity by charging the battery. However, when the battery is full, there can be no more regeneration, therefore some other type of drag is required. This could be from the brake-pads, but that can be destructive and wasteful. In a normal vehicle, some engine-braking can be accomplished by not applying the accelerator, and allowing air pressure and friction from the engine to provide some drag. It's no mystery why the Prius engine is running while in B-mode. To provide drag without braking or regeneration, the engine is bleeding off energy by compressing air, when the other two options are not possible or desirable.
So it looks like you're starting to answer my real question. But are you sure that you know what you're talkin about? Are you sure that it's using actual engine compression to help slow you down after the battery is full. I understand the battery can't help slow you down by charging when it's full because it's already full. My gen2 is not really showing me how much regenerative action is happening and I'm having trouble Discerning when the actual brakes are being applied and wasting energy. So if putting it in the B mode increase is regenerative braking when possible can I further increase the regenerative braking by pushing the brake pedal? Or does that max out the regenerative braking simply by letting off the gas pedal?
It did this in my Ford Escape hybrid in L gear. It is using the 2nd motor to spin the engine to waste some of the excess energy when the battery is full. If the hill was more steep you would hear the engine rev higher. A Tesla does this and has settings to adjust how aggressive it is except it is impossible to do at full charge.
I don't have this kind of slope nearby. On my European Prius, I can force EV (below 50km/h). I wonder what happens in B mode in EV only: 1- charge faster (gears ratio on electric motor only), 2- starts ICE to use gears ratio on ICE, 3- it does 1 then 2 depending on battery levels to prevent overcharging. Or maybe I don't need to force EV at all.
