Author Topic: Mk4 Press Release with videos and more pictures than in magazines  (Read 10213 times)

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #15 on: October 24, 2019, 08:33:43 PM »
A transmission is the device that conveys the power from where it is generated to where it is used. A Constantly Variable Transmission has a continuous range of effective ratios. An electric drive does not. It has a single ratio (or in the case of a bypass clutch, two fixed ratios).

https://en.wikipedia.org/wiki/Continuously_variable_transmission
Trasmission, in this case, is what you find after the petrol engine crankshaft and before the wheel bearings. So both the two electric motors, that can also be generators, are included in the transmission, in this case made by two electric motors, regulator, battery and cables.
In a transmission, by definition the ratio is the number you gain dividing rpms of the power inlet (in cars is petrol or diesel engine) by the outlet (wheels). Manual gearboxes have several ratios, each gear is one, and you can calculate them in two ways: one is counting the number of gear teeth (also the final drive, meaning the pinion and ring gear of the differential), so you will obtain the first gear ratio, the second gear ratio, the third and so on. The other way is dividing the rpms, and also in this case each gear will give you the ratio given by the different rpms.
In our cases,  a belt&pulley transmission have an effective continuos range of ratios, because the ratio between inlet and output rpms continuosly changes. So we call it CVT. But also electric drive does the same, because the ratio between inlet and output rpms continuosly changes.
I know, it was the same for me, before  studying as mechanical engeneering. Only then I discovered that the  continuosly variable transmissions is a big family, called CVT, where belt&pulley are only a sub-branch. Car enthusiasts  think that CVT are only the belt&pulley because they only know this kind of cvt, but the family is bigger. The "trick", in the case of I-MMD, is considering the two electric motors not as motors but as part of the whole transmission system, as they are essential to vary the ratio between petrol engine and the wheels. Infact Honda, in the technical papers, calls the I-MMD as E-CVT.
https://www.hondarandd.jp/point.php?pid=966&lang=en


Hope you can read it, in case I can  provide the PDF.

« Last Edit: October 24, 2019, 08:38:28 PM by jazzaro »

Jocko

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #16 on: October 24, 2019, 08:36:30 PM »
Well Honda got it wrong then!

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #17 on: October 24, 2019, 08:40:38 PM »
Well Honda got it wrong then!
Hahahahah yeah!
This is the article abstract:
Summary
A highly efficient SPORT HYBRID Intelligent Multi-Mode Drive system was developed in order to achieve a balance between the joy of driving and measures to address climate change and energy issues. The developed power train is composed of the engine, an electric coupled CVT with a built-in motor and generator, a Power Control Unit, and an Integrated Power Unit. The built-in motor was given higher torque, higher output, and higher efficiency by using reluctance torque and raising the voltage. The Power Control Unit was made more compact and power was increased by enhancing the unit’s heat dissipation performance, and it was made more efficient by using a low-loss chip. As a result, the motor achieves maximum torque of 307 Nm and maximum output of 124 kW, while the Power Control Unit achieves a voltage increase of 700 V and total output of 400 kVA. The Power Control Unit including the motor achieved a maximum efficiency of 96%.

John Ratsey

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #18 on: October 24, 2019, 08:51:15 PM »
I'm having trouble understanding why use two motors instead of one (which must add cost) unless one is powering the front wheels and the other is powering the back wheels.

I believe that the CR-Vs i-MMD has a direct drive mode used at higher speeds to avoid the losses of the electric transmission. Does the system in the new Jazz include this mode or does it use the generator (+ battery if needed) > electronics > motor for all operating conditions?

Another aspect which I hope that Honda has addressed is to ensure rapid warm-up of the engine by, for example, restricting fresh air to the engine compartment under cold conditions. Cold petrol engines guzzle fuel.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

culzean

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #19 on: October 24, 2019, 08:52:52 PM »
Looks like Honda using their F1 drive train experience to make hybrid  - they got it right once the McClaren roadblock was removed..
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #20 on: October 24, 2019, 09:23:30 PM »
I'm having trouble understanding why use two motors instead of one (which must add cost) unless one is powering the front wheels and the other is powering the back wheels.

I believe that the CR-Vs i-MMD has a direct drive mode used at higher speeds to avoid the losses of the electric transmission. Does the system in the new Jazz include this mode or does it use the generator (+ battery if needed) > electronics > motor for all operating conditions?

Another aspect which I hope that Honda has addressed is to ensure rapid warm-up of the engine by, for example, restricting fresh air to the engine compartment under cold conditions. Cold petrol engines guzzle fuel.
"Two motors" is a little bit confusing, I agree.
The I-MMD has two motor-generators: one is linked to the petrol engine and can be a generator (converting the mechanical energy from the petrol engine to electricity) but also a motor, used to softly start the petrol engine. As Toyota hybrids, in the i-mmd the petrol engine works only when needed.
The other motor, the biggest, is linked to the differential: as a motor it gives power to the wheels, but releasing gas or braking it recharges the battery as a generator.
I don't know if the system of the new jazz will have the direct drive, there are no technical specs avaiable. At this moment I've seen three i-mmd systems, Accord, CRV (with a 2.0l) and Insight (with a 1.5l), and they all have the direct drive. Let's wait for further news..
About heating... I read a review about the Insight I-mmd (could be  by car&driver, my memory lacks) and I was surprised by the reported poor mileage in very cold weather; the petrol engine works not only for electric traction, but also for cabin heating, and the heat request keeps the engine running when usually it would be stopped.
Another tip; Jazz will have an electric climate compressor, powered by the high voltage battery, so the cabin will be cooled even with the petrol engine off for some minutes.

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #21 on: October 24, 2019, 09:25:36 PM »
Looks like Honda using their F1 drive train experience to make hybrid  - they got it right once the McClaren roadblock was removed..
Systems are deeply different, so I dont' think they could use F1 experience.  F1 is an advertisement...

Downsizer

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #22 on: October 24, 2019, 09:58:47 PM »
Jazzaro's comment about CVT triggered an intriguing (but unimportant!) discussion about the meaning of "transmission" in this context.  The Oxford dictionary refers to "The mechanism by which power is transmitted from an engine to the axle in a motor vehicle", and I have difficulty classifying electric cables as a mechanism.  So I'll stick to my view that the Mk4 Jazz does not have CVT.  I think it will have a fixed ratio transmission at higher speeds.
« Last Edit: October 24, 2019, 10:07:49 PM by Downsizer »

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #23 on: October 24, 2019, 10:23:27 PM »
mmhmh general dictionaries imho are not the better instrument to understand definitions about very specific fields, mechanics, electronics, anatomy...
I prefer to trust in my university books and in engineers who designed this systems, I-mmd, HSD or other cvt without belts, they all talk about CVT.
Another example:
https://www.hydraulicspneumatics.com/200/TechZone/HydraulicPumpsM/Article/False/86140/TechZone-HydraulicPumpsM
No mechanics, only pumps, pipes and hydraulic motors, and this is a CVT, and the reason is still the same.
We can close the OT or open a new discussion.
« Last Edit: October 24, 2019, 10:26:15 PM by jazzaro »

John Ratsey

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #24 on: October 24, 2019, 10:38:44 PM »
Another tip; Jazz will have an electric climate compressor, powered by the high voltage battery, so the cabin will be cooled even with the petrol engine off for some minutes.
That's useful information. I would hope that the system can be run backwards to serve as a heat pump (about 4x more efficient than direct electrical heating) and it could be used, not only for warming the cabin, but also for initial warming of the engine. Once the engine has warmed up then, when it is running, it can be used to provide the cabin heating. That would be progress and a useful step towards achieving good fuel economy for short trips and during cold weather.
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jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #25 on: October 24, 2019, 11:14:35 PM »
It would be nice, but I don't think they will use this system. Too much complex (it means expensive) and with poor efficiency; heat pump is more efficient than electric heating (infact some EV use it), but less efficient in a hybrid vehicle where heat is free, coming from  the petrol engine:  The heat pump would use energy produced by the engine, why do this if you can pick it directly from the heated cooling liquid?
Warm up: now petrol engines have specific strategies for warmup, written to reduce warmup time; specific cam phasing (many engines use VTC), specific ignition and injection times and specific hardware, as cooled exaust manifolds for fast liquid heating and separate cooling circuits (head separate from the crank); simplier and cheaper than other systems.
« Last Edit: October 24, 2019, 11:16:12 PM by jazzaro »

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #26 on: October 24, 2019, 11:15:22 PM »


This is the climate compressor of the present Fit Hybrid, sold in Japan, the new one should be similar to this.
Another peculiarity will be the brake pump: as all hybrids like Toyotas, Hyundais and the CRV, the pedal does not push directly the pump, but moves a sensor connected with an ECU; electronics decide if braking only with the electric generator (regenerative braking), or adding  hydraulic pressure to brake calipers. Toy do the same since the first Prius, so since 1999, twenty years..
https://www.marklines.com/en/report_all/rep1235_201312#report_area_2
See last pictures
« Last Edit: October 24, 2019, 11:28:39 PM by jazzaro »

culzean

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #27 on: October 25, 2019, 09:31:33 AM »
@Jazzaro
Honda have always used a fixed volume scroll type aircon compressor on all their models,  not just hybrid.  That is why there is a clutch that keeps dropping in and out, other makers use the more complicated 'swash plate' variable piston stroke unit which can vary its volume from full to very little so can stay connected rather than keep being disconnected from drive.

https://en.wikipedia.org/wiki/Scroll_compressor
« Last Edit: October 25, 2019, 11:45:37 AM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

jazzaro

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #28 on: October 25, 2019, 10:11:40 AM »
My old renault had a Sanden variable displacement compressor,  and I miss it; more complicated, maybe more expensive but also definetly more comfortable using low gears and low  gas.

culzean

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Re: Mk4 Press Release with videos and more pictures than in magazines
« Reply #29 on: October 25, 2019, 11:56:38 AM »
Looks like Honda using their F1 drive train experience to make hybrid  - they got it right once the McClaren roadblock was removed..
Systems are deeply different, so I dont' think they could use F1 experience.  F1 is an advertisement...

Every advanced technology,  be it space exploration or F1 will filter down to everyday products,  and the regen / energy recovery and  electric power control used in F1 will undoubtedly bring advances in efficiency and reliability to hybrid vehicles - after all both race cars and road cars are looking for more power from a given amount of fuel.  That is why the rules for hybrid F1 cars were introduced to push the envelope of efficiency.

https://jalopnik.com/heres-how-hybrid-technology-in-formula-one-has-evolved-1837063286
« Last Edit: October 25, 2019, 11:58:55 AM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

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