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2011 Chevy Volt
But Volt's true nature may actually be an improvement, plus early reviews are complementary

In the week when auto editors turned in their first reviews of test drives of General Motors' upcoming 2011 Chevy Volt, there's been a bizarre twist that's largely overshadowed these initial impressions.

In a wild twist, Larry Nitz, GM's executive director of electric and hybrid powertrain engineering, has revealed that the gasoline engine actually will drive the Volt mechanically.

Previously, GM had maintained that the Volt was a battery electric vehicle (BEV).  When the battery's 40-mile range (since revised to "25 to 50 miles") was nearing exhaustion, a turbocharged 1.0-liter 3-cylinder gasoline engine kicked in, supply electrical current directly to the batteries and motor to provide more than 200 extra miles in range.

That platform was known as "E-Flex".  But unbeknownst to anyone, GM was pulling a bait and switch.

Today, Mr. Nitz revealed that 
actual powertrain.  The Volt, it turns out, is not a BEV like the 2011 Nissan Leaf.  It is actually a plug-in hybrid electric vehicle (PHEV) like the 2012 Ford Focus or 2012 Toyota Prius EV.

The internal combustion engine (ICE) -- now a 1.4L 84 hp 4-cylinder design -- and the 149 hp permanent-magnet AC electric motor both feed into a planetary gear set and three electronically controlled, hydraulically activated multi-plate clutches.  The resulting automatic transmission is marvel of electro-mechanical engineering offering a blend of efficiency and power.  The entire powertrain is bolted together to minimize noise, vibration, and harshness (NVH) and reduce space usage.

Arguably this advanced transmission is much better for customers than what GM initially 
said it was offering.  As Ford Motor Company pointed out in our recent interview with their head of electrification, BEVs suffer from poor performance in cold or hot weather, as the battery's performance deteriorates sharply. 

So why the bizarre farce on GM's part in claiming its BEV was really a PHEV, when the actual design would be more beneficial to the majority of customers?  Mr. Nitz claims that GM had to deceive the public in order to secure its patents on its unique transmission.  Now with the patents in hand, he was free to go public with the new powertrain platform, dubbed "Voltec", he says.

Turning to what GM had intended to be the focus this week, 
MotorTrend and The Detroit News have taken their first drives in the upcoming PHEV and are quite enthusiastic.

The Detroit News writes:

After I drove more than 32 miles on electric power only — in a very un-eco-friendly manner — the Volt’s little engine began powering the car. This was the moment I had been waiting for: It’s one thing to power a car with batteries, but it’s revolutionary to have a gas engine supply the power to electric motors.
The succession of power is more seamless than a presidential election. The engine is quiet and keeps humming along. There’s never a glitch, a pause or a moment when the engine noticeably kicks on or off. For the most part, once the initial battery charge is drained, the engine produces the electric power to drive the motor. 
...

Most of all, there's nothing to adjust to in the Volt. My 75-mile trip used a total of 0.9 gallons of gasoline. But I would have been happy to drive farther. 

And MotorTrend opines:

The Volt is no sports car, but it blows Toyota's plug-in Prius away (9.8 seconds to 60 mph), and runs neck and neck with a 2.4-liter Malibu in acceleration and handling tests. Figure-eight performance is virtually identical at 28.4 seconds and 0.59 g, and the Volt's 119-foot stops from 60 mph are just 3 feet longer-impressive, given its 226-pound weight disadvantage and low-rolling-resistance tires. (The Prius weighs 376 pounds less than the Volt, yet it just matches its 0.78g lateral grip, trails both Chevys by 0.4 second on the figure eight, and needs 131 feet to stop from 60 mph.)

Based on these reports it appears that GM's "surprise" of the ICE hooking up directly to the transmission to drive the wheels seems indeed to be a good one.  On the other hand, many will likely dwell on the fact that GM pulled a bait-and-switch on the customer.  

After all, some customers really want an honest-to-goodness BEV and may now being a bit bummed that they instead ordered what essentially amounts to a souped up plug-in hybrid.  Others have been vocal critics of the vehicle (and GM in general) and will likely jump on GM's deception as a platform to attack the vehicle (and GM in general).

Perhaps GM was right -- they had to mislead the public to protect their intellectual property.  But the move was certainly a very bad decision in terms of public relations.  GM can only hope that the public settles down and comes to realize the bottom line -- that it's offering them a superior package than what it initially promised to deliver.



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RE: MPG is all that matters
By Solandri on 10/12/2010 12:29:13 AM , Rating: 3
quote:
Even with this explanation I'm pissed. Part of the reason people loved the series hybrid idea is that the battery provides 100% of the actual propulsion. At which point you can replace the ICE with a fuel cell, or a bigger battery, or solar, or whatever else you want without changing the vehicle's performance.

The Volt can still do that. All that's changed is that instead of the electric motors driving the wheels directly, there's a drivetrain between them and the wheels. A secondary motor hooked up to the ICE is also connected to this drivetrain.

If you think about it, it makes a *lot* more sense to do it this way than the pure electric model people thought it was going to be. In the pure electric model, the electric motor drove the wheels - always. When the battery ran out of juice, the ICE would drive a generator which converted the mechanical energy into electricity, which would be sent to the electric motors, which would turn it right back into mechanical energy. You're probably looking at 80%-90% efficiency there tops, probably more around 75%.

The way GM is doing it, while the battery has juice, the car is driven purely by the electric motor. You lose a tiny bit of energy in the drivetrain, but it should be minor (they're typically 98%-99% efficient at transferring power). If the battery runs out of juice, the ICE gets a direct mechanical linkage to the wheels thus eliminating any conversion losses.

Bottom line is, the primary goal here is energy efficiency. The direct mechanical linkage between the ICE and drive wheels is more efficient than having to convert mechanical energy, to electric, back to mechanical energy. The only people who should be upset about this are people whose primary goal is the elimination of ICEs, even if it causes lower energy efficiency. Those people are not environmentalists, they're social engineers trying to make the world conform to their flawed (less efficienct) view of how the world should work.


RE: MPG is all that matters
By DominionSeraph on 10/12/2010 3:05:55 AM , Rating: 2
Does the system balance torque so the ICE operates at wide-open throttle to both charge the battery and aid the driveline? Because if it doesn't, while the mechanical linkage may be efficient, you're losing efficiency in the ICE.


RE: MPG is all that matters
By Solandri on 10/12/2010 6:04:05 AM , Rating: 2
Yes, that occurred to me after I posted. But any decrease in ICE efficiency due to not operating at ideal RPM has to be less than the efficiency losses in converting the power to electric and back to mechanical energy. If that weren't the case, auto makers would be redesigning every ICE car in production to replace the mechanical transmission with an electric generator -> electric motor setup.

Since that isn't happening, it's safe to conclude the a mechanical linkage with sub-optimal ICE RPM is more efficient than an electrical linkage with optimal ICE RPM. Automakers have been trying for decades to obtain the holy grail of a continuously variable transmission. If it were possible to do that using a generator and electric motor, they'd have done it already. They haven't done it, ergo the efficiency losses in a generator -> electric motor combo exceeds the efficiency losses from running the ICE at sub-optimal RPM.


RE: MPG is all that matters
By ilkhan on 10/12/2010 4:01:22 PM , Rating: 2
What I read is that at highway speeds, the ICE uses some of its output to directly power the wheels, the generator doesn't put out enough juice to power the wheels at freeway speeds on its own without the battery providing additional juice. Thus the problem. It may be better for simplicity but it kills the concept of series hybrid.
Also as mentioned below, mechanical simplicity takes a huge hit this way.


RE: MPG is all that matters
By MozeeToby on 10/12/2010 5:04:05 PM , Rating: 2
Well, close. The generator probably does put out enough electricity to power both electric motors directly, the problem is that the second motor (the motor that is necessary to reach freeway speeds) is busy functioning as the generator. It simply isn't available to provide power to the wheels because it is busy charging the battery. So, since this electric motor already has a connection to the drive shaft (to help the primary at freeway speeds) and to the ICE (to charge the battery) they just hook up both connections at once.

So, if you had, for example, a hydrogen fuel cell that could supply enough electricity to charge the battery faster than both motors deplete it at highway speeds, you could drop that in as a replacement for the ICE. You just remove the mechanical connection to the secondary motor, make a software change to the gearing system, and everything else stays the same. You could even do the same thing with an ICE, but you'd have to bring along your own generator to make it work.

Honestly, except for a pretty big leap in complexity (and therefor maintenance costs) it seems to be a better design. Personally, I would have preferred a single drive motor and a direct serial connection, but this is, in a different way, a very brilliant design.


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