How will the Chevrolet Volt be better than a Toyota Prius plug-in hybrid?

I should have stated that I don't see these discussions as useless. They are indeed informative. When they start to degrade into a my $&#@ is bigger than yours type of argument the value is lost. I guess my point was to encourage the discussions but on friendlier terms since we are all on the same team.

 

The 1/0.15 factor is included for a number of reasons, the main one is to assign utility to the energy sources. As I mentioned the political reason both parties agree with CAFE standards is that consumption of oil harms the country. There is wide agreement that high oil use is not sustainable, and high importation hurts both economics and national security. Polution from cars especially in the city is also a problem with reliance on gasoline, just not so much the prius.

Different energy sources are not created equal. Electricity can be created from a wide array. You may choose as your yardstick simple efficiency, but for most Americans that is not a valid measure.

Most of us choose other measures. I'll leave you with this discussion about gas versus electricity.
http://priuschat.com/forums/environ...ehicles-simply-move-tailpipe-coal-answer.html

That is only valid if your measure is fuel to wheels efficiency, and ignore regional differences in power generation, and personal choices of those buying the cars. As I said I find the 94mpge number low when you include things like national security, sustainability, pollution, and economics into account. The car and driver article used a cost of car argument which IMHO is more valid than a efficiency argument.

But do we care about the efficiency of evnow's hydro power, or my wind? Or can those using it decide sustainability is more important than efficiency? What about the future when 60% CC natural gas replaces 37% gas turbines because of night consumption. Do we need to only look at today's average grid? Then ignore future scarcity of gasoline?

 

EPA said a gallon of gas has 114,984 BTUs so if you convert that energy to electrical energy (mathematically), you get 33.7 kWh. So they said 33.7kWh is equivalent to one gallon of gas.

Gasoline engine is very inefficient. Even Prius engine is capable of extracting 38% of the energy and get 50 miles to a gallon.

However, the battery and electric motors are much more efficient. Volt can go 94 miles with 33.7kWh. That's where 94 MPGe comes from.

These two numbers (50 MPG and 94 MPGe) are pump(plug)-to-wheels efficiency. It measures from your gas pump(plug) all the way out to the wheel. Volt's battery and electric drivetrain is superior (71% vs. 38%) in this case.

Those numbers don't include how we got a gallon of gas or 33.7kWh of electricity (well-to-pump). That's where the DOE formula comes in handy. DOE said electricity generation and transmission is 30.3% efficient. Petroleum refining and distribution is 83% efficient. In this case, gasoline is superior (83% vs. 30.3%).

If you take both into consideration, you get well-to-wheel. That's basically getting the oil out from the well -> refinery -> gas pump -> Prius -> wheel. For the Volt, coal mine -> power station -> transmission line -> Battery -> wheel. I used coal as an example because that's where majority of our electricity is from. This is the worse case.

As gwmort pointed out, this still doesn't include oil well exploration and drilling. The same for coal mines and other sources used to generate electricity.

 

94 MPGe is fine as long as we acknowledge that it doesn't include 30% electricity generation+transmission efficiency. Just don't claim Volt is more efficient because the number is higher.

DOE's formula should have already taken account of electricity generation efficiency from various energy sources. As they say, YMMV. If you live in Niagara Falls, Volt or EV would be awesome. If you live in Hawaii, it is the complete opposite. To compare, we need to take the average.

I too agree that as we clean up our grid, become more efficient and petroleum become more scarce, DOE should update the numbers in the formula. As of right now, the real equivalent MPG for the Volt is 34 MPGe when powered by average electricity. Again, YMMV.

 

Here is the to-date data for my Volt for another data point (4/22/11 to 10/24/11):

7570.7 total miles, 6544.5 EV miles, 1026.2 gas miles (86.4% electric)

Gas used = 28.69 gallons
Electricity used = 1782.4 kWh

Gas = 35.8 mpg
Electric = 3.671 mi/kWh or 27.24 kWh/100mi

Gas miles are primarily highway miles on mostly one long trip and electric miles are a combination of highway and surface streets. My overall average electric rate (based on total monthly bill amount) is $0.11/kWh. Electric usage for Volt charging is logged with a TED 5000 on the charging circuit. My last gas purchase was on June 7th (3.08 gallons).

 

It's nice finally seeing real-world data like that. It makes me think the push to reach a wider audience is going to come from within, where current Volt owners grow frustrated from watching the market being gobbled up by GM's own efforts... ECO, Diesel, eAssist... in addition to the plug-in hybrids from Toyota & Ford.

There's only a finite amount of time available to establish the market and substanitally lower the price of Volt to make it competitive. Getting a serious foothold in middle-market is much more of a challenge than most enthusiasts have come to realize.

People like me get ridiculed for warnings, but history has already pointed out failure to move quickly can result in a very rude awakening.

Ask yourself what mainstream buyers are really attracted to and how much they are willing to pay for it.
.

 

We can agree there, and I never made that claim. The 94 MPGe is equivalent epa efficiency from power from the plug. It makes no attempt to figure out utility of efficiency from the fuel source, as mpg never did. If you add the average grid efficiency versus the refinery efficiency the relative number will get lower, but I don't think these are the most important things.

32.8% seems quite low, especially if we consider average world wide coal is around 35%. Now US coal is less efficient, but natural gas in the us is much higher, and I have no idea how they handle nuclear, hydro, or wind. It may simply be an old fossil number. Agree source is important, and there is much more to utility than efficiency. Certainly even without considering externalities price needs to be considered.

I

I really question that as average electricity, and it needs a giant foot note which reads, if efficiency is all that matters we need to shift all electric to combined cycle natural gas.

 

The Volt was designed to mainly run on electricity and have that sort of electric powertrain "feel" (ie. quick torque, smooth, quiet). The Volt does not recharge the battery (except keeps small buffer) even when the Volt is running in Charge Sustaining (CS) mode because they want you to charge at home. Even in CS mode the car was *designed* to STILL give the electric powertrain "feel". This is all mentioned in articles, interviews, presentations etc. It was a specific design goal.

The Volt designers ALSO had a unique problem. What about the owners that have a driving pattern that allows them to mainly run on the battery/electricity and hardly ever run on gas. Doesn't gas go stale? Also what about the vapors in the typical tank?

Special Gas Tank Caters to All-Electric Chevy Volt Drivers
Special Gas Tank Caters to All-Electric Chevy Volt Drivers

Why the Volt requires premium gasoline? (Hey if you used 12 gal in 7000 miles in 7 months how much extra did that cost you?!? 12*$0.30=$3.60 = big whoop)
Why the Volt Requires Premium Gasoline

 

How about use gas for very high power demands for a simplier solution?

 

This is a problem toyota tried to address with the bladders, then because of problems with them changed the design in gen III. The numbers game though will have a prius do much better on the test.

I don't think it is a problem that the volt uses premium, but the ICE is not as efficient as it could be. This makes the explanation sound like BS. Perhaps on the 2013 model they will be flex fuel and increase efficiency. GM used an off the shelf engine that was not designed to be efficient and boosted hp by using premium.

 

Your last sentence is far from the full story of it. They tuned it in many ways that is different.

Have you read the SAE "2011 Chevrolet Volt Development Story" or the "Chevrolet Volt: Charging into the Future" book. While it is true they used an existing engine in their line up because of development time it is not used in a standard way...not by any means.

For example:

Judged by its individual components, Volt’s 1.4-L four-cylinder combustion engine resembles its nearly identical cousin in the Chevrolet Cruze. It has got an aluminum DOHC head with four valves per cylinder. Its hollow-frame iron cylinder block is a thin-wall casting, making it nearly as light as a comparable aluminum block while retaining iron’s inherent strength and noise-damping qualities.

Derived from GM’s global Family Zero of small-displacement gasoline inline triples and fours, the Volt engine was designed for efficient operation. Its hollow camshafts are manipulated with two-step variable electrohydraulic phasers. Its lubricant is distributed through a variable-displacement flow-control oil pump to reduce parasitics under light load conditions. The thermostat is map-controlled.

There is no starter motor; the car’s generator motor handles that task. And the engine’s undersquare bore/stroke promotes good low-and mid-range combustion efficiency, particularly in turbo versions.

But a closer look, and a drive in the Volt, show this is not a typical Family Zero unit (nor is it turbocharged). It is governed to 4800 rpm, the speed at which the engine typically runs when the Volt’s powertrain management controller calls for the generator to engage.

There are unique control algorithms (Engine Maintenance and Fuel Modes) that start the engine every 45 days and run it for up to 10 min, in case the owner has been driving solely on battery power, to lube the internal surfaces and run the diagnostics. It’s an off-the-shelf engine almost invisibly modified to serve the Volt’s series-hybrid operating mode.

“With our propulsion architecture, the role of this engine is completely different from any other car in the marketplace today, or from what we currently know is coming,” said Pam Fletcher, GM’s Global Chief Engineer, Hybrid and Electric Engineering. She noted that the engine is calibrated to operate “completely differently” than engines in the Cruze or other conventional powertrains.

“We did all of our development around maximum efficiency,” noted Fletcher, who also serves as the chief engineer of GM’s plug-in-hybrid program. “It was a different game than the one we usually play in balancing power and efficiency, because this engine’s really set up to run like a generator.”

The engine’s role in Volt allowed the powertrain development team many degrees of freedom for calibration, as the car’s electricgenerator and traction motors deliver positive and negative torque at a wide speed range. The engine thus does not respond directly to demand from the driver’s right foot as in a conventional vehicle, because you are effectively driving the traction motor, not the ICE.
<snip>

 

So we see things about a lower governor speed and lack of a turbo. Neither of these things increase efficiency. It has different algorithms which may make it run more efficiently, but we do not know. It definitely needs different algorithms to make sure the lubricant and gas won't go bad, and that it does.

GM had said they used the engine to cut development time. This I believe. To boost maximum efficiency using a smaller turbo generator engine as originally in the show car. If we look at other hybrids trying to be efficient use Atkinson cycle valve timing. The prius adds EGR. The mazda skyactiv uses electronic valving to move between atkinson and otto cycling, DI, and higher compression to achieve better fuel economy. I am sure gm can use at least valve timing and perhaps DI and/or EGR to increase efficiency. As few gasoline miles as you drive it hardly matters though.

 

It is a little more complicated than efficiency. Then needed to blend the goal of efficiency with Noise, vibration, and harshness (NVH). No doubt they could have made it run differently (more WOT as an example) BUT the goal was still to give an electric feel during CS, get decent MPGs, and make the car pleasant since you may have just got out of Charge Depleting (CD) mode where there was ZERO engine noise. Hope that and the below help explain more how complicated the integration was. I sincerely appreciate it as a "end-user". It is very smooth. At highway speed you can't tell when the ICE/GG turns on during the CD->CS transition ... except the dash change from a battery to a fuel pump <grin>.

SAE article:

Integrating the ICE with the car’s electric drivetrain consumed much development time, Fletcher said, with multiple iterations of control code developed and tested.

“We put an enormous effort into making the ICE pleasant and unannoying to the customer when it comes on,†she said. “We could have chosen to operate it at one fixed speed and load, or perhaps a couple fixed speeds and loads, where you have the balance of maintaining battery charge and not always dissipate charge of the battery, and pick a point that’s very efficient—a very specific BSFC [brake-specific fuel consumption] ‘island.’ But such a powertrain would be very awkward to drive.

“We could still make the propulsion system smooth and responsive to driver input, but from all the driver’s sensory perceptions it would be terribly awkward,†she said. “We recognized that as being very important. So we made a lot of choices and spent a lot of development to make it a comfortable, smooth, quiet, pleasant-driving vehicle as well as making efficiency a big priority.†Algorithm and control development was a main focus of Fletcher’s team, as was working with its colleagues developing the clever new 4ET50 transaxle, based on GM’s Two Mode hybrid technology.

“The engine operates at or near WOT [wide-open throttle] pretty much all the time that it’s on,†she said. “There are a few unique conditions where it doesn’t. One of those cases is we do have an ‘idle’ condition, where we run the engine at less than WOT. To do this, we had to find an rpm point that’s pleasing from an NVH standpoint.â€

 

Well despite the £33,000/$52,700 price tag in the UK, the Ampera/Volt is getting some good prerelease reviews;

New Vauxhall Ampera Hatchback Car Review | Parkers

 

It has variable timing according to the quoted article. A new engine not having it would be odd at this point. Same for EGR, they have long been used to control cylinder temperatures and NOx emissions. My 1996 Taurus had an EGR system. Would does the Prius do with it that is different?

I do agree they can do better, but cost and time constraints were a factor. The Audi A1 Etron claims manage around the same CS economy as the Volt with a 254cc Wankel rotary.

 

I agree with scott that one goal was low NVH, and they seemed to have done that. There is a big difference between vvt and atkinson valve timing. The prius, FFH, HSH, make the intake valves open much later to reduce pumping losses.

An EGR system puts cooled exhaust gasses back into the engine to allow for more efficiency and less polution at lower fuel to gas (air + exhaust) systems. Yes they have been around for a long time, but this adds to the efficiency band at lower power levels.

The mazda engine uses DI, and gm originally had talked about using DI in the cruze engine but cut this efficiency feature to cut cost.

As I said there were numerous goals, but in the case of the volt engine but mazda skyaciv and the prius engines were designed to run more efficiently. GM traded off things like cost, development time, and NVH. They do have more development time and adding a couple of hundred of dollars to cost to make the engine more efficient might make a good trade off.

 

I'd like to see more way outside the box thinking, like the micro turbines Jaguar is investigating for a PHEV supercar prototype.

 

Heater??? In Florida???

Safest motorcycle you'll ever ride in/on. BTW, my Xebra has a powerful heater that takes about 10 seconds to start putting out heat. As for A/C, cars never used to have that.

See, it's all a question of lifestyle choices. Americans today CHOOSE to live far from work, then they CHOOSE to drive gas-guzzling behemoths. I made the choice to sacrifice a little bit to drive electric.

A Corvette is a nice-looking car, but to get the acceleration of a Tesla Roadster you'd need a Lamborghini or the very top, most expensive Porsche. Or another Tesla Roadster.

Of course, some people enjoy operating a manual transmission and hearing the gawd-awful bone-shattering roar of an unmuffled engine, and you miss out on that with a Tesla because the torque curve of the motor is so wide it doesn't have any gears, just smooth acceleration from zero to 125 mph (a speed I'd never get anywhere near) and nothing to make any noise except the tires on the pavement.

You're the one who brought up the chocolate rabbits, for what reason I cannot imagine. But I'm glad you liked the ramble.

 

Would a 254cc engine fall within emission control legislation/requirements? My understanding is that wankel engines struggle on their emissions. I also understand that engines under 300cc are exempt from US emission regs - I could be wrong on that.

 

According to GM, a Corvette Grand Sport starting at $55,000 will do 0-60 mph in 3.95 seconds. The Corvette Z06 starts at $75,000 and has the same engine as the Corvette ZR1 that Wikipedia says will do it in 3.3 seconds.




[ame=http://en.wikipedia.org/wiki/List_of_fastest_cars_by_acceleration]List of fastest production cars by acceleration - Wikipedia, the free encyclopedia[/ame]