Popular Mechanics gets behind the wheel of the pre-production Chevy Volt and first experiences the car in pure-electric and sustained-charge modes.
This post is an excerpt of an article from Popular Mechanics. You can read the full post (with video) on their website. Written by Barry Winfield.
LOS ANGELES—We’ve been following the Chevy Volt as it has progressed through many milestones before it became a development mule based on the 2011 Chevy Cruze last May. That test drive was completed entirely in electric-only mode. Today, we had a chance to slide behind the wheel of a Volt that looks and feels much closer to production. We experienced the car in both pure-electric and sustained-charge modes, when the conventional gas engine powers an on-board alternator to supply the needs of the electric motor when the batteries reach an elected state of discharge.
The Volt is still about a year away from production, with an intended launch date of November 2010. But for chief engineer Andrew Farah, the process has been remarkably condensed.
The prototype Volt we drove in the parking lot of the Dodgers Stadium in downtown Los Angeles is what Farah calls a 65-percent write-off vehicle, meaning it’s about 65-percent of the way to full production standards. As such, it had a few technical bugs already identified and rectified for future cars. Still, this prototype is a fully representative vehicle in terms of structure and drivetrain.
Electric propulsion systems are well known for their smooth and quiet operation. So the unobtrusive cycling of a gasoline engine is considered a crucial aspect of this kind of hybrid system. Consumers simply won’t tolerate a system that doesn’t operate seamlessly. Here is how the Volt performed.
The Specs
The Volt uses a three-phase AC induction motor rated at 120 kilowatts, or 160-horsepower, powered by a six-foot long, 375-pound array of lithium-ion cells mounted low along the Volt’s floorpan. Though Farah wouldn’t say precisely how much the Volt weighs at this point (we suspect it will tip the scales at around 3500 pounds), he did mention that much work has been done to keep the center-of-gravity as low as possible, to help diminish a driver’s perception of mass. Of course weight mounted higher in the chassis would result in more noticeable roll.
The engine is a normally aspirated 1.4-liter inline four-cylinder unit from GM’s global Family Zero range, manufactured in Flint, Michigan, and it is hooked to a 53-kilowatt alternator to provide current for the Volt’s electric motor once the battery pack has discharged about half way. To prolong battery life the cells are never allowed to recharge higher than about 80-percent of maximum, and they are never permitted to discharge more than about 50-percent unless an emergency occurs, and “limp home mode” is triggered.
Careful cell management is key to efficient utilization, not to mention the safe operation of lithium-ion cells, some of which have been known to fail in spectacular pyrotechnic fashion unless stringent temperature controls are in place. The Volt has dedicated cooling and heating systems in place for the battery pack, along with elaborate cell-condition monitoring mechanisms for optimal efficiency.
The chassis is based on GM’s Delta architecture, similar to that underpinning the new Cruze model, which promises contemporary ride and handling performance.
Continue reading about the Volt drive, sport mode and recharging at Popular Mechanics…
You can also check out more content from Popular Mechanics:
- Cornell’s 100-MPG X-Prize Entry First Test Drive (Video)
- 2009 LA Auto Show Report: Mitsubishi PX-MiEV Concept
- PLUS: More GM Plug-in Cars on the Way
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Very interesting. I hadn’t realized that the gasoline engine would never be used to recharge the battery, but it sounds like it’s more efficient to feed the electric motor directly. I guess some people might have expected that, but I think there must be a tradeoff here — in order to feed the motor directly, the gasoline engine will not necessarily be running at peak efficiency all the time (or so I would assume). So I guess they found that the loss of energy from recharging the battery is greater than the gain of running the engine at peak efficiency all the time. I find that somewhat surprising, but of course I trust that they have studied this thoroughly.
Very interesting. I hadn’t realized that the gasoline engine would never be used to recharge the battery, but it sounds like it’s more efficient to feed the electric motor directly. I guess some people might have expected that, but I think there must be a tradeoff here — in order to feed the motor directly, the gasoline engine will not necessarily be running at peak efficiency all the time (or so I would assume). So I guess they found that the loss of energy from recharging the battery is greater than the gain of running the engine at peak efficiency all the time. I find that somewhat surprising, but of course I trust that they have studied this thoroughly.
I didn’t realize that either regarding the engine not charging the batteries, but it does make sense that it’s not efficient to do so.
“And it seldom needs to rev at a high rpm, since the control computers on board the Volt can vary the alternator load and maintain high efficiency (cranking out plenty of juice) with lower revs. ”
From the above sentence, it sounds like they can achieve the optimal gas-engine rpm by adjusting the alternator load, so it may be the best of both worlds in a sense.
I didn’t realize that either regarding the engine not charging the batteries, but it does make sense that it’s not efficient to do so.
“And it seldom needs to rev at a high rpm, since the control computers on board the Volt can vary the alternator load and maintain high efficiency (cranking out plenty of juice) with lower revs. ”
From the above sentence, it sounds like they can achieve the optimal gas-engine rpm by adjusting the alternator load, so it may be the best of both worlds in a sense.
It will be very interesting to see what kind of mileage they get when running purely off of the gas engine and how that compares to a car of similar weight and aerodynamics that uses a similar gas engine connected directly to the powertrain (rather than going through an electric motor intermediary). Of course, that kind of direct comparison might not actually be possible.
It will be very interesting to see what kind of mileage they get when running purely off of the gas engine and how that compares to a car of similar weight and aerodynamics that uses a similar gas engine connected directly to the powertrain (rather than going through an electric motor intermediary). Of course, that kind of direct comparison might not actually be possible.
Probably the Chevy Cruze would be the best comparison. The Cruze is purported to get 40+ mpg with a 1.4L turbo engine. If it comes in near that (especially since the downward adjustment of EPA mileage estimates starting in 2008), that would be quite an achievement for a car of that size (bigger than the Cobalt XFE which already has best-in-class fuel economy, 25/37, and power).
Probably the Chevy Cruze would be the best comparison. The Cruze is purported to get 40+ mpg with a 1.4L turbo engine. If it comes in near that (especially since the downward adjustment of EPA mileage estimates starting in 2008), that would be quite an achievement for a car of that size (bigger than the Cobalt XFE which already has best-in-class fuel economy, 25/37, and power).