- Oct 28, 2010
At Witz' End: Observations after driving the Chevy Volt (and getting 26.1 and 81.5 mpg)
Chevrolet Volt – Click above for high-res image gallery
"The Chevrolet Volt is an electric vehicle that is capable of being your only car," said Volt Marketing Director Tony DiSalle at the Volt media launch briefing. "You have the freedom to 'fuel up' at home, yet you're not tethered to a charge station. You can't always plan your day around charge opportunities." He added that General Motors is counting on very positive feedback from Volt early adopters thrilled by its "unprecedented customer experience."
The Volt's promise, first made at a December 2006 media briefing prior to the concept's January 2007 Detroit Auto Show debut, was that it would run on inexpensive energy off the grid for the first 40 miles, then go as far as needed on electricity generated by a small ICE. It would be a non-fuel-burning, tailpipe-emissions-free electric vehicle (EV) for at least the first part of each day's drive, then a fuel-efficient compact the rest of the way. Thus, it would eliminate "range anxiety," that sweaty-palm fear of running out of battery before you run out of trip.
This all sounded good, but the skepticism of many leaving that briefing four years ago was largely justified: how well would this unique series-hybrid system work; would GM have the commitment and resources to get it done; and – even if so -- could it be sold profitably at an affordable price? Now that the Volt is finally here, we know it's a very nice car. Find out what else we learned after the jump.
Based on the same platform as Chevy's all-new 2011 Cruze sedan, the Volt is about the same size and even looks a little Cruze-like, even though it has an aero-optimized shape and is a 5-door hatchback, not a sedan. Its Chevy-signature twin grille ports are covered by aluminum-look bars, its interior is completely different, and its two-passenger back seat is less roomy due to the centrally-located battery pack.
The interior is a mix of conventional (a nice Cruze-like steering wheel with convenient audio and cruise controls, stalks for turn signals and wipers, comfy seats and PRNDL shifter) and unique. The iPod-like shiny plastic vertical console (looks better in grey than white) offers touch buttons for audio, climate and standard navigation, plus the electric park brake and propulsion on/off. Fits and materials are good, with soft upper dash and door-panel pads and nicely grained plastic elsewhere. Only the contrasting "high-tech wallpaper" pattern on the doors struck a jarring note to my eyes.
A "coin stack" graph on the left indicates EV range, while a graphic rotating wheel on the right zips up and down to show power flow out of the battery and regen back to it. In between is a compass over a large digital speedo, plus readouts for trip miles, range (electric and gas), fuel used and average fuel economy. A knob on the left rotates through displays for tire pressures, engine oil life, two trip odometers and a helpful "tutorial" mode.
GM claims a total range of "up to" 350 miles on full battery and 9.3-gallon gas tank, and that's how we started our drive. At 10.9 city/suburban miles, driving normally in "Normal" mode, we noted 38 miles EV range remaining for a projected total of 48.9. (The two other selectable modes are "Sport" and "Mountain," the former trading some range for performance, the latter reserving some battery energy for long upgrades.) At 19 miles, we stopped at GM's Warren, MI. Technical Center for a briefing with 27 miles of EV range remaining -- a projected total of 46 at that rate of usage.
The "Voltec" (formerly "E-Flex") propulsion system begins with a 111 kW (149-hp) electric drive motor that generates a healthy 273 lb-ft of torque from zero rpm for strong launch response. There's no shifting or powertrain noise – just smooth, swift, silent acceleration. At higher cruise speeds, the smaller 55 kW (73-hp) motor/generator joins in to keep the drive motor in its most efficient range (a 10-15-percent efficiency gain).
When the battery runs down, the 84-hp DOHC dual-VVT 1.4-liter ICE fires up (almost undetectably) and operates in its most efficient speed range (2200-4200 rpm) driving the motor/generator to keep electricity flowing to the drive motor. At higher speeds with the battery depleted, both the motor/generator and the ICE assist the drive motor through the complex and clever planetary gearbox for best efficiency, though the engine can't power the car on its own. EV purists find this controversial, but if it increases efficiency, why would you not do it?
It may also be controversial that this little range-extender engine requires premium fuel (mostly). But Volt Powertrain Chief Engineer Pam Fletcher explains that high-octane gas adds 5-10 percent efficiency by enabling a higher compression ratio and more spark advance. Why not have it recharge the battery instead of providing just enough juice to power the car. "It would be inefficient to charge the battery using gasoline," she said. "We don't want you to pull into your garage with a full battery. That would defeat the purpose."
The 435-lb. GM-engineered (except for the cells) battery pack holds 16 kWh of energy in 288 liquid-cooled lithium-ion-phosphate/manganese cells. Every cell is precisely temperature controlled and micro-balanced by four individual controllers. While the original intent was to use just 50 percent of the pack's energy to extend its life and keep it far away from low and high state-of-charge extremes, the engineers now have opened that window to 65 percent – hence the revised 25-50-mile EV range claim (vs. the original 40). GM says the pack is designed to last 10 years in normal service and warrants it for eight years/100,000 miles.
Following the briefing, we drove 16.8 city miles, some in Sport mode with the heater on, before changing drivers. With four miles of electric range remaining, our projected total had slid to (19 + 16.8 + 4 = ) 39.8 miles, and the gasoline fuel-economy meter still said "250+" mpg – really, that should read "infinity," since we had consumed no gas at all. Some eight miles later, we noticed that the range-extender engine had started and the gas range meter said 247 miles. Should you run the gas tank dry, by the way, the battery reserve allows about five more miles to find a station.
We arrived at a lunch stop at 34.1 miles (53.1 total) with 240 miles of gas range remaining. We had burned just 0.3 gallons of gas and achieved gas/electric composite fuel economy of 112.7 mpg. After lunch (with no battery recharge), we drove 48.1 gas-only city/suburban miles, some of them aggressive, at a respectable 33.9 mpg. Our total trip, counting the first roughly 40 on electric, came in at a very impressive 81.5 mpg.
A few days later (during North American Car of the Year testing), I reset the B trip odometer and flogged a battery-depleted Volt hard in Sport mode on twisty back roads. I found it surprisingly quick, agile and fun despite its low-rolling-resistance tires and 3,781-lb curb weight. I averaged just 26.1 mpg on that spirited drive, but the A trip meter (which factored in other testers' earlier EV-only and gas-powered driving) said 54.2 mpg. Not bad at all.
So, the Volt is what was promised: a "pure" electric vehicle, up to a point. After that, it's a series hybrid – except at higher cruise speeds, when it morphs temporarily into a uniquely-driven parallel hybrid. But if this set-up enables owners who drive short distances most days to do it on zero fuel, yet provides fuel-efficient compact-car extended range when needed, what's the downside?
Well, there are a couple of big ones: the engine, complex gearset and sophisticated controls add a major cost increment over a battery-only electric; and limited availability of vehicle-size lithium-ion packs will limit Volt production for the first few years, at least.
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Award-winning automotive writer Gary Witzenburg has been writing about automobiles, auto people and the auto industry for 21 years. A former auto engineer, race driver and advanced technology vehicle development manager, his work has appeared in a wide variety of national magazines including The Robb Report, Playboy, Popular Mechanics, Car and Driver, Road & Track, Motor Trend, Autoweek and Automobile Quarterly and has authored eight automotive books. He is currently contributing regularly to Kelley Blue Book (www.kbb.com), AutoMedia.com, Ward's Auto World and Motor Trend's Truck Trend and is a North American Car and Truck of the Year juror.