They require much more active computer control to work though so they aren't logically simpler in my opinion, but mechanical simplicity is what makes the biggest difference.
There are certainly better more approachable sources though so I leave this as an option as the info is there, but can take a moment to understand.
Four axis, like a square pinned at the corners if you know the relative position of two elements you know the position of the others. This is the basis for most traditional machines.
Five axis is floppy. And usually avoided traditionally.
The synergy drive is a five axis machine mechanically. But has two electric motor generators. By varying the speed of the motors you can control the gear ratio of the mechanical path. Since the motor speeds are indignantly variable so is the mechanical path. You end up with continuously variable transmission with a mechanical power path and an electric one in parallel. And it doesn't suck like pure mechanical ones.
Totally genius.
Also, YouTube helps. Search for “Power Split Device” or “e-CVT”.
Regarding other hybrid tech, it’s a bit of a crapshoot. I basically use ChatGPT with search enabled to have sources, and then ask how the system works. It’s never in the marketing materials, I guess most don’t care.
My takeaway was the same as some of the other posters here, the system is an engineering tour de force. Simpler than the gas version, proven reliability, and efficiency not too far off the theoretical limit of gas-burning drive trains.
Seeing how simple the whole mechanism is, I totally get why the empirical reliability is so good.
Not to mention that the lecturer shows and explains things very clearly.
Highly recommended!
https://www.youtube.com/playlist?list=PLeFzfl0Q8rQUOHwFNOMTu...
He goes into the practicalities of owning/maintaining/repairing as well as the engineering.
The Hyundai felt like driving a regular automatic, so it would occasionally lunge awkwardly and spin the engine in situations where Toyotas switch to EV mode.
Sure it had better fuel economy, but I can't stand having a car not react immediately to my input or make noise when it shouldn't.
But yes, in that the power transmission is variable (e-CVT, right?), and that sounds a bit weird. You’ve spent so much time hearing how the engine gets louder with acceleration that it feels weird when the engine behaves slightly differently.
But again, that doesn’t bother me enough to buy a less reliable system.
Actually every vehicle I've driven was CVT/e-CVT. 14 Corolla, 18 RAV4, 21 Highlander hybrid and 24 Integra. All super reliable. I'd still say CVT bothers me and I love it every time I get to rent a vehicle with traditional automatic.
The computer has an idea of "At this low RPM the engine is most efficient, at this high RPM it produces maximum horsepower". So if you floor it, the computer in either a CVT or a hybrid will bring the engine to full power and it will just sit there as the car accelerates.
The engine is getting loaded up and putting out more torque, and the throttle is opening, but it isn't really revving. In mine it does slowly climb from maybe 4,000 to 5,000 RPM, but it doesn't do the "rrrrRRRRRR... rrrrrrrRRRRR..." like a transmission with fixed gear ratios.
Anyway revs do go up over a certain speed, but you need to be on the Autobahn to legally test it.
The revving complaint is such a tired trope among car reviewers, especially German ones. Every reviewer without exception mentions how CVTs rev unnaturally and have a rubber-band effect. They just can't get past their expectation bias.
The worst thing is that it's not even true anymore for Toyotas latest gen. There is no rubber-band effect at all anymore, in fact because of the electric motors I get instant response. A regular car with gears or a turbo is way more sluggish. The only way I see constant high revs is to drive above 160 km/h (100 mph) on the German autobahn. Anything less and it just purrs along quietly.
I'm spoiled from years of Priuses now, and driving gas cars, even fancy and expensive ones, feels bizarrely primitive. The lag between the pedal and the response, and the complex relationship between the input and the response, feels antiquated and arcane.
Also at least once I almost went "woah, horsie" as the car lunged forward because I tapped the accelerator a moment after it shifted to a lower gear without me noticing.
It used to be even worse. I had an opportunity to drive a 2005 BMW 7 series in a city where the speed limit was 30km/h. Unfortunately the gearbox was from a time way before traffic calming etc. went mainstream, so it couldn't decide which gear to pick. I ended up switching to manual gear selection mode.
I haven't felt that since I've been driving my CVT ICE for so long.
Then again, a coworker told me the CVT is likely to break before 100,000 miles. So.... thinking of buying a Prius. I love Priuses.
A caveat though. I used to have a Škoda Fabia with a chain drive, and I did end up changing it, as it started making the tell-tale sound when stop-go.
In the context of hybrids though, I fully expect that chain to last the lifetime of the engine. The engine is under significantly less load than in a traditional ICE, so less stress on the chain. Also, for 100k mileage, the motor-hours that the engine has worked are less than in an ICE due to the engine regularly being off.
On all of our other cars (Toyota), the belts needed to be serviced at X miles, but it was actually a cheap and quick procedure.
After 2017 Ford started using belts to drive the oil pump in F-150 engines (and possibly other Ecoboost engines). I have seen 100k teardowns of failed engines and the belt is not looking good at that point. If the belt breaks the engine is toast by the time the operator realizes what is going on.
My Land Cruiser has a timing belt. I replace it every 90k miles per Toyota's specifications. My Tundra has the same engine, except that it has a timing chain. I've never bothered to replace the timing chain.
A timing chain is preferable as long as it isn't something like a Jaguar/Land Rover. The chain in those doesn't matter because they use plastic tensioners that eventually become brittle at crack/fail.
Chains were very common in American cars and trucks for decades and they did need replaced after 150k-200k miles. I replaced the one in my 1993 Ford 5.0 at about 150k hard miles and it made a dramatic difference in performance (solved knocking/preignition on hills).
Don't forget the Mazda CX-50 Hybrid that was just released. Using the Toyota Hybrid from the RAV4 with the elegance and beauty of Mazda design.
:hide_the_pain:
I have no idea what Toyota’s strategy with the Sienna is.
A mechanical CVT with belts and pulleys with changing diameters is even worse.
What the hybrids (e-CVT ones) have though is basically a planetary gear set, where the gears are put together at the factory, and stay there for the life of the car.
To me that’s not a gearbox. At least not in the traditional sense. Transmission sure.
This page has a neat PSD simulation to help grok what happens:
I think it only works from a computer though!
My goal is usually to drive my vehicle all the way into the ground, and I guess that’s what happened to my Prius except it happened around if not before 150,000 miles.
I have a Prius that's at 100k right now. Repairing the battery is within my abilities but I'm concerned that if one or two cells fail, more will be right behind it.
I could see how there could be situations when someone tries to sell you into changing all the cells, even when that’s not necessary.
I think a pure EV with a small range extender not connected to the drivetrain mechanically- like the BMW i3 REX is the way to go. It’s even simpler and lighter than the Prius system, allowing for a much larger battery and more powerful electric motor.
Doing things 'weird' usually makes them cheaper and less crowded/faster as well- as a result of less demand.
As somewhat of an old timer (turning 43), I remember the techie population seemed to overlap a lot with the car enthusiast population a long time ago. Nearly everyone at my first job (small startup) was a car nerd. A lot of engineering and tech goes into cars after all.
Somewhere along the way a lot of techies became very anti-car.
There are plenty of other things to tinker with.
Having driven a lot in my youth, it's just not something I enjoy regardless. I'd rather spend the time and resources on other things. Even taking a longer bike ride to the store is preferred because it's exercise, almost everyone on the trail nods or waves back, and I know my choice is better for everyone in the community.
At a certain level of utility/space, cars just stop being that fun. Well, until you get to the vans, those are fun in their own weird way.
There are some fun weird vans. I've always loved the Toyota HiAce, Mitsubishi Delica, and other strange Japanese minvans with weird features like built in karaoke machines, beverage coolers, tiny diesel engines, and real truck 4x4 systems. Also love the old VW vanagons.
They used to run (tongue in cheek) ads for the Boxster with the slogan "The more kids you have, the more practical it becomes" and that it fits "Two child seats. Up front." There's some truth to that- if you have a large family you will likely have multiple cars, it can still make sense for one of them to just take two people for 1 on 1 activities.
When I was in Ireland for work, I saw that a huge fraction of the farmers use MKIV TDIs for their farm work vehicles- they're all over the place pulling huge trailers full of livestock and hay, and still using half the fuel of most cars that are unloaded.
Overall the Boxster is a surprisingly practical car- it was very cheap (cheaper than an old Prius of the same age) but now appreciating in value with age, can use a 3+ carpool lane with 2 people, is tiny so easy to park anywhere, and it is actually very reliable and low maintenance.
I assure you there is no bait- it’s an example of things that would make an everyday chore fun to me, and needs no justification. I would suggest you do what would make it fun to you.
So I'd rather get the prius-like ergonomics and comfort.
I use Linux, EMacs with vim keybindings and a dark color palette. Coding this way makes me feel good, I like the aesthetics. If they tried to force me to use Windows, and an IDE with a light color palette, I’d seriously consider quitting. It’s totally irrational, but it is what it is :D
Of course cars suck in cities, but they are great in rural areas.
Or, you could reengineer your too-short life so you waste less time driving.
It’s fine if you like driving and want to have a nice car - connoisseurs abound in all fields. But for 99% of people it’s not an issue worth optimizing for.
Bold claim. Sitting in traffic in manual or auto ICE is a nightmare compared to a Tesla.
That is, a series hybrid, like a diesel locomotive?
The range extender basically gives you protection from range anxiety, but isn't used at all in normal use of the vehicle. On the i3, it only starts the engine when the battery is nearly empty, but some people do software mods to be able to use the vehicle as a true series hybrid, and run the engine continuously for doing long distance freeway driving without stopping to charge.
And grants you maintenance anxiety.
Where I live charging infrastructure is good enough that a 300-400km range EV is completely sufficient. Range extenders is a niche solution.
I do agree about the Prius, though. It feels like driving a dishwasher.
For me, the hybrid is fun to drive. I've never experienced any unresponsive inputs or lack of feedback in performance. The fun comes in at trying to keep the gas engine off as much as possible -- without going becoming a hypermiler and irritating other drivers -- both in city and long distance driving.
I regularly drive both a 2011 Prius and a 2023 BMW X1 “mild hybrid”, I’ve also test driven an iX1 electric and X3 “real” hybrid recently (all practical family cars).
In order of increasing accelerator-input-to-actually-moving (at low speed) delay:
iX1 electric (best) Prius X3 hybrid X1 mild hybrid (worst, dangerously bad)
That is to say, every time I get into the 14 year old Prius I think “wow this is nippy” after having driven the 2 year old X1, which we’ve nicknamed “the lag wagon”.
Toyota really nailed the driving ergonomics of the gen2 Prius, given the constraints. Yes, it’s a slow to accelerate at high speeds, but it’s still really nice drive around town.
If only Toyota made bunch of toy models for THS and built couple 2-door hybrids so that more people would get it. I suppose it's a case of innovator's dilemma, but it's so unfortunate.
https://www.youtube.com/watch?v=3eC5FFoCq4s ("It Turns Out, Hybrids Are Really Hard On Engines")
https://www.autoweek.com/news/green-cars/a34667856/the-updat...
https://hondanews.com/en-US/honda-automobiles/releases/relea...
I also have now an hybrid Corolla (the station wagon version the US does not get. Because we all now Station wagons are the superior form of car.)
But that’s a good thing. I own a Toyota Corolla hybrid myself, and hybrids are one of those things that I can say I’ve completely changed my mind about. I used to dislike the idea of hybrids, because I assumed that the overall system complexity must be higher than either an ICE, or an EV. And I’m a sucker for simple systems, so I thought it’s either EV, or nothing.
Then I looked into how hybrids work. Specifically Toyota hybrids. And came away totally amazed. It’s an amazing system, and much simpler than a traditional ICE car. It doesn’t really have a gearbox, or a clutch, or a starter. The engine is a normal atmospheric engine, so no turbines, overcompression, and the issues that come with it. Furthermore, the engine is typically configured to use the Atkinson cycle, which puts less stress on it. And, the engine has a chain drive, so no belts to change, and by design gets stressed a lot less than in a traditional ICE, because the stop-start load is carried by the electric motor. Also, it can’t really have trouble starting in cold weather, much like an EV. All of that boils down to crazy reliability.
I’m at a point where if I’m looking for a car that uses fuel, it’s only cars that use the Toyota hybrid tech (or similar) that I’m looking at. At the moment it’s just Toyota, Lexus, most Ford hybrids (but not all).
Other companies have hybrids that are liable to my original concerns about massively increased complexity. As an example, VW hybrids have an electric motor within their DSG gearbox. So you have all the complexity of their modern ICEs (turbines, DSG, whatnot) plus additional hybrid related complexity.