1. Attachments are working again! Check out this thread for more details and to report any other bugs.

New VW Diesel Could Match Hybrid Mileage

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by bwilson4web, Aug 9, 2013.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
    27,068
    15,372
    0
    Location:
    Huntsville AL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Source: New VW Diesel Could Match Hybrid Mileage | TheDetroitBureau.com

    Rascal that I am, I challenged them to a mileage race:
    I know, it is wrong to taunt them . . . but it is fun.

    Bob Wilson
     
    Flying White Dutchman likes this.
  2. godzillaismad

    godzillaismad Member

    Joined:
    May 17, 2006
    199
    94
    0
    They reckon diesels are fun to drive... I wonder in what way they are referring to? Is it because it shoots out black soot on heavy acceleration, or is it because it is shooting out cancer causing particulate matters? Low end torque is what they always brag about, but if you want a race car, diesels won't cut it... Look at this thread from Club Lexus Forum, Well the IS300h is no slouch! - Club Lexus Forums

    IS300h won by a length at the end, even though the "official" figure suggests otherwise!
     
  3. seftonm

    seftonm Member

    Joined:
    Apr 7, 2006
    408
    78
    2
    Location:
    Winnipeg, MB
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Yes, I get great fun out of contributing to cancer o_Oo_Oo_O o_O Funny that you say diesels don't cut it as race cars, there are a few that have done well such as the Audi and Peugeot endurance racers.

    I just enjoy the ride, handling, and combination of mpg and turbo torque. Never made any black soot on heavy acceleration, if I did that would detract from my fun.
     
  4. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    I've got to say they said hybrid not prius, and the new diesel may give hybrids a run for their moeny. Say someone is mostly a highway driver 25% city - 75% highway and they like manual transmissions. If this new beast gets 32/46 then combined it will be 41 mpg. That will best most hybrids. The camry hybrid is very efficient 43/39 but in that driving mix gets 40 mpg, 1 less than the tdi. Now the diesel fuel does have more energy, but these are efficient cars. Choice is good, and the new engine improves the tdi with more efficiency and more hp. Remember YMMV. Some will prefer the manual deisel (fun to drive), many other will like the eCVT (smooth). If you are a traffic jam driver hsd is supperior. If you are an open road driver, I would prefer a manual (but I am in a small minority and I drive 60% city, 40% highway):)
     
  5. southernguy

    southernguy Junior Member

    Joined:
    Dec 21, 2011
    55
    21
    0
    Vehicle:
    2012 Prius
    Model:
    Two
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    12,470
    6,862
    2
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Volkswagen Passat MPG Reports | Fuelly (Diesel)

    It looks competitive to a Prius v, but not a Prius Liftback. The wagon is not competitive with the v.
    Toyota Prius MPG Reports | Fuelly (Liftback)
    Toyota Prius v MPG Reports | Fuelly
    Volkswagen Passat MPG Reports | Fuelly (Diesel wagon)

    Even 7% improvement they talk about, 43 MPG to 46 MPG will not bring it even.

    Fuelly is an inherently biased source, as owners that do not care about MPG do not report, but I can think of no reason it is not equally biased for every car.

    (Austin Green quoted me as I was editing, he did not miss my text, I just had not posted my calculator math)
     
  7. austingreen

    austingreen Senior Member

    Joined:
    Nov 3, 2009
    13,527
    4,057
    0
    Location:
    Austin, TX, USA
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    The article is about a new more efficient diesel that will be offered in the 2015 my. That should do better. Prius also is do for a redesign around then, so the new one of those will do better also. We should be happy about the new more efficient cars.
     
  8. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    21,597
    11,224
    0
    Location:
    eastern Pennsylvania
    Vehicle:
    Other Non-Hybrid
    If you see a diesel shooting out black smoke, it is at least ten years old, and likely needs a tune up.

    The DPF has taken care of the particulates. A diesel car made in the last decade emits less particulates from the tailpipe than the Prius.

    Mazda is taking their 6 with diesel to the racing circuit, and has won.
    Mazda runs diesel at Indy - Chicago Tribune
     
    austingreen likes this.
  9. southernguy

    southernguy Junior Member

    Joined:
    Dec 21, 2011
    55
    21
    0
    Vehicle:
    2012 Prius
    Model:
    Two
    But the passat is not comparable to Prius HB. Much bigger car. Comparable to Camry
     
  10. JimboPalmer

    JimboPalmer Tsar of all the Rushers

    Joined:
    Apr 14, 2009
    12,470
    6,862
    2
    Location:
    Greenwood MS USA
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    I am not who brought up the Passat, sorry.
     
  11. VicVinegar

    VicVinegar Member

    Joined:
    Jun 21, 2013
    261
    47
    0
    Location:
    Northern Virginia
    Vehicle:
    2013 Prius
    Model:
    Three
    Maybe they can design a high pressure fuel pump that doesn't prematurely fail to go with that new motor.
     
    cwerdna and godzillaismad like this.
  12. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,530
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    It is obvious that this upcoming diesel does not match up to the better hybrids, let alone the Prius, on environmental score alone. However at least in the US, for the vast majority of people emissions are not important and fuel economy is something of a middling priority at best. Actually, my impression is that people decide on an amount of money they are comfortable spending each month for fuel, and so long as the car they want falls in that money budget they consider the fuel economy 'good.'

    In 2012 dollars, mainstream US consumers follow this rule of thumb:

    Code:
    Gas Price	Threshold MPG
    2.0		20
    3.0		30
    4.0		40
    ....
    
     
  13. Scorpion

    Scorpion Active Member

    Joined:
    Feb 6, 2013
    440
    162
    2
    Location:
    Lincoln, NE
    Vehicle:
    2007 Prius
    Model:
    IV
    I am wondering if just putting in some very basic regen functions ('mild hybrid') would help these diesels meet regs. without having to resort to exhaust after-treatment.
    Also be interesting to see what the cost difference is between the two, as hybrid components are dropping in price.
    It would seem to me that most of a diesel's emissions are during acceleration, so an electric boost would be a big help.
    No need to even stop the engine at idle (if they can't figure out how to w/o clogging the filter.)
    Just a simple hybrid system, low-cost, like Buick's E-assist..........would be interesting to see what emissions result.
     
  14. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    21,597
    11,224
    0
    Location:
    eastern Pennsylvania
    Vehicle:
    Other Non-Hybrid
    The trouble some emission for diesel is NOx. The nature, and part of its efficiency, of the diesel has the the engine in lean burn under idle and light load. It probably isn't completely out of lean burn until full throttle. The high temperatures and lean fuel mixture are the perfect condition for NOx formation. The main reason for switching to ULSD was so that catalytic convertors could be installed on diesel vehicles to control NOx.

    Particulates can be formed more readily while acceleration. This is simply because more fuel is being dumped into the cylinder. Soot forms when the the mix is too rich. The DPF takes care of it. On older diesels without a DPF, the excessive smoking is because the engine is out of tune. Some do this on purpose thinking the engine will produce more power. It's just wasting fuel.

    The Skyactiv-D can already meet regs with the better diesel over seas without extra treatment. I think that means nothing more than what a gasoline car needs. The Mazda6 will also have a start/stop system and regenerative braking as options.
     
  15. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,530
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    If by overseas you mean Europe, their emission limits are more lax than the US, in no small part to accommodate diesels. The EU continues to have one set of standards for diesel and another for petrol (from wikipedia):

    Euro Emissions.png

    So it is not a case of better diesels or higher quality fuel, it is simply lower standards. Euro6, slated to start late 2014, is reigning in diesel emissions although if I am reading the table correctly the regs are set up to let diesels trade Nox for HC or vice versa.

    For giggles, compare the *future* Euro6 diesel limits to the Prius G3 from 2010:
    CO 0.258
    CO2 emissions 89 g/km
    HC 0.058
    Noise level 69 dB(A)
    NOx 0.006
     
  16. Whirldy

    Whirldy Junior Member

    Joined:
    Aug 5, 2013
    89
    15
    0
    Vehicle:
    2013 Prius c
    Model:
    One
    diesel = torque! :)
     
  17. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,530
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    All the way up to ~ 40 mph or the next red light or car in front, whichever comes first.

    Yaaaaawwwwn. Did diesel lovers not get a chance to suckle as infants ? They seem deprived.
     
    Whirldy likes this.
  18. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,530
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    Bottom line: if these diesel cars did not suck, there would not be a need to spin results like ignoring city MPG.
     
    godzillaismad and john1701a like this.
  19. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
    27,068
    15,372
    0
    Location:
    Huntsville AL
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    It turns out the reason diesels and ordinary gas engine cars do not compete in urban driving has to do with partial-power operation. It is easily seen in the test loop.

    In urban driving, the hybrid engine operates at a higher power setting than the vehicle needs. This excess power is 'banked' in the traction battery. Once the load falls off and there is available traction battery power, the engine is turned off and battery power sustains momentum. The key is the hybrid engine never operates at the inefficient, low power setting diesels and ordinary gas engines must use when moving in urban traffic.

    It takes about the same amount of power to spin a similar sized, gas or diesel engines when they have no fuel. Except for the piston ring friction on the power stroke, this is fairly close to the mechanical energy loss of any similar sized engine.

    The mechanical energy loss is going to be in the same order of magnitude as the starter motor draw, ~3 hp (~2.2 kw). The difference is the gas and diesels are always paying this overhead price. The hybrid cheats by cycling off the engine and using the banked, traction battery energy to sustain urban speed . . . and not paying the same engine mechanical overhead.

    Three identical, Prius sized cars at 40 mph will need about 8 hp. For any given period of time, the diesel and gas engined versions will pay 3 hp of energy just to spin the engine, 3/(8+3) ~= 27% is lost due to mechanical overhead. But the hybrid will only operate the engine about 50% of the time, at a high enough power setting when it runs to bank the 8 hp plus a little overhead, 3/(8+3+8) ~= 16% mechanical overhead, just 50% of the time, or ~8% overhead for the same interval as the gas and diesel are paying ~27% overhead. At urban speeds, the hybrid is roughly 3 times more efficient.

    A math model can be refined to include other factors such as round-trip, electrical losses, and additional weight. Compared to the engine mechanical overhead, these losses are 'in the noise.'

    At highway speeds gas, diesels, and hybrids are all paying the same energy overhead so they get parity there. But as highway speeds slack off, the hybrid trick begins to reduce the proportion of engine mechanical overhead in a way no ordinary gas or diesel will ever match.

    Bob Wilson
     
  20. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,530
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    Parenthetically, this is the underlying reason why P&G works.

    My arithmetic comes out a bit different though ...
    The Prius uses say 5 kW to move the car through it's various frictions, and 1.1 kW to spin the ICE
    The Diesel uses say the same 5 kW to move the car, but double the power to spin the ICE, 2.2 kW

    Added up, the Prius advantage is 6.1/7.2 ~ 15 % less fuel. Yet the Prius in practice uses closer to 40% less fuel in urban driving, so I have always presumed other factors come into play. Diesels *should* do quite a bit better than regular petrol cars because they do not have air restriction, but somehow they disappoint. Too bad really. If diesels could match hybrids by just adding a start/stop ICE that allowed gliding at urban speeds, they would have a lease on life.