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CNet review: Jetta Hybrid beats even diesel fuel economy

Discussion in 'Prius, Hybrid, EV and Alt-Fuel News' started by cwerdna, Dec 4, 2012.

  1. cwerdna

    cwerdna Senior Member

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    2013 Volkswagen Jetta Hybrid Review - Sedan - CNET Reviews


     
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  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    After spending a decade claiming TDI diesels were the way to go, this is more pheasant than crow and welcome. I noticed from one comment that VW will have to deal with the legacy of their earlier publicity campaigns but . . . not my problem.

    I agree that this looks to be at least as good has the Honda Civic and has the potential to improve. After a decade, the Honda IMA appears to have reached its design limits. The Honda IMA may be less expensive but this little Jetta sounds OK.

    Bob Wilson
     
  3. ItsNotAboutTheMoney

    ItsNotAboutTheMoney EditProfOptInfoCustomUser Title

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    That'd be why they're going to replace it with a new 1-motor system with a clutch.
     
  4. telmo744

    telmo744 HSD fanatic

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    Why keeping low displacement engines when jumping to hybrid systems? It has been proven there is a good margin do FE increase using Atkinson. But with a fixed-ratio gearbox, it is hard to control...
    VW, please change design to 21st century best tecnologies!
     
  5. Trollbait

    Trollbait It's a D&D thing

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    Because down sized engines are a big area of fuel economy gains. Untill there's a plug all the energy is still coming from gasoline. Atkinson increases efficiency but at the expense of power. In hybrid systems where the ICE does most of the heavy lifting, the engine displacement will have to increase. It can still come out ahead of the smaller Otto, but the smaller Otto is likely already paid for, or its R&D can spread out over straight ICE models.
     
  6. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I see variable intake valve duration and angle with fuel injection and O{2} feedback as the ultimate destination. This has the potential to eliminate the throttle body leading to fewer moving parts.

    I'm not so fond of exhaust valve tricks because I think the right answer is cooled exhaust being fed to the intake manifold at high power settings. This keeps the EGT within a safe range for the catalytic converter as well as improving BSFC at high power ranges.

    As for turbo-chargers . . . well if they'll make it a turbo-altnerator-charger, I could get behind that especially if water injection were available. This would further reduce the EGT and improve total system efficiency. A smaller 'glass-pak' muffler and the problem is solved. The nice thing is a turbo-alternator-charger could also solve turbo lag and avoid the twin-sized turbo kludge seen in some vehicles.

    Bob Wilson
     
  7. hill

    hill High Fiber Member

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    Mark, one of my car pool partners has a TDI and I'll tell him the good news once he gets in from the service garage. They're tracing an intermittent wiring/lighting problem. o_O
    .
     
  8. austingreen

    austingreen Senior Member

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    Not really, I don't think the prius gets damaged by toyota selling the tundra.

    I say to vw welcome aboard the hybrid vehicle band waggon.

    Yep, honda needs to get with the program and a clutch was an obvious improvement. What is not so obvious is that these new transmissions + clutch + flywheel + lithium battery seems much better than the cvt in the original ima.

    You will note hyundai seemed to have built such a system fairly inexpensively in its sonata hybrid. Sonata hybrid reviews seem to indicate that hyundai needs to work on the transmission and software.

    Take a look at skyactiv(and fiat and bmw). DI and combustion cavity optimization can run fairly well at high power settings. The variable lift system eliminates the need for a throttle body. Exhaust valve tricks do wonders for speedy warm up and remove part of the desire for cooled egr.

    What you are talking about is called a hybrid turbo charger. It combines a exhaust generator with an electric super charger and electronics to operate both. The problem right now is cost, and on most milage tests they don't improve on mpg versus a regular turbo charger.

    If we are talking efficient turbos for hybrids, the bmw 2L seems to fit fairly well. It has a twin scroll turbo, instead of a twin turbo, this helps with scavenging. It has variable lift, so it operates in miller cycle modes when not at full load, and the turbo provides boost down to 1250 rpm. This seems like a better engine type for a high powered vehicle like the hihy or bmw 3. Unfortunately the hihy and activehybrid 3 both use 6 cylinder engines.

    For the jetta, I don't see the bang for buck for a turbo this small. A 2L atkinson seems like it would cost less and be just as efficient. The transmission might be a little different though.
     
  9. fotomoto

    fotomoto Senior Member

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    One has to wonder why the didn't use a diesel ICE; especially for Europe.
     
  10. austingreen

    austingreen Senior Member

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    We don't need to wonder, VW told us. They said the extra mpg were not worth the extra cost.

    We don't really have a confirmation on how much less fuel a diesel world consume, but my guess versus that turbo it would only be about 10%, but they would need to add the extra weight + particulate filter and urea tank etc to pass us emissions and Euro 6.
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The 13-to-1 or better expansion ratio of an Atkinson engine approaches diesel ratios and the engine stress is significantly less than the gas Otto engine they are usually based upon. They also have significantly less stress (and lighter weight) than the diesel. Then there is the remaining emissions problem due to extreme lean-burn generating NO{x}.

    The lower volume of air-to-fuel of a stoichiometric ratio leads to CO{x} with CO{2} being preferred. These can be reduced in the three-way catalytic converters that also neutralize the relatively low levels of NO{x} products. My understanding is some diesels have to inject fuel in the exhaust periodically to keep their NO{x} systems working right

    Still, you may get your wish from the Peugeot 508.

    Bob Wilson
     
  12. acdii

    acdii Active Member

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    Nice, too bad its a VW. Not very impressed with the cars the last time I looked at them a few years ago, and I don't think things have changed much since then.
     
  13. austingreen

    austingreen Senior Member

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    A popular method for cleaning the particulate filter is injecting fuel in the exhaust then burning it off.

    NOx is handled in a SCR (selective catalytic reduction) often using an extra tank of urea. SCR can work without urea, but this often involves modifications that make the ice less efficient.

    It is questionable what levels of NOx and particulates are safe. Emissions requirements for NOx have stopped lean burn gasoline engines like the one in the original honda insight or use of stratified charge lean mixtures for low power levels in gasoline direct injection from being sold in the US. Perhaps the regulatory agencies should examine what is safe from an NOx point of view as this does hurt efficiency or add cost and inconvience.
     
  14. acdii

    acdii Active Member

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    I don't think the EPA gives a hoot what it does to the pocket book as long as it meets their rules. The latest being the E15 gas they approved that 95% of the cars on the road today cannot use.
     
  15. austingreen

    austingreen Senior Member

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    If it is dangerous polutant levels then that would be fine, but AFAIK this is just about making the numbers smaller. The NOx emitted from new cars is far bellow what EPA says is safe.

    What we have in new CARB rules is a 73% reduction in NMOG + NOx between 2008 model years and 2025. This may require many cars to either be less efficient than they should be or will require more expensive emissions control equipment. This will continue to slow efficiency improvements of the fleet. If you want Fuel Cell vehicles, I guess making gasoline powered vehicles more expensive and less efficient might be a good goal.

    Higher levels of alcohol increase NMOG but reduce NOx. All I am asking is that NOx requirements are actually needed for pollution control, and not just reduced continuously because 2 large bureaucratic bodies like to see numbers going down. Raising the price of new efficient low pollution vehicles keeps more older higher polluting vehicles on the road.
     
  16. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Jetta TDI sales dropped 23% in Nov from Oct. Perhaps due to the hybrid version coming out.
     
  17. SageBrush

    SageBrush Senior Member

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    Torque and driving dynamics afficionados can buy turbo petrol cars a lot cheaper, AND not put up with the lousy reliability. Hyundai is eating VW's lunch. Fuel economy does not come into play really, because the diesel's better MPG is offset by the higher fuel price in the US.
     
  18. El Dobro

    El Dobro A Member

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    It could be that word's getting out about the high pressure fuel pump and the ice in the intercooler problems with the TDIs.
     
  19. Sergiospl

    Sergiospl Senior Member

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    Diesels cost more to service and $0.77 ct more than the price of regular gas today in Central Florida. Fuel-up a Prius with 10 gallons of regular, the diesel will cost an extra $7.70 for the 10 gallons.
    CITGO - 7600 Sun Vista Way - Orlando - SE, FL - Orlando Gas Prices
     
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  20. acdii

    acdii Active Member

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    Exactly! Diesels should be kept in trucks where they belong. You dont need all that torque in a car. Another reason you dont see Diesel hybrids, the CVT can't handle all that torque.