Fuel Miser: Diesel Volkswagen Polo Blue Motion Hits 60 MPG

http://www.edmunds.com/insideline/do...ticleId=116314

 

Ahem, if you don't like the test, game it.

This is a press release product. When it arrives and we see the EPA numbers, there will be something to talk about. Right now, it sounds like they are using a manual transmission . . . another Apples-to-rotten comparison.

Bob Wilson

 

I understand the apples-to-rotten problem, but why don't any of the available hybrids come with a manual? If a manual can get better mpg too bad if the hybrid maker chooses not to offer the manual, I'll compare what's available as apples-to apples. I only own manuals, and if it costs $1000 less for a manual so much better for the manual, in my opinion it's a con against a hybrids not the TDIs if I were considering between the 2. Give me a hybrid with a manual to compare and I would.

 

Two of the Honda hybrids had a manual transmission option: (1) Insight and (2) first generation Civic.

I'm not sure if the GM 'hybrids' are available with a manual transmission.

Bob Wilson

 

I think it's difficult for manufacturer's to justify a manual transmission in the US these days. Drivers abroad have preferred them quite widely for their fuel efficiency, but folks in the US seem to have trouble shifting and talking on cell phones at the same time. (I too have never owned anything without a manual transmision...I panic when I come to a stop and my left foot doesn't have a pedal of its own.) I think it becomes even more difficult to justify manuals when CVTs are so darned good at transmitting power. The driver loses control over the gear ratio, but the manufacturer has also done away with the lossy torque convertor in favor of a clutch that only slips when moving off the line. It sucks for enthusiasts but it seems to work OK.

As for GM, my understanding of the two-mode hybrid system is that it is specifically built around a four-speed automatic gearbox with a planetary gearbox on one of the ends. That seems to preclude a GM manual transmission hybrid unless I misunderstand their concept.

And as for VW's Polo Blue Motion, good for them! Any clean high-efficiency vehicle is a worthwhile vehicle in my book. Options are good for everybody, and VW will sell loads of them somewhere in the world. Fortunately US isn't the be all and end all of markets for automobiles. In the end that may save our posteriors when we really get pinched on fuel and need lots of efficient ways to use it.

 

I was referring to the new models, why they discontinued the manual I do not understand. Seems from the database the manuals kick butt as I would expect.

 

This kind of thing makes me really mad.

It just shows that the auto manufacturers don't care at all about trying to improve fuel economy.

All they've done is add some plastic aero-bits, switched the tyres and put a longer 5th gear in. It cost them nothing extra to build, but goes 14% further per gallon, with just the barest minimum of effort. Why don't they do this for EVERY vehicle in the lineup? :<

Exactly the same thing happened with the Astra ECO4 over here in the UK. Vauxhall were offered a tax advantage to make low CO2 cars, so applied to a standard Astra DTi: plastic undertray, LRR tyres and longer 4th and 5th gear. The net result was a car that managed 75 mpg (US) at highway speeds - way better than the standard car.

It cost no more to make or buy, but guess what - they dropped it. Grrr! Please bring it back Vauxhall!!

 

Yes it's puzzling what automakers haven't done that seems like no-brainer improvements.

My Element MT is geared so at 80mph it's spinning 4000rpm. But insanely the 5spd transmission is the same basic case as the 6-speed available on Honda's sportier vehicles. For less than $200 of parts I can turn my 5 into a 6 and I will be doing this soon. The extra gear drops the revs to 3200@80, still high but a huge improvement. This has been done by someone on my Element forum and he's gotten 30+mpg immediately on his first 2 tanks. This could be applicable for lots of Honda 5spds. This should have been standard from day one.

 

In the case of the Toyota Hybrid Synergy Drive, there is no clutch, and no mechanical slippage of any kind anywhere in the drive train. Whether the wheels or turning or not, the gas engine (ICE) is on or off, or either of the two electric motors are providing torque or generating current (or one generating while the other is driving) is controlled by the computer/power control system. The wheels, both electric motors, and the ICE are always fully mechanically engaged through the Power Split Device which is a planetary gear arrangement with fixed gear ratios.

The one electric motor determines the effective gear ratio between the ICE and the wheels, and the other motor is for adding or taking torque directly to/from the wheels. The two motors also act as the ICE alternator and starter, and can operate without the rechargeable batteries (but the car can not operate without the electric motors).

Assuming that the batteries are not being used (neither charging nor discharging), then a "low" gear (high ratio from the ICE to the wheels) is "emulated" by letting the first motor, MG-S, act as a generator providing current to the second motor, MG-T. Overdrive (low gear ratio) reverses that letting MG-T provide current to drive MG-S (but now MG-S is spinning in the opposite direction from the low gear case). Using the motors to transfer energy from one to the other to achieve different effective gear ratios is less efficient than using mechanical gears, but overall system efficiency, including the temporary storage of excess energy in the batteries gives better overall efficiency than what is possible with only an ICE and a manual transmission.

-- Alan

 

This does provide the advantage of continually variable ratio. Toyota's Latest Lexus model uses two planetary gearsets to allow both a switch in the mechanical gear ratio, with the elecrtic motors not needed to handle as much of the load to provide a CVT effect (in only needs to vary across the "gaps" between the physical gears). Using a variable gearset in line with a manual transmission might work, but would probably not be understood by most drivers.

In all of these designs however, the actual hybrid system actually replaces the standard transmission, the only exception is the Honda Hybrid design which integrates the motors into the flywheel. I do believe these should have retained the manual transmission, though I suspect the reason that the '06 model dropped is a combination of the low popularity of manual transmissions, and extra work to get the valve-sealed "EV" mode to work with a transmission not under computer control.

As for the topic of vehicles seeing improved efficiency from taller gearing and slight aerodynamic mods, there is no good reason not to do those changes. An exception might be if said aerodynamics changes say introduce lift or some other undesired effect, but that's very doubtful from things like belly pans and small spoilers in front of the tires. Other features that could very easily be done include insulated bottles to store hot coolant overnight (faster warmup for improved efficiency), and blocking the grill/radiator opening with louvers or a sliding door that would only let in enough airflow over the radiator as actually needed (decreased drag).