Volt may become a parallel hybrid

[RobertSmalls]

Volt shock - Telegraph

Until now the car's hybrid driveline has operated with wholly all-electric drive, but poor high-speed performance and power-generation losses are forcing GM to consider powering the Volt/Ampera directly from its petrol engine at high speeds (read our Vauxhall Ampera prototype review). The move would be possible without major engineering as the planetary twin-clutch transmission already has a direct mechanical link between the engine and wheels.

This is good news for people who are interested in maximum gas-mode fuel economy. Powering the wheels through a transmission is the most efficient use of a range extender. The range extender should only need to operate at highway speeds, so you wouldn't need many gear ratios, and the engine could be kept near peak BSFC with the electric motor being used to add or subtract power if needed.

It does create some questions about how Chevrolet will differentiate the Volt from the Prius, how much of a development delay this change would create, and why the previous version had a direct mechanical link between engine and wheels if it was intended to be a series hybrid from the get-go.

[Patrick]

It's about time they got their heads out of their butts.

[NeilBlanchard]

They could also get better efficiency by charging the battery and running the ICE at a constant RPM -- something you cannot do with an ICE driving the wheels.

[cfg83]

RobertSmalls -

When the Volt was announced, I thought, okay the Volt is incorporating the "Prius Plug-In" retrofit concept, and now it's becoming even more like a Prius.

Looks like the Autobahn influenced the decision :

General Motors is about to dramatically re-engineer its Volt/Ampera extended-range battery car to better suit it to high-speed European use.
...
During the car's development, GM increased the capacity of the petrol engine from one to 1.4 litres to maintain the charging performance, but the single-speed electric motor starts to run out of torque at speeds above 50mph, affecting motorway and overtaking performance.

CarloSW2

[cfg83]

Neil -

Originally Posted by NeilBlanchard

They could also get better efficiency by charging the battery and running the ICE at a constant RPM -- something you cannot do with an ICE driving the wheels.

That's what I thought, but in one of our previous Volt threads I posted a tidbit where the Volt engineers abandoned constant RPM in favor of a "range" of variable RPM/load settings.

CarloSW2

[Patrick]

Originally Posted by NeilBlanchard

They could also get better efficiency by charging the battery and running the ICE at a constant RPM -- something you cannot do with an ICE driving the wheels.

I think the Prius can do it with the ICE driving the wheels, due to the planetary gearbox.

[Nevyn]

Just one more way to push the Volt further into the future.

[dcb]

Straight series sucks, guess they had to find out the hard way.

[dcb]

I think it is very telling though.

According to that article, the 71hp hp gas motor is struggling to keep the car going 50mph

the 149 hp electric motor on batteries can go at least 100mph

it should take no more than 1/4 of 149 hp to go 50mph

so of the 71hp in the gas motor, no more than 37 hp make it to the wheels via the "electronic transmission"

the transmission of power in this series configuration is %52 efficient at best.

It certainly doesn't add up, if this is the case, how did they ever figure on 50mpg in range extended mode? Something isn't right here.

[gone-ot]

...sounds to me like an automotive shell game: "electro-MPG" under one shell, "gas-MPG" under another...shuffle sufficiently and dazzle the audience into believing they're BOTH the same MPG result.