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AutoBlog: How did GM arrive at 230 mpg for the 2011 Chevrolet Volt?

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Filed under: Hybrid, Chevrolet, GM, Alternative Fuel

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Neither General Motors nor the EPA are making declarative statements about how, exactly, the 2011 Chevy Volt will achieve it's much-touted 230 mpg rating that was announced today. GM's most clear statement (available in full after the break) says that some consumers "may be able to be in pure electric mode on a daily basis without having to use any gas" and that "key to high-mileage performance is for a Volt driver to plug into the electric grid at least once each day."

Without access to the actual method that the EPA is tentatively going to apply to plug-in vehicles (we have requests for clarification out to the EPA), all that GM's Dave Darovitz would tell us is that the number is "based on city cycles and we're not really talking in detail yet." Instead, the press release says that:
Under the new methodology being developed, EPA weights plug-in electric vehicles as traveling more city miles than highway miles on only electricity. The EPA methodology uses kilowatt hours per 100 miles traveled to define the electrical efficiency of plug-ins. Applying EPA's methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving. At the U.S. average cost of electricity (approximately 11 cents per kWh), a typical Volt driver would pay about $2.75 for electricity to travel 100 miles, or less than 3 cents per mile
.

Frank Weber, vehicle chief engineer for the Volt, told AutoblogGreen that the EPA's method takes into account the two extremes: People who plug in every chance they get and therefore barely ever need gasoline and people who never plug in (if you're buying a Volt and never plug it in, we'd like to offer you a bridge or two. Call us). By figuring out what the average driver will do with the Volt, the EPA has declared that 230 mpg is reasonable. Weber said, "The number is in the ballpark, it is not unrealistic. The moment you are driving shorter trips, or you go on longer trips and look at your average fuel economy, this number is achievable."

Keep in mind, that 230 mpg number is only valid in city driving, though GM claims that the Volt's combined mpg rating will still be in the triple-digit range. Though the EPA has yet to finalize its methodology, we have come across a calculation that makes sense. According to a commenter on TTAC.com, the EPA would first drive a PHEV with a full charge until it reaches a charge-sustaining mode, after which it completes a normal cycle of 11 miles. The Volt, therefore, would presumably go 40 miles before activating charge-sustaining mode, and then travel another 11 miles for a total of 51 miles. Thus, GM can claim the Volt will achieve 230 mpg based on 51 miles of driving during which only .22 gallons of fuel would be used. Likewise, if we know the Volt would use .22 gallons of fuel while traveling 11 miles in charge-sustaining mode, we can calculate that it would achieve 50 mpg while traveling with the generator on.

However, as you can read in this detailed PDF from NREL, there is much more to think about in calculating the fuel economy of a PHEV than simply how far it can go on a single charge and then what its "regular" mpg rating is. We'll just have to wait until the EPA finalizes its methodology for testing these types of vehicles before we can say for certain how GM arrived at the magic number of 230 mpg.

[source: GM, NREL]

Continue reading How did GM arrive at 230 mpg for the 2011 Chevrolet Volt?

How did GM arrive at 230 mpg for the 2011 Chevrolet Volt? originally appeared on Autoblog on Tue, 11 Aug 2009 12:33:00 EST. Please see our terms for use of feeds.

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So, if you plug in your car all the time and the gas engine is not ran. Won't the gas in the tank get old and need to be stabilized?

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Won't the gas in the tank get old and need to be stabilized?

I got old and need to be stabelized too.

0511-0812-2704-1146_Black_and_White_Clip

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So, if you plug in your car all the time and the gas engine is not ran. Won't the gas in the tank get old and need to be stabilized?

This has been brought up a number of times, so I would expect it is addressed. At the very least, it'll be a comment in the owner's manual saying something about using up the fuel in the tank at least every couple of months. A more aggressive approach might include some kind of fill-up tracking system in which the engine will run whether you leave that mode or not, and burn off most of the fuel, and then indicate the need for a fill-up.

It'll be interesting to see if anyone decides they want to be all-electric, and thus just plain start removing components like the gas tank or gasoline engine from the car. Or even leave everything in place, but fully drain the fuel tank and just leave it empty and dry.

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well if just about every car has an oil life meter, how hard would it be for them to make a fuel life meter?

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It'll be interesting to see if anyone decides they want to be all-electric, and thus just plain start removing components like the gas tank or gasoline engine from the car. Or even leave everything in place, but fully drain the fuel tank and just leave it empty and dry.

yes, but won't the engine be used for a/c and heat, at least most the time? or at least balance the drain from them. but it would be something to see if a cali car got all that taken out, just to see how far the battery could go then. guessing it could be as much as 400-500lbs?

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The mileage for the Volt is going to vary so greatly, and the cost to operate it in EV mode will vary just as greatly from state to state, that this whole idea of applying a miles per gallon rating to it seems simply absurd.

KWH ranges from 7 cents to 20 cents depending on your location.

I still have my doubts that the Volt will be as efficient as everyone claims it is. It is loaded down with an electric motor, batteries, gas engine, and gas tank. Everyone thought hybrids would be super efficient when they first came out too, and it was proven that they could be. But when real drivers got their hands on them in real world conditions, the mileage was much less.

By figuring out what the average driver will do with the Volt, the EPA has declared that 230 mpg is reasonable. Weber said, "The number is in the ballpark, it is not unrealistic.

"in the ballpark" and "declaring 230 mpg as reasonable" are things that auto magazines should be doing, not the EPA as it gives a vehicle an official rating of any kind.

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KWH ranges from 7 cents to 20 cents depending on your location.

We're at 4-5 cents per kwh here. :neenerneener: Lots of hydro 'round these parts.

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I still have my doubts that the Volt will be as efficient as everyone claims it is. It is loaded down with an electric motor, batteries, gas engine, and gas tank. Everyone thought hybrids would be super efficient when they first came out too, and it was proven that they could be. But when real drivers got their hands on them in real world conditions, the mileage was much less.

I remember how the hybrids (And Toyota in particular) were villified for using the very EPA estimates they were forced to use by law.

Fast forward to 2009 and GM is willingly quoting only part of a draft standard, without any background info, as run on a pre-prod model and knowing full well that while flashy, it is pretty meaningless.

As we get more information it is also geting more apparent that GM is stacking the deck when they talk about "up to 40 miles". Can I listen to the radio?

In an attempt to mitigate the future FOG anti-media rant:

After this spectacle, we should EXPECT a backlash when consumers take their Volts for long highway or city drives and find they actually get 30-40MPG. GM made a CHOICE to trumpet this 230MPG number. The 20-30MPG variation of the Prius under the old EPA standard is going to seem like nothing compared to the Volt's 200MPG variation.

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So if it has a 10 gallon fuel tank, I'll be able to go 2300 miles on a single tank of gas?

I don't think so.

This MPG rating is completely dishonest. I know if a gas powered car is rated at 30 miles to the gallon and it has a 10 gallon tank, it will go 300 miles on a full tank. The Volt needs to be rated that way as well. The problem is that the real mileage might be closer to 40MPG. Who would spend $40k on a compact eco car when they can get a Prius with better mileage for less $?

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So if it has a 10 gallon fuel tank, I'll be able to go 2300 miles on a single tank of gas?

I don't think so.

This MPG rating is completely dishonest. I know if a gas powered car is rated at 30 miles to the gallon and it has a 10 gallon tank, it will go 300 miles on a full tank. The Volt needs to be rated that way as well. The problem is that the real mileage might be closer to 40MPG. Who would spend $40k on a compact eco car when they can get a Prius with better mileage for less $?

Thats also a somewhat dishonest way of looking at it because most people wont drive a Volt much further than what they can get on an overnight recharge.

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GM needs to be up front with people and explain that the Volt is ideal for those who commute less than 40 miles each day. And if they drive a significant amount more than that, sell them on an alternative option that gets better highway mileage. The bad part is, that alternative option doesn't really exist yet.

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They're also going to have to make sure they remind people that if they want to use no fuel, they need to plug it in nightly. I know a lot of people (myself included) who dont pay attention to how much juice their cell phone has, will they be different with their cars knowing that not plugging it in wont necessarily strand them?

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Just finished an interesting read from Dr. Jeffrey Friedberg - a former Head of MIT Nuke Dept. He said that if world consumes energy at a rate of 500 Quads (1 Quad = 1,000 Giga Watts), and the entire system went nuke with assuming automobiles on plug in capability, the known nuclear fissile fuel is enough to supply for 20,000 years. That is of course if all the plants were breeder reactors.

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Just finished an interesting read from Dr. Jeffrey Friedberg - a former Head of MIT Nuke Dept. He said that if world consumes energy at a rate of 500 Quads (1 Quad = 1,000 Giga Watts), and the entire system went nuke with assuming automobiles on plug in capability, the known nuclear fissile fuel is enough to supply for 20,000 years. That is of course if all the plants were breeder reactors.

1 Quad makes Doc Brown's 1.21 GW Delorean sound like a toaster. I wonder how long will the fissile fuel last if we all switch to driving those? ;-)

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1 Quad makes Doc Brown's 1.21 GW Delorean sound like a toaster.

I'd love to have a toaster in my kitchen that could only operate on a bolt of pure lightning. That's damn manly.

Edited by whiteknight
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GM needs to be up front with people and explain that the Volt is ideal for those who commute less than 40 miles each day. And if they drive a significant amount more than that, sell them on an alternative option that gets better highway mileage. The bad part is, that alternative option doesn't really exist yet.

That, and if you drive much less than 40 miles (or apparently 32 miles city) the Volt is not right for you as you will be paying for a lot of battery that you don't typically use. (e.g. if you drove 20 miles/day the Volt wouldn't use any gas, but a Prius which is ~$20,000 less expensive would use less than 150 gallons/year).

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