WeberAuto
3 HN recommenders · recommended in 7 months, 2023–2026
39:08 · 1.7M views · Jan 23, 2021
Weber State's Professor Kelly explains the Toyota RAV4 Hybrid transaxle, including its planetary gearset eCVT and all nine operating modes. It also covers how the engine reaches nearly 40 percent thermal efficiency.
HN points to it as the clearest hands-on explanation of how Toyota hybrids work.
7 comments from Hacker News
I understood after I watched the brilliant Weber Auto video on it, published 5 years ago[0]. I liked it so much I "gently" encouraged my partner to get a Yaris hybrid, which gets about 69mpg average. It's not unusual to see 80+ on individual trips. She was a little sceptical about having an auto at first, because us Europeans still think it's 1980 and that manuals are superior, but she came around after a few minutes of driving. To be fair, though, classic "slushbox" autos actually were/are garbage, as are chain actuated CVTs. The hybrid system gets you immediate acceleration like an electric, none of this awful lag you get with a slushbox. It's hilarious to me that 34mpg is considered remarkably good, though. I know it's a "minivan" but my Golf GTI gets 42mpg and is actually fun and arguably cool. I can also fit 5 people, furniture, and 2.4m lengths of timber in it comfortably. [0] this video
The planetary gear "eCVT" systems that Toyota and Ford use in many models are mechanically a lot simpler than a traditional automatic or sequential manual transmission. Few moving parts and no clutches at all. I don't know what the long term reliability of those drivetrains is is but I wouldn't be surprised if it's measurably measurably better than a traditional transmission + engine. There's a long educational video from Weber State University that gives a good walkthrough of what's going on in those things. this video
Toyota's eCVT? Not at all. The gas engine can drive the front wheels directly. [LINK] Conceptual explanation of the system. this video Weber Auto giving an extensive hands on explanation.
A quick Web search seems to indicate that's either a) not actually a CVT at all, or at best b) a planetary gear used as a power-splitting device to connect electric and ICE power sources to a conventional CVT. So this compares rather favourably, by actually being a geared CVT, which Toyota's "eCVT" apparently isn't at all. Sources: [LINK] (From: [LINK] ) this video (Long, 39 min!) Ooh, aah, now I get it (I think): Yes, the output RPM of the "eCVT" is indeed continuously variable. But that's just how all planetary gearboxes with two power inputs (as here, ICE and e-motor) work: The output RPM is a function of both the input RPMs, a (weighted) average of them if you will. So you can vary the output RPM while holding one of the input RPMs constant, simply by varying the other input RPM. Here Toyota presumably wants to keep the ICE working at the most economical RPM, while allowing the vehicle to move at varying speeds, which they achieve by varying the RPM of the electric motor. (In practice, Toyota uses two electric motors, but AFAICS the principle also applies to just one. TBH I'm not sure why they need two, but then I'm only halfway through that long video.) So yeah, the "eCVT" is kind of "a CVT", but only if you have two power sources simultaneously. It can't apply a continuously varying gear ratio from just one power input to a power output, which is what is usually meant by "power transmission". TL;DR: This can vary the gear ratio from a single power source to your wheels; To
> Toyota-style hybrid drives could be a lot lighter The hybrid electric motor in a Toyota is already pretty comparable in weight to the motor in TFA, but obviously much less powerful. You can see the main hybrid motor of a RAV4 at [0]. If memory serves both the Camry and RAV4 hybrid models are only 2-300 lbs heavier than their gas counterparts. 0: this video