Edmunds dealer partner, Bayway Leasing, is now offering transparent lease deals via these forums. Click here to see the latest vehicles!

Honda Accord Hybrid vs. Toyota Camry Hybrid

24567

Comments

  • robertsmxrobertsmx Member Posts: 5,525
    Sample size of 12 is not enough, but sample size of 1 you or someone else quoting is good?

    Lost to the atmosphere through what?

    You answered (part of) it yourself… “The difference will be directly related to the friction loss due to high RPM of the engine.” Much of the loss will be directly in the form of heat.

    BTW, Atkinson cycle engine does not make sense for ICE only car unless it is supercharged.

    Why? (I will discuss more after you respond)

    3 cylinders will have more fuel in it compare to the same amount of fuel spread out in the 6 cylinders

    Energy out is related to energy in. If a set up is producing excess energy (out), it must use excess energy (in). VCM is designed around the premise of minimizing the excess AND reduce frictional and pumping losses.

    With six cylinders in place, the engine will produce excess power. With half the cylinder count, the power may not exactly be half, but close (considering the realities).

    In the Japanese mode of estimating mileage, Honda 3.0/V6 with VCM has shown 27% improvement. As I mentioned earlier, 2005 Odyssey will have VCM with its 3.5 liter V6 and we will see if it shows considerable improvements. If 15-20% improvement on highway happens, it would be a big improvement, with a powerful 4500 lb. Minivan getting the fuel economy of a compact car.

    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.

    Ultimate goal of these technologies is to improve mileage. Nothing is perfect, every design is full of compromises. And I was surprised to learn that Toyota had to go a long way to trim 400 lb off from Prius. By adopting a milder setup for nearly as real life fuel economy, Honda could actually add more sound deadening material and underbody aerodynamics on an otherwise identical Civic sedan body without adding too much weight. It’s about balance.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "Sample size of 12 is not enough, but sample size of 1 you or someone else quoting is good?"

    We quoted numbers from EPA and Consumer Report standard testing. Your data is from 12 hard-core hybrid drivers. According to that database it shows that even the classic Prius gets higher mpg than HCH. You tell me if that is accurate.

    "If a set up is producing excess energy (out), it must use excess energy (in). VCM is designed around the premise of minimizing the excess AND reduce frictional and pumping losses."

    I totally agree with you about the VCM premise of reducing frictional and pumping losses by half. The excess energy out is in question here. Are you saying Honda's V6 engine is incapable of making only 25 hp(in our example)? The lowest it can achieve by throttling is 50 hp? What I am saying is, there is no excess energy out to begin with, just inefficiency from excessive throttling.

    "In the Japanese mode of estimating mileage, Honda 3.0/V6 with VCM has shown 27% improvement."

    Hmmm interesting. Current Accord LX V6 EPA city gets 21 mpg and I4 gets 24 mpg. That V6 VCM 27% improvement(26.7mpg) could probably be achieved by driving purely on 3 cylinders(performance sacrifice). Clearly it is not real city driving.

    "Nothing is perfect, every design is full of compromises."

    Sure but better design has less compromises. In term of weight by HSD design, Prius sits nicely between traditional Corolla and Camry. The performance that HSD gained from the extra 50KW motor over IMA, using the same space, is enormous. The efficiency, room and lower emission gained are obvious too. Full hybrid is more efficient than a mild one.

    About Atkinson/Miller cycle...

    image

    Note: Classic Prius test data from an Independent source. Prius engine can produce 12KW (16hp) with 35% efficiency. Perfect for cruising on highway.

    image
    Classic Prius ICE torque below 1,500 RPM is very weak but electric motor complements the design.

    Atkinson cycle does not make sense for ICE only car because Atkinson cycle engine make very low torque at low RPM(0-1,500 RPM). Atkinson cycle engine can maintain 35% to 37% efficiency from 1,500 to max RPM while Otto cycle peak efficiency is about 32%. Unless you supercharge Atkinson cycle to make up for low end torque, it isn't applicable for any ICE only car.

    The reason Atkinson cycle makes sense for a hybrid is because of high torque electric motor. AC brushless 50KW motor used in Prius can output 295 lbs-ft torque from 0-1,200 RPM.
    image.
    04 Prius 50KW motor performance. Blue is the torque curve and red is horsepower curve.

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    I hope you see why I think Prius is a better buy than HCH from my other replies. If not, I'll make a list for you. :)

    Dennis
  • robertsmxrobertsmx Member Posts: 5,525
    EPA estimates and CR "standard testing" do not reflect anything close to reality that the sampling on the website provides. If things were that simple, everything would be so predictable.

    Are you saying Honda's V6 engine is incapable of making only 25 hp(in our example)?
    No. You bring up several technical details, yet ask questions such as these. I quoted gearing limitations a while ago. Recap that, there is the answer.

    better design has less compromises

    Very true. But who determines compromises? Is developing a new engine around a very specific transmission choice, extensive "weight fixing" considered compromise?

    27% improvement(26.7mpg) could probably be achieved by driving purely on 3 cylinders(performance sacrifice)

    You're not sacrificing performance nothing when the vehicle is cruising. In fact, without it, you would be consuming more energy for nothing. Open up the throttle and the cylinders get back to work!
  • robertsmxrobertsmx Member Posts: 5,525
    Atkinson-Miller cycle engines may have reduced pumping loss (primarily due to reduced compression), but that also affects their output. So, and as you said earlier, it is more effective with supercharger or electric assist. There goes a major compromise.

    Supercharger comes with its own set of issues, including pumping losses and cost. In the end, it might be better to adapt to something that is proven and widely used. I believe the last car we saw with Atkinson-Miller cycle engine was Mazda Millenia (2.3 liter V6). With supercharger, it produced 210 HP (?) and was often compared to its 3.0 liter V6 counterpart. Why did Mazda not continue with the engine? Instead, Mazda is now using Ford Duratec to address its V6 needs.

    Accord Hybrid does not need a “special” engine. It is going to use an engine that is used by non-hybrid cars, one that is already among the most powerful, cleanest, most compact, lightest and arguably the most fuel miser V6 of its class around, and widely used. That’s no compromise, that’s just the beginning.

    Add VCM to it, to improve fuel economy by way of cutting down on losses probably most noticeable on highways, and add electric assist to it to help in city driving economy.

    Choice between mild and full hybrid is based on compromises as well. Honda engineers must have considered the Honda 80 kW AC motor that has been around since the early 90s, and currently being used in FCX. But then, they also ventured into a lighter and more compact package and developed the DC motor for Insight, and later, improved it for Civic Hybrid.

    And FCX is heavy at about 3500 lb (Honda refrains from calling it a hybrid though, since its prime mover is only the electric motor, with ultra capacitor used to store the charge acquired from the fuel cell stack). And much of the weight might be from the necessary reinforcements not just the AC motor.

    Civic Hybrid is about 63 lb. heavier than Civic EX (2675 lb. compared to 2612 lb., both with manual transmission). There are subtle differences and the hybrid probably saves a few pounds by using a more compact/lighter gasoline engine but may give up the same with addition of sound deadening and aero pieces.

    OTOH, as Auto World reported, Toyota had to go lengths to shave off 400 lb. from the curb weight of Prius to the current 2890 lb. To get something, you have to give up something. That’s compromise.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "EPA estimates and CR "standard testing" do not reflect anything close to reality"

    True, YMMV depending on your driving style. MPG difference between two cars shown by two different standard testing should be relative to the mpg difference in the real word. Therefore, Prius(HSD) should get higher mpg than HCH(IMA).

    "I quoted gearing limitations a while ago. Recap that, there is the answer."

    So, the answer to my question is YES. Accord V6 is incapable of making only 25 hp(in our example). This is not because the engine is technically incapable but rather, due to it's 5-speed transmission limitation. I did address that issue by suggesting the use of a better transmission rather than VCM. Use 6-speed, 7-speed, or mechanical CVT to address this design flaw.

    "Is developing a new engine(Atkinson) around a very specific transmission(ECVT) choice"

    You know what is ironic? Toyota did not develop a new engine for HSD. They used the same Otto cycle engine and turn it into Atkinson cycle engine just by changing the VVT-i timing. VVT-i in Prius vary the inlet camshaft timing over 43 degrees of crank angle, instead of 3 degrees. Fundamental change in timing of intake changes everything. Expansion ratio is greater than compression. Pumping loss is virtually eliminated. Emission is lower. Torque output is almost flat. Engine efficiency gained by about 15%. I expect to see a new engine designed with Atkinson cycle in mind from the ground up in the 3rd generation of HSD.

    You can read more about their implementation of Atkinson cycle. http://perso.wanadoo.fr/mc-engine/atkin/corps.htm
    image
    OPERATION: (at 50% load)

    • Steps 1 to 6: intake at atmospheric pressure;
    • 7 and 8: load control by using Late Intake Valve Closing (in this case, 50%), the excess gases taken in are forced back into the intake manifold (back flow);
    • 9: the intake valve closes, imprisoning the required charge in the cylinder;
    • 10 and 11: compression at 10:1;
    • 12: ignition, followed by an expansion at a 20:1 ratio.

    May I remind you to think about the need for a transmission in the first place. What is the ultimate purpose of a manual, automatic, or mechanical CVT transmission?

    Technically, HSD does not have a transmission! HSD achieves CVT functionality by the use of combining RPMs from ICE and a electric motor; thus a hybrid. A full hybrid(HSD) does not inherit the need for a transmission from the traditional ICE only cars. The design is mechanically more simple than a traditional cars! In contrast, a mild hybrid(IMA) still require the need for a transmission plus electric powertrain components, making it even more complex than a ICE only car. A huge difference!

    Your argument reminds me of that UPS ground TV ad. The guy who was in charge of shipping was complaining because they started to use UPS. His problem was sitting there and do nothing because there were no problem to deal with. You are basically saying, HSD transmission choices are limited because HSD does not need a transmission. Your other argument of IMA being simpler because IMA's electric powertrain is smaller(10KW) is a weak one.

    "You're not sacrificing performance nothing when the vehicle is cruising"

    The "japanese mode" of testing is to cruise and never stop? The first impression I got was the city driving conditions of Tokyo. I dont' think cruising is possible over there. It is clear that they were driving in the city and avoiding all six cylinders from activating to achieve 26.7mpg; therefore sacrificing performance. I understand that VCM can give V6 power at an instant.

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    So, and as you said earlier, it is more effective with supercharger or electric assist. There goes a major compromise."

    I agree with you regarding Mazda's failure with Atkinson/Miller engine. How is it a compromise for a hybrid? Electric torque is "free" or available by design in the first place. Note: Atkinson ICE and electric motors are like ying and yang achieving balance.

    "Add VCM to it, to improve fuel economy by way of cutting down on losses probably most noticeable on highways, and add electric assist to it to help in city driving economy."

    Again, VCM is necessary to fix design flaws of a transmission and a Otto cycle engine. V6 240hp engine was required to make up for delays of mechanical power build-up and low-end torque. If electric power provide low-end torque at an instant response, why do you need 240 hp in the first place?

    HSD has proven to have power efficiency of 1.91%. I estimated that Camry hybrid will only need 127 hp engine to out perform a 240 hp ICE only car.

    "they also ventured into a lighter and more compact package and developed the DC motor for Insight, and later, improved it for Civic Hybrid."

    HSD uses an AC synchronous-type motor, which is a high-efficiency DC brushless motor with AC current. Furthermore, by arranging the permanent magnets in an optimum V-shape, the drive torque is improved and the output is increased, producing the highest output per unit of weight and volume in the world.

    "Toyota had to go lengths to shave off 400 lb. from the curb weight of Prius to the current 2890 lb."

    04 Prius is still using steel body frame. Majority of the parts are non-extoic unlike the Insight. With Toyota track record, they will be returning a profit from the 04 Prius soon like the classic Prius. Looking at the results, HSD is more powerful, fuel efficient, simpler, reliable, and cheaper to produce. Camry hybrid(HSD) will further the gap comparing to Accord hybrid(IMA).

    Dennis
  • robertsmxrobertsmx Member Posts: 5,525
    The "japanese mode" of testing is to cruise and never stop? It is clear that they were driving in the city and avoiding all six cylinders from activating to achieve 26.7mpg; therefore sacrificing performance.

    Japanese testing mode or any other “standard” tests (EPA and CR methods included) have flaws, and should not be used as reality which can change based on a variety of factors.

    I don’t understand your concern on “sacrificing performance”. Why do you assume that? VCM is designed to shut down cylinders when performance is NOT needed. It turns them on instantly when performance IS needed.

    I’m assuming that THS and IMA work similarly when the vehicle is at a stop with the accessories on (air conditioning). So, the gasoline motor will have to be running/idling overriding the idle-stop feature.

    I’m sure Accord Hybrid will also have idle-stop feature, but with accessories on, only half of the cylinders (hence only half of the displacement) will be at work. The fuel economy and emissions would match that of a 1.5-liter engine in those situations.

    Engines are most efficient when operating at max load. This is easier to obtain with smaller displacement. During cruising, which would you rather have, a 1.5-liter engine operating near max load, or a 3.0-liter engine nowhere close to operating near max load? If you choose the latter, you would hear no argument from me. If you pick the former, you would have seen the point of using VCM.

    I did address that issue by suggesting the use of a better transmission rather than VCM. Use 6-speed, 7-speed, or mechanical CVT to address this design flaw.

    And the flaw is? The amusing thing here is that Honda IMA could offer, CVT, a conventional automatic (any number of ratios), a manual, or even a clutch less manual. That’s flexibility, not a flaw.

    You are basically saying, HSD transmission choices are limited because HSD does not need a transmission
    HSD HAS a transmission, just a different kind of CVT. It still uses gear ratios (a continuous range of, as is true with any CVT).

    BTW, I stand corrected. The DC motor in Insight adds 36 lb.-ft (10 lb.-ft less than the version in Civic Hybrid), but the peak torque jump is 25 lb.-ft, however at different rpm. The 1.0-liter gasoline motor, by itself, develops 66 lb.-ft at 4800 rpm, but the combined peak torque occurs at 2000 rpm with 91 lb.-ft.
  • robertsmxrobertsmx Member Posts: 5,525
    VCM is necessary to fix design flaws of a transmission and a Otto cycle engine.
    Multiple ways to look at it:

    You take an existing engine, add VCM to improve its operating load characteristics.
    You take an existing engine, modify it to work on Atkinson-Miller cycle to improve its operating load characteristics.
    I’m not sure I would call either of them “perfect” because they are ways to reduce mechanical imperfections.

    If electric power provide low-end torque at an instant response, why do you need 240 hp in the first place?
    Car driving is more than getting to 15 mph. Horsepower is needed for performance. Just having low end torque and little horsepower isn’t going to cut it. If it could, Toyota would had been wiser setting the red line in Prius in 1500-2000 rpm range.

    I will be tossing around numbers based on assumptions, but it would make for a decent argument here. Lets us assume Honda has developed a 30 HP electric motor (develops peak power at 5500 rpm) and about 80 lb.-ft off-idle (800 rpm) to 2500 rpm (we do know that Honda has showcased several prototypes with 30-50 HP electric motors, may be one of those will be part of the Accord Hybrid).

    The Honda 3.0-V6 with VCM (in Japan) is rated at 247 HP @ 6000 rpm. Let us assume that the power output from the electric motor drops to about 23 HP @ 6000 rpm. Maximum peak power in this case would be 270 HP @ 6000 rpm, about the power output of a good 3.5 liter V6 (at the same engine speed).

    Now, let us focus at the low-end torque. The 3.0-V6 develops 185 lb.-ft at 2000 rpm. With electric assist, the net torque output at 2000 rpm would be about 265 lb.-ft (comparable to a good 4.0 liter V8 at this engine speed). With a 100 lb. IMA system (estimate), using existing conventional power train, 270 HP @ 6000 rpm, 265 lb.-ft @ 2000 rpm in a 3500 lb. family sedan delivering 30-40 mpg (city or highway) with potentially PZEV emissions rating will earn more than bragging rights.

    And if Honda mates this hybrid motor to its slick 6 speed manual, 0-60 run of 5.5-6.0 seconds would change a lot of perception that people have regarding hybrids. It would be interesting if Camry Hybrid with 127 HP can do that.

    04 Prius is still using steel body frame. Majority of the parts are non-extoic unlike the Insight.
    Primary goal with Insight was to minimize weight (its gasoline engine weighs only 124 lb.), hence use of lighter materials and the most basic platform that Honda uses (Struts up front, with semi-independent rear, I bet Prius uses similar), and without compromising safety ratings requirements.

    You cannot deny the issue of weight with HSD. Yes, Prius uses much of the same material as a conventional car does, but unless Auto World was dreaming about 1500 kg without weight savings, Toyota had to change things to put it under 2890 lb.

    The only way we can argue for or against this is by replacing powertrain in Corolla with that of Prius and see how weight grows. HCH has shown it using Civic chassis, as is.

    Looking at the results, HSD is more powerful, fuel efficient, simpler, reliable, and cheaper to produce.
    We can argue all day on power, fuel efficiency, reliability and simplicity (to me, IMA is a much simpler application). But, how do you conclude HSD being cheaper?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "I don’t understand your concern on “sacrificing performance”."

    VCM is designed to save fuel without sacrificing performance. My concern is how they achieved 26.7mpg and how misleading it is. We both can agree that EPA numbers are higher than in reality right? We drive in more aggressive, faster, and worse conditions than EPA test "routes". And yet Accord 4 cylinder only get 24mpg. So, to achieve 26.7mpg with V6 VCM, it must be purely driving with 3 cylinders at all/most of the time. "Japanese mode" must mean driving with 3 cylinders to get the most MPG, regardless of traffic conditions. Unrealistic. That's all.

    04 Prius uses electric A/C powered from 1.5KW HV battery. It can actually shut down ICE if not needed. So, Prius could make 750cc Atkinson engine emission or no emission at idle when A/C is on.

    " If you pick the former(I assume you meant 3.0L), you would have seen the point of using VCM."

    In ICE only cars, VCM will reduce half of PP and PL problems in certain situations. Atkinson cycle engine will virtually eliminate PP and PL in all cylinders in every situations.

    You are thinking only in term of ICE only cars. In hybrid, you would not need 3.0L to begin with because you have to count the electric half also. Because electric boost is instant, hybrid can afford to have smaller ICE. VCM will make less sense for hybrids.

    "And the flaw is?"

    The flaw that I was talking about is in 04 Accord where 240hp engine was equipped with a 5 speed transmission. The result is inability to throttle down to minor load situations, such as highway cruising. Sure it offers with 6 speed. It can even offer with CVT but with the extra cost.

    In HSD, there is no inefficiency due to transmission because HSD does not have a transmission. HSD is always in the top gear and lowest gear at the same time! You might be wondering how can it be? HSD can achieve this because there is only one gear ratio that is permanently engaged. A continuous range of ratio is achieved by rotating an electric motor forward or backward depending on the ICE RPM and the speed of the car! There is no reverse gear either, the main 50KW motor just spin backward. That is why HSD can save about $1,000 without producing a transmission.

    C&D Test Results:

    Prius Top-gear acceleration
    30–50 mph 5.5
    50–70 mph 7.9

    BMW 530I Top-gear acceleration
    30-50 mph: 13.3
    50-70 mph: 12.3

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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 Member Posts: 1,443
    it'll also be interesting to see if they can make these cars for a profit.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    Can you add this board to appear in Hybrid catagory from Town Hall page? Thanks.

    Dennis
  • robertsmxrobertsmx Member 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.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    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 Member 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 Administrator Posts: 11,146
    Done - thanks for pointing that out, Dennis!

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

    MODERATOR /ADMINISTRATOR
    Need help navigating? kirstie_h@edmunds.com - or send a private message by clicking on my name.
    Share your vehicle reviews

  • usbseawolf2000usbseawolf2000 Member Posts: 759
    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 Member 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.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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 Member Posts: 590
    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.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    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 Member Posts: 590
    What does it stand for?

    I'm guessing it's a Honda proprietary thing?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    IMA = Integrated Motor Assist. That's what Honda calls their hybrid design. In another word, mild hybrid.

    Dennis
  • andy71andy71 Member 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 Member Posts: 18,949
    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.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    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 Member 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 Member 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 Member Posts: 18,949
    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 Member 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.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    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 Member 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. :-)
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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 Member 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?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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 Member 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?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "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
  • SylviaSylvia Member Posts: 1,636
    A newspaper reporter is looking to interview owners of hybrid vehicles who live in the midwest. Bonus points awarded to Michiganders who drive hybrids and respond to this query. Please send daytime contact info and a line about your vehicle choice to jfallon@edmunds.com by Friday, May 21, 2004.
    Thanks,
    Jeannine Fallon
    PR Director
    Edmunds.com
  • robertsmxrobertsmx Member Posts: 5,525
    How do you figure adding 295 lb.-ft (produced between 0-400 rpm) to torque from ICE (at the same rpm)?
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    How do you figure adding 295 lb.-ft (produced between 0-400 rpm) to torque from ICE (at the same rpm)?

    The 295 lbs-ft torque is from 50KW MG2 which is connected to the crankshaft. There is some minor error but the result 0.4 g is correct. The "Max torque at the wheel" has been corrected.

    Max torque at the wheel: 4.113 x [(82x0.72)+295] lbs-ft = 1,456 lbs-ft

    ICE 82 lbs-ft torque is split and deliver only 72% to the wheels. Plus 295 lbs-ft torque support comes from MG2. This is equivalent of the 1st gear as I explained this before. MG2 can output 295lbs-ft torque from 0-1,200 RPM.

    Dennis
  • Kirstie_HKirstie_H Administrator Posts: 11,146
    A reporter is looking to interview folks anxiously awaiting the arrival of the Ford Escape Hybrid, Lexus RX 400, etc. Please respond to jfallon@edmunds.com with your daytime contact info and some thoughts on the vehicle no later than 2pm Pacific on Monday, May 24, 2004.
    Thanks,
    Jeannine Fallon
    PR Director
    Edmunds.com

    MODERATOR /ADMINISTRATOR
    Need help navigating? kirstie_h@edmunds.com - or send a private message by clicking on my name.
    Share your vehicle reviews

  • reneesfreneesf Member Posts: 6
    I called several dealers today about the hybrid accord; as the cost factor is important to us. The sales manager said he wasn't sure-but he guessed the accord hybrid would go for $30,000 plus. Does anyone have any info about this to share?
  • robertsmxrobertsmx Member Posts: 5,525
    295 lb.-ft from the electric motor is available only between 0-1200 rpm. The torque rating goes down rapidly after that.

    And the ICE does not produce 82 lb.-ft at any of those engine speeds.
  • robertsmxrobertsmx Member Posts: 5,525
    My guess would be about $28.5K (without NAV). This, assuming that the Hybrid will have everything that EXV6 does, and more.
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    "295 lb.-ft from the electric motor is available only between 0-1200 rpm. The torque rating goes down rapidly after that.
    And the ICE does not produce 82 lb.-ft at any of those engine speeds."


    HSD is unlike Honda IMA design where ICE to electric motor is bolted producing static 1:1 RPM ratio.

    MG1 = 3.6 * ICE - 2.6 * MG2 (equation 1)

    MG1 max RPM is at 10,000 RPM or -10,000 RPM(spin backward). Therefore, when 50KW MG2 is at 0 RPM, ICE can be at 2,778 RPM. At MG2 1,200 RPM, ICE can be at 3,644 RPM. Atkinson cycle ICE's torque curve is also extremely flat. To reach HSD ideal maximum thrust, MG2 electric power delivery rate is instant and ICE power delivery(RPM adjustment) is extremely fast due to the help of MG1.

    I used the peak Accord engine torque curve to get maximum thrust also. Accord would not be able to achieve max torque at 0 mph (1,000 idling RPM) either. I also did not account for the loss in torque converter which is about 5% loss.

    Here is MG2 torque relationship with Prius speed. Approximate Thrust with the ICE is in parenthesis.
    0 mph - 295 lbs-ft(0.39g)
    20 mph - 295 lbs-ft(0.40g)
    40 mph - 148 lbs-ft(0.21g)
    60 mph - 96 lbs-ft(0.14g)
    80 mph - 66 lbs-ft(0.10g)

    MG2 = 59.1 * MPH (equation 2)

    50KW MG2 torque reduction with speed is consistent with traditional manual, automatic, CVT gear behaviors. The higher the gear, the less torque is put in the wheel.

    Dennis
  • usbseawolf2000usbseawolf2000 Member Posts: 759
    Accord Auto Tranny Torque Output. Note: Peak ICE torque used.

    1st Gear - 427 lbs-ft
    2nd Gear - 244 lbs-ft
    3rd Gear - 167 lbs-ft
    4th Gear - 119 lbs-ft
    5th Gear - 91 lbs-ft

    Prius HSD Torque Output. Note: 72% of Peak ICE torque used because PSD splits 28% to generate electicity.

    0 mph - 354 lbs-ft(295+59)
    20 mph - 354 lbs-ft(295+59)
    40 mph - 207 lbs-ft(148+59)
    60 mph - 155 lbs-ft(96+59)
    80 mph - 125 lbs-ft(66+59)
    100 mph - 114 lbs-ft(55+59)

    Looks like Accord auto's torque output drops quicker than Prius.

    Dennis
  • robertsmxrobertsmx Member Posts: 5,525
    I think you forgot that Accord also uses an axle ratio (the overall gear ratio would be much higher than just the gear ratio). That being said, and going back to your previous post, engine rpm is tied directly to wheel rpm. To translate 1200 rpm to 3600 rpm (crank), there would be a need to divide (not multiply) the rate by three, meaning a three times as much tall ratio. This is not needed in a one to one correspondence (as is true in current IMA applications).

    I did the same math for Civic Hybrid, and turns out the max g&#146;s would be 0.44 for either transmission. And that bodes well with the performance numbers that Civic Hybrid posts, limited by its net horsepower (93 HP at peak).

    If your math is valid, Prius should delivery a steady 0.40g thrust throughout the rev range, and should beat cars that have &#147;only&#148; peak thrust better than that. But it doesn&#146;t.

    That said, with Accord Hybrid, I suspect Honda will once again target a thrust in the range of 0.55-0.60g. Anything more could pose traction issue for the front driver. Ideally, I wish Accord Hybrid would use in-wheel motors to power the rear wheels, but that is just wishful thinking at this point.
This discussion has been closed.