Archive for November 9th, 2009


Nov 09

Lutz Says Volt SS a Possibility, Cadillac Converj Reportedly Greenlighted for Production

Cadillac Converj

Cadillac Converj

[ad#post_ad]The Chevy Volt is designed to have a sporty feel.  It will cover 0 to 60 in under 9 seconds and can chirp its wheels from a stopped position to to instantaneous torque.

Engineers have found a balance to both achieve 40 miles of gas free driving yet still allow the car to deliver a feeling of power.  It is estimated driving the Volt will as though it has a 250 horsepower engine.

Recently GM vice-chairman Bob Lutz was asked whether GM was moving away from performance cars instead focusing on fuel efficiency.

He responded “as the trend grows for vegetarianism the fruit and vegetable isles will expand but the meat counters won’t go away.”  He predicts performance cars will exist because there will always be buyers, but they will become electrified.

“I would forecast that certainly there will be a growing trend to high performance hybrids,” he said.

When specifically asked if we would one day see a Volt SS he said with a wry smile “I would not discount that possibility.”

“That Voltec architecture with the lithium ion battery and the small engine gives us all kinds of possibility on when we run the engine, when we don’t run the engine, how hard we run it, how fast we charge the battery and so forth,” he said.  “So if we want to sacrifice a little bit of fuel efficiency in the interest of performance and still get over 200 miles per gallon, we can do that any time”

Shortly after this interview the Detroit News reported that anonymous GM sources indicate the Cadillac Converj has been greenlighted for production. In fact Lutz’ wry smile in the video may be due to that fact.

An official announcement is likely coming soon.

The Converj will offer increased performance out of the same battery pack with some limitation in range. Lutz once said the car would cost the same as two Volts, or about $80,000.

The source also said it could be a few years for the Converj to make it to showrooms. I would also expect a name change in this case.

Source (Fox)

and (Detroit News)

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Nov 09

Engineering Design of the Chevy Volt’s Two Electric Motors

Chevy Volt Powertrain

Chevy Volt Powertrain

[ad#post_ad]I had the following discussion with Alex Cattelan who is the Volt’s Chief Powertrain Engineer. It explains for the first time anywhere in more depth how the Volt’s two separate electric motors function.

The design of the electric motor, is there a separate generator or does the motor itself just turn the other way and act as a generator?

Very interesting question. There are two motors. One is considered the traction motor and the other one is the generator. However, and they are two motors, the traction motor is  higher-powered and designed specifically to meet the traction requirements.  The generator is designed to efficiently couple to the engine to generate what we need and match the efficiency band of the engine as much as possible in all the operating modes. So we look at that motor as coupled with the engine in system and then we also have a traction motor.

Some of the interesting pieces though of this are, for example, in EV operation I have two motors on board and I typically use the traction motor only to drive the vehicle. However, I do have some mechanisms to couple those motors and in some points of operation these two motors can be coupled and have a more efficient state.

Does that produce more power if they’re coupled?

It’s actually not additive for power, it’s actually the way it’s architected, and a lot of this is proprietary so I can’t get into the full architecture, but what it does is optimize the rotating speed and the losses of the motors so in certain states its better to operate both to propel the vehicle and in some states its better to utilize more of the generator and less of the traction motor. In some states its more efficient to use more of the generator and have more of the traction motor actually be a generator. That would be for example in coast down situation often we use our traction motor as a generator on regen.

We do have the ability to utilize both motors in propulsion mode.

The issue is and the direct answer to your question is we do have a primary traction motor and a primary generator motor and they are designed specifically for those levels of operation. However, we have a little bit of flexibility in exactly how we use them.