General Motors' Voltec drivetrain, the range-extended plug-in setup used on the Chevrolet Volt and the new 2014 Cadillac ELR, is among the most advanced drivetrains on the roads.

That's not to say there isn't room for greater improvement though, and that's exactly what GM is doing.

In fact, as Charged EVs reports, there are far more differences between the drivetrain used in the Volt and the newer ELR than the on-paper figures give them credit for--and developments found in the ELR are only likely to make future Volts and other Voltec vehicles even more efficient.

Befitting Cadillac's more upmarket image, GM engineers have endowed it with a little more power and a few extra features over the Volt on which it's based--including a paddle system on the steering wheel for increasing or reducing braking regeneration.

But under the skin, it's advancements in the electric motor, the control systems and software that really separate the two vehicles.

According to Tim Grewe, Cadillac ELR powertrain Chief Engineer, GM upgraded "everything" in the ELR, compared to the Volt. The drivetrain layout and hardware are largely the same, but detail changes to the control systems are where the real work has taken place.

For example, engineers have found a way of using the harmonic oscillation of electrical pulses from the inverter to boost the motor's capabilities.

Grewe describes it as "third harmonic injection", though it's also known as pulse width modulation, and allows GM to push the electric motor harder without unwanted noises and vibrations.

Precise control of the magnets in the motor has also allowed the team to liberate more performance and efficiency without generating unwanted heat.

2014 Cadillac ELR 'Regen on Demand' paddle shifters

2014 Cadillac ELR 'Regen on Demand' paddle shifters

With the batteries, GM has made best use of the opt-in statistics gathered from Volt drivers to learn about the load profile of the batteries. This has allowed the team to control the batteries more precisely, and push them harder to access more power. Essentially, a wide redundancy margin has been reduced using real-world data, without sacrificing real-world usability, safety or longevity.

The ELR also uses a real-time optimizer to assess the driver's requirements and deliver the right mix of responsiveness and efficiency for any given situation. The Volt already has such a system, but the ELR's is once again more advanced, based on knowledge from real-world data.

It isn't clear how many of these advancements will make it onto the current Volt--if any--though they're almost certain to be incorporated into future models using the Voltec drivetrain.

And by then, knowledge gleaned from the refined system on the ELR may lead to even greater improvements.

As Grewe says, it's all about improving control of how the system operates--and real-world knowledge from the Volt has helped the ELR operate even better.


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