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.
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.
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.
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.
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.
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!
"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.
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.
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.
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.
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
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
@@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
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.
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!
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.
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.
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)
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.
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.
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
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!
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 love Prius videos, even though I don't own one they're relaxing. Prius drivers are so easygoing. Refreshing from all those crazed soccer moms I see on the road who give me road rage when I don't go 0-60 in 5 seconds.
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)?
Hi, from the Caribbean Puerto Rico... thanks for info. I need maintenance for my 2016 Prius you recommend "sintectic oils or convencional oil??? thanks
While the engine may be turning in "B" mode, it is not getting any gas or spark, just air. By the way, "B" mode is great for stop-and-go traffic as it slows you down nicely whenever you take your foot off the gas pedal.
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.
Weber Engineering explain Prius transmission very well, it’s a University Prof I think, at Utah State. The only grey area he left was the friction plate, clutch-type device - seems to be a safety-relief situation with that, it can be forced to scrape around inside a permanently clamped compact ring housing, but there’s no normal use or actuation of it as a clutch at all. It’s a ‘torque let-off’ device for sort-of emergencies only. Weber describes Toyota’s system very well, I watched it a couple of times. As others realised way before I did, this ‘synergy drive’ is not in fact the BS I originally thought it was (before I got the car and looked into it), and certainly not the conventional CVT design, that the likes of Nissan use. The Nissan ones have all the failings I thought the Toyota design had, pulleys, torque convertor wasting energy, a weirdly complex belt that needs to grip but also slip (!), and the belt is made of metal stampings, formed into a belt - it’s a darn good try, but not a patch on Toyota’s Prius design, which was much better by gen 3 eliminating the chain drive previously incorporated. In the deepest recesses of my brain, a little voice says the Toyota system is really a variation on the principle of the differential, but with twiddly extras-on as it were. It does not LOOK like one, but it has several diff-type gear assemblies buried inside it, and the MG1 and MG2 by this ingenious method, sit in a simple straight line with the engine. It avoids all the friction plates of a conventional auto transmission, by the MGs kicking-in to do something-or-other. Weber does explain it well, I don’t. I am just glad it’s not wet friction plates all over the place. No conical pulleys and weird belt that needs to grip but also slip up and down the rise of the pulleys, and it’s a belt that relies on PUSH effort, not PULL like you ( I ) would expect. After all, that’s how every chain and belt in almost every system anywhere, works, by tension. Anyway, this was a good exposition of the system, and I learned a lot from the other commenters. My takeaway is that ‘B’ mode is not exactly EV one-pedal driving, and is for being used sparingly, for where road signs say ‘engage low gear now’ on hills etc. I do use it for short stretches where speed humps mean you go fast and slow a lot, like as if it were second gear on a manual clutch car. The strain isn’t much because it’s not downhill, it just saves me applying the brake/regen braking all the time. Take care all. Oh, PS…have all the motoring journalists stopped talking about Regen Brakes finally, showing that they originally thought these were physically a separate set of brake units?! There were a few in the beginning. Said things like ‘The regen brakes wear instead, so your ordinary brakes last longer’ and so on. I cringed. This motor journalism, was the actual job of these people, with luck they now do something else, a lot better. It’s a relief to know that (having just scrapped my old Volvo 5-pot with conventional auto transmission) my newly-acquired Prius gen 3 has a lot of the parts that wear, gone. No torque convertor, so more efficient. The ‘creep’ you feel when you ‘engage’ the D mode of the tiny gearknob, is entirely simulated. It mimics the torque convertor creep but is merely one of the MGs being ‘told’ to do that!
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
While going downhill, the dealer told me to keep driving in D mode. Once your battery is fully charged, you can shift into B mode. Also, they say "B mode" is very useful while driving in the snow ( I guess it's because that helps slow down the car without touching the brake pedal, which is a good thing when you have to deal with icy/snowy roads )..have you ever had the chance to try it?
B is to keep friction brakes cool (avoid deforming). So if you're going downhill and the battery is nearly full, use B mode. This happens normally on big hills with fully loaded car.
the dealer said, the dealer said, the most misleading conception that i always heard people said. listen to this guy he knows what he is talking about, and please read the manual, it will explain to you, and there is no part that said you need to fully charge the battery before engaging B mode.
@@hunterhalo You can engage B-mode any time you drive, but if you do, energy that otherwise be regenerated is wasted as friction in the combustion engine. That's why it is advised to use B-mode only after the battery is full, to maximize regenerative braking.
Problem is, then you're burning fuel to use the engine to slow down. If you use the brakes then the car puts that energy into charging the batteries instead, so you can get that energy back later to accelerate again, saving fuel. The car doesn't use the brake pads unless you stamp on the brakes, which is why they last for so much longer than on other cars. The only time you need to use B mode is when you need to do a lot of braking and the batteries are full, so there's nowhere for the excess energy to go. B mode burns fuel to shed that excess energy.
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?
I had the super full battery recently as well and initially assumed that not having EV mode at that moment meant a problem with the car. Then I checked the manual and it said that when the battery is showing completely full it means that it is simultaneously running hot. So the car stops using it for a bit in order to cool it off.
Good video. You can tune it up by looking into the Prius 'CVT'. It is not a true CVT (what engineers mean when they use that term) because it has exactly ONE gear. The Prius never shifts out of that gear--it is always in that gear. Many people are confused by Toyota's 'CVT', probably because Toyota wants to confuse folks about this. One gear sounds bad, but Toyota makes it work.
Decent video but there is far more to B mode on an engineering level if you understand and have been trained on the transaxles in these cars. You mention that you don't understand why the gas engine is running and that there is no reason for that when in B mode. The gas engine is ALWAYS going to run in B Mode and there is a very good reason for it. Each motor generator in the transaxle is operating in "reverse mode" or "regenerative braking" mode when you engage B mode. Your main propulsion MG is always going to be in regen braking mode when off throttle and in D (at least in gen 2 Prius), but in B mode, all MGs go into regen. This means that each stator winding in the transaxle (ex MG1 and MG2 windings) that sits around the permanent magnet rotor that makes the motor generator is grabbing DC current from the HV battery and passed back to the stator windings of each MG. By passing this current through the windings and inducing a magnetic field in the motor generator due to the permanent magnet spinning, it does two things....it makes the motor generator much harder to spin thus acting as a brake...and it also produces electricity. The car has to do something with the power that has been created, either use it or dissipate it. If the computer determines that the power is not needed and the HV battery is charged at the time, assuming foot-off-throttle.... the engine ECU disables the engine's fuel system and MG1 (responsible for engine starting and acting as a power generator) continuously spins the engine over as in a crank-no-start condition in a regular car, only the engine in a Prius spins at the MG's rotational crank speed which is much faster than a regular ICE starter spins the engine at an RPM much lower than idle in order to start the intake, compression, power and exhaust cycle. This allows the MG in the transaxle to burn up the excess power that has been created and not needed. It is going to sound like the engine is running when in B mode, but its actually just being spun over by the MG at a "running speed" which is all dependent on gearing and rotational speeds of the driveline components and planetary gears inside of the transaxle. So, when you hear the engine running, it is not running as long as your foot is off throttle because the ECU has the fuel system disabled, it's being spun over at speed by the Motor Generator in the transaxle to burn up excess power that is not needed. Hit the throttle in B mode and suddenly engine power comes back and fuel is delivered and seamlessly you have power from the engine again. The transaxles in these cars are brilliant masterpieces of engineering.
Finally a detailed explanation of what's really going on. Thank you Chris Corbett. But one answer that's still kind of foggy for me. When going down a long Steep Hill with B enabled in a Gen 2 Prius does that increase the regen? If so does it increase it to its Max? And then of course once the battery is full it spins the motor to help slow you down. So if it increases the region to the max then any further deceleration due to me pushing the brake pedal is definitely due to friction breaking? And if you're in B mode And re gen is increased but your battery is not yet completely full is it Also spinning up the engine? I'm simply trying to better understand exactly what's going on so that I can avoid wasting energy. They build cars for stupid people I wish I'd simply have a button for engine braking and a button for Max Regen
I agree with your comment on CVT. Imagine you have a car with a CVT, you know what that means, and you know what your vehicle is capable of. Then imagine that vehicle simulating shift points. How disappointing is that? CVTs with fake shifts annoy the snot out of me. I took a $5k loss on a brand new Subaru because the fake shifts drove me bonkers. (the touchy accelerator and steering really threw me over the edge though). CVTs are fantastic when they work the way they were designed.
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
symmetry08 there's no B1 B2 unfortunately, but we balance the energy input and output in B mode, that's why the engine kick-in to create heat loss as load (free pumping with no fuel injected) , it also rev higher according to the excess regeneration resulting is a dynamic effect (the car mimic engine-brake harder the more you press the brake pedal)
Where you were coming back down in B mode and the car slowed below 25 MPH, I would have dropped over to Neutral for a few seconds to pick up speed, as opposed to stepping on the gas. When the speed picked up adequately, I would quickly bump it into Drive and back into B mode. This has been very effective for me, and I now have 137K miles on my 2011 Prius with no battery or engine problems. Best tank to date was over 600 miles, averaging 65.2 MPG (all in-town driving in a single day.
Alternately, you can go between Drive and B mode. That's what I do when I'm coming down I-70 from a day of skiing. I can usually control my speed to match traffic this way, rarely touching either the gas or brake pedals all the while charging the battery.
B mode in a Prius simply spins the ICE without firing it to simulate engine braking. In effect it diverts energy through the engine rather than the generator as it won't provide the level of retardation required for steep descents. The reason you see that the engine is on is because the crank angle sensor reads as if it running, when ofcourse it's not. Don't use it, it is dumping the kinetic energy that you can otherwise divert to the battery pack. Lightly touch the foot brakes to increase the field strength of MG1 and maximise the efficincy.
This is incorrect. There is no direct connection between the wheels and the engine in a prius. Both D with light brakes, and B mode regen and charge the battery. Eventually however, the motor will start and it will reduce regen. I suspect something begins to overheat. Regen charges the battery very quickly.
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.
It's basically the same as L gear. B stands for Engine Braking. If the battery isn't fully charged, it charges the battery too.
So should I use b instead of braking when possible
@@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.
4:14 B mode
God's man
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.
Thank you for the detail on this!
Indeed, no other transmission type has so few moving elements & so much abilities.
🐙🐍🐲🐈
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.
Very nice description, thank you for taking the time to provide some more input!
This video could have been 20 seconds long.
Thank you
100% and was the “B” ever even defined? I fell asleep. I think it means battery. Fill up battery. Bumps up the idle. Should’ve been the video title
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!
Just experienced this today. CO is getting a pretty good winter coat.
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.
And b mode will charge vape pen and prius battery same time!!
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.
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.
I like how some people talk a lot thinking they know it all when they don't. 😂
@@brianmef71 Ok, then go ahead and drive with B mode all the time if you think it is the best way to save fuel.
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.
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!
"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.
It stands for breakfast
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.
Just found your channel. Just saw you explained Prius stuff. Subscribing. :). Keep it coming :).
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.
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.
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
I just subscribed. Good luck getting from 9.99K followers to 10,000. I was hoping I would be the one to push you over the edge.
Thanks for posting. this explains it better than the dealership did when i bought one.
Thank you for all the videos you post. I find it very informative. I drive a 2013 Prius.
Thank you very much!
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
I absolutely love the Toyota Prius. Fantastic car.
Excuse me what
@@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
Thanks. Your video helped me understand this 3 year long mystery in my brain.
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.
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!
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've had my 2016 Prius for seven months and love it and almost have 30,000 on it now, I do a lot of driving. About 5000 miles a month
I had wondered what the B was for, thanks for the explanation.
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.
Thank you for sharing this information. I just bought our first prius today. Cool stuff to know
Excellent ! Straight talking, no hype. Thank you.
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)
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.
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.
I thought b was for badass
Bird screamer69 No it’s b for bitch so who ever drives a Prius is a bitch
😂😂😂😂😂
@@fabian_la1102 I would be butthurt too if I was driving an old Fred Flinstone car. Good thing I get almost 50mpg saving alot of $$$
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
That is awesome to hear! I love hearing about the reliability on these cars being so good. That was one of my top reasons for purchasing.
Did you replace the wiper motor
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!
Well done and thanks. Now I know how to drive my new Prius beauty. cheers
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.
Thank you just got 2 2018 Prius two cars for me and my wife very informative
Awesome, enjoy!
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.
Is it ok to use b mode to slow down on the highway when the traffic up ahead is slowing down or still
@@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.
@@cutflow2 does the engine come on with "not full" battery? prime? in B 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.
not too sure about auto B mode? mmm
I use B mode on my gen 2 Prius for emergency breaking situations or going down steep hills and needing to apply additional break force.
It's also good in traffic, save a lot of work to put on the brake.
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.
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.
Awesome this vid helped a lot! Thanks man!
I really need more Info. like this, well done... Thanks
I have maxed out the bars on my 2010 Prius using B mode in the Smokey Mountains.
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.
Except that the engine doesn't come on for a while in B mode, and the engine also eventually starts in D mode when using regen down a long hill.
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?
en.wikibooks.org/wiki/Toyota_Prius/Driving_tricks
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.
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.
Good advice!
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.
唐托尼 brake*
Great explanation. Thanks from Poland 😊
You are welcome!
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.
Thanks for info B mode. 👍✔
you do that all the times ? - looking to the rear when backing up (instead of just relying on the camera)
Thanks so much for this video, I was trying to figure it out
Glad I could help!
quick question... how do you lay two videos on top of each other?
Question. Why does the engine continually run when come to a stop, in B?? I think it also has something to do with battery. Thx
I love the videos man thanks a lot
You're welcome!
Excellent explanation .
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
It's not a cover, that's standard on this interior color option in the Prius Two trim level.
Had 2 of them (prius) in a row now and they ran very smoothly
I love Prius videos, even though I don't own one they're relaxing. Prius drivers are so easygoing. Refreshing from all those crazed soccer moms I see on the road who give me road rage when I don't go 0-60 in 5 seconds.
Hahahaha.
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)?
Hi, from the Caribbean Puerto Rico... thanks for info. I need maintenance for my 2016 Prius you recommend "sintectic oils or convencional oil??? thanks
How often should I clean my cooling fan ( blower) for my hybrid battery . I have a 2016 ct 200h
Do all Prius like yours have cvt? I drove one and it felt like it shifts gears
While the engine may be turning in "B" mode, it is not getting any gas or spark, just air. By the way, "B" mode is great for stop-and-go traffic as it slows you down nicely whenever you take your foot off the gas pedal.
Great video man
Hi. Im from EU, sorry for my english. How many liters engine takes in first 3km on cold start?
Can you shift to B while the car is still going or do you have to fully stop?
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.
My guess is that since your foot is off the brake, it needs to use the battery power to hold the car in place. Seems normal to me.
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.
@@PattyKuluCakes prep for departure?
Do you need to press break before shifting from D to B?
Weber Engineering explain Prius transmission very well, it’s a University Prof I think, at Utah State. The only grey area he left was the friction plate, clutch-type device - seems to be a safety-relief situation with that, it can be forced to scrape around inside a permanently clamped compact ring housing, but there’s no normal use or actuation of it as a clutch at all. It’s a ‘torque let-off’ device for sort-of emergencies only. Weber describes Toyota’s system very well, I watched it a couple of times. As others realised way before I did, this ‘synergy drive’ is not in fact the BS I originally thought it was (before I got the car and looked into it), and certainly not the conventional CVT design, that the likes of Nissan use.
The Nissan ones have all the failings I thought the Toyota design had, pulleys, torque convertor wasting energy, a weirdly complex belt that needs to grip but also slip (!), and the belt is made of metal stampings, formed into a belt - it’s a darn good try, but not a patch on Toyota’s Prius design, which was much better by gen 3 eliminating the chain drive previously incorporated. In the deepest recesses of my brain, a little voice says the Toyota system is really a variation on the principle of the differential, but with twiddly extras-on as it were. It does not LOOK like one, but it has several diff-type gear assemblies buried inside it, and the MG1 and MG2 by this ingenious method, sit in a simple straight line with the engine. It avoids all the friction plates of a conventional auto transmission, by the MGs kicking-in to do something-or-other.
Weber does explain it well, I don’t. I am just glad it’s not wet friction plates all over the place. No conical pulleys and weird belt that needs to grip but also slip up and down the rise of the pulleys, and it’s a belt that relies on PUSH effort, not PULL like you ( I ) would expect. After all, that’s how every chain and belt in almost every system anywhere, works, by tension. Anyway, this was a good exposition of the system, and I learned a lot from the other commenters. My takeaway is that ‘B’ mode is not exactly EV one-pedal driving, and is for being used sparingly, for where road signs say ‘engage low gear now’ on hills etc. I do use it for short stretches where speed humps mean you go fast and slow a lot, like as if it were second gear on a manual clutch car. The strain isn’t much because it’s not downhill, it just saves me applying the brake/regen braking all the time. Take care all.
Oh, PS…have all the motoring journalists stopped talking about Regen Brakes finally, showing that they originally thought these were physically a separate set of brake units?! There were a few in the beginning. Said things like ‘The regen brakes wear instead, so your ordinary brakes last longer’ and so on. I cringed. This motor journalism, was the actual job of these people, with luck they now do something else, a lot better.
It’s a relief to know that (having just scrapped my old Volvo 5-pot with conventional auto transmission) my newly-acquired Prius gen 3 has a lot of the parts that wear, gone. No torque convertor, so more efficient. The ‘creep’ you feel when you ‘engage’ the D mode of the tiny gearknob, is entirely simulated. It mimics the torque convertor creep but is merely one of the MGs being ‘told’ to do that!
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
Good feedback, I'll have to look at that!
While going downhill, the dealer told me to keep driving in D mode. Once your battery is fully charged, you can shift into B mode. Also, they say "B mode" is very useful while driving in the snow ( I guess it's because that helps slow down the car without touching the brake pedal, which is a good thing when you have to deal with icy/snowy roads )..have you ever had the chance to try it?
B is to keep friction brakes cool (avoid deforming). So if you're going downhill and the battery is nearly full, use B mode. This happens normally on big hills with fully loaded car.
the dealer said, the dealer said, the most misleading conception that i always heard people said. listen to this guy he knows what he is talking about, and please read the manual, it will explain to you, and there is no part that said you need to fully charge the battery before engaging B mode.
Hi there,
Can I shift the gear to B mode while gear is on D and the car is moving?
@@aysennooris2340 yes! NO problem, done it many times!
@@hunterhalo You can engage B-mode any time you drive, but if you do, energy that otherwise be regenerated is wasted as friction in the combustion engine. That's why it is advised to use B-mode only after the battery is full, to maximize regenerative braking.
Can you use b mode to slow down on the highway when the traffic up ahead is slowing down or still
RTFM. It says that in "B" mode engine breaking is used in addition to regenerative breaking. This is why the engine is turning at 25 mph.
Thank You for this Video😎👍
B mode is also very useful in low speed very busy traffic, keeps not to touch to break very often.
Problem is, then you're burning fuel to use the engine to slow down. If you use the brakes then the car puts that energy into charging the batteries instead, so you can get that energy back later to accelerate again, saving fuel. The car doesn't use the brake pads unless you stamp on the brakes, which is why they last for so much longer than on other cars. The only time you need to use B mode is when you need to do a lot of braking and the batteries are full, so there's nowhere for the excess energy to go. B mode burns fuel to shed that excess energy.
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 like to B mode for going around sharp corners on Highway ,it help you keep in Control
I love theToyota Prius 2016 sport suspension too
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?
it should have a fuel cut off for when the engine is being driven by the cars inertia, this is what happens in all modern cars.
Is this the same for the Camry Hybrid?
Thanks. I'm a flat lander and had no idea what B mode was for.
How's this any different than down shift into L in any traditional automatics? I do that all the time in my old car?
I had the super full battery recently as well and initially assumed that not having EV mode at that moment meant a problem with the car. Then I checked the manual and it said that when the battery is showing completely full it means that it is simultaneously running hot. So the car stops using it for a bit in order to cool it off.
good point! what year?
@@nationofgandhis my Prius is 2009
Good stuff!
Good video.
You can tune it up by looking into the Prius 'CVT'. It is not a true CVT (what engineers mean when they use that term) because it has exactly ONE gear. The Prius never shifts out of that gear--it is always in that gear. Many people are confused by Toyota's 'CVT', probably because Toyota wants to confuse folks about this. One gear sounds bad, but Toyota makes it work.
Thank you, and I'd love to see a video about the internals on the transmission for these cars.
jettlash1000 : Does it have to be a video? Would you settle for words and pictures?
I think the engine stays on in B mode so it can additionally slow down the vehicle in the same way when you downshift a gas vehicle down the hill
I did not have any ideas, great video
Thank you!
Decent video but there is far more to B mode on an engineering level if you understand and have been trained on the transaxles in these cars. You mention that you don't understand why the gas engine is running and that there is no reason for that when in B mode. The gas engine is ALWAYS going to run in B Mode and there is a very good reason for it. Each motor generator in the transaxle is operating in "reverse mode" or "regenerative braking" mode when you engage B mode. Your main propulsion MG is always going to be in regen braking mode when off throttle and in D (at least in gen 2 Prius), but in B mode, all MGs go into regen. This means that each stator winding in the transaxle (ex MG1 and MG2 windings) that sits around the permanent magnet rotor that makes the motor generator is grabbing DC current from the HV battery and passed back to the stator windings of each MG. By passing this current through the windings and inducing a magnetic field in the motor generator due to the permanent magnet spinning, it does two things....it makes the motor generator much harder to spin thus acting as a brake...and it also produces electricity. The car has to do something with the power that has been created, either use it or dissipate it. If the computer determines that the power is not needed and the HV battery is charged at the time, assuming foot-off-throttle.... the engine ECU disables the engine's fuel system and MG1 (responsible for engine starting and acting as a power generator) continuously spins the engine over as in a crank-no-start condition in a regular car, only the engine in a Prius spins at the MG's rotational crank speed which is much faster than a regular ICE starter spins the engine at an RPM much lower than idle in order to start the intake, compression, power and exhaust cycle. This allows the MG in the transaxle to burn up the excess power that has been created and not needed. It is going to sound like the engine is running when in B mode, but its actually just being spun over by the MG at a "running speed" which is all dependent on gearing and rotational speeds of the driveline components and planetary gears inside of the transaxle. So, when you hear the engine running, it is not running as long as your foot is off throttle because the ECU has the fuel system disabled, it's being spun over at speed by the Motor Generator in the transaxle to burn up excess power that is not needed. Hit the throttle in B mode and suddenly engine power comes back and fuel is delivered and seamlessly you have power from the engine again. The transaxles in these cars are brilliant masterpieces of engineering.
Finally a detailed explanation of what's really going on. Thank you Chris Corbett. But one answer that's still kind of foggy for me. When going down a long Steep Hill with B enabled in a Gen 2 Prius does that increase the regen? If so does it increase it to its Max? And then of course once the battery is full it spins the motor to help slow you down. So if it increases the region to the max then any further deceleration due to me pushing the brake pedal is definitely due to friction breaking? And if you're in B mode And re gen is increased but your battery is not yet completely full is it Also spinning up the engine? I'm simply trying to better understand exactly what's going on so that I can avoid wasting energy. They build cars for stupid people I wish I'd simply have a button for engine braking and a button for Max Regen
Do I need to change gear oil in the auras and Prius ?
Will using B mode accelerate the charging speed of the battery?
Is this only for descend ? Or ascend too ?
Always press accelerator slightly to allow ev mode to engage.
Can I shift from B to D mode at the end of the hill while driving?
Technically... the engine is not "running"... it's just spinning faster... to duplicate downshifting... and not sucking down gas!
The poor mileage he is getting indicates it is burning gas...
I agree with your comment on CVT. Imagine you have a car with a CVT, you know what that means, and you know what your vehicle is capable of. Then imagine that vehicle simulating shift points. How disappointing is that? CVTs with fake shifts annoy the snot out of me. I took a $5k loss on a brand new Subaru because the fake shifts drove me bonkers. (the touchy accelerator and steering really threw me over the edge though). CVTs are fantastic when they work the way they were designed.
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 think, those engineers have put an additional B1,B2 and B3 modes so that to vary power of recycling and how fast it will descend.
symmetry08 there's no B1 B2 unfortunately, but we balance the energy input and output in B mode, that's why the engine kick-in to create heat loss as load (free pumping with no fuel injected) , it also rev higher according to the excess regeneration resulting is a dynamic effect (the car mimic engine-brake harder the more you press the brake pedal)
Where you were coming back down in B mode and the car slowed below 25 MPH, I would have dropped over to Neutral for a few seconds to pick up speed, as opposed to stepping on the gas. When the speed picked up adequately, I would quickly bump it into Drive and back into B mode. This has been very effective for me, and I now have 137K miles on my 2011 Prius with no battery or engine problems.
Best tank to date was over 600 miles, averaging 65.2 MPG (all in-town driving in a single day.
Nice one!
Alternately, you can go between Drive and B mode. That's what I do when I'm coming down I-70 from a day of skiing. I can usually control my speed to match traffic this way, rarely touching either the gas or brake pedals all the while charging the battery.
This acctually helps
B mode in a Prius simply spins the ICE without firing it to simulate engine braking. In effect it diverts energy through the engine rather than the generator as it won't provide the level of retardation required for steep descents. The reason you see that the engine is on is because the crank angle sensor reads as if it running, when ofcourse it's not. Don't use it, it is dumping the kinetic energy that you can otherwise divert to the battery pack. Lightly touch the foot brakes to increase the field strength of MG1 and maximise the efficincy.
This is incorrect. There is no direct connection between the wheels and the engine in a prius. Both D with light brakes, and B mode regen and charge the battery. Eventually however, the motor will start and it will reduce regen. I suspect something begins to overheat. Regen charges the battery very quickly.