Lexus Remains Uncommitted to Plug-In Hybrid Technology

Levi

Tech that would be worth for ICE, is infinitely variable timing (cam-less).

I remember reading a patent that, IIRC, was owned by Toyota, which described a solenoid-controlled valvetrain. It had a pair of valve springs on each valve. One pushes the valve open and the other closed. When the system is off, the springs hold the valve in a partial-open position. The valve stem is made f a non-magnetic material (titanium?) with a ferromagnetic piece in the middle, between the springs. There are then two electromagnets, one above and below, which alternate on and off to pull on the ferromagnetic piece, which opens and closes the valve.

It's a neat idea. I don't know how energy efficient it would be because that would take a lot of electrical power to make it work, but it does have the benefit IVVTL. Perhaps, with more advanced materials and electronics, it could work. I'm not 100% sure that my description is accurate since I saw that patent about 5 years ago. If I can find it again, I can post a link.

Edit: https://patents.google.com/patent/US6332446

TheNerdyPotato

I remember reading a patent that, IIRC, was owned by Toyota, which described a solenoid-controlled valvetrain. It had a pair of valve springs on each valve. One pushes the valve open and the other closed. When the system is off, the springs hold the valve in a partial-open position. The valve stem is made f a non-magnetic material (titanium?) with a ferromagnetic piece in the middle, between the springs. There are then two electromagnets, one above and below, which alternate on and off to pull on the ferromagnetic piece, which opens and closes the valve.

It's a neat idea. I don't know how energy efficient it would be because that would take a lot of electrical power to make it work, but it does have the benefit IVVTL. Perhaps, with more advanced materials and electronics, it could work. I'm not 100% sure that my description is accurate since I saw that patent about 5 years ago. If I can find it again, I can post a link.

Edit: https://patents.google.com/patent/US6332446

It looks exactly like Freevalve by Koenigsegg. Didn't know Toyota patented it.

Levi

It looks exactly like Freevalve by Koenigsegg. Didn't know Toyota patented it.

Not the same, but they perform the same function. Here's a youtube video that explains the Freevalve. Spoiler: Freevalve is mostly pneumatic instead of all-electric.

Joaquin Ruhi

Ever since I started reading about Nissan's VC and Mazda's Skyactiv-X, I've been wondering whether the two could be combined, or if it was even worth doing so. Alas, the automotive press, to my knowledge, has remained silent on this subject. Yours is the first comment and guesstimate I've ever seen on the subject.

I think my estimate was based on a very old EPA paper from ten years ago. In that analysis they projected the timeframe for ICE technologies to trickle down into mainstream. They correctly predicted dual VVT, dual-injection, and Miller-cycle operation to become standard before 2020. They incorrectly predicted continuous VVL to be cheap enough to be widely adopted, but as of 2018 only BMW and FCA use it extensively (while Honda/Nissan/Toyota limited CVVL to selected applications).

VC is a pre-requisite for HCCI operation to avoid nasty NOx problems. My prediction is that Mazda will keep refining Skyactiv-X and come close to 48% thermal efficiency around 2025, while the industry play catch-up until near 2030 (SkyActiv-G was almost 5 years ahead of its time).

mediumhot

I'm personally mostly interested in their RWD hybrid program and I'm curious if they will ever achieve price parity. It's so freakin complex and they keep on adding more stuff to it (like 4 speed auto) that I'm wondering if they have a long term plan for it at all.

I do agree the multi-stage THS is unneccessarily complex. Ever since the original GS450h they kept adding components to the system that it has blown up in complexity and weight. Meanwhile their transverse FWD hybrid package has become really cheap, compact, efficient, and gets the job done.

From one literature review that I read recently, it seems that TMC had never had consistency in its RWD hybrid programs. Their longitudinal hybrid powertrains are always experimental and not optimized for mass production. They have the same problem with their E-Four applications, which are super complex and inefficient.

The fundamental problem is still their battery tech (or their conservative approach to new battery tech), which lacks in both power density and energy density, so they have to make up the deficit from mechanical tricks here and there.

The 500h is certainly impressive as it beats the old 600h system in every aspect imaginable. But they could do much, much better than that. The multi-stage THS needs consistency and modularity so engineers could keep working on refining it, instead of trying something new every time they need to develop a new hybrid system.

mediumhot

Their RWD hybrids might end up being PHEVs with ICE range extenders to justify the price spread between gasoline model and hybrid in RWD vehicles. I don't know I'm just guessing here but what I do know is that $10,000 difference between RWD car with the gasoline engine and exact same RWD car with exact same gasoline engine with mounted hybrid components will get them nowhere.

They won't be doing a RexEV on RWD because it makes no sense. What is your reasoning that it makes sense? RexEV and serial hybrid are both stupid ideas for high-power applications. That's why GM went down the same input-split serial-hybrid route on 2nd gen Volt.

mikeavelli

While the Nissan's new engine is a marvel, the specs don't really wow anyone. Barely a bump over the VQ engine in regards to MPG and power is average.

100kW(134hp)/L with 40% maximum thermal efficiency. That's the impressive part about it. Nobody builds any turbocharged engine even close to that kind of specs. Well I guess to the general public it's a little bit hard to comprehend. What they do understand is that it's mated to a hated CVT. What a missed opportunity there.

They also claim it has same level of NVH as V6, at least they have that going for them. But Honda said their 2.0T is as good as V6 too and we all know what happened to the new Accord.

@ssun30 Upcoming Skyactiv-X is nowhere close to hybrid level efficiency though, few first drives that report mpg, it was way below hybrid or diesel... for instance:
https://jalopnik.com/i-drove-mazda-s-holy-grail-of-gasoline-engines-and-it-w-1800874806
https://www.autocar.co.uk/car-news/...review-new-compression-ignition-petrol-engine
https://www.autoblog.com/2018/01/26/mazda-skyactiv-x-review-compression-ignition-engine/

with lower rpm range driving... so real life 14% improvement with faster engine and NVH like a diesel. Also price less than a diesel but more than petrol. It is also not replacement for their diesel, so it clearly wont get diesel mpg numbers, let alone hybrid.

@spwolf I'd say let's wait for the production version before making any conclusive comments. Engine calibration is one of the later engineering stages so I'm sure the press prototypes are far from final.

Mazda could certainly need Toyota's help on full hybrids. I wonder how far their strategic alliance will go. Maybe when TMC feels secure enough it will buy out Subaru and Mazda.

ssun30

@spwolf I'd say let's wait for the production version before making any conclusive comments. Engine calibration is one of the later engineering stages so I'm sure the press prototypes are far from final.

Mazda could certainly need Toyota's help on full hybrids. I wonder how far their strategic alliance will go. Maybe when TMC feels secure enough it will buy out Subaru and Mazda.

Question is if they want to buy them, and vice versa... also Suzuki too.

As to the hybrids, problem with using this and hybrids is cost.

Reviews mentioned how mild-hybrid tech was off, this is start/stop system, so thats partially what would bring official numbers up a bit, but not real life. I dont expect changes to increase MPG, only NVH since despite heavy sound proofing, it apparently is knocking away to the oblivion still.

They also are expected to unveil new diesel by 2019, so they would not be doing diesel if they expected these numbers to be actually much higher. It is apparently not replacing their diesel, rather be mid-spec upgrade for their petrol engine lineup.

spwolf

Reviews mentioned how mild-hybrid tech was off, this is start/stop system, so thats partially what would bring official numbers up a bit, but not real life.

I don't understand this sentence, in particular the word "off". Did you mean that "mild-hybrid was unavailable for the press prototype" or "mild-hybrid was off-target when it comes to MPG"? Did Mazda plan to combine SkyActiv-X with mild hybrid? I could be missing something here.

spwolf

it apparently is knocking away to the oblivion still.

Care to explain? Was the press prototype engine knocking? It sounds funny since No.1 rule for drivetrain engineer is never allow a knocking engine on the road.

ssun30

I don't understand this sentence, in particular the word "off". Did you mean that "mild-hybrid was unavailable for the press prototype" or "mild-hybrid was off-target when it comes to MPG"? Did Mazda plan to combine SkyActiv-X with mild hybrid? I could be missing something here.



Care to explain? Was the press prototype engine knocking? It sounds funny since No.1 rule for drivetrain engineer is never allow a knocking engine on the road.

It was turned off... I would guess it is new 48v system that will also turn off engine at low speeds like 7mph, not just at stop. So it will help with in town mpg.

As to knocking, very loud despite a lot more special sound deadening... But that's something they will have to fix by launch, so it should not be that bad . However I suspect it will sound always like diesel.

Knocking won't be ever completely solved , it happens when it changes between combustion methods. Engine has been strengthen to diesel like level to deal with this.

krew

Internal Combustion Engines Remain Priority at Toyota

90% of all Toyota vehicles will still have a gas or gas-electric powertrain by 2030.

View the original article post

Anyone remember the Yaris Hybrid R concept from about 5 years ago? That was a sick little concept car. Too bad they never actually built one for production.

https://newsroom.toyota.eu/toyota-yaris-hybrid-r-420hp-hybrid-powertrain-details-revealed/

I guess the tech is still in development in some form or another. E-Four AWD is coming, and was mentioned in the OP's linked article.

Speaking of which, the OP article states that E-Four will feature 30% more torque than the current systems. A quick search on Google says that the Prius AWD has a 5kW rear axle motor while the larger Highlander features a 50kW motor. Both of those are a far cry from the dual 60HP/45kW motors on the HybridR.

I've seen a statement somewhere recently that the Avalon/ES won't be getting AWD "yet." Perhaps, it'll be on the hybrid versions. Perhaps, they'll make a HybridR-inspired version of the V6, which could be a beast with the upgraded rear axle motors and KERS-style regenerative braking.

In other words, 1-1.5 million BEVs or FCEVs by 2030. That's a lot of underpromising considering chinese and japanese domestic markets could eat up 500k in capacity each. Let's hope they overdeliver.

When I was making speculations on the powertrain lineup for the next IS, I came across an idea that never appeared to me in the original analysis: could Toyota have already teased what hybrid systems their future GA-L vehicles will have?

I originally thought it's weird they did not show any other GA-L based hybrid system other than the multi-stage. But we know this is a very expensive system that will unlikely be used on an IS. The multi(four)-stage is an evolution of the GS450h drivetrain with the two-stage Ravigenaux gear system; that was an expensive drivetrain as well, which is why GS450h were manufactured in very limited numbers. For the IS300h they had a dedicated longitudinal hybrid system which is more powerful than the transverse hybrid 300h on the ES or NX. In the press release we didn't find any place for a similar low-cost hybrid system for GA-L: the one above the THS-II 2.5L is obviously destined for the next Highlander and RX which are transverse FWD.

My speculation is that Toyota will no longer make separate longitudinal and transverse hybrid systems (with the exception of the multi-stage at the top, obviously). Instead their new parallel-axis hybrid systems could be easily modified to fit in either types of layout. This further reduces cost and make integration of hybrid powertrain much easier.

I think it's safe to say the next IS300h will feature a variant of the 215hp THS-II 2.5L system. Performance and MPG numbers are therefore quite easy to predict now. It does leave the question though what they are going to do to replace the 450h system on the RX?

Lexus UK manager (largest market in EU by far) confirms Lexus will have plugins for sale in 2020:

Do you see any benefit in moving to plug-in hybrids and fuel cell vehicles in the next few years?

Some of our models will have a plug-in – we can’t confirm specifically which ones yet – in around two-and-a half years’ time. We haven’t got a date for [fuel cells], but it will be on the back of LS. There’s no firm commitment in time to introduce it, but I would imagine the next two or three years is realistic.

http://evfleetworld.co.uk/qa-ewan-shepherd-md-lexus-uk/

- LS will be only fuel cell for Lexus
- Multiple models for plugins on sale by 2020.
- This will be based on market - for instance in UK, plugins are 3/4 of EV/PHEV sales due to incentive package.
- In China Toyota says 10 models on sale in 2020. This is going to be EVs due to the incentives favoring EVs.
- Toyota is also preparing for EV production in USA in 2020. We have had reports about them working with suppliers in NA on EV from 2016 and 2017. So maybe new Rav4? Since it is locally produced.

I am thinking that Lexus can easily do PHEV versions of all of their hybrid systems, like Toyota did for Prime. If they can bring the costs down, and new TNGA already accounts for this, we could see extra 10 kwh in battery capacity for plugins, which also unlocks extra 100hp in power... so IS300h becomes 300hp vehicle... LS500h becomes 450hp vehicle. All these cars have powerful electric motors already, just like Prius did, question is just of maximum battery output which is limited by size of the battery.

In regular hybrid mode, they would have maybe 20-30hp extra, but in performance mode it could have extra 100hp at the cost of "consumption".

A thought I just had was maybe they're going to come out with more new/updated engines that are not in the Dynamic Force family. For example, the 2GR-FE/FSE have been replaced with the -FKS variant instead of an all-new "V35A-FKS." Specifically, I believe that the 3UR (Tundra, LX570, etc...) will get an -FKS update. The Tacoma's 2TR may also get such an update.

This would mean that the trucks can get new engines without taking up any of those 2 slots above or that 1 below the V35A-FTS in the graphic posted by the OP. As I understand, that set of DF engines should only cover the next couple years. These relatively minor updates can be a cheap stopgap while Toyota decides on what to work on next.

TheNerdyPotato

A thought I just had was maybe they're going to come out with more new/updated engines that are not in the Dynamic Force family. For example, the 2GR-FE/FSE have been replaced with the -FKS variant instead of an all-new "V35A-FKS." Specifically, I believe that the 3UR (Tundra, LX570, etc...) will get an -FKS update. The Tacoma's 2TR may also get such an update.

This would mean that the trucks can get new engines without taking up any of those 2 slots above or that 1 below the V35A-FTS in the graphic posted by the OP. As I understand, that set of DF engines should only cover the next couple years. These relatively minor updates can be a cheap stopgap while Toyota decides on what to work on next.

i think all the non-tnga updates have already been done.

so those two engines will certainly include truck V8.

spwolf

I am thinking that Lexus can easily do PHEV versions of all of their hybrid systems, like Toyota did for Prime. If they can bring the costs down, and new TNGA already accounts for this, we could see extra 10 kwh in battery capacity for plugins, which also unlocks extra 100hp in power... so IS300h becomes 300hp vehicle... LS500h becomes 450hp vehicle. All these cars have powerful electric motors already, just like Prius did, question is just of maximum battery output which is limited by size of the battery.

In regular hybrid mode, they would have maybe 20-30hp extra, but in performance mode it could have extra 100hp at the cost of "consumption".

That's not how the maths works for input-split hybrid. The hybrid transaxle can only handle a limited amount of power so for PHVs the maximum combined output is not the sum of the ICE and the traction battery (it is for regular hybrids because their batteries are very small). TNGA hybrids focus heavily on 'motor downsizing', which means the motors are designed to be minimum size required to achieve the designed output for regular hybrid operations. That's why the Prime has that clutch to allow both MG1 and MG2 to drive the wheels in EV mode. Bigger hybrid systems might gain a few horsepower, but 100hp extra is highly unlikely. The multi-stage still has some over-provisioning, so it could be the only one getting significant gains.

One of the members on this forum has major good news, but that can wait until ready to dispel.

10kWh of battery capacity, with 100% conversion efficiency (not happening) would convert into 13.4 horsepower hours. Meaning 1hp for 13.4h or 13.4hp for 1h. You could theoretically get 100hp out of it, but only for less than 5 minutes at a time. Of course, as ssun30 stated, the powertrain (motors, gearbox, etc...) has to be capable of handling the extra power.

TheNerdyPotato

10kWh of battery capacity, with 100% conversion efficiency (not happening) would convert into 13.4 horsepower hours. Meaning 1hp for 13.4h or 13.4hp for 1h. You could theoretically get 100hp out of it, but only for less than 5 minutes at a time.

You could easily get 75kW(100hp) out of a 10kWh battery, it's not even 'just theoretical'. The 8.8 kWh unit from the Prims already makes 70kW(93hp). PHV batteries are usually rated at 5-10C, which means the (numerical value of) power is 5-10 times the capacity. At 7.5C a battery will completely discharge in 8 minutes (60/7.5), but all ratings are 'peak values', the definition of which varies. Usually it's a 15-second burst or 30-second burst scenario (to simulate an overtake maneuver, for example). Most of the time the vehicle will be cruising at 80-120kph and only requests 15-40kW of power, but manufacturers rarely disclose 'sustained cruising power' for batteries.

Carmaker1

One of the members on this forum has major good news, but that can wait until ready to dispel.

am curious

ssun30

That's not how the maths works for input-split hybrid. The hybrid transaxle can only handle a limited amount of power so for PHVs the maximum combined output is not the sum of the ICE and the traction battery (it is for regular hybrids because their batteries are very small). TNGA hybrids focus heavily on 'motor downsizing', which means the motors are designed to be minimum size required to achieve the designed output for regular hybrid operations. That's why the Prime has that clutch to allow both MG1 and MG2 to drive the wheels in EV mode. Bigger hybrid systems might gain a few horsepower, but 100hp extra is highly unlikely. The multi-stage still has some over-provisioning, so it could be the only one getting significant gains.

If they decided on this, they already future proofed the system... new 300h's main motor still has 118hp.

Question is if they believe this to be right action to take, not if it is possible - it certainly is, just the question if they decide to do it or not.

ssun30

You could easily get 75kW(100hp) out of a 10kWh battery, it's not even 'just theoretical'. The 8.8 kWh unit from the Prims already makes 70kW(93hp). PHV batteries are usually rated at 5-10C, which means the (numerical value of) power is 5-10 times the capacity. At 7.5C a battery will completely discharge in 8 minutes (60/7.5), but all ratings are 'peak values', the definition of which varies. Usually it's a 15-second burst or 30-second burst scenario (to simulate an overtake maneuver, for example). Most of the time the vehicle will be cruising at 80-120kph and only requests 15-40kW of power, but manufacturers rarely disclose 'sustained cruising power' for batteries.

indeed, and recharging is question of mpg, nothing else... they can simply recharge with engine more to get back some of the power, but yes this will decrease MPG substantially... but will give you really a sport hybrid.

Right now every hybrid that Toyota has only one mission - to increase mpg. Only with recently introduced UX and ES, they started mentioning more about sports mode that gives more battery power. This was possible before as well but it would decrease mpg so they did not care about it.

ssun30

You could easily get 75kW(100hp) out of a 10kWh battery, it's not even 'just theoretical'. The 8.8 kWh unit from the Prims already makes 70kW(93hp). PHV batteries are usually rated at 5-10C, which means the (numerical value of) power is 5-10 times the capacity. At 7.5C a battery will completely discharge in 8 minutes (60/7.5), but all ratings are 'peak values', the definition of which varies. Usually it's a 15-second burst or 30-second burst scenario (to simulate an overtake maneuver, for example). Most of the time the vehicle will be cruising at 80-120kph and only requests 15-40kW of power, but manufacturers rarely disclose 'sustained cruising power' for batteries.

You're right. I don't know what I was thinking when I wrote that. Maybe the range limitations that spwolf mentioned. I had just got back from a week vacation and my brain was (and still is) frazzled.

TheNerdyPotato

Maybe the range limitations that spwolf mentioned.

german phevs, while really bad in general, have mode that lets engine recharge battery aggressively.... so it could actually work pretty well in HSD, but again question is what about getting pretty bad mpg since engine would be running at higher rpms all the time to recharge battery faster.

and it in all my reviews of phev's reading, this has been mentioned 1 or 2 times... and it is a major problem but i guess if they dont care about Porsche Phev losing half of ev-power after some aggressive driving, would they care about Toyota/Lexus?

Carmaker1

One of the members on this forum has major good news, but that can wait until ready to dispel.

new V8 in upcoming Tundra?

spwolf

german phevs, while really bad in general, have mode that lets engine recharge battery aggressively.... so it could actually work pretty well in HSD, but again question is what about getting pretty bad mpg since engine would be running at higher rpms all the time to recharge battery faster.

and it in all my reviews of phev's reading, this has been mentioned 1 or 2 times... and it is a major problem but i guess if they dont care about Porsche Phev losing half of ev-power after some aggressive driving, would they care about Toyota/Lexus?

Because they don't understand the concept of things working to perfection. They're so blinded by the fact that while at times they may push out dynamically superior cars, they can't manage to hold a damn candle to what Lexus (and to a greater extent Toyota) is able to do. The only exception to this is Porsche, even then, Toyota are much more ahead of them in terms of hybrid technology, and also the fact that they're taking great care of how the battery will live during its lifetime, so they make everything about it toned down and understressed, because for most buyers, they want something with no frills. The only issue to this is the god-awful CVT that's mated to the engine, but if it had the 8-speed automatic or even the multistage-hybrid system transmission, it would do the car wonders in terms of performance, also having pretty good fuel economy at the same time. It's reached to that point for me that CVT's in this day and age are quite dangerously slow. Would you sacrifice five, or maybe if all hell goes loose, ten miles per gallon (I know it doesn't even make that much of a difference, but I'm trying to make a point here), even though with a CVT is horrendously slow, and can really hurt you in terms of performance? Sometimes performance is necessary, because that allows the driver to do crucial things when on the road, like passing, overtaking, or launching off the line in important situations. I also feel like it won't also make a huge difference in fuel economy either. This is the only thing that I feel the Germans are edging out the Japanese. Nothing else.

F1 Silver Arrows

... also the fact that they're taking great care of how the battery will live during its lifetime, so they make everything about it toned down and understressed, because for most buyers, they want something with no frills.

This was mentioned and TMCs hybrid reviews, battery lifetime, replacement cost etc... funny how now this problem does not exist with German hybrids.

I have to say I do not dislike CVT on hybrids.

spwolf

If they decided on this, they already future proofed the system... new 300h's main motor still has 118hp.

I don't think latest THS allows full parallel hybrid operation, so some of MG2's power will always come from MG1, which is taken from the engine. The bigger hybrid systems are indeed sized (88kW for 2.5 and 80kW for 2.0) to allow EV operation without assist from MG1, so they could in theory get more power from the bigger battery in HV mode. There are just too many variables in a serial-parallel hybrid that analyzing the power balance is almost impossible for non-experts so I'm not making any more predictions.

spwolf

indeed, and recharging is question of mpg, nothing else... they can simply recharge with engine more to get back some of the power, but yes this will decrease MPG substantially... but will give you really a sport hybrid.

Right now every hybrid that Toyota has only one mission - to increase mpg. Only with recently introduced UX and ES, they started mentioning more about sports mode that gives more battery power. This was possible before as well but it would decrease mpg so they did not care about it.

Remember, serial-parallel hybrid allows regen and electric drive at the same time (ICE->MG1->MG2+HVB). A more aggressive regen strategy will not impact MPG too much, because it is also shifting the engine to a more efficient operating point. It means missing out on some kinetic energy recovery opportunities since the battery is likely to have a higher SoC, but KERS only accounts for about 20% of MPG gains on serial-parallel hybrids.

On a parallel hybrid, you are just wasting fuel to charge the batteries, which is incredibly inefficient (my BYD Qin, for example, requires 10kW of power from ICE to recharge the battery at 5kW). Parallel hybrids rely more on KERS for regen, and their load-shifting is not nearly as efficient. This is why those German PHEVs are basically useless when the traction battery runs out. In that situation the hybrid system just becomes dead weight. Luckily for them, the battery has a lot of capacity, so unless the user drivers like a hooligan it's unlikely to run out.

F1 Silver Arrows

The only issue to this is the god-awful CVT that's mated to the engine, but if it had the 8-speed automatic or even the multistage-hybrid system transmission, it would do the car wonders in terms of performance, also having pretty good fuel economy at the same time. It's reached to that point for me that CVT's in this day and age are quite dangerously slow. Would you sacrifice five, or maybe if all hell goes loose, ten miles per gallon (I know it doesn't even make that much of a difference, but I'm trying to make a point here), even though with a CVT is horrendously slow, and can really hurt you in terms of performance? Sometimes performance is necessary, because that allows the driver to do crucial things when on the road, like passing, overtaking, or launching off the line in important situations. I also feel like it won't also make a huge difference in fuel economy either. This is the only thing that I feel the Germans are edging out the Japanese. Nothing else.

Here's a quick lecture on how input-split hybrids work. The engine is not mated to a CVT. In fact THS does not even have a transmission: it is the transmission. The planetary-gear system is what decouples engine speed from wheel speed. This is why it can operate like a CVT. This is also why it is the best: super simple, super efficient, and, believe it or not, cheaper than a parallel hybrid. After all, a parallel hybrid still needs a costly automatic transmission.

Traditional CVTs are slow off the line because they are designed to operate at highway speeds. It is possible to optimize CVT for acceleration but it just means losing fuel efficiency during cruising. That problem is easily solved by adding a launch gear to the CVT, which is what Toyota did recently. But that's irrelevant in a hybrid, because MG2 provides enormous amount of torque at start. But just like any electrified vehicle, the performance of hybrids is mostly determined by the software, not the mechanical components themselves.

I will again bring the China-only Corolla/Levin hybrids to this discussion, because honestly TMEC Suzhou did the best job at making hybrids that are not annoying to drive. The Corolla hybrid is tuned for two scenarios: 0-50kph and 30-60kph acceleration which are the most common on chinese roads (starting from a green light and accelerating onto a highway ramp). At these speeds the hybrid system employs electric boost very aggressively, almost ramping up to maximum output instantly, unlike the Prius that just bogs even at WOT. To compensate for that, they also employ more aggressive regen strategies. Their market campaign repeatedly show the Corolla outrunning the BMW 320i or the Audi A4 TFSI. The end result is very positive; people recognize hybrids as not only more fuel efficient but also very fast.

An overly conservative software is what gave the Prius a terrible reputation. To preserve battery and maximize MPG, the hybrid system is programmed to, well, do nothing. The Corolla hybrid uses an identical hybrid system found on the Gen 4 Prius, but the two couldn't be further apart in terms of driving quality. The fuel economy for the Prius and the Corolla hybrid is 4.3L/100km and 4.7L/100km respectively. That's a 9% difference, but the Prius also had tons of aerodynamic and weight-saving tricks so I would say the actual advantage is less than 5%.

To continue with the discussion, I would like to point out that the single biggest problem with THS right now is the battery. It's too small, too weak, and it's NiMH. It's a consensus in the automotive industry that other components of the THS are at least two years ahead of competition, but it could have more potential if not for the outdated battery tech.

It's almost a miracle the Prius can get over 50MPG with a 1.3kWh (NiMH)/1.0kWh (Li-ion) battery pack, of which only 40% of the capacity is actually usable to preserve the battery. This means at anytime, the hybrid system only gets 1.8MJ of energy reservoir to work with. It's like managing your finances with a very small bank account. Therefore it needs to very carefully balance boost and regen. Early generations of Prius use a very primitive system based completely on throttle input, which means MPG is heavily dependent on driving style. It is well known Prius hypermilers are constantly monitoring battery SoC and driving in a manner to not waste any regen opportunity. The latest Gen 5 has some predictive measures based on machine learning, but it still needs to constantly predict when the energy is needed. For example, it may not know a driver will be climbing a long gradient and recharge the battery accordingly.

Having a bigger battery brings a ton of benefits. Let's say if the Prius is equipped with a battery half the size of the Prime's, i.e. a 4.4 kWh 35kW Li-ion unit (compared to the 1.0kWh 20kW Li-ion unit). Such a battery would only weigh 20-25kg more.

>>The battery can discharge much deeper, since it needs to discharge fewer cycles for a given energy consumption compared to a smaller one. The 4.4kWh unit could make 50% of its SoC available and that will be 8MJ of energy reservoir.
>>Having an energy reservoir over four times as large gives the car much more flexibility without much prediction of what the driver is going to do next. For example, it could simply brute force a gradient with the extra energy it stores. Again, the bank account analogy applies here. You are much more flexible with when and how much to save up or spend if you have a bigger account.
>>Since the battery has more power, the car can operate in EV mode more frequently and at higher speeds.
>>The car will be more powerful in general, that's pretty straightforward.

This is why I said the Prime is what the Prius needs to be in the first place. It's very encouraging to hear that the Prime's battery pack is now marginally more expensive than the NiMH unit on the regular Prius. I think for the next generation they need to design a modular battery system for regular hybrids and plug-ins, for example a 5kWh 40kW 'block' that can be combined into different configurations.