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Detroit, 3:46 AM
Tue Nov 10
27 posts in the last 24 hours
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08/12/09
23 is pretty good! Isn't that what an Acadia gets...
08/12/09
Now here's a thought. Just a little experiment. Let's suppose we've got Joe Typical. He's not the guy the Volt is aimed at, he's the guy the Malibu was designed for. But for whatever reason, the poor bastard is behind the wheel of a Volt for a month. Maybe he's Joe Birkenstock's cousin, and they're trading houses for the summer.
So Joe Typical is driving the Volt. And he doesn't give a northbound rat's southbound end about plugging the damned thing in. He wants a Slurpee, so into the car he gets, and down the street he goes. And when he gets back, he parks it. There shall be no plugging.
In Joe Typical's operating regime, what kind of mileage will the Volt deliver? I think that's a truer representation of the vehicle's actual fuel economy. Dragging in the outlandish claims of a PHEV's fuel economy too often makes it look like those first magical miles, when the batteries are still hot from the Browns Ferry plant, are free. And they aren't.
08/12/09
08/12/09
If you drove as gingerly as possible, and took the Volt on a 300 mile road trip, your economy would be nowhere near the advertised numbers, it would be much worse. By the same token, if you drove it 10 miles to work and home every day, charging it completely at night, your economy would be nowhere near the numbers advertised. In fact you wouldn't use any gas at all.
The question is, how do you express all that as a single number? The answer, apparently, is "poorly". The EPA test is extremely poor at this. Yet the result of the test has a significant financial impact on the company making it, the person buying it, and maybe even the schlub 10 years from now trying to trade it in as a clunker.
It isn't about blame and fault, it's about a ridiculous standard and the ridiculous consequences of it.
08/12/09
If you read the SAE spec for computing energy usage and the DOE procedure computing equivalent mpg, you'd see you are totally incorrect.
The SAE spec instructs you how to compute the amount of energy an electric car uses to complete the EPA cycle. The DOE procedure instructs you how to convert this energy into an equivalent mpg number for CAFE purposes so that these types of vehicles can be included in a manufacturer's fleet average.
08/12/09
[gm-volt.com]
"If you drive under the EV distance its infinite."
They are emphatically not reporting MPGGE.
08/13/09
08/13/09
08/13/09
Correct. But GM cannot make that claim for an EPA approved mpg number because the test procedure specifies how to convert energy used to an equivalent mpg. The EPA needed to do this or a manufacturer could build one EV and their CAFE number would become infinite. using the DOE and EPA procedures, the number comes out to 230 mpg.
08/14/09
In reporting 230 MPG, GM DID NOT CONVERT electrical energy from the batteries to equivalent gallons of gas. They made this clear on their own page.
They are not reporting 230 MPGGE, nor are they claiming to. They are reporting an average distance of 230 miles for each gallon of gas burned, supplemented by recharging at night.
I do not dispute the accuracy of that number-- that the average user will be able to go 230 miles for every gallon of gas they burn, while also recharging every night. I do, however, view the claim "230 MPG" to be incomplete at best, and misleading at worst.
I used the numbers you quoted and 5th grade math to calculate 61.535 MPGGE ONLY FOR THE EV OPERATION-- pure electric, gas motor shut down. GM has stated explicitly that this is what the car does for approximately the first 40 miles.
I never claimed to be able to calculate the MPGGE for the entire city cycle-- the number GM/EPA needs to report.
I used 9th grade math to determine the sort of mileage (true MPG) the volt would have to achieve when operating as a hybrid for a couple of hypothetical total lengths of the testing cycle in order to report 230 MPGGE for the cycle. The conclusion is that 230 MPGGE is not a reasonable claim, because the car would need to make truly astronomical mileage (true MPG) when operating as a hybrid.
I further used 5th grade math to show that, regardless of the length of the cycle, the hybrid phase would have to have a mileage of MORE than 230 mpg to achieve the overall 230 MPGGE.
What number below 230 MPG do you envision combining with 40 miles of 61.535 MPGGE performance in order to calculate an overall 230 MPGGE?
That is a moot point, though, since we have now seen the GM page linked to previously where GM admits that, in reporting "230 MPG", they did not bother accounting for the power consumed in charging the batteries however many times they'd be charged in those 230 average miles.
MPGGE is a much more useful metric than GM's incomplete accounting. We don't know what the car's MPGGE rating will be, but we can be asssured it will be below 230 MPGGE. If the statistically average user in GM's calculation recharged the batteries several times in those 230 miles, the official number may be well below 230 MPGGE.
08/14/09
Oh, I HAVE paid attention. The only link I've found that you posted is:
[gm-volt.com]
which is NOT GM's own page but a web site run by a physician. If you've posted a link to a real GM page, please enlighten me.
On GM's (Chevy's) page:
[www.chevrolet.com]
they clearly state that they expect the EPA city rating to be 230 mpg. They have to follow the EPA's procedure to calculate this number and that's what it comes out to be, whether you approve or not.
And they are NOT "reporting an average distance of 230 miles for each gallon of gas burned, supplemented by recharging at night." They are reporting what the Volt achieved on the EPA city cycle calculated per preliminary EPA rules for extended range vehicles. This is a pretty clear concept so I find it hard to believe you're having so much trouble understanding it.
Again, the 230 mpg number GM is reporting is what the Volt achieved on the EPA city cycle calculated per preliminary EPA rules for extended range vehicles. That's all.
And once more, PLEASE, stop attributing numbers to me which you have made up. You keep using this 40 mile range which has no relation to the EPA city cycle. I'm guessing you still haven't read SAE J1634.
And when you state you are calculating numbers based on "a couple of hypothetical total lengths of the testing cycle" when you don't even know the true length of the cycle or what amount of energy would be used to complete those cycles, what you really are saying is that, I made up some numbers and then used 5th (9th) grade math to arrive at these valid conclusions."
I can't make you stop invoking my name in an attempt to provide some credibility for your bogus calculations so all I can do is, again, ask you to PLEASE stop attributing your flawed calculations to numbers you claim I supplied.
08/12/09
08/12/09
I will fault the EPA if their testing formula permits milage equivalents to be calculated on a basis that does not involve the supplemental engine for the city test. Nor could I support a rating system that converts kWh to gasoline gallons on the basis of current retail pricing.
GM has placed itself in a risky position. They must now meet or exceed their unfounded claim for the performance of the Volt, or risk being seen as failures. If they only get certification for 220 mpg people will say that they've fallen short. Similarly, if the performance claimed can't be equalled by the public over a wide range of conditions, there will also be a backlash. In situations like this, it is far better to underclaim and then overperform.
08/12/09
08/12/09
if i push it 95% of the time...
08/12/09
08/12/09
FWIW, Tesla's own calculations show ~250 MPG equivilant, not using the EPA figures, which jives with what GM is claiming here.
08/12/09
It sounds more like GM is claiming numbers based on a conversion factor of electric power to gasoline that's completley different from what the EPA actually uses.
That's it exactly. GM is using the following conversion factor:
8 kWh = 0 gallons of gas.
GM admits it here:
[gm-volt.com]
Of a user's "actual" MPG, they say "If you drive under the EV distance its infinite."
08/13/09
I see no where in that link where Larry says that GM did not follow the EPA procedure for calculating mpg,
08/14/09
No mention of the kWh form the wall charger.
"You go through this calculation that accounts for the fuel use and you come out with a number and the number is 230."
Again, No mention of the power from the wall charger.
"If you drive under the EV distance its [the number GM calculated] infinite."
Possessive pronoun aside, they would not calculate infinity MPG for any distance if they were accounting for the power from the wall charger.
"How about the petroleum equivalence factor (PEF), is that included?
There will be on the label itself an accounting for the gasoline equivalent of KWH used. That’s a separate conversion that will get melded in another way and is not included in the MPG estimate."
Meaning they didn't account for the kWh of power from the wall charger.
"So in summary, Nitz explains that the average Volt driver charging his car nightly can expect to burn one gallon of gas for every 230 miles traveled over time based on the behavior of a particular random population that was studied in 2001."
Yet again, the power from the wall charger is not mentioned.
The acronym MPGGE appears nowhere. I've quoted above the only place where "equivale*" appears in the post.
I misspoke when I said GM didn't do "that" in reply to your comment. I didn't catch taht you'd switched from claiming that 230 MPG really meant 230 MPGGE and that it was a reasonable number.
They're saying they followed the EPA's methodology, presumably for CAFE ratings. As I've been saying all along, if the EPA accepts "230 MPG", then I don't particularly fault GM for exploiting that loophole. I won't fault Toyota for doing the same when the prius gets plug-in capabilities. Or Tesla claiming 0 MPG.
I will, however, fault the EPA in that case. And anyone who pretends that 230 MPG tells the complete story.
08/12/09
08/12/09
08/12/09
08/12/09
She's a diesel.
08/12/09
08/12/09
The problem is keeping the walrus from taking it back.
08/12/09
08/12/09
My absolute favorite one, Dr. Phil on the TV and a cat watching, the cat asks, "Howd dey get Lolrus into a suit?"
And my wife answered, "Dey fills de suit wif squids and Lolrus jumps right in!"
08/11/09
08/11/09
That's nothing - I just designed a car that will get... a BIIIIILLLION miles per gallon.
08/11/09
*Millimeters Per Gazillion gallons of gas
08/11/09
08/11/09
08/12/09
08/11/09
08/11/09
That is so last year!
08/11/09
08/12/09