Toyota Unveils Fuel-saving Technologies for New Prius

Ken also stated that US Gen3 was heavier due to additional equipment (federal bumpers, etc)

 

We should be a little careful discussing the traction battery. The gen 4 NiMH traction battery has the same capacity as the GIII and GII. It's a 201V 6.8 A-Hr battery. But that tells us little. How much the system allows us to draw is what is important. I'm pretty sure I saw that figure in the media release, but it was expressed in different units and I'm too lazy to convert.

At any rate, what are we discussing regarding how the car will perform? How fast it is from 0 to 60 MPH, top speed, 1/4 mile time?
I have said it before and been challenged but I'll say it again, HP output is only really important for top speed. At lower than top speed, how the system converts power between torque and rotation rate is what sets acceleration. The presented graph in the media file shows the car is "faster" to speed than the GIII. But only over a certain range of speeds - those used in "normal driving".

Now here is where I disagree with some. -I- don't care if the car can't beat (insert car make and model here) down the road. I only care if the car can perform well in legal and normal driving. -AND- do so getting the best mileage of any other production car on the road in North America. Just like the GII and GIII did. From what I've read so far, it does just that, and probably better than the GII and GIII.

Another thing I have said before and will say again, to meet advanced crash worthiness expectations, most new cars will get heavier. They have for the last many years, and I expect them to continue that. The exception would be the case where a previous model was poorly designed. The GIII was not poorly designed, and neither is the G4 from what I've seen so far. So it's a little heavier, even with "high strength steel" chassis parts, due to added pieces to protect the occupants from extreme collision forces.

Further, a little weight was added, due to the unending complaints of current owners that the car is "a rattle machine", "noisy", etc. Noise insulation is NOT light, contrary to the opinion of some posters. Just go out and purchase some at an audio store to find out. Toyota appears to have doubled (approximately) the amount used. Just that alone could add 50 lbs to the car. So some of the weight lost in using the "high strength steel" was given back to make the car quieter. I am also happy about that.

Finally, I still can't figure out why so many of you dislike the white finish interior. -I- hate it when things I'm supposed to operate are black. I can't see the controls, or things I may have dropped inside! White is good!!

 

i don't have to have the last word.

 

Depends how you do it. I did 4 doors took 1.5 rolls of Peel-n-Seal, 5.3lbs each. So with floor panels under 20lbs is doable. If you use heavy stuff and wallpaper it then yes, it is going to add weight.

I'
m guessing when they said lighter they were intended to use plastic and Aluminum, then it got on chopping board.

 

LOL, I probably could but I thought this was adequately descriptive and boring enough!

Nice that you agree.

 

Really you think there is overall 10% efficiency making 121hp into somehow equivalent to 134HP? Where do you think it is coming from?
Improvements mentioned are in relative to losses.
For example they reduced the losses in transmission by 20%. That means earlier transmission losses are 5%(typical), now it is reduced by 20%, means, losses became 4% now. So total transmission efficiency goes up by 1%, making 96% now vs previous 95%. (not total system efficiency). Total system efficiency might change by something like 0.25%.

It is not a joke to improve overall efficiency of the system by 10% without some kind of new innovative system. If the system somehow magically improved by that much, it will show in wheel BHP (Dynamometer). Of course I wish, Toyota can do some magic here, but common sense says otherwise.

 

Actually, it is already available since the 2nd Gen Prius: "A 2-way flow type air conditioning unit that changes the 2-way flow operation if specified conditions are met, is adopted. Under 2-way flow operation, the system introduces external air and internal air simultaneously, discharges warm internal air to the foot area, and the fresh, dry external air to the upper area. Thus, it realizes both excellent heating performance and demisting performance." (see this)

Regarding performance, i was also surprised to see the rather lower power figures at more or less equal weight, but I could imagine the following reasons:

1. With the 4th Gen, Toyota tries to increase again the attractivity to people that are willing to buy an unconventional car. Buyers of the first and second generation bought the car not for its performance but because they wanted a car with outstanding fuel economy, accepting that it its not really fast in the sprint and topspeed and looking a bit ugly. It was also a statement against the silly performance competition. Going further into the direction of more power, Toyota would possibly gain more interest from conservative car buyers but would also imply that the car is lacking something. Also, the distinctiveness that attracted buyers of the early models, would be gone and its image get diluted. If the new Prius has the same performance as the 3rd Gen, but can offer a better ride comfort and lower noise, while providing outstanding fuel economy, it would in my view return to its original idea. Other cars are available for people looking for more power.
2. The 3rd Gen Prius is rather slow in acceleration, as compared to cars with conventional drivetrains with even less horsepower. IMHO, the subjective feeling is even worse (try the VW 1.4 TSI or Ford 1.0l Ecoboost engines, both stated at ~120 hp). Although this doesn't matter for me, some potential car buyers are disappointed from the subjective perception of the 136 hp. Maybe Toyota will just lower this figure in order to also lower the expectations and put clear that this car is not meant for performance. If the peak power will be lowered to 120 hp, but would be made available in a broader range of driving conditions, the Prius could still accelerate as quick or even faster as the current model. (I am quite sure that the peak power is not continuously available, but correct me in this)

Anyway, I am very much looking forward to the first test drive

 

20% less loss PCU, means that is overall efficiency improvements in the range of 1%-2% at best. Typical high efficiency inverters operate in the range of 95% efficiency (including $150 pure sine wave inverter). Of course all those add up to improve overall efficiency. When overall system efficiency is calculated, it is multiplier of all system efficiencies, so in the end it is going to be very minimal overall system efficiency improvement.

When engine efficiency is improved to 40% from 38.5%, the output quoted is with new efficiency, that is at flywheel. That takes into consideration of low viscosity oil, valvetrain, heat recovery etc etc. Higher efficiency does not automatically translate into more power, but it is more fuel efficient relatively per given output, depending on target tuning. Here Toyota opted to keep the efficiency at reduced power. (as usual Atkinson cycle is less powerful as we know already, despite being more efficient than usual/modified otto cycle).

Believe me, I wanted to be more efficient at the same time more powerful, and hope Toyota somehow does the magic. Main reason I was looking for more power is, it is nerve wrecking during the merges with Prius, when we try to merge from 40MPH line into fast moving HOV at 70 MPH in the gaps. I do like the fact it would be quieter, which I think helps a lot on long drives.

But as I said, based on information we have so far, wisdom says, do not expect it.

 

They already announced weight though... it is going to be 22lbs heavier in Japan for mid spec model compared to previous mid-spec model. It might be 20-30lbs different for USA/Europe since we might get different equipment in base models. So we might end up with situation like with RX, where Euro press said it was lighter while US press said it was heavier than before, same cars but with different base equipment.

Only thing we dont know anywhere in the world is total hp and 0-60. And there are still 71 days before the car goes on sale in Japan, let alone Europe or USA where we have probably 80-100 days of wait. Only 30 days before the launch, we will get full info like pricing and specific equipment and models.

 

If I understand correctly you are addressing two power paths. ICE power delivered mechanically and Battery power delivered electrically when available and needed.

What about the portion of the ICE power that is delivered electrically? That is a multi step path so small losses add up and savings in those losses become more significant.

 

Potentially they can add up, but we are talking about acceleration, when max power is ICE, and Battery+Motor. During this time any ICE power taken over electric path reduces/drops the power even more.

All these add ups could compensate tiny bit, but it is not going to compensate for 2-3hp let alone 8-10 HP, esp at partial electric load path, it would be miniscule.

But as it has been mentioned by some members, gearing would help for initial acceleration, but with less HP it will runout steam much before vehicle reaches target speed.

 

System power = ICE peak power + Battery peak power.
They have announced 28% increase in battery power, this alone adds about 10 hp to system power. Together with the improvements in components efficiency - yes, I believe same 0-60 time can be achieved with slightly lower ICE power, better ICE torque curve and smaller MG2 with less power and torque. Remember Gen 3 MG2 is over sized (60 kW).
Unlike an airplane or a locomotive, vehicle full system power demand is very brief - a matter of seconds, so small and powerful battery can cope with this.

 

0-60 times are not good indication of power and weight. At the performance end of the spectrum it is usually indication of grip, at lower end right gearing and low end torque. 1/4mi is usually better gauge on overall car performance.

It is likely Gen4 will have better 0-60 times, but may have slower 1/4mi, which is fine, it is a Prius? I think what we may also see that Gen4 has longer passing time from 65 to 85 MPH.

 

There are two factors here related to Battery and Motor.

What we know so far about the battery is charge rate increase, not actual amp delivery. Means it accepts the charge faster than older battery. This helps in rapid energy recovery during braking. But I am also guessing amp delivery might have also improved(not mentioned anywhere), but not to the same extent.

Even if the battery amp delivery is increased(Source), the motor(Sink) which leverages should have capability to leverage that. Previous motor is more powerful, has more HP and Torque. New motors have less.

Simple example akin to that, you upgraded your battery to 12v 100AMP battery with very high CCA from 12v 60AMP battery, but downgraded your bulb from 12v 65W to 12v 55W bulb. The net of it is your illumination goes down despite you increased battery capacity.

There are couple of scenarios, it is still possible(but that raises combined output which Toyota does not give out): Here is my theory!!

Previous Gen Motors are rated for more power, but never could leverage power because of limited AMP delivery of the battery. But higher power rating was given to send more power via electrical path to wheels instead directly from ICE. (This is to manage gearing ratios better). But there will be some efficiency loss because of conversion (ICE -> Gen-> Motor).

New generation, with improved low end torque(Torque in early RPM range, and broader torque curve) of ICE, more power is sent directly in mechanical path than electrical path(because of improved Torque curve, new gearbox and ratios), leaving more headroom for Motors. Now motors have less conversion work, but rather leverage improved battery AMP delivery to add more torque in addition to ICE(Provided battery has charge at that instance).

But in general it will increase the combined max output of the system which Toyota didn't quote. That is why I am suspecting, it would not be more than current combined output. I am guessing acceleration would be in the same ball park or little worst.

 

Are you suggesting that Toyota went from over sized MG2 (Gen 3) to under size (Gen4), making it the weak link in the chain? Why would they do this?
I suggest that MG2 in Gen 4 is properly sized enabling it to handle all currents into it.

 

Source: 2016 Prius Hybrid Vehicle Engineering, by Sunsuke Fushiki, pp 30



So we need to understand the original vehicle performance:


In graphic form:

With 9.7 seconds, also reported by Edmunds, it appears the 0-60 times are very likely to be better. How much is still an open question as the acceleration graph has no Y-scale.

Guess we'll have to review every Prius announcement with rapt attention for the next 60-90 days.

Bob Wilson

ps. We dropped our Consumer Reports subscription after 'reverse engineering' their scoring system and discovering:

1. Hard PASS/FAIL for a 10 second acceleration 0-60 mph
2. Driver comfort, major factor: seat and quiet
3. Steering through cones "handling"

Every one of these is addressed in the new Prius. But there is more.

The "Bell The Hybrid" effort appears to be based on data that statistically look to be a by-product of "A" pillar size. The Prius-pedestrian accidents, especially in good weather and cross-walks, appears consistent with "A" pillar blocking of the driver. The new "A" pillar is a fraction of the size of the ZVW30.

IMHO, every 'short coming' of the ZVW30 has been addressed.