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I think that GM has missed the mark by a bit and they need to stick with it and work it out. It is too expensive and a bit too small -- the backseat in particular is only good for up to 6' tall people.
They took an off-the-shelf cast iron 1.4L 4 cylinder block, and they are running the it in a low efficiency mode; varying the RPM depending on the load -- the engine should be run at a single fixed RPM and charge the battery directly in as short a time as possible; and then it gets shut off. They have three clutches -- it should have ZERO clutches. The only transmission should a single speed reduction gear.
They need to design a smaller displacement low RPM high torque 2 or 3 cylinder engine that has it's valves and intakes and exhaust all fine tuned to hit it's peak efficiency at a single RPM.
The engine's output only has to meet the *average* power use of the electric drive motor, by using the battery as a buffer. It would warm up more quickly, and should only have to run 1 hour for every 2 or 3 hours of driving, after the initial charge is used.
The engine would weight half as much, and the cooling system would be half the size. No clutches and no multi-speed transmission means a lot less weight, as well. Hopefully their next gen battery cell costs far less and is more powerful -- GM has invested in a battery company that makes cells that are ~$125/kWh vs the $500-600/kWh and it could have much greater range, as well.
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