2016 Yaris MOT adviseries

[Catlover]

So  Bob, if the purpose of B mode is to slow the car specifically on steep descents how can it increase mpg…. That’s beyond logic.

[Red_Corolla]

Hi Bob,

I did my research through watching some video demonstrations on YouTube, there is good information on there with helpful animations if you're prepared to look for it.

Like yourself, I am also an electrical engineer but I am still in my forties. So, while I've done my time with Y-Delta starters, I'm also reasonably up to speed with the basic principles of inverter drive technology and that makes it easier to understand the concepts, I think.

Regarding your tests, I can only assume that a bit more adaptation in your driving style might be required to get the best out of it. Like I said before, in D mode, regenerative braking is applied through very gentle pressure on the brake pedal, but press too hard and you quickly reach the limit of what the system can recover and it begins to apply friction via the traditional braking system. So, you have to get used to braking very early and really maximising your stopping distance if you want best results.

[TonyHSD]

B mode when selected will generate more electricity when lift off the gas first in comparison if you lift off gas while going downhill in D mode. However it is no needed to select B all the time as when quickly accumulate more energy and top up the Battery it will then start the engine and using petrol to waste the energy as we have discussed that matter few times previously therefore best to stay in D all of the time with very few exceptions when going long down hills and you don’t want to be on the brakes all the time , any other case it will be better to stay in D and manage the regenerative brake with the brakes. Btw when using the brakes is unavoidable and you have to come to a complete standstill better to stop faster with more help of the brake system for two reasons: 

1. To keep brake discs and pads rust free

2. You store more energy into the Battery since the regenerative braking is at max capacity. 

Using B mode in winter on slippery conditions like ice and snow may not be a good idea because when engine provides resistance to slow down the car and if the tyres loose grip it might lock the driving wheels and put you into a dangerous situation like unable to steer L or R while front wheels are locked similar to cars without ABS, I have not experienced that yet and no 100% sure it will be the case but make sense to me. Just stay in D and manage everything with brake pedal. 👍

[Stopeter44]

Hi Bob,

Reading through your posts, it sounds to me as if you have maybe misunderstood the regenerative braking process, and have, sort of, understood it backwards. The regen braking is what the car uses first of all to slow down, such as when coasting, or when lightly applying the brakes (On the Yaris IV, the hybrid power meter indicates up to three levels of regents braking, and I have seen level two quite often, and even level 3). You can feel the brakes "bite" when mechanical braking takes over.

I have had my Yaris for just over 2 months and adapting from purely mechanical brakes to regen & mechanical has been a gradual learning curve. I brake earlier these days, than when I drove an ICE car, with practice you can get down to almost a complete stop, depending on conditions, or course, using regen. @Red_Corolla has succinctly, I think, explained "B" mode.  As yet, I have never felt the need to use it.

It took me a while to understand the whole hybrid system, with the help of you tube videos from the car care nut and weber automotive university. 

[BobHos]

4 hours ago, Red_Corolla said:

No, the 'engine braking' description is exactly what it does, but it can still do some regeneration at the same time. See my last post for the full explanation of how it's achieved.

I have just carried out very careful testing:-

I had 2 identical runs in my car with the following results:-

Run 1 for 20minutes on a 40mph road with 6 roundabouts, 4 junctions and 2 sets of traffic lights without using "B" mode gave a total run since start of 59mpg.

Run 2 identical to run 1 but using "B" mode for anticipated slowing gave total run since start of 68.3mpg.

I was very careful to ensure that the style of driving, etc was the same for both runs.

These results are similar to several other tests/observations in the past as I said earlier in my post.

[Stopeter44]

2 minutes ago, BobHos said:

Run 1 for 20minutes on a 40mph road with 6 roundabouts, 4 junctions and 2 sets of traffic lights without using "B" mode gave a total run since start of 59mpg.

Run 2 identical to run 1 but using "B" mode for anticipated slowing gave total run since start of 68.3mpg.

I was very careful to ensure that the style of driving, etc was the same for both runs.

These results are similar to several other tests/observations in the past as I said earlier in my post.

To be sure you need to do the first run with "B" mode and the 2nd one without, but even so, other variables can make a difference, especially if the first run is starting from cold. Let's just say, that your results are contrary to Toyota's own recommendations and many sources on the internet, but, once the world was flat !

[BobHos]

7 minutes ago, Stopeter44 said:

To be sure you need to do the first run with "B" mode and the 2nd one without, but even so, other variables can make a difference, especially if the first run is starting from cold. Let's just say, that your results are contrary to Toyota's own recommendations and many sources on the internet, but, once the world was flat !

Don't know if the order of the runs in "B" mode would have made much difference but I will certainly perform other test runs later with "B" mode in the first run. The first run was not with the car cold, my wife had just returned with the car. I should also have explained that both identical runs were out and return each to avoid differences in gradient, wind, etc.

[BobHos]

8 minutes ago, BobHos said:

Don't know if the order of the runs in "B" mode would have made much difference but I will certainly perform other test runs later with "B" mode in the first run. The first run was not with the car cold, my wife had just returned with the car. I should also have explained that both identical runs were out and return each to avoid differences in gradient, wind, etc.

To my simple mind it seems that in "B" mode the engine may still be connected to the drive train and drives motor/gen 1 as a generator feeding power back to the Battery causing increased "engine braking"

[BobHos]

1 minute ago, BobHos said:

To my simple mind it seems that in "B" mode the engine may still be connected to the drive train and drives motor/gen 1 as a generator feeding power back to the battery causing increased "engine braking"

Wowee!! ........now I am an apprentice - soon be a master mechanic at this rate.

[BobHos]

5 hours ago, Catlover said:

So  Bob, if the purpose of B mode is to slow the car specifically on steep descents how can it increase mpg…. That’s beyond logic.

See my later re[plies/posts Joe

[Cowgirl]

I’m new to hybrids and automatic cars, so stupid question, can you change gears from Drive to B while moving or should you change gears at a complete stop?

[TonyHSD]

8 minutes ago, Cowgirl said:

I’m new to hybrids and automatic cars, so stupid question, can you change gears from Drive to B while moving or should you change gears at a complete stop?

Hi, 

yes you can change between D and B while the car is in motion,  this is how they are re designed to work. You can also switch to N and and return to D if necessary but in general all you need is switch to D when going forward and to R for reverse, that’s all. B mode for going long downhill, it is similar to lower gear on manual transmission, engine braking., once you finish going downhill flip the gear position back to D and drive just in D. 👍

[BobHos]

14 minutes ago, Cowgirl said:

I’m new to hybrids and automatic cars, so stupid question, can you change gears from Drive to B while moving or should you change gears at a complete stop?

You can change while the car is moving.

[Red_Corolla]

10 minutes ago, TonyHSD said:

Hi, 

yes you can change between D and B while the car is in motion,  this is how they are re designed to work. You can also switch to N and and return to D if necessary but in general all you need is switch to D when going forward and to R for reverse, that’s all. B mode for going long downhill, it is similar to lower gear on manual transmission, engine braking., once you finish going downhill flip the gear position back to D and drive just in D. 👍

You can also think of it as the low gear selection on a traditional automatic where you could manually select 1st or 2nd and it would hold in that gear. That feature was also intended for extreme hill descents and that's what the B mode is trying to replicate. But it's been widely misinterpreted as a boost to the hybrid system and perhaps that's why some models, like mine, are seeing it replaced by a sport mode where you use the paddles to select a low ratio as though it were a semi-automatic.

I think it should be common sense that the two different modes both have a reason d'etre. One cannot be better than the other in every scenario, or else that would mean Toyota have been getting it wrong for 25 years.

[BobHos]

Thanks all for your replies, comments, thoughts, personal explanations on the theory of hybrid engine braking and recommendations for optimised driving, etc.

Joining the forum has certainly been stimulating and has made me delve deep into my somewhat limited mental library on  mechanical, electrical and automotive fundamentals and principles. 

Tonight I have read several, somewhat limited, articles on line about the hybrid engine braking "B" mode system and they all fall short of a clear definitive detailed explanation of how it actually works in practice. Many talk about the older concept with the non-hybrid engine  but several also allude to the electrical regenerative aspect of the hybrid system, In truth I think that it is only the vehicle designers who truly know what actually happens in their particular vehicles and, I am sure, that the detailed individual theory and design will be carefully guarded from widespread knowledge and publication in such a fiercely competitive industry.

Anyway, I am not going to wrack my old "grey matter" anymore. I am content in the knowledge that my Yaris does function in a very satisfying and economical fashion when I use the "B" mode for anticipated braking situations. I am convinced by the observations and tests I have done that electrical regeneration is certainly involved in the process resulting in significant improvement in fuel consumption.

I only joined the forum to post about cracking brake pads and wearing components of front suspension members and I have not had much response on those issues.

Thanks to all contributors  ( only been posting a couple of days and now graded as apprentice. Wonder if I have time left to get up to Master Mechanic or other?)

 

[BobHos]

As a post note I would like to say that the tests I did today were very carefully done to ensure that the results were reliable.  For 2 off identical twenty minute journeys the results categorically convinced me that my method of using the "B" mode  is a highly fuel-efficient method of driving a Toyota Yaris hybrid. (10mpg difference for the tests)'

[Catlover]

On that basis my Prius should be capable, with the right conditions, to achieve over 100mpg!  I dont think I will be trying it.

[BobHos]

50 minutes ago, Catlover said:

On that basis my Prius should be capable, with the right conditions, to achieve over 100mpg!  I dont think I will be trying it.

Meant to ask you before Joe are you quoting instantaneous mpg figures or what? I am quoting journey ("average from start") figures which are a true indicator of actual fuel usage.

If you are quoting true average from start figures of 90+mpg then the Prius is a phenomenal machine,

 

 

[TonyHSD]

8 hours ago, BobHos said:

As a post note I would like to say that the tests I did today were very carefully done to ensure that the results were reliable.  For 2 off identical twenty minute journeys the results categorically convinced me that my method of using the "B" mode  is a highly fuel-efficient method of driving a Toyota Yaris hybrid. (10mpg difference for the tests)'

Ok, although I disagree 90% with you Robert on that B mode matter  I am not going to argue about it.
We are all adults here and take responsibility for our own understanding and actions therefore no problems each of us can make own decisions in what mode to drive its own car 👍 I agreed with you only 10% about the B mode that indeed adds extra Battery power immediately after been switched because both ice provide resistance but motor generators also provide resistance. Engine resistance happens with vacuum (cylinders compression) where motor generators resistance comes from regenerative capability. When the car travel at low speeds under 10-15mph the engine even may not start at all when B mode is selected and only provide resistance with electric motors doing so will add extra power to the Battery, increase overall ev time and achieve higher mpg. All that will happen in specific low speed scenarios only and on short time basis.

Toyota hybrids also does not like traction Battery to be full or well over 50% soc. On longer journeys over 20min and faster motorway driving using B mode will unnecessary top up your battery and the question is what happens next?!
The engine will start burning fuel to discharge the battery to more appropriate levels, and charge and discharge cycles will become more often and all that will add heat and extra fuel spent.

Many car owners mistakenly use B mode in hybrids because they compare B mode with full electric cars where the later does not have engine to provide brake resistance and all happens entirely by the electric motors and obviously extra regeneration goes straight to the battery. Evs also has a huge batteries where almost impossible to top them up full while in regen mode but hybrids batteries are small, they actually are like big capacitors that charge and discharge small amounts of power quickly and many times. 
I also have done experiments using B mode after completing my downhill run and the car feels horrible, engine is running unnecessarily, the gas pedal becomes extremely sensitive and overall experience it is not pleasant, I only use B mode when going downhill but even then not using it often because I like to use the brakes instead and keep the warmer, cleaner and rust free. 

Robert, I believe that using often B mode and your overall low mileage drive are likely the reason to have issues with your brakes. After getting your car fixed I can highly recommend to you instead of driving in B downhill let the car in N neutral from time to time and use the brakes continuously until you come almost to complete stop, more often you do that less often you will have issues with the brakes.👌 

Regards 👍
 

[Catlover]

to Bob, I cannot quote your question because you quoted a previous post of mine and then you typed within the box.

So you asked were my figures instantaneous. No.   I quoted for a 100 mile journey, a 50 mile journey, and I stated what the whole life of the vehicle average. The Prius was designed to cut through air.     
I traded in a 2010 Gen3 Prius for the 2016 Gen4. I drove 102 mile t collect the Gen4. On that journey going there the Gen3 did 66mpg. I said to the sales chap I expect my home journey in the Gen4 to be at least 10mpg better. That’s when I did 92mpg. That was my first journey in the Gen4.

When I did 96mpg we had been on holiday in Gloucester. Even on holiday touring the Cotswolds there were days I did over 80mpg. Coming how we decided not to use the M6, instead we did the A roads, including A49. We stopped for a break outside Telford. The 50 mile journey home was 96mpg. I did put photos of the dash showing these figures on here. Probably still are. 
 

[BobHos]

Thanks for that detailed explanation Tony.

You are obviously very knowledgeable and have taken the time to explain the finer detail of the dynamics of the intricate system and procedures. I daresay everything you say is correct, not least the issue of a fully charged Battery having a negative impact on fuel efficiency. I will certainly bear that in mind if I have longer trips away from the city. Nevertheless it is a fact that the way I mostly use the car does have the benefit of improved fuel efficiency. Although some might contest it I am not stupid and have looked after my cars for these past 60 or so years. Up until my problems with my back these past few years I always did most of my own routine maintenance including brake maintenance and replacements. I am not able to remove wheels and inspect/repair brakes now but I do know how to look after them as I drive. I wrongly posted that the cracking brake pad issue was an advisory, it was just a general inspection report at the time the MOT was done and I suspect that the issue is more to do with manufacture than driving issues. Visual inspection without removing the wheels shows discs to be fairly good but I do need to get a garage to do a more detailed inspection. The brakes are certainly quite noisy for a few miles after starting.

By the way I do have the engine dynamics screen displayed when I drive and I do pay attention to the level of Battery charge. Musy admit, diving a hybrid is much more interesting compared to older ice motors.

Regards

Bob

[BobHos]

45 minutes ago, TonyHSD said:

Ok, although I disagree 90% with you Robert on that B mode matter  I am not going to argue about it.
We are all adults here and take responsibility for our own understanding and actions therefore no problems each of us can make own decisions in what mode to drive its own car 👍 I agreed with you only 10% about the B mode that indeed adds extra battery power immediately after been switched because both ice provide resistance but motor generators also provide resistance. Engine resistance happens with vacuum (cylinders compression) where motor generators resistance comes from regenerative capability. When the car travel at low speeds under 10-15mph the engine even may not start at all when B mode is selected and only provide resistance with electric motors doing so will add extra power to the battery, increase overall ev time and achieve higher mpg. All that will happen in specific low speed scenarios only and on short time basis.

Toyota hybrids also does not like traction battery to be full or well over 50% soc. On longer journeys over 20min and faster motorway driving using B mode will unnecessary top up your battery and the question is what happens next?!
The engine will start burning fuel to discharge the battery to more appropriate levels, and charge and discharge cycles will become more often and all that will add heat and extra fuel spent.

Many car owners mistakenly use B mode in hybrids because they compare B mode with full electric cars where the later does not have engine to provide brake resistance and all happens entirely by the electric motors and obviously extra regeneration goes straight to the battery. Evs also has a huge batteries where almost impossible to top them up full while in regen mode but hybrids batteries are small, they actually are like big capacitors that charge and discharge small amounts of power quickly and many times. 
I also have done experiments using B mode after completing my downhill run and the car feels horrible, engine is running unnecessarily, the gas pedal becomes extremely sensitive and overall experience it is not pleasant, I only use B mode when going downhill but even then not using it often because I like to use the brakes instead and keep the warmer, cleaner and rust free. 

Robert, I believe that using often B mode and your overall low mileage drive are likely the reason to have issues with your brakes. After getting your car fixed I can highly recommend to you instead of driving in B downhill let the car in N neutral from time to time and use the brakes continuously until you come almost to complete stop, more often you do that less often you will have issues with the brakes.👌 

Regards 👍

 

Sorry I replied to your post earlier without using the quote feature (newbie error)

hanks for that detailed explanation Tony.

You are obviously very knowledgeable and have taken the time to explain the finer detail of the dynamics of the intricate system and procedures. I daresay everything you say is correct, not least the issue of a fully charged battery having a negative impact on fuel efficiency. I will certainly bear that in mind if I have longer trips away from the city. Nevertheless it is a fact that the way I mostly use the car does have the benefit of improved fuel efficiency. Although some might contest it I am not stupid and have looked after my cars for these past 60 or so years. Up until my problems with my back these past few years I always did most of my own routine maintenance including brake maintenance and replacements. I am not able to remove wheels and inspect/repair brakes now but I do know how to look after them as I drive. I wrongly posted that the cracking brake pad issue was an advisory, it was just a general inspection report at the time the MOT was done and I suspect that the issue is more to do with manufacture than driving issues. Visual inspection without removing the wheels shows discs to be fairly good but I do need to get a garage to do a more detailed inspection. The brakes are certainly quite noisy for a few miles after starting.

By the way I do have the engine dynamics screen displayed when I drive and I do pay attention to the level of battery charge. Musy admit, diving a hybrid is much more interesting compared to older ice motors.

Regards

Bob

 

 

[BobHos]

1 hour ago, BobHos said:

Toyota hybrids also does not like traction battery to be full or well over 50% soc. On longer journeys over 20min and faster motorway driving using B mode will unnecessary top up your battery and the question is what happens next?!
The engine will start burning fuel to discharge the battery to more appropriate levels, and charge and discharge cycles will become more often and all that will add heat and extra fuel spent.

Hi again Tony. I have been thinking about what you said about motorway driving, etc (see quote above)and I would have thought the only problem when the Battery became fully charged would have been that regenerated power back into the Battery would not happen so, in this situation, regenerative braking would not be an option either in "D" or "B" mode. This would only be during the instant that the Battery is fully charged but that situation would be constantly changing depending on the ever changing dynamics of the drive and interplay of electric motors and engine, etc.

[TonyHSD]

2 hours ago, BobHos said:

Thanks for that detailed explanation Tony.

You are obviously very knowledgeable and have taken the time to explain the finer detail of the dynamics of the intricate system and procedures. I daresay everything you say is correct, not least the issue of a fully charged battery having a negative impact on fuel efficiency. I will certainly bear that in mind if I have longer trips away from the city. Nevertheless it is a fact that the way I mostly use the car does have the benefit of improved fuel efficiency. Although some might contest it I am not stupid and have looked after my cars for these past 60 or so years. Up until my problems with my back these past few years I always did most of my own routine maintenance including brake maintenance and replacements. I am not able to remove wheels and inspect/repair brakes now but I do know how to look after them as I drive. I wrongly posted that the cracking brake pad issue was an advisory, it was just a general inspection report at the time the MOT was done and I suspect that the issue is more to do with manufacture than driving issues. Visual inspection without removing the wheels shows discs to be fairly good but I do need to get a garage to do a more detailed inspection. The brakes are certainly quite noisy for a few miles after starting.

By the way I do have the engine dynamics screen displayed when I drive and I do pay attention to the level of battery charge. Musy admit, diving a hybrid is much more interesting compared to older ice motors.

Regards

Bob

Hi Robert, you are welcome. 
Hybrids are indeed interesting machines and they do have a bit from both worlds ev and ice internal combustion engine vehicles.
Toyota hybrids particularly are unique and always both powers work together, it is very simple way of how the magic happens but it is not common, actually only Toyota/ Lexus cars does it and therefore it maybe a bit strange at first glance to many people even those with great experience to understand how exactly everything works. I have always been a car enthusiast but never involved in hybrids until 2012 when I started a private hire driver job with Prius, since then I deep divide into the technology and learned a lot and I drive a hybrid ever since. 
I actually drive a bit more than usual 200 miles plus every day and also I am the only person who look after my cars with small exceptions where I need to take the car to a garage for recall work or new tyres fitting, wheel alignment and mot or AC regas, that’s all anything else is my job to do it and all that gave me an opportunity to improve my knowledge about these cars and share here with you and also Lean from all of you similar experience, most of the people here I communicate are my dads age or even older and I respect each and everyone 👍

By recommendations from other members I also bought a Carista obd 2 adapter and with help of some smartphone apps I can monitor what  actually happens under the bonnet when I am driving the car, see engine temperature, rpm, load, Battery temps, voltage, state of charge and whether is charging or discharging, really helpful stuff., something that might be of interest to you if you want to buy and use similar or same gadget here is the link https://www.amazon.co.uk/Carista-Bluetooth-Adapter-Scanner-Technology/dp/B00YVHGTBM/ref=sr_1_1_sspa?keywords=Carista&qid=1646138426&sr=8-1-spons&psc=1&smid=A2FFESA4WJEXUA&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExT0NSMzJaWTlGMkoxJmVuY3J5cHRlZElkPUEwMDA5MTc0SU5ETFUwRkJBVUlFJmVuY3J5cHRlZEFkSWQ9QTAzNTM2NzIzREVOSUdIWUQ4MTdHJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

the app  that I use are Carista own app paid subscription £50 per year, dr. Prius paid subscription £11 per year and Hybrid assistant free on android. For the B mode and fuel consumption imo it needs to be measured brim to brim and not from the screen display as display only shows the fuel consumption for a certain time, let say last trips but the overall picture may change during the complete full tank cycle and figures can be off. I have no official information about B mode only what is written in the car manual but I think is there as back up only and not a usual driving option to increase efficiency, just as back up, lower gear when going downhill and prevent brakes from fading although this is almost impossible in hybrids 👍

[preperationlaunch]

@BobHos for some concrete figures I've acquired on my Yaris mk3 for you.

Coming down a reasonably steep hill at 40-50mph, I've noted some of the figures coming through my ScanGauge.

At approx 40mph, below the EV cut off, max regen into the Battery is about 50 amps sustained using the cruise control to maintain speed.

If I move into B mode, Battery charge current drops to approximately 25 amps, sustained and motor generator 1's current consumption increases as it starts to rev the engine. The engine goes from 0rpm to ~2000rpm. The engine starts spinning as soon as the gear selector is moved to B, irrespective of state-of-charge. Deceleration is greater than if using cruise control, but regeneration is significantly reduced.

Above the approximately 45mph cut-off, MG1 spins the engine at 992rpm anyway, to stop MG1 from spinning too quickly. (Plantary gears are magic).

For comparison, max regen current I see is generally around 100 amps under heavy braking, but this tails off and clearly can't be sustained for long.

This journey has been repeated dozens of times with similar results.

Equally, around town, B-mode will not engage the ICE in a power-wasting scheme at lower speeds, it's smart enough not to. You may well be finding that you're simply benefiting from putting slightly more power into the Battery around town. Light braking which isn't enough to engage the friction brakes will probably net you similar gains.

As another matter of interest, and one @TonyHSD alludes to, when the battery is 'full' at Toyota's ~80% limit, the car is very eager to discharge itself, and will continue to spin the engine on the flat, as well as being somewhat more spirited in how much power the electric motors will provide.