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Eight 2011 Chevy Volts took the 1200-mile roadtrip.  (Source: Jeffrey Sauger for General Motors)
The Volt is withstanding the rigors of road testing admirably

The first preproduction models of the 2011 Chevy Volt hybrid electric plug-in vehicle were built earlier this year.  Since then, the vehicle has been put through a number of rigorous tests.  Starting yesterday, a fleet of eight Volts launched on the most ambitious test of the vehicle to date: a 1,200 mile road trip.

Chevrolet Volt chief engineer Andrew Farah is among those making the round trip from the Milford Proving Ground through Ohio, Pennsylvania, Maryland, West Virginia, before returning home.  The drive will take a few days and will require approximately 4 tanks of gas.

The drive is dubbed the "65-Percent Drive" according to Autoblog, which in GM-speak means the test drive made when 65 percent of the vehicle's hardware and software is done.  Reportedly, GM is actually about 90 percent done, but is just sticking to its traditional naming.  GM will complete 70, 80, 90 and 100 percent drives in coming months.

One thing GM is still tweaking is how much power from the gas-engine generator to put directly to the electric drive motor, versus using the generator power to charge the batteries.  GM is finding that frequently putting the power directly to the motor improves performance.  However, the generator will still charge the batteries in some cases, as well.

The engine will be run between 1,200 and 4,000 rpm, using factors like speed and power load requirements to decide on the necessary speed.  GM wants to keep the engine between 30 to 100 percent load, as higher loads reduce pumping losses.  GM was tight lipped about fuel economy under the old method (sustained charge) or the new method (variable speed, some power going directly to the electric motor). 

The company did say that the prototypes are getting good mileage -- over 300 miles on a tank of gas -- when operating in generator mode.  This is in addition to the vehicle's 40 mile all-electric range.  Another interesting test will be when GM runs the car's gas engine on E85 ethanol fuel.  The vehicles are FlexFuel designs, so they can enjoy both gas and ethanol.

As to the battery mode, the batteries are performing well and aren't getting too cold or too hot, both conditions which can degrade performance.  The cars aren't yet reaching the 40 mile target on a charge, but GM expects to pass that milestone on the next test, with tweaking.  On the trip, GM is testing vehicles both running on a depleted battery charge, and a full charge.

GM is also looking to fine tune and minimize noise, vibration, and harshness (NVH).  Currently, the gas engine typically won't turn on until the car is moving, at which point the noise will be drowned out by the wind and road noises.  GM, nonetheless, is pleased with the performance, and plans to further reduce NVH by tweaking vehicle parameters that effect the road and wind noise.

Other GM engineers were off testing Volts at Pikes Peak in Colorado.  One key concern is whether the Volt will reach a "tipping point", where the gas engine can't sustain battery charging, and the battery becomes depleted below the typical minimum of 30 percent charge.  Even a strenuous 14-mile trip to the 14,000-foot summit was unable to overwhelm the 100 hp generator, though, so it appears that the "tipping point" will never be reached in real world situations  -- if GM's claims hold true.

A critical test to come will be how the vehicle performs in cold weather.  In cold weather, the Volt starts with the generator running, to help heat up vehicle and jump-start performance.  Battery performance typically suffers incrementally worse degradation, the colder it gets (this is a major argument for ultracapacitors which perform favorably, but are more expensive).

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RE: Loads
By 91TTZ on 10/16/2009 11:14:02 AM , Rating: 3
They don't mean higher than 100%. They mean that the closer you get to wide open throttle, the more efficient the engine operates due to lower pumping losses. At idle or at low throttle settings your butterfly valve is nearly closed which is a huge restriction in the intake (obviously).

RE: Loads
By mcnabney on 10/16/2009 2:55:26 PM , Rating: 2
You are missing something.

The small gas engine on the Volt does not have a throttle. It is either on and running or off. This allows it to be tuned to operate at peak efficiency and without the additional complexity typical automobile engine have.

When it is running any additional power not sent to the wheels is stored in the battery.

RE: Loads
By mcnabney on 10/16/2009 3:08:52 PM , Rating: 2
Actually, I am really not understanding the need for a 100hp generator. The battery is used for strong acceleration. Why would they design it to need 75k watts. That is insane. In fact, I am uncertain of the car's electrical system being able to handle voltage that high.

RE: Loads
By mcnabney on 10/16/2009 3:13:52 PM , Rating: 2
Just checked. It is a 71hp (53KW)generator. That sounds about right.

Also, this is never mentioned, but the car could easily power your house in the event of a blackout/disaster. In fact, it could power 5-10 homes.

RE: Loads
By Keeir on 10/16/2009 7:40:42 PM , Rating: 2
Sadly, this was not part of the Feature set for Volt 1.0.
I think it would be a great value add... It is supposedly part of the studies for Volt 2.0

RE: Loads
By Spuke on 10/16/2009 7:09:11 PM , Rating: 3
The small gas engine on the Volt does not have a throttle. It is either on and running or off.
Read the article. It says the gas engine will run between 1200 and 4000 rpm so, yes, it will have a throttle.

This allows it to be tuned to operate at peak efficiency and without the additional complexity typical automobile engine have.
There's nothing complex about a throttle. You have a hole with a round plate in the middle. A computer keyboard is more complicated.

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