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sequential gears in 2019 rav4 hybrid

10K views 14 replies 8 participants last post by  pikeviewer 
#1 ·
Hello, everybody! I am a new user waiting for my 2019 AWD Rav4 Hybrid, sometimes in June. I was wondering what is the logic of the sequential gears: I only tested the 2 wheel drive and I noticed that the sequential gears work at low speed, but, if you go at full throttle, the ECVT no longer lets you change gears (or better you can only shift them down).
Does anybody have an explanation for this? It seems to be counterintuitive, after all, one should be more likely to use sequential mode in sporty driving.....
Thks and rgds
 
#2 ·
A more important functional use of controlling your gears is going down steep inclines where you want the engine to help prevent unwanted acceleration without overly relying on the brakes. These shifting choices could help starting in snow (if you can successfully up-shift) and getting out of sand etc. if the dedicated "driving modes" aren't enough.

Number of times used on my 2011 Highlander: zero.
 
#3 ·
Covered pretty well in the manual, and worth reading,
There are no gears, actually. Its just changing the RPM of the electric motors and ICE in relation to each other. The 4 different settings are speed dependent, lower settings not being possible at higher speeds.

Also good to note that using the sport shifter reduces your regenerative charging by as much as 60%.
 
#4 ·
What RDG said -- there are no gears. It really isn't an "eCVT" because there is no CVT. It is just computerized signals to various motors and brakes on the wheels and axles. There should be a link in a thread here to a great YouTube animated video done by a German engineer on the "Prius system".

The Sport mode mimics gear changes, but doesn't really do anything else.
 
#6 ·
Toyota hybrid vehicles actually do have variable gear ratios and actively changes the ratios while driving. This is how the ICE can drive at freeway speeds without blowing up, when MG1 and MG2 are not as active.

There is a planetary gear set built into the Power Split Device which controls the ratio continuously, resulting similarly as a CVT in which there are unlimited gear ratios in between the highest and lowest ratios. However, because it is a planetary gear setup, there is no shifting belt like seen in a CVT. Toyota calls this eCVT. Similar, but different.

So yes, with sequential gear shifting standard, the driver can "up" shift and "down" shift, and the vehicle while change the ratio to mimic the commands using the eCVT inside the Power Split Device.

And as a note, when at full throttle, you should not feel the need to have to "shift" gears, as it would only result is less efficiency. The eCVT does all the work for you by keeping the gear ratio at the most efficient for acceleration both in power and fuel efficiency. Your RPM will stay at the highest power point until you lay off the gas. This is most likely why sequential shifting it's not enabled at this point.
 
#7 ·
I respectfully disagree about gear shifting although the effect is similar. The planetary gear set does not change gear ratios. It changes the mix of gas and electrical power being delivered. The gear ratio from the ICE to the wheels is fixed at a ratio similar to a top gear. Instead of down shifting, power from the electrical motor (MG2) is added when additional torque, such as when starting out or when accelerating, is needed.

The ICE doesn't blow up at highway speeds because it is already (and always) in top gear.

Again, this is a proven and well documented fact: The planetary gear set does not change gear ratios. It does change the amount of torque being delivered to the wheels which feels like gear changing. The manual "shift" changes the mix more abruptly and holds that mix to feel like gear shifting.

Here is a link to a good description of the PSD. Note that is says "It acts as a CVT but with a fixed gear ratio": http://eahart.com/prius/psd/
 
#11 ·
I'm glad to see the discussion is remaining polite, as this is a very complex issue.

This animated video by a German engineer does a pretty good job of explaining the Toyota system, even though he calls is "Prius Hybrid Drive"... ;-)

 
#12 ·
Good video. While we're at it, I'll clarify something I said earlier: "The gear ratio from the ICE to the wheels is fixed at a ratio similar to a top gear."

What is actually fixed is the amount of torque that the ICE puts out through it's fixed gear ratio in it's connection to the sun and ring gears. The ICE can spin at different speeds (including down to zero) relative to the wheels and therefore change the amount of power going to the wheels (and/or battery), but the eCVT doesn't multiply torque through gear ratio change.
 
#14 ·
You said "This is how the ICE can drive at freeway speeds without blowing up, when MG1 and MG2 are not as active."

This is not quite true. There is a fixed ratio between the speed of MG2 and the wheels. There are then a large number of combinations of ICE and MG1 speeds that are possible, depending on how much power is needed from the ICE. Some of those combinations have MG1 spinning backwards at max RPM (and thus quite active).

The relative speed and direction of MG1 and MG2 and the ICE determine the effective gear ratio. See Toyota Prius - Power Split Device for an animated model of the Prius, which works essentially the same (but with different ratios and RPM limits).
 
#15 ·
Actually that blog is giving wrong information by saying that the eCVT changes gear ratios. Now we know where you got that idea! You were misled. They try to simplify it by saying gear ratios change when it is actually primarily the mix of torque from gas and electric sources.
 
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