Jackson: …If you are willing to pay for a 200 – 300 mile range, it’s much less likely that you’ll be interested in an EV which also carries an engine, based on what we hear on the site and elsewhere. Many see the engine as a necessary evil, and would jump at the chance for a pure electric with reasonable range…

Not me. There’s another factor I weigh very heavily —avoiding top-level single-point failures. For example, if an ice-powered car’s fan belt breaks the car will stall out from overheating within a few miles. Or if a critical component in an EV’s controller fails it will also be stranded. However, careful attention to eliminating all credible SPFs in an EREV with fully redundant propulsion systems/power sources can virtually eliminate the likelihood (and danger) of EVER being stranded on the roadside.

/I “preached this sermon” at length to key members of GM’s Volt engineering team years ago —and although I haven’t reviewed a Volt FMECA, I believe they avoided credible SPFs wherever possible.

There are at least 3 reasons why the 1.4L I-4 engine was used:

1) It was already designed and available. The same engine powers the non-electric Cruise which is based on the same platform. Don’t forget that GM, despite a bailout, is still a bit cash-challenged. They were also a bit rushed to get the car out, in order to benefit from a favorable (though likely limited) political climate for EVs.

2) Running a larger engine at modest rpms in the middle of it’s range is more efficient that revving a smaller engine near it’s max. The original concept would have had a 1L I-3 (which would have been designed from scratch; see point #1)

3) It is quieter. GM wanted, as much as possible, to make CS-mode imperceptible to the driver (and indeed most Volt drivers report that they need the control panel to tell when the mode is active). The perception GM wants is that the Volt is electric first and foremost, a hard claim to sell if you suddenly hear a raucous leaf-blower noise.

It may be that a small engine would be more efficient if precisely tuned to a single-speed output at higher revs, but it wouldn’t be quiet. With greater AER and EREV as a known quantity, this might not be a show stopper.

There is also the problem of buffering a smaller, constant generator output to the more spiky needs of actual driving. This would put a greater strain on the battery pack, since it adds up to more charge/discharge cycles (which affects it’s overall life). A larger pack, as we discussed, would make this less of a problem, since the strain on each cell would be smaller at greater capacities; but I still think this will have to wait until (at least) the costs come down. By this time, the batteries may be better as well.

The smaller engine would weigh less, as you pointed out; but even at higher energy density, 100-120 mile AER will increase the weight of the pack, in turn.

I do not believe that an EREV will ever be offered with an AER much over the 100-120 mile figure I cited above. Keep in mind that the battery cost improvements which help EREV also helps BEVs. Since there is no engine power to buffer, BEVs may be able to get by with less resilient (and less expensive) batteries.

The difference will come down to philosophy, I think. Will you mainly recharge at home, or out on the road? If you choose to recharge mainly at home, and depend on gas for the rest, the EREV is for you (and it may still cost less). If you are willing to pay for a 200 – 300 mile range, it’s much less likely that you’ll be interested in an EV which also carries an engine, based on what we hear on the site and elsewhere. Many see the engine as a necessary evil, and would jump at the chance for a pure electric with reasonable range.

The greater the electric range, the more the engine becomes a seldom-used burden for the vehicle to carry. There is also an issue with gas going stale in the tank waiting to be burned. The current Volt sometimes needs the gasoline changed along with the other fluids after long periods with no CS-mode.

George McDermand: I see the Volt as a bridge vehicle. A transition car between gas and pure electric. The next step “Volt 3″ would be a 160 mile range Camery sized car with a tiny gas engine 600cc to 800 cc which produces enough juice to maintain 65 mph on level ground. If I remember my math It takes about 19 hp. As the battery is depleted the ERE (emergency range extender) starts. When the engine is running a small percentage of it’s power is slowly charging up the battery to maintain a minimum level of charge for variations in road conditions. Think about it. The Prius was the first step mostly gas engine with an electric helper. The Volt is the next step. Call it an electric with a medium size battery and a middling gas engine. The next step I think is a big battery with a small auxillary engine. That concept will be necessary for years as the country is large and it will take years for fast charging stations to be common.

Ahh, I miss those discussions here. A couple or more years ago, this kind of comment was much more prevalent. I suggested some of these things myself. Now that the Volt is actually on the road, with a possible attenuation of production in it’s near future, basic engineering issues and imagination seem less prominent. Too bad.

I agree especially about the large battery and small auxiliary engine. Part of what will make this possible is a battery able to cycle more deeply, to buffer a constant output from a smaller engine without degrading prematurely. I think the battery should be sized to provide 24 – 30 Kwh; the amount one might expect to recharge overnight at home with a conventional electric service (110/220 @ 150 – 200 amps in the US). You would be using the auxiliary engine in lieu of problematic over-the-road fast charging, though one could do that as well.

Consider that there will need to be a “bridge” vehicle for years to come if EV infrastructure becomes more established, and something like, say, Hydrogen becomes the next new thing. You won’t initially find a new fuel everywhere, but you’ll still be able to find a plug or fast charger.

Welcome aboard, Bob!