Quick Spin: 2011 Chevrolet Volt charges toward production

AutoBlog.com
by Sam Abuelsamid
Nov 30th 2009 at 11:58AM

2011 Chevrolet Volt

 
Like many modern cars, the Volt doesn’t uses a fob instead of a key with a start/stop button on the left side of the center stack next to the shift lever. Pressing the button produces a green glow from within. We shifted into Drive and rolled out silently with the Volt running purely on battery power as we circled the loop trying to run down the battery so we could experience the charge sustaining mode.

Above the start-stop button are two other buttons with Leaf and Sport labels. It turns out that the default operating mode for the Volt actually limits the maximum output of the motor to 90 kW (121 hp) in order to help maximize efficiency. The Sport mode releases an additional 20 kW bringing the output up to the full 145 hp. Even in the normal mode, the instant torque of the electric motor means that the Volt feels strong accelerating from a stop. We didn’t do any official timing, but with Sport mode engaged, the Volt certainly felt like it could hit 60 mph in the mid-eight second range.

When we drove the Cruze mule last spring, the electric drive system behaved pretty flawlessly except for a couple of hiccups with the brake system, which is a fully blended system that combines friction braking with regenerative braking. We specifically looked for those hiccups in this Volt and couldn’t get the brakes to misbehave. Farah acknowledged that there are still a few glitches in the brake software and calibration work is still being done. Even at this point, 11 months from Job 1, the brakes feel better than they do on many hybrids using the same system.

Another feature of the Volt is the Low position on the shift lever. The Volt doesn’t actually have a transmission as such, just a reduction gear. There is no actual low gear. The Low position provides increased regenerative braking when the driver lifts off the pedal. In Drive, lifting off gives about 0.1 g of regen braking, similar to what you get in a conventional vehicle from engine braking. In Low, the lift off regen is boosted to about 0.25-0.3g, about what you get from downshifting. The main purpose of this is to save the brakes when going down a long hill.

Eventually the battery meter dipped down toward the 0 miles left point. When running on the battery, a battery meter dominates the left side of the LCD display with the ghost of a gas gauge above it. As the car switches from charge depleting to charge sustaining mode, the gauges switch place. On the right side of the display is a power gauge. A mode button on the left side of the dash swaps the energy gauge over to the other side and eliminates the power gauge for a simpler layout.

Getting into charge sustaining mode doesn’t necessarily mean the engine starts up right away. In fact there is nothing in the car that tells the driver that the engine is running. According to Farah, the intent is to make everything as transparent as possible for the driver. He tells us that the Volt team is designing the car for mainstream audiences rather than the hyper-miling crowd. They wanted people to just get in the car and focus on driving rather than watching all the gauges and trying to eek out every last foot from a gallon of gas.

We didn’t even realize the engine started for the first time until we came to a stop and heard it running. The most noticeable thing at first was when the engine shut off. Farah told us that the team was not yet satisfied with the engine shut-off quality and is continuing to calibrate it. While it was noticeable, we still felt the shut-down smoothness was better than many current production hybrids.

When we first talked to GM about the Volt three years ago, the thought was that the engine would simply run at a constant speed to maintain the battery charge. As development has continued, that strategy has evolved. The output of the engine/generator is based on the needs of the battery and motor, not what the driver is demanding. As the level of the battery changes, the generator is controlled to provide the necessary, electrical output. The engine speed in turn is selected to maximize the load on the engine. An engine runs most efficiently at full load. If the electrical demand is low, a lower engine speed is used in conjunction with the generator control to get the desired load.

Currently the engine can operate in a range of about 1,400-4,000 rpm. According to Farah, the maximum engine speed will likely be reduced as they finalize the calibrations, although he didn’t say how much. As we continued running in charge sustaining mode, we were never able to feel the engine start and stop while the car was in motion. However, after a series of hard accelerations we were able to occasionally hear the engine running when it went into higher rpm modes. The sound was similar to or better than most other comparable compacts, but Farah was adamant that it was not good enough. Additional work is still being done both on the engine control and the general vehicle noise, vibration and harshness (NVH) properties to improve this. Farah admitted that more road noise was still coming through on these IVER vehicles, especially in the back of the car, than was desirable.

In terms of handling, the Volt felt capable but obviously we couldn’t evaluate much in a parking lot. Body roll was reasonably well controlled, a behavior aided by have the 400-pound battery pack mounted low in car. In fact, according to Farah, the Volt’s center of gravity ended up being about two inches lower than the Cruze. We did toss the Volt around a bit in the corners and it felt reasonably well balanced below 8/10ths, but that did turn to understeer as we pushed harder. Farah declined to say how much the Volt weighs, but he did tell us that weight reduction efforts have brought the weight of the base car (minus the battery) down to about the same as a comparable conventional car. So the Volt weighs about 400 pounds more than a Cruze, which should put it at around 3,500 pounds.

It’s been a tough three years for General Motors since we first learned about the Volt. The automaker has gone through bankruptcy and emerged as a smaller company that is majority owned by the U.S. government. When we first wrote about the Volt, many of our readers groused that it was nothing more than smoke and mirrors, a simple publicity stunt. As we’ve followed the development since then, the proportion of people who think the Volt is vaporware has shrunk somewhat, although many still doubt whether the car can succeed commercially.

Now that we have driven the car in both charge depleting and charge sustaining modes, we can say that this car is definitely not vapor. The Volt is real and it certainly appears to work. Whether it can actually hit 40 miles on a charge, what mileage it will get in charge sustaining mode and how long the battery will last are questions that remain for another day.

View additonal photos and read the original article at http://www.autoblog.com/2009/11/30/2011-chevrolet-volt-quick-spin/