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Hybrid Vehicles Toyota Prius Toyota Prius vs VW Golf TDI
531 messages, Last post on Dec 03, 2009 at 5:29 PM
You are in the Toyota Prius Forum. Your Host is pf_flyer
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Replying to: pf_flyer (May 27, 2008 3:50 pm) When I calculated this for all vehicles in the spreadsheet at 70 mph, the Prius stood out as having the lowest force (hence least work performed over a given distance) of any of the cars, at 110 pounds. Interestingly, the Chevy Cobalt was second at 118 pounds, along with Honda Civic and a couple of Hyundai / Kia. The Golf's (Rabbit's) force was 137 pounds, OK but not spetacular, and 25% greater than the Prius'. Kudos to the Prius for being efficient of form. It's doing the least amount of work to transport four people. But does that mean it is more fuel efficient than the Golf? Not necessarily. Fuel efficiency is a measure of work output / energy input. It is a fraction, up to 1.0. It is a measure of the efficiency of the powertrain, really. In this case, the SI engine with CVT and regeneration vs. the diesel with manual (or automated manual) gearbox. Here's where talking MPGs falls apart if you are trying to compare powertrain efficiency. MPG doesn't tell you how much work has been done (miles isn't work, it is just distance), or how much energy was used (gallons of what?). More information is needed. Fortunately, for a steady state, like 70 mph, we can calculate the force from the abc's. We can also look up the amount of energy in a gallon of fuel (gasoline, diesel) here: http://www.afdc.energy.gov/afdc/fuels/properties.html So efficiency = work / available fuel. Work = force * distance, so efficiency = force * MPG / LHV of fuel. For a steady 70 mph on flat ground, the only thing I don't know is how many MPGs each vehicle gets. Let me assume that the '09 Prius gets 52 MPG and the Golf gets 46 MPG at 70 mph. Someone may have better figures, but I think these are reasonable from http://www.fueleconomy.gov/mpg/MPG.do?action=browseList. The fuel efficiency of the Prius is then 33.4% and the Golf is 33.3%. I don't think you could get any closer than that. Again, kudos to the Prius, because matching the efficiency of a diesel with an SI engine is hard to do. However, using this analysis, you can calculate that any diesel, whether Golf or 7000 pound Cummins pickup is over 30% efficient at this steady speed. So Kudos to diesel technology, regardless of what sheetmetal it is surrounded by, for being efficient. Most SI powered vehicles are about 25% efficient at this speed. In the city, any hybrid will be more efficient than a diesel because of regeneration and stop/start, unless the diesel also has those technologies. Final thought, if Volkswagen could get the roadload (abc's) of the Golf to be the same as the Prius, it would get 10% better MPGs than the Prius because there is 10% more energy in a gallon of diesel than gasoline.
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Replying to: 104wb (Sep 17, 2009 8:05 am)  least 100 years. (there are other reasons for this but we are just talking fuel mileage here) So as a result, D2 will retain the 20-40% advantage. So while 50-52 mpg in a Prius is great, what would be wrong with a diesel Prius 70/73 mpg?
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Replying to: ruking1 (Sep 17, 2009 8:27 am) I don't understand what you meean by refining out natural consequences. Diesel has 10% more energy than gasoline. That's a good thing for vehicle range, A diesel Prius would get higher mileage. That would also be a good thing.
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Replying to: 104wb (Sep 17, 2009 8:45 am) I should state my TDI's real world consumption 70 mph, to be in excess of 59 mpg. I say in excess (inxs) because I can easily get 59 mpg 75 mpg with bursts to 80/85 mpg. So at a steady 70 mpg...(I swag) 60-65 mpg. This would be what, 15 mph better than the Prius? Not bad for the aerodynamics of a brick, eh? Of course this probably would be dismissed out of hand by the Prius folks? 
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I think if you took a prius and a golf tdi and rolled them into a ball you'd have a really fun to drive, super efficient automobile. Call it the Priolf or the Golfius.
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Replying to: thammer62 (Sep 17, 2009 10:06 am)  So for example if you get a statistically average VW and have great independent shop support, those are not real issues anymore.  Indeed if what I read is true, good Toyota dealer repair service is about as rare as hens teeth.
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Replying to: ruking1 (Sep 17, 2009 8:55 am) Since you can't actually buy it anymore, nor will you be able to in the future, dismissing is easy. It's hard to take the comparison seriously when the vehicle doesn't even meet minimum emission criteria and it forces you to shift gears yourself. Show me an automatic shifting diesel-fueled vehicle that is at least as clean as a common new non-hybrid gasser that delivers an average (city & highway combined) of 50 MPG, then reminder yourself that Prius is even cleaner. Face it, non-hybrid diesel simply doesn't cut the mustard. .
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Interesting article from WSJ on the impact of C4C on VW and BMW diesel sales, including the Jetta TDI. Also discusses the general barriers to adoption of diesels in the U.S. A couple mentions of the Prius, but mostly it's about diesels: http://online.wsj.com/article/SB10001424052970203440104574401103200521582.html
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Replying to: john1701a (Sep 17, 2009 4:31 pm) Face it, a 70 mpg Polo beats 50 mpg hybrid gasser by 40%. Interesting that you are of the burning more is actually better than burning less point of view. And you wonder why America actually burns more??? I would not have a clue why........... Of course 12 to 17 k cheaper drawfs what Toyota asks for the Prius. I'd try to keep it out of the country too, if I had the adversarial attitude that EPA, CARBS and seemingly you have also. Really in terms of competition ,the Camry hybrid more matches the Jetta in hp (147 hp vs VW TDI 140 hp. Torque (the real motivator) is somewhat mismatched 138# ft vs TDI's 236 #ft. Also the EPA is 33c/34h/34 comb vs TDI 29c/40h/33 comb. Camry is app $2,800 more MSRP. |
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Replying to: ruking1 (Sep 17, 2009 5:03 pm) A Polo diesel for $10,000? Bring it over, I'll buy one!!
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