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Honda Accord Hybrid vs. Toyota Camry Hybrid

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  • "Multiple ways to look at it:"

    Honda solves half of the problems by putting a higher speed/price transmission and add cost/complexity to the engine with VCM.

    Toyota virtually eliminate all the problems by removing the need for a transmission and changing engine cycle to Atkinson without any compromise. Simple! Many credits were given to this design with awards.

    "It would be interesting if Camry Hybrid with 127 HP can do that."

    Camry hybrid with 4 cylinder ICE(127 hp) estimate was to beat 04 Accord V6 with 240hp in performance. It might even be a competitive with Accord V6 hybrid in performance and will lead in fuel economy and low emission.

    "IMA system (estimate).... family sedan(Accord V6 hybrid) delivering 30-40 mpg (city or highway) with potentially PZEV emissions rating will earn more than bragging rights."

    Hybrid fuel consumption will be directly related to ICE displacement and the power of electric powertrain. The more a hybrid can stay in electric mode, the less fuel it will consume. IMA design is going to loose to HSD in fuel economy department.

    It will be very interesting. The hard part will be to wait until those cars become available.

    Dennis
  • venus537venus537 Posts: 1,443
    it'll also be interesting to see if they can make these cars for a profit.
  • "Civic Hybrid also uses cylinder deactivation, with three of four cylinders shutting down during deceleration. This allows for more efficient energy recovery via regenerative braking."

    How does HCH disable 3 cylinders? Do they actually stop moving? Do the valves for those 3 cylinders stay open or close? I am thinking the 3 cylinders still move while the vales were left open to eliminate pumping loss. Thanks.

    Dennis
  • Can you add this board to appear in Hybrid catagory from Town Hall page? Thanks.

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    I'm not sure how cylinder management in HCH has been implemented. But in the Accord Hybrid (and Odyssey), they keep running except for the fact that they don't burn fuel. This video of Honda 3.0 liter V6 w/VCM illustrates that.

    27.3 mpg (or 11.6 km/l) is an estimated fuel consumption number in Japan similar to the EPA estimates here in the USA. It involves a standard test procedure, probably more like "mixed" driving (not necessarily just cruising on the highway in which case, the V6 should return far better number than the American version gets which is 30 mpg). The gear ratios are identical.

    hybrid can afford to have smaller ICE.
    True. But sometimes people want more power. I expected Honda 2.4 liter I-4 to get electric assist in production car first, but Honda surprised me. Not bad to change the perception that many hold against hybrid cars.

    VCM will make less sense for hybrids.
    Wrong. VCM appears to compliment electric assist quite nicely. In Civic, cylinder shut down mechanism supposedly improves the efficiency of energy recovered via regenerative braking. VCM probably will do the same.

    HSD can save about $1,000 without producing a transmission.
    HSD has:
    Transmission (E-CVT)
    Gasoline Motor
    Electric Motor

    IMA has:
    Transmission (choice of Auto/CVT or Manual)
    Gasoline Motor
    Electric Motor

    Just because HSD is designed to work with E-CVT does not mean there is no transmission.

    The C&D numbers you posted for 530i is for manual transmission. Top gear acceleration for cars with manual transmission as tested by C&D involves NO SHIFTING. So, if there are six gear ratios, the car is left in the sixth gear.

    OTOH, in an auto/CVT, the test results in automatic shifting of ratios.
  • That VCM video shows when 3 cylinders are inactive, their valves stay closed. The load in the 3 active cylinders will be more than double because of weight/burden of the all 6 pistons. The ultimate goal of VCM is only to minimize worse case scenarios of an Otto cycle engine.

    I don't find VCM technology exciting because when Honda is trying to minimize their engine's worse cases, Toyota has virtually eliminated them since 1997. To put things into perspective, HSD Atkinson cycle engine's worse case is at least 15% more efficient than VCM engine's best case!

    Another issue in the same paradigm is the transmission of two hybrid designs. When Honda is trying to make their transmission more efficient by adding more speed or creating mechanical CVT, Toyota completely eliminated the need for a transmission(no middle man). Again, we are taking about "trying to reduce extreme losses" versus "completely eliminated losses". HSD is in a league of it's own. How much more of a KA can it get?

    "VCM appears to compliment electric assist quite nicely. In Civic, cylinder shut down mechanism supposedly improves the efficiency of energy recovered via regenerative braking."

    HSD can shut down all cylinders so MG1 can recapture all the energy back from the pistons. HSD can also "traditional" engine brake by throttling and narrowing the exhaust valves. I wouldn't call it a complimenting feature. It is a common sense.

    "But sometimes people want more power."

    Power alone is not important. What is important is how fast and smoothly a drivetrain can deliver power. I will provide a graph that will sum it up.

    image.

    Prius HSD powertrain delivers power quicker and smoother than 2.4L engine with 4-speed auto transmission in this situation. Prius 76hp ICE vs Camry 160hp ICE. Maximum horsepower rating of ICE tells very little about the true performance.

    "Just because HSD is designed to work with E-CVT does not mean there is no transmission."

    Then, show me the location of the HSD transmission. You can use the pictures I posted or your own. Just show me where the E-CVT that you are talking about.

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    Let me start by quoting that there is no perfect way of getting things done. Neither Otto-Cycle nor Atkinson-Miller Cycle is perfect. If any were, one of them would not exist.

    Likewise, Honda has two designs of its electric motors at its disposal to develop its hybrid technology: One, using powerful (but bulkier) “prime-mover” 107 HP AC Synchronous motor, and the other using compact, lightweight “assist-type” Brushless DC motor (current production versions rated at 13 HP, in Insight and in Civic Hybrid). We don’t know which version and how powerful the Accord Hybrid will use. Indications point to 30 HP electric motor, whether AC or DC, remains to be seen. The choice usually involves some compromise. That’s a fact.

    In either case, characteristics of gasoline ICE and electric motor compliment each other well. I doubt most “drivers” would care for a locomotive like driving experience (diesel locomotive engines are usually series hybrids and require NO transmission given their extremely narrow operating range). In fact, I would love to see sports cars like S2000 and RX-8 get electric assist, to provide the best of both worlds.

    Speaking of power, it is true that peak power isn’t the end of it. But at the same time, if there is little power, no matter how smooth or quick the delivery is, it will be less than welcome. One of the reasons current hybrids get bashed for, is just that. They lack power. If a hybrid system could provide more power while delivering 40-50% improvement in fuel economy and reduction in emissions, the critics will have little to argue about, and rightfully so.

    Regarding “gearbox” in Prius, the planetary gear set is just that. It may have only a single ratio, but it serves the purpose that a typical CVT would (other than that a typical CVT would continuously vary the gear ratio to maintain engine speed while car accelerates). If you say that HSD does not need transmission, you must acknowledge that it needs a planetary gearbox.
  • Kirstie_HKirstie_H Posts: 10,916
    Done - thanks for pointing that out, Dennis!

    FYI, we're looking at the possibility of having a separate section for hybrids. Stay tuned.

    MODERATOR
    Need help navigating? kirstie_h@edmunds.com - or send a private message by clicking on my name.
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  • I agree with you that neither Otto cycle or Atkinson/Miller cycle is perfect. Neither of them are ideal for all type of vehicles. Otto cycle engine had proven to be the most suitable for ICE only cars because it balances pros and cons very well while keeping it's simplicity. It does not mean Otto cycle is the best choice for hybrids. What used to be a compromise in ICE only car may not be a compromise in a hybrid because ICE is only half of the equation. It has been proven that HSD implementation of Atkinson/Miller cycle combined with electric supercharger is a better design for hybrid cars. One can not have narrow vision on just the ICE. One must open one's vision wider and see the whole hybrid drivetrain.

    I am not sure why Honda will need to use bulkier AC motor to get more power. Toyota's light and compact 50KW(67hp) DC motor that runs on AC electricity is already making 295 lbs-ft torque from 0-1,200RPM. The best of both AC/DC worlds. Maybe Toyota 100KW motor can maintain 295 lbs-ft torque from 0-2,400 RPM. We'll see.

    I can understand why performance oriented drivers bash the current hybrid offerings. Current hybrids were designed with low emission in mind. A small engine was chosen to achieve low emission. A better fuel economy is just a side-benefit of it. Many performance oriented drivers fail to fully see power and fuel efficiency of hybrids. HSD and IMA designs yield complete distinct results.

    Toyota HSD double the power and the speed it delivers. HSD power delivery is as fast or faster than ICE only car with double the max horsepower engine rating. i.e: Prius with 76hp ICE can perform like a Camry with 160hp from 0-60mph. Prius delivers more power and quicker in 30-50mph test. In HSD, ICE and electric motors loads even out to 50:50 therefore, fuel economy also double.

    Honda IMA improves power delivery by about 24%. HCH with 85hp ICE performs like the Civic LX with 117 hp. In IMA, electric motor contributes only 1/4 of the total power, fuel economy improvement should be no more than 25%. Note: My previous calculation in msg#21 is incorrect. I used 93hp which is the electric assist power and I compared it to the 127hp Civic EX instead of LX.

    Permanently engaged Planetary gear set is not a transmission. It simply split or combine power; thus Power Split Device(PSD). It is the Synergy between Internal Combustion Engine and an electric motor that creates the "effect" of smooth acceleration. Therefore, the name Hybrid Synergy Drive(HSD). A mechanical CVT achieves the same "effect" with the use of pulley, belts and cones; requiring a separate hardware. HSD does not require a dedicated transmission to achieve CVT "effect". It simply create it by synergy of a hybrid drivetrain.

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    Theoretical arguments are all good but in the end, results count. You look at specifics, in terms of the goals that the hybrids strive for: fuel economy, low emissions and lately, performance, and then conclude if the overall design works, or not. There is no design that doesn’t make a compromise. It sounds almost unacceptable to you that there is a compromise in HSD.

    I am not sure why Honda will need to use bulkier AC motor to get more power.

    “Bulkier” is a relative term. Bulkier compared to the current set up in Civic Hybrid and Insight. We can’t compare the heft of the 80kW Honda AC Synchronous motor to that of 50kW Toyota AC Synchronous motor until they are compared side by side. So far, Honda hasn’t used its AC motor in any vehicle other than EV-Plus (all electric vehicle) and FCX (the production fuel cell vehicle). It there a possibility that Honda might, in a hybrid? Yes.

    Current hybrids were designed with low emission in mind. A small engine was chosen to achieve low emission. A better fuel economy is just a side-benefit of it.

    And now is the time to serve just the two aspects of it, and add to performance, hence the need for more horsepower. I would had been delighted to see Honda Dual Note (2001 Tokyo Auto Show) see production, a 400 HP hybrid sedan capable of delivering 40+ mpg, seating four, and just for bragging rights, with a top speed of 186 mph and 0-60 in low 4 seconds. Oh well, we might!

    Honda IMA improves power delivery by about 24%

    That would depend on the size of the electric motor. So far, Honda is happy with use of smallish electric motor, and a small battery pack. At present, it appears, the priority is to cut down cost and create a compact package while maximizing everything that hybrids are supposed to. This will allow addition of electric motors by simply “plugging in” to conventional vehicles, as has been seen with Insight, Civic Hybrid, and likely to be seen with Accord Hybrid.

    HCH with 85hp ICE performs like the Civic LX with 117 hp.
    Not exactly, only at low rpm. Civic LX would still win the race on an acceleration ramp because of higher horsepower. I would love to see Honda use 1.5 liter engine offered in Jazz (or Civic’s own, 1.7 liter VTEC-e used in Civic HX) with a slightly more powerful IMA in the next Civic Hybrid.

    Permanently engaged Planetary gear set is not a transmission. It simply split or combine power; thus Power Split Device(PSD).

    You could call it that, but you need this “power split device” with this hybrid system. You don’t, with IMA.
  • "Theoretical arguments are all good but in the end, results count."

    My calculations were based on results of current HSD and IMA hybrid offerings. EPA, Consumer Report and many hybrid owners confirmed that Prius gets higher MPG than HCH even though Prius is larger and in mid-size class.

    "I would had been delighted to see Honda Dual Note"

    That car sounds so much like Toyota Volta. =D That concept car uses the drivetrain that will be in HH and 400H. Let's see who can bring out the production car that meets that kind of claim first.

    "That would depend on the size of the electric motor. So far, Honda is happy with use of smallish electric motor, and a small battery pack."

    There could be possibilities that technical difficulties prevented Honda from putting larger electric motor and battery. Some of the issues I see are:
    IMA can not
    - Recharge battery when the car is at stop
    - Assist and generate electricity at the same time
    - Electric assist is inefficient due to static 1:1 RPM ratio with ICE


    I want to clear up the last issue. In IMA, electric motor must spin at the same RPM with the ICE. This cause inefficient electric support at high RPM.

    HSD's Planetary CVT is a dynamic 3-way CVT. This simple design creates 3-way CVT between ICE and MG2, ICE and MG1, and between MG2 and MG1. ICE:MG2 ratio depends on MG1 RPM. ICE:MG1 ratio depends on MG2 RPM. MG2:MG1 ratio depends on ICE RPM. MG1 is the 10KW Motor/Generator. MG2 is the 50KW Motor/Generator. Planetary CVT can adjust RPM of ICE and electric motors to it's most efficient state. For example, ICE could be at 3,000 RPM and MG2 could be at 1,200 RPM and still providing maximum torque.

    "you need this “power split device” with this hybrid system. You don’t, with IMA."

    PSD is so small and should not weight more than 15 lbs. Planetary gear set is also found in Honda Civic traditional automatic transmission with much more complexity.

    One thing I have not address yet is the weight of HSD. Current HSD do weight a little more than traditional cars.

    Prius Internal Combustion Engine + 10KW Electric motor + 50KW Electric motor + E-CVT
    image

    Above Prius HSD powertrain weights about the same as comparable traditional car ICE with a transmission. Traditional car also need alternator and starter which MG1 replaced. Electric motors in Prius also reduces the size and weight of the brakes due to regenerative braking also. The only extra weight in Prius is the 99 lbs HV battery. The battery weight is also offset by smaller gas tank. Prius carry about 8 gallon of gas less than Camry. That is about 50 lbs of gas weight saving while providing higher driving range.

    99 lbs Prius Ni-Mh environmental friendly battery with 10,000 cycles usage until reduction to 80% of the original capacity.

    image.
     
    When you are looking at a car size segment that weights about 3,000 lbs in average. The weight difference is very minor.

    Dennis
  • wco81wco81 Posts: 495
    From a portion of an article from the SJ Mercury News:

    ``The next 18 months to two years is really going to tell the tale for Americans and hybrids,'' said Lindsay Brooke, senior manager for market assessment at CSM Worldwide, an auto industry forecasting firm in Farmington Hills, Mich.

    That's because a dozen or so hybrids will hit the market, and they'll bring the technology to sport-utilities, trucks and luxury vehicles.

    Brooke said hybrid versions of full-size trucks from General Motors and SUVs from Ford, GM and Toyota will ``get more of a critical mass going.'' Larger vehicles will help demonstrate the benefits of hybrid more effectively, too, he said, as small cars tend to get better gas mileage anyway.

    Honda will add its third hybrid, a gas-electric version of its Honda Accord V-6 sedan, later this year. Toyota is expected to offer hybrid versions of many of its vehicles, including the Camry sedan, the No. 1 car in America, in the not-too-distant future.<i/>

    Looks like Toyota is noncommital about when the Camry Hybrid would come out. Camry is already the number one seller and Prius is also a big seller. So why upset the production and sales momentum of either?

    It's interesting that the article refers to a dozen new hybrid models in the next 18-24 months. Maybe when Toyota comes out with a Camry Hybrid, they will also do a hybrid version of its sister model, the Lexus ES330.

    Prices notwithstanding, there should be healthy demand for luxury hybrids.
  • Motor Trend listed Camry Hybrid in 2006. Looks like it is going to be a looooooong wait considering how popular hybrids are getting. And I can't wait to see how HSD will put IMA to shame. ;-D

    HSD simply has a more efficient ICE to begin with. A more powerful electric drivetrain. Plus many different flexible ways/paths for energy to flow between mechanical and electrical forms. A superior design compared to IMA.

    I do like simple idea of IMA but in practice, it is more complicated than HSD or even the traditional car. I wouldn't be surprise if Accord hybrid starts to use Atkinson/Miller cycle engine.

    Dennis
  • wco81wco81 Posts: 495
    What does it stand for?

    I'm guessing it's a Honda proprietary thing?
  • IMA = Integrated Motor Assist. That's what Honda calls their hybrid design. In another word, mild hybrid.

    Dennis
  • andy71andy71 Posts: 96
    The media is giving so much publicity to the Prius but rarely mentions the Civic Hybrid. Is the Prius that much better than the HCH?
  • backybacky Twin CitiesPosts: 18,784
    Probably not the right board for this, but... "better" is relative. Perhaps the Prius is more popular because it's about the same price as the Civic but offers better fuel economy, more passenger room (especially rear seat leg room), and the utility of a hatchback. Plus it offers some features not available on the Civic like nav system and VSC. But the Civic offers the choice of a CVT or a 5-speed transmission, looks and operates like a conventional car, handles like a regular Civic (which is pretty good), and is available at a discount and without a long wait. Whether it's that much better than the Prius is up to each buyer to decide.
  • From technical point of view, Prius is the leader in hybrid technology. The drawbacks(waiting list) that Backy mentioned are the result of Prius superiority. The transmission is the middle man between the engine and the road. Prius took out this middle man and go engine direct, making the car more efficient and responsive.

    Dennis
  • zitchzitch Posts: 55
    Err... last I checked, you still need something to "transmit" torque between the engines and the wheels. The engines are not "directly connected" to the wheels. From what I see (from the documentation that you linked to!), there is still gears in the PSD. It is still a type of transmission, much like "slush"boxes, manuals, and CVTs are transmissions. While I do agree that the PSD is superior to the others, You really shouldn't be making the following statement: "The transmission is the middle man between the engine and the road. Prius took out this middle man and go engine direct, making the car more efficient and responsive."
  • oldboyoldboy Posts: 59
    My speculation is that Toyota will use a 4 cyl model, probably the XLE, with the Prius motor (maybe the Highlander motor?) to achieve 6 cyl performance with superior mpg. Using their more expensive model with goodies would enable them to price this hybrid mid-way between the Prius and Highlander, and at the top end of Camry prices, so as not to interfere with sales of these other vehicles. Toyota claims that their Prius is already profitable, and no doubt a high-end Camry would be profitable as well. Does any one have any information about this, or perhaps a different opinion?
  • backybacky Twin CitiesPosts: 18,784
    Well, I have another opinion... the Prius motor will be insufficient for the Camry, which weighs more than the Prius. IMO they will use the HSD powertrain from the Highlander, meaning a V6.

    I saw a news article today (in print, I think in the Star Tribune, Newspaper of the Twin Cities, confirming the Camry hybrid will be a 2006 model and also stating Toyota's annual sales goal for it is 100,000. That makes sense given Toyota's goal of selling 300,000 hybrids a year by 2006.
  • oldboyoldboy Posts: 59
    So if they do use the HSD powertrain from the Highlander, it is bound to be with the upper end XLE model Camry. That would deliver the performance of an 8 cyl, and perhaps put the HAH to shame! Toyota will likely wait until the HAH comes out later this year, before they make any statement about their plans for the Camry. It looks like it will be a year behind the Honda, 2006 versus 2005 model year.
  • "last I checked, you still need something to "transmit" torque between the engines and the wheels."

    A physical medium that transfers power from drivetrain to the wheels is not a transmission. A gas engine car without different gear ratios(a transmission) will either have limited power delivery and speed. Transmission was invented as a "work around" to overcome this deficiency by providing many suitable gear ratios between drivetrain and the wheels.

    "The engines are not "directly connected" to the wheels."

    That's true. The drivetrain goes through reduction gears(to reflect RPM at the wheels) and differential before power reaches the wheels. HSD drivetrain is capable of providing a continuous variable torque and power output without the need of a dedicated transmission hardware from 0-100+mph. There is no changing "manipulation" of torque between drivetrain and the wheels. That's what I mean by HSD "engine direct" power output.

    "there is still gears in the PSD"

    Planetary gearset with six permanently engaged moving parts itself is not a transmission. It simply splits and combines power, therefore Power Split Device(PSD). It is the Synergy between electric motors and Internal Combustion Engine that creates continuous variable power output. The most I can stretch is, HSD has integrated transmission functionality.

    Dennis
  • I hope Toyota offer both I4 and V6 TCH models. V6 TCH might be a bit overkill because it'll perform something like a Volta concept car. =D I believe Altima hybrid with HSD using Li-ion battery will also come out by 2006. 2006 will be a very interesting year!

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    A physical medium that transfers power from drivetrain to the wheels is not a transmission.

    Actually, it is, unless the crank is directly tied to the wheels in a gasoline motor. A &#147;transmission&#148; is a unit designed to &#147;transmit&#148; power to the wheels, and since there isn&#146;t enough torque to move, the &#147;transmission&#148; uses &#147;torque multiplier&#148; that we refer to as &#147;gear ratio&#148;. You could have one, several, or &#147;almost&#148; infinite (within a range to be practical).

    HSD drivetrain is capable of providing a continuous variable torque and power output without the need of a dedicated transmission hardware from 0-100+mph. There is no changing "manipulation" of torque between drivetrain and the wheels. That's what I mean by HSD "engine direct" power output.

    The planetary gearbox itself is the &#147;transmission&#148;. It exists for a reason, and doesn&#146;t in other cars (where a more &#147;conventional&#148; transmission is used). The continuous variance of torque is via continuous torque multiplication as the torque is &#147;transmitted&#148; to the wheels. And that is manipulation of torque between the engine and the wheels.

    If you disagree, explain to me what you mean by &#147;continuous variable torque&#148; and how a 2900 lb. car can move with little torque (combined) that comes from the power train (as little as just 88 lb.-ft at 4500 rpm).

    And why 2006, I'm looking forward to Fall 2004. :-)
  • "A &#147;transmission&#148; is a unit designed to &#147;transmit&#148; power to the wheels, and since there isn&#146;t enough torque to move, the &#147;transmission&#148; uses &#147;torque multiplier&#148; that we refer to as &#147;gear ratio&#148;. You could have one, several, or &#147;almost&#148; infinite (within a range to be practical)."

    If there is only one gear ratio, it would not be a "torque multiplier", contradicting your own definition of a transmission. Would you still consider a car to have a transmission if it has only one gear ratio from the drivetrain to the wheel? HSD contiously vary power output in the drivetrain, not with a dedicated hardware between wheels and drivetrain.

    "The planetary gearbox itself is the &#147;transmission&#148;. It exists for a reason, and doesn&#146;t in other cars (where a more &#147;conventional&#148; transmission is used)"

    Permanently engaged planetary gearset with six moving parts is not a transmission. Automatic transmission in a traditional car has multiple planetary gearsets. The reason planetary gearset exist in HSD is to combine or split power between two power sources. Honda IMA uses a clutch between ICE and electric motor to achieve the same thing. Would you consider that clutch a transmission in IMA design?

    "If you disagree, explain to me what you mean by &#147;continuous variable torque&#148; and how a 2900 lb. car can move with little torque (combined) that comes from the power train (as little as just 88 lb.-ft at 4500 rpm)."

    HSD always split 72% of ICE torque to the wheel. 28% always go to the MG1. However, horsepower split is controlled by RPM of MG1 and the ICE. If HSD wants to put all the power to the wheel, MG1 would be at rest(82lbs-ftx0rpm/5252=0hp). If HSD wants to put all the power to MG1(to generate electricity), the car has to be at rest. Variable RPMs of MG1 and ICE would equate to how much hp get into where.

    For the situation you described where ICE is at 4500 RPM, it would be making about 80 lbs-ft torque since ICE peak torque is 82 lbs-ft at 4200 RPM. Therefore, PSD will output 57.6 lbs-ft(80*0.72) to the wheel. The other 22.4 lbs-ft torque has to come from the 50KW MG2.

    HSD's continuous various power output is the team work of ICE, two electric motors and a power caching device(battery). They are essential/necessary components of a hybrid and their synergy effect eliminates the need for a dedicated hardware for the role of a traditional transmission.

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    If there is only one gear ratio, it would not be a "torque multiplier", contradicting your own definition of a transmission. Would you still consider a car to have a transmission if it has only one gear ratio from the drivetrain to the wheel?

    Yes, and it does not contradict my definition. Read (again) how I defined &#147;transmission&#148;.

    HSD contiously vary power output in the drivetrain, not with a dedicated hardware between wheels and drivetrain.

    A unit that transmits power to the wheels from the power unit (like gasoline/diesel/electric motor) is transmission. You can call it by any name, and it can work differently than others. The job is still the same.

    Honda IMA uses a clutch between ICE and electric motor to achieve the same thing. Would you consider that clutch a transmission in IMA design?

    Clutch can be a part of transmission. It is not a transmission system by itself.

    "If you disagree, explain to me what you mean by &#147;continuous variable torque&#148; and how a 2900 lb. car can move with little torque (combined) that comes from the power train (as little as just 88 lb.-ft at 4500 rpm)."

    For the situation you described where ICE is at 4500 RPM, it would be making about 80 lbs-ft torque since ICE peak torque is 82 lbs-ft at 4200 RPM. Therefore, PSD will output 57.6 lbs-ft(80*0.72) to the wheel. The other 22.4 lbs-ft torque has to come from the 50KW MG2.

    In a &#147;normal&#148; car, a gear ratio in the transmission could provide torque multiplication by a factor of about 13.00:1. If the engine were producing 76 HP at 4500 rpm (hence, 88 lb.-ft at 4500 rpm), ignoring drive train losses, the net torque at the wheel would be 13 * 88 = 1100+ lb.-ft.

    In case of Prius, are you suggesting that the car will get a net torque of only 82 lb.-ft at that engine speed, to move 3100 lb. or more?
  • "A unit that transmits power to the wheels from the power unit (like gasoline/diesel/electric motor) is transmission. You can call it by any name, and it can work differently than others. The job is still the same."

    You are playing with the word "transmit" now. To you, differentials, drive shaft, and wheel axles are part of the transmission because you need them to "transmit" power to the wheels. Do you ever wonder why they have their own name?

    "Clutch can be a part of transmission. It is not a transmission system by itself."

    In IMA design, a clutch is used to combine or split power between dual powertrain. HSD uses planetary gearset. Explain to me why you consider planetary gearset a transmission system by itself yet you consider a clutch in IMA "can be a part of transmission"?

    "In a &#147;normal&#148; car, a gear ratio in the transmission could provide torque multiplication by a factor of about 13.00:1."

    Yea? How come Honda Accord I4 manual 1st gear ratio is 3.267 ?

    "In case of Prius, are you suggesting that the car will get a net torque of only 82 lb.-ft at that engine speed, to move 3100 lb. or more? "

    BTW, 2004 Prius weights 2,890 lbs. You asked for a situation where HSD net output of 88 lbs-ft torque at ICE 4,500 RPM so, I gave it to you. If you are asking for HSD drivetrain to simulate power output of the 1st gear, I can also provide it to you.

    In order to achieve torque multiplier of the 1st gear(about 4x), HSD taps into the electric motor. As I explained it before, PSD will always split 57.6 lbs-ft torque from the ICE directly to the wheel. Additional 295 lbs-ft torque will come from MG2. HSD net torque output can be 352.6 lbs-ft. That comes out to equivalent 1st gear ratio of about 4.3 (352.6 lbs-ft/82 lbs-ft).

    Dennis
  • robertsmxrobertsmx Posts: 5,525
    Transmission… transmits. There is no &#147;play&#148; involved here. In IMA, there is no &#147;additional&#148; clutch is involved. In IMA application with manual transmission, the ultra-thin brushless DC motor is squeezed between the ICE, and the flywheel (which is followed by the clutch for the manual transmission). In fact, the electric motor becomes a part of the flywheel (so a lighter flywheel is needed).

    Click here for a picture

    Yea? How come Honda Accord I4 manual 1st gear ratio is 3.267?

    First Gear Ratio: 3.267
    Axle Ratio: 4.389
    Overall Drive Ratio in First Gear: 3.267* 4.389 = 14.34

    So, effectively, there is a torque multiplication factor of 14.34 in Accord I-4. I mentioned 13.00 as a benchmark. You thought that was high? How about 16.5:1 in Honda CRV?

    Ignoring &#147;gearing effect&#148; of wheels, and drive train losses, an equivalent of 14.34 * 161 = 2308 lb.-ft is produced at the wheels at 4500 rpm in first gear. Actually, you can estimate g&#146;s (the thrust) using these numbers. Assuming 15% loss, and total weight (vehicle + occupant) of 3300 lb, and wheel size of 25 inch.

    Maximum Thrust = (0.85 * 161 * 14.34 * 24) / (3300 * 25) = 0.57g

    What is the maximum thrust (calculated/observed) in a Prius?
  • "In IMA, there is no &#147;additional&#148; clutch is involved."

    You are right. I must of been thinking about Mercede's hybrid design where there is an additional clutch between two electric motors.

    "What is the maximum thrust (calculated/observed) in a Prius?"

    Assuming 10% loss because HSD does not have alternator and AC belt draining away energy. Additionally, HSD power output bypass complex traditional transmission in order to reach the wheels.

    Prius Final drive ratio: 4.113
    Max torque at the wheel: 4.113 x (82+295) lbs-ft = 1,450 lbs-ft

    Prius Maximum Thrust(g) = (0.90 x 1456 x 24) / (3137 * 25) = 0.40 g
    Accord(auto) Max Thrust(g) = (0.85 x 161 x 2.652 x 4.438 x 24) / (3366 x 25) = 0.46 g

    Not bad for a 3,137 lbs Prius with only 82 lbs-ft ICE torque!

    Dennis
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