Honda v. Toyota hybrid system

[Gas Jazz]

Hi John

I understand / agree with your observations with optimisation of engine revs etc where there are gears to change drive ratios as in a normal or cvt gearbox.

However, for the Jazz e CVT when in engine mode the engine is “locked” to the drive wheels by the fixed ratio reduction gears - a bit like riding a single speed bicycle. This being the case I’m not sure how revs can be optimised without impacting on road speed.

Having said this it’s all very clever and I’m not!

[nowster]

There are actually several different operating modes:

* Pure EV
* ICE driving generator, electric motor driving wheels
* Pure ICE "overdrive"
* ICE driving wheels and generator
* ICE driving wheels with electric motor assist
* Regeneration (via main electric motor)

I also wonder if the generator is also used in reverse as a starter motor for the ICE.

[John Ratsey]

However, for the Jazz e CVT when in engine mode the engine is “locked” to the drive wheels by the fixed ratio reduction gears - a bit like riding a single speed bicycle. This being the case I’m not sure how revs can be optimised without impacting on road speed.

I suspect that such optimisations are matters of a few percent which help the overall mpg, but are less than the efficiency gain by using direct drive which avoids the generator / power conversion / motor losses.

The vehicle's behaviour sometimes has us puzzled but I think we can be sure that it's guided by the objective of achieving maximum overall efficiency.

I also wonder if the generator is also used in reverse as a starter motor for the ICE.

Yes. Both motors can be used as generators or vice versa. Hence the term "two motor hybrid" although, at any time, only one is a motor and the other a generator.

Another situation when the generator attached to the engine becomes a motor is when going down a long fairly steep hill and, once the battery is full, the system goes into engine braking mode. It took me over six months to first notice this taking place.

[Jeff15]

I cannot get over how seamless the whole thing is between the engine and battery power, it is a clever piece of technology.

[sportse]

Driving on the motorway yesterday I had the power display up - it was switching between direct engine drive, hybrid drive and regeneration over a few seconds… totally seamlessly as without the display up you wouldn’t know.

I think Honda should call it a ‘range extender EV with a direct cruise gear’ rather than just saying it’s a hybrid.

The system is much more advanced than Toyota’s.

[nowster]

I cannot get over how seamless the whole thing is between the engine and battery power, it is a clever piece of technology.

Apart from when the petrol engine audibly kicks in at low speeds to charge the HV battery, in normal driving it's impossible to tell when you're in one power mode or another. It's really smooth.

[Kenneve]

That's because in all conditions except high speed cruising, the car is driven by the electric motor, with power coming from either the battery, or the generator, or both. The only time the car is driven directly by the engine, is in cruising speeds above around 55mph, when a clutch closes to provide direct drive.
If more power is required, then the clutch opens and the vehicle reverts to electric drive, with the engine speed increasing to power the generator as required.
Its still possible that at low power requirements, or downhill,  even at 70+mph, that the system will revert to EV mode and the driver is totally unaware of the changes, unless watching the instruments.

[Hicardo]

Having owned both Toyota Auris hybrid and the Honda mk4 jazz hybrid, I think yes I also prefer the Honda for the reasons already stated, lively, so smooth, great economy.  The Toyota is a great system too, plus its proved incredibly reliable.  One thing I prefer on the Toyota though is the ability to choose when to go into EV mode.  its really useful for sitting around with electrics on and engine off for ages drinking coffee and not having to worry at all about battery depletion.  BTW im not a cabbie, I just like to sit around drinking coffee and chatting in the car 

You can get a similar effect in the 'ev button free' Crosstar by turning off the a/c and opening the windows.  this way the traction battery will last ages before starting the engine when parked. 

 

[nowster]

That's because in all conditions except high speed cruising, the car is driven by the electric motor, with power coming from either the battery, or the generator, or both. The only time the car is driven directly by the engine, is in cruising speeds above around 55mph, when a clutch closes to provide direct drive..

Actually, I've occasionally seen the cog on the display at speeds below 50mph. I've also seen the cog with electric assist.

[Hicardo]

never seen a cog.  what view are you using pray  . I tend to use the simple view 99pct of the time, and fuel consumption the other 1pct 

[Kenneve]

I've also seen the cog with electric assist.

Not sure about that.
Page 7 Engine (Direct Drive), of the Power Flow display, shows the Engine driving the car (with cog), but the HV Battery is being charged, not discharged!

[John Ratsey]

I've also seen the cog with electric assist.

Not sure about that.
Page 7 Engine (Direct Drive), of the Power Flow display, shows the Engine driving the car (with cog), but the HV Battery is being charged, not discharged!

I've seen both. There can be direct drive with a trickle of electricity being used to get the battery charge up to 70% and there can also be direct drive with some assistance from the battery (eg for some acceleration or adverse gradient). Once the battery gets to 30% charge and if more power is still needed than the engine can produce at the revs determined by direct drive then the vehicle will switch to electric drive.