Volkswagen TwinDrive - The People's Plug-in

[killerrd2]

Besides having a choice of either a diesel or gas engine (which the Volt does not) here is yet another advantage to the German version:

Here's a key difference: When the Chevy Volt's battery pack drops to a level low enough to demand assistance from the range-extending engine, the generator hooked to the engine doesn't charge the batteries, it powers the electric motors directly. And that engine has no mechanical link to the wheels. The TwinDrive Golf's 1.5-liter diesel is positioned such that at certain speeds above 30 mph, the engine can be mechanically coupled to the single-speed gear-reduction transmission in order to drive the wheels directly while also turning the generator that charges the batteries. VW claims its diesel can drive the car more efficiently in these conditions than the electric motor can.

Source:
http://blogs.motortrend.com/6566713/...-in/index.html

[killerrd2]

More photos:

http://blogs.motortrend.com/6566713/.../photo_01.html

[megeebee]

Interesting. Lots of good ideas there.

But this is one of the comments posted at MT:

"range-extending engine, the generator hooked to the engine doesn't charge the batteries, it powers the electric motors directly"

That is completely contradictory to everything I have read, even on MT. Everyone has stated the motor will never driver the wheels, only keep the batter charged. Once the battery is at 40%(?) the motor only keeps it at that level, not power the electric motors. Has this changed?

I'd like to know this too.

[calgaryhhr]

Wow, this TwinDrive Golf seems pretty incredible. I would make this my choice over the Volt because of the available all wheel drive option.

[ARCANGEL]

Yea this sounds very inticing.

[K-1]

PistonsFan (I think) posted a visual of the 6(?) operating conditions a while back. The range-extender does charge the batteries to maintain a minimum SOC.

[john1701a]

Originally Posted by killerrd2

The TwinDrive Golf's 1.5-liter diesel is positioned such that at certain speeds above 30 mph, the engine can be mechanically coupled to the single-speed gear-reduction transmission in order to drive the wheels directly while also turning the generator that charges the batteries.

GM's own Two-Mode took that advantage one step further, by offering a direct path along with some gearing.

There's always some type of tradeoff. For the FULL hybrids, they do well with cruising with very little battery power available. For any type of plug-in, including Volt, they do well by avoiding use of the engine.

For the right balance for consumers... efficiency vs. price ...is the challenge.
.

[megeebee]

Originally Posted by john1701a

For the right balance for consumers... efficiency vs. price ...is the challenge.
.

Absolutely correct. This is a fear I have regarding the Volt. Getting a few Hollywood B-listers won't be enough to make the program profitable.

[MechEng]

Originally Posted by megeebee

Interesting. Lots of good ideas there.

But this is one of the comments posted at MT:

I'd like to know this too.

Here is my understanding of how the Volt range extending mode will work.

The engine will have differing set points. Lets say at 1500rpm it produces 18KW's of energy and at 2000rpm it produces 25KW's of energy.

Now lets say the car is cruising at 70MPH consuming ~20KW of energy. The battery hits the magic state of charge of about 30% and the generator comes on. Initially the Volt will turn on the generator at 2000rpm producing 25KW's of energy. 20KW's will go direct to the electric motor and the remander will charge the battery. When the battery hits about 35% SOC the generator will then turn down to 1500rpm producing 18KW's of energy. All 18KW's will go to the electric motor while the remaining 2KW's will come from the battery. When the battery hits 30% the process repeats.

The numbers used are just made up for demonstration purposes but this is my understanding of how the process works.

This way the engine can be tuned with variable intake and exaust manifolds and variable valve timing to be efficient at a series of specific rpm's.

I don't see how Volkswagen's mechanical process is going to be more efficient. As a the gearing and clutches + having to tune the engine to run at all rpm ranges will have higher losses than the Volt's specific tuned ICE to generator to electric motor to differential to wheels setup.

[MonaroSS]

One secret aspect to Volt is that being on the Delta II platform, just like the Opel Astra, GM can use the Two-Mode Diesel Hybrid drive it developed for Astra (see link below).

So all GM needs to do to replicate this Golf is to drop the Astra Two-Mode diesel drive into the Volt and combine it with say a half sized battery pack, the so called 20-mile option, and Volt suddenly becomes a lot cheaper but still makes very efficient mpg figures.....

Put the Astra Two-Mode diesel drive into Cruze plus Volts battery pack and control technology and it gets even cheaper.....

http://www.greencarcongress.com/2005...eils_two_.html

[WishIhadatruck]

I think MechEng stated fairly well what the Volt will do approximately.

I think the article was incorrect in saying the Volt doesn't offer a diesel option. In reality at this moment neither car is in production so neither offer it but if you look at what is possible the Volt can easily offer a diesel. That is one of its strengths, you can get extended range from a gas motor (gas, E85, etc.), diesel motor, or fuel cell. The VW is probably limited to either gas or diesel since it requires the mechanical link for steady state cruising which a fuel cell obviously doesn't offer. Whether GM offers a diesel in the Volt (in Europe if anywhere) is anyones guess but it certainly can if it wants. It will only make it more expensive however.

MonaroSS, it bugs me to read the link you provided. It was just another reminder of GM's promise of the 2-mode.

the packaging of the two-mode system as essentially a transmission replacement will allow the application of the system in a wide variety of vehicle formats. This is one way to bring hybrid technology to a wide range of vehicles more quickly.

Where are all the vehicles with the 2-mode if it is so easy to allow new applications? Where is the 2-mode Malibu? 2-mode Traverse? 2-mode Equinox? 2-mode Cobalt or Cruze? Kind of depressing. Hopefully some of these products see the light of day eventually and GM puts the 2-mode to good use beyond its current applications.

[megeebee]

Originally Posted by MonaroSS

One secret aspect to Volt is that being on the Delta II platform, just like the Opel Astra, GM can use the Two-Mode Diesel Hybrid drive it developed for Astra (see link below).

So all GM needs to do to replicate this Golf is to drop the Astra Two-Mode diesel drive into the Volt and combine it with say a half sized battery pack, the so called 20-mile option, and Volt suddenly becomes a lot cheaper but still makes very efficient mpg figures.....

Put the Astra Two-Mode diesel drive into Cruze plus Volts battery pack and control technology and it gets even cheaper.....

Sounds great.

These are very expensive technologies to be applied to a lower market car, though. Do you suppose GM is planning to do what you describe?

[Bravada]

VW is doing a great job at spinning an inherently less efficient technology. That's about it.

But I do believe VW might just as well bring the car to the market cheaper and make it more popular than GM with the Volt.

[MonaroSS]

Originally Posted by megeebee

Sounds great.

These are very expensive technologies to be applied to a lower market car, though. Do you suppose GM is planning to do what you describe?

I think it will come down to volume of sales and that will depend on the price of gas in the future. If oil spikes again and stays there a while then the volumes and demand will make these technologies more viable.

[Bravada]

The problem here is that both companies took approaches quite uncharacteristic of their usual conduit. GM went for expensive technology with the assumption they are making an unusual, special product that will pay for it. Volkswagen went for the smallest common denominator trying to utilize as much of the olden tech they've already got to keep the unit cost low and streamline the route to the market.

The more I think about it, the more I believe VW is actually right here. You can't out-Prius the Prius, this was a one-off Toyota managed to pull and others have to just get over it. The very next opportunity is making the hybrid your USUAL car, not a SPECIAL car. If VW indeed succeeds, the Volt will be instantly obsolete, rather than market-leading.