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Ravigneaux Gearset

Discussion in 'Prius v Main Forum' started by Emcguy, Feb 12, 2015.

  1. Emcguy

    Emcguy Member

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    I've been reading up on the Lexus Hybrid Drive and think that the inclusion of a ravigneaux gear set in the next prius would be a winner. Instead of been tuned for high speed driving, like some current 150MPH sedans, it could easily be modified for extra performance at 'normal' speeds. I especially think this is worthwhile in our v, whose mileage suffers from an increase in the final drive ratio.
     
  2. telmo744

    telmo744 HSD fanatic

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    The Prius ICE is very efficient even at high rpm, I don't see why the mileage would suffer in the Prius v related to final drive ratio...
     
  3. rjparker

    rjparker Tu Humilde Sirviente

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    I agree, a way to change the final drive ratio on a lightly loaded v would help mpg.
     
  4. bisco

    bisco cookie crumbler

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    anything for mpg's is worthwhile. i wonder if t has done any testing.
     
  5. catgic

    catgic Mastr & Commandr Hybrid Guru

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    EMCGuy – I agree, something like the Ravigneaux Gear Set or an “Over Drive”/”Two-Speed Axle” w/ 3.267:1<>3.703:1 Final Drive Ratios on the next generation Prius v Station Wagon would be a welcomed fuel economy focused enhancement.

    I did not/do not like the fact that Toyota elected to jack up the Final Drive Ratio of the 1.8 Liter I4 (2ZR-FXE) powered Prius v Station Wagon by 13%, because of just a couple hundred pounds additional Curb Weight. I think the only slightly, 234-pounds (106.1-kilograms), heavier Prius v Station Wagon would have performed well with the 1.8 Liter I4 (2ZR-FXE) powering it through the Gen 3’s 3.267:1 Final Drive Ratio. The v Station Wagon’s 13% higher, 3.703:1 Final Drive Ratio contributes, in large part, to why the v Station Wagon’s 44 City/42 Combined/40 Highway MPG Fuel Economy numbers are 13.7% City/16.0% Combined/16.7% Highway lower in MPGs compared to the Gen 3 Hatchback, which is propelled by the very same 1.8 Liter I4 (2ZR-FXE) ICE/HSD System.

    I would like to see the engineering numbers and/or marketing strategy, which caused Toyota to set and keep the Final Drive Ratio of the Gen 3 Hatchback & PiP at 3.267:1, while deciding to increase the Final Drive Ratio of the 1.8 Liter I4 (2ZR-FXE) powered Prius v Station Wagon by 13% -- raising it from the lower 3.267:1 ratio used in the Gen 3 Hatchback & PiP to the thirstier 3.703:1 final drive ratio of the 2012-2015 Prius v Station Wagon.

    Below is a listing of the Final Drive Ratios, Curb Weights and Coefficients Of Drag over the years in the Prius family. The list includes gasoline engine displacement and curb weight for each Prius generation-type. As can be seen, the Prius v Station Wagon only weighs 234/144 pounds (106.1/65.3 kilograms) more, respectively, then do the Gen 3 Hatchback & PiP. However, considering it is only an additional few extra 234/144 lbs (106.1/65.3 kilograms) being propelled by the v Station Wagon, I wonder why Toyota’s Prius engineers elected to bump up the Final Drive Ratio of the 1.8 Liter I4 (2ZR-FXE) powered Prius v Station Wagon by 13% to a 3.703:1 final drive ratio.

    Prius Final Drive Ratios, Curb Weights & Coefficients Of Drag
    2000-2003 Gen 1 (1.5-Liter ICE, Curb Wgt 2765 lbs & CdA 0.29) - 3.905:1
    2004 – 2009 Gen 2 (1.5-Liter ICE, Curb Wgt 2921 lbs & CdA 0.26) - 4.113:1
    2012 – 2015 Gen 3 (1.8-Liter ICE, Curb Wgt 3040 lbs & CdA 0.25) - 3.267:1
    2012 – 2015 PiP (1.8-Liter ICE, Curb Wgt 3130 lbs & CdA 0.25) - 3.267:1
    2012 – 2015 v (1.8-Liter ICE, Curb Wgt 3274 lbs & CdA 0.29) - 3.703:1
    2012 – 2015 c (1.5-Liter ICE, Curb Wgt 2500 lbs & CdA 0.28) - 3.190:1
    [Aussie v/Alpha/Euro + (1.8-Liter ICE, Curb Wgt 3450 lbs/1565 kgs & CdA 0.29) - 3.703:1]

    It is noteworthy that the Australian 7-Seater Prius v Station Wagon weighs in at a heavier 3450 lbs (1565 kgs) Curb Weight. This 410 lbs (186 kgs) in added Curb Weight of the 7-Seater Prius v Station Wagon, over the 3040 lbs of the Gen 3 Prius Hatchback, may well be what drove Toyota to increase the Final Drive Ratio of the Prius v/Alpha/Euro + to 3.703:1 --- and we who are driving the North American 5-Seater Only version of the Prius v Station Wagon, which is 176 lbs/80 kgs lighter, and likely could have functioned-performed well with the lower 3.267:1 ratio, had to live with this “Single, Unified, Globally-Driven 3.703:1 Final Drive Ratio.”
     
    #5 catgic, Feb 12, 2015
    Last edited: Feb 13, 2015
    Emcguy likes this.
  6. kithmo

    kithmo Couch Potato

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    It may be related to carrying capacity. Toyota probably think that customers who buy a v are going to utilise it to the full.
    You may be grateful for the higher ratio when you're fully loaded.
     
  7. The Electric Me

    The Electric Me Go Speed Go!

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    Ravigneaux Gearset

    I've read his whole series of books.









     
  8. bisco

    bisco cookie crumbler

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    can't wait for the next installment!(y)
     
  9. telmo744

    telmo744 HSD fanatic

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    Prius v final ratio has to do with the maximum speed the (higher) drag allowed by thet 99HP ICE, that should make MG2 spin at its fastest speed, matching the highest motor efficiency possible at all situations.
     
  10. catgic

    catgic Mastr & Commandr Hybrid Guru

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    “HSD Fanatic” Telmo – What is your source for this Final Drive Ratio selection information? How do you know that Toyota’s selection of the 3.703:1 Final Drive Ratio for the Prius v Station Wagon was driven by Maximum Speed, CdA & MG2 considerations.
     
  11. telmo744

    telmo744 HSD fanatic

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    Because those were the considerations for designing PSD for 3Gen Prius...
     
  12. catgic

    catgic Mastr & Commandr Hybrid Guru

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    “HSD Fanatic” Telmo – My question was about what is your source for how Maximum Speed, CdA & MG2 considerations were the primary drivers used in selecting 3.703:1 as the Final Drive Ratio for the Gen1 1.8 Liter I4 (2ZR-FXE) powered, 3274 lbs w/ CdA 0.29 2012-2015 Prius v Station Wagon, not how they were used to select 3.267:1 as the Final Drive Ratio for the 1.8 Liter I4 (2ZR-FXE) powered, 3040lbs w/ CdA 0.25 Gen3 Prius 2010-2015 Hatchback.
     
  13. telmo744

    telmo744 HSD fanatic

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    There is no source. One vehicle has a top speed according to its engine (or system) nominal power and CdA (should be road load instead). That "limit" is a rule of thumb to calculate the final drive, which MG2 is connected to.
    Since nominal power is the same, and imposing A equal for both cars and weight, the ratio between max speed 3gen and max speed prius v should be roughly the 3rd root of Cd(3Gen)/Cd(Prius v). In one shot, using the Cd values you brought, the 180km/h limited 3Gen power plant is down to 171km/h in the Prius v. We have still to find CdA (or road load) for both cars to provide more accurate results.
     
  14. JeremyB

    JeremyB Junior Member

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    Just going off of easy Google results, the curb weight different (268 lbs) is 9% more for the Prius v than the Prius. However, the Prius v CdA (Cd*A) is ~27%* greater than the Prius, and a RR + CdA that is 20% greater @55mph (using ecomodder to calculate). The Prius gets ~20% greater mpg than the Prius v, which make sense. I don't think the final gear ratio change really hurts the Prius v's highway numbers - it's just physics.

    The Ravigneaux Gearset could help at low loads where the engine is at a low rpm and the MG1 is at a high rpm. In this situation, changing gears to drop the MG1 rpm would increase transmission efficiency since more of the power wold flow through the gear teeth path instead of MG1-to-inverters-to-MG2, which is a much less efficient path.

    *Prius
    Curb weight = 3072 lbs + 150 lb driver
    RR = 0.08
    CD = 0.25
    A = 24.8 ft^2

    Prius v
    Curb weight = 3340 lbs + 150 lb driver
    RR= 0.08
    CD = 0.29
    A= 27.1 ft^2
     
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  15. CR94

    CR94 Senior Member

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    That's right, and that's part of the reason the final-drive ratio is different from the hatchback's. Another reason Toyota made that ratio change is to ensure you can back up a steep grade when necessary.
     
  16. Quentin

    Quentin Member

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    I guess I'm in the opposite camp. I'd rather the 2.5HSD have made its way into the v. I think the mileage would have been effectively the same while being much more pleasant to drive in the WV mountains.

    A double wishbone rear suspension is also something I'd like to see. Hopefully when the v sees the 2nd generation on the new Toyota global platform, they'll see fit to put a sportier rear suspension under it. (Based on the insane amount of Prii v that I saw in Japan a few weeks ago, I'm pretty confident that a 2nd gen will happen.)
     
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  17. J L

    J L Junior Member

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    I'd also agree on the independent rear suspension. I especially like multi-link suspension designs, as they offer the best compromise of smaller packaging, good ride quality, and good handling.

    But as far as I see it, the majority of Prius v customers will worry more about cost to own rather than handling. So it remains questionable whether or not Toyota spend the extra money to design an independent rear suspension if their market research tells them they don't have to.

    And besides, I'm rather impressed that they managed to make the current Prius v a car that can handle well in the first place.
     
  18. Air_Boss

    Air_Boss Senior Member

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    Agreed. Handles quite well on the 17" rubber.
     
  19. JeremyB

    JeremyB Junior Member

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    I'd be curious how much the 2.5HSD would drop fuel economy, but I agree that the 1.8HSD is outmatched on hills at interstate (70 mph) speeds. 4,000 rpm up every hill gets annoying. I can only imagine in WV or CO.
    I find it ironic that the Gen III Prius folks say that temps should be ICE>MG1>MG2, else you're working it too hard. In the summer, I see MG1>MG2>ICE while on the interstate.

    I'd like to see an independent rear suspension (not a strut system), but not sure I'd want to pay for it. Haven't Autocrossed it yet, but it seems to handle decently enough on the roads.
     
  20. catgic

    catgic Mastr & Commandr Hybrid Guru

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    JeremyB – Curiosity about “how much the 2.5HSD would drop fuel economy” would kill both the cat…as well as killing Catgic’s 50+ MPG lifetime “Hybrid $mart” gas mileage. The 28% smaller displacement, less fuel thirsty 1.8-Liter 4-Cylinder ECVT Hybrid Synergy Drive in the Prius v Station Wagon (Starting MSRP: $26,675) facilitates me keeping my lifetime fuel economy bumping along in the low 50s MPGs. Dropping in a 2.5-Liter “Atkinson” I4 to replace the v(vee)’s 1.8-Liter “Atkinson” I4, would likely drag my current low-to-mid 50-ish, 125%± of EPA MPG-FE running average fuel economy down through 50 MPG, into the high 40s MPG numbers. I want a hybrid vehicle that can deliver 50-ish MPG-FE to me. Even a skilled, “Hybrid $mart” driver piloting a v-wagon being propelled with the thirstier 2.5-Liter “Atkinson” I4 would have to hump hard to break into and stay in the 50s MPGs zone.

    Looking at Toyota’s calculated Official EPA MPG numbers for the 2.5-Liter 4-Cylinder ECVT Hybrid powering the Avalon (Starting MSRP: $36,470), and Camry (Starting MSRP: $26,790), one might expect Official EPA fuel economy numbers in the range of 40-43 City/40-41 Combined/39 Highway for a 2.5-Liter “Atkinson” I4 powered Prius v Station Wagon versus the 44 City/42 Combined/40 Highway of the current v-Station Wagon powered by the 1.8-Liter “Atkinson” I4.

    Before my v-Station Wagon, I owned a Prius HB Sedan. It delivered MPG-FE in the high 50s. However, I found the sedan to be a tad too small, and lacking in driver comfort and cargo hauling volume, as compared to the roomier and more comfortable v-Station Wagon with its 50% more cargo space. While the sub compact Prius c delivers very good fuel economy numbers, making it a good Point “A”-To-Point “B” & Return daily commuter car, it is too small to meet my overall personal comfort, passenger livery, and cargo hauling requirements. Likewise, the 2.5-Liter 4-Cylinder ECVT Hybrid powered Avalon and Camry do not make the overall versatility and fuel economy cut, nor does the gasoline swilling 27 City/28 Combined/28 Highway AWD-i 3.5L V6 ECVT Hybrid Highlander (Starting MSRP: $47,750).

    In MY2012, Toyota hit my personal versatility, fuel economy, needs, wants, and MSRP “$weet $pot” when they rolled out the v-Station Wagon powered by the fuel misery 1.8-Liter 4-Cylinder ECVT Hybrid Synergy Drive. If Toyota’s Marketing geniuses were to replace the v(vee)’s 1.8-Liter “Atkinson” I4 with a thirstier 2.5-Liter “Atkinson” I4, they would be in danger of loosing my demographic as a Toyota Hybrid customer.

    Since I do not “Horse” my v(vee) around, and I drive it “Hybrid $mart” like it is “On Rails,” the current suspension in the v-Station Wagon works fine for me. The 1.8HSD serves me very well while delivering 50-ish MPG running averages driving up and down Florida’s hills and dales, and along the beaches. My Pv5 comfortably cruises along on the open highway at the 70 MPH Max Posted Legal Speed Limit (MPLSL), with adequate reserve power available to execute passing excursions up into the 80 MPH range. Traffic density permitting, and if I am not in a real hurry, I usually cruise along at an electronic cruise controlled set speed of 66 MPH. For 100% “Highway” driving, when cruising along at Interstate speeds of 66 MPH versus the MPLSL of 70 MPH, and running on “Up Pressured” P215/50R17 Toyo Proxes A20s, my Pv5 delivers 45-47± MPG averages.

    As far as hill and mountain climbing performance goes, I do not find the 4,000± RPM “screaming” of the v(vee)’s 1.8-Liter “Atkinson” I4 when it spins up the power required to negotiate up-slopes to be annoying, but rather the “$inging $ound Of $avings.” I view it as the small, tolerable amount of hill climbing performance I give up to keep from having to dole out more from my wallet due to more frequent visits to the gas station.

    For the record, I think the 3.703:1 Final Drive Ratio in the v(vee) is a big contributor to the “Hit” in “Highway MPG.” I have been consuming oxygen on the planet long enough to remember “Over Drive (OD)” in America’s “Land Yachts.” “OD” made a difference in “Highway MPG.” I would like the Next Gen Prius v-Station Wagon to have a two-speed Final Drive Ratio. One at 3.703:1 for “Around Town” speeds, and “OD” at 3.267:1 for cruising at “Interstate/Open-Road/Highway” speeds.