Toyota: Volt is 15-20% less efficient than Prius PHV

Even if it's in a different language, would you happen to have the link to the original article?

I searched Google News (English) for combinations of words to find any similar articles, and I found none yet. I found one article of a university that intends to compare the two vehicles once they are able to get their hands on the vehicles. I would also assume that Toyota would need a Volt in their possession before they can perform a true comparison. None the less, I am still interested to see your article. Thank you for sharing.

News.Google.com search of "Volt Prius PHV" .. http://news.google.com/news/search?aq=f&pz=1&cf=all&ned=us&hl=en&q=Volt+Prius+PHV

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So, we should really expect 40 mpg Volt. May be the extra 1,000 pounds reduces that to 30-35 mpg we will see.

 

Thank you, the 15-20% efficiency number is interesting.

I do not have a general purpose model and 'efficiency' is a difficult term unless we have the before and after definition along with the units. But if we were taking 'tank-to-wheel' efficiency, the conversion of liquid fuel to distance, this could be right:

• What is Volt 'range extender' Atkinson, Otto or some mix?
• Is battery used as 'range extender' throttle?
• Is the ICE-to-wheel mechanical path real?

What it really takes is having a Volt to test and the first models won't be in public hands for another month or two.

Bob Wilson

 

The content of the statement was not clear if he was referring to the Volt's CS mode or the EV mode.

PHV Prius has usable 3.5 kWh battery energy. 14 miles EV range was derived by 250 wh/mile. If Volt use the same energy consumption, 8 kWh comes out to 32 miles EV range. Due to Volt's additional weight, if you subtract 20%, you have 26 miles EV range.

 

15-20%:

Always ?
Overall average ?
or .. a specific test condition (most likely)

Then you end up with marketing weasel statements like "up to 20 less efficient."
I think we all understand the obvious, that ICE output direct to the drivetrain is more efficient than incurring conversions losses by shunting the energy through a genset and battery and out again -- even before talking about relative ICE efficiencies.

The problem arises in my mind however when the serial drivetrain has the option to be more or less efficient and the designers choose certain control logic for performance reasons. At that point we have an apples to oranges comparison. I am not defending the Volt -- I personally find much to dislike in the design, but this is different than jumping to conclusions re: HSD vs serial power train designs.

I admit I am jumping ahead of the gun here, but my strong guess is that a large fraction of ICE output in CS mode ends up going through the battery so that 80+ kw max power is always available, avoiding the situation all Prius drivers experience of puny power when the battery is tapped out. Choices, choices. GM is hostage to its own 'power to be free' marketing for the past 40 years, while Toyota can sell a car that has power without compromise 99% of the time.

 

Volt has 3 clutches (I believe 2 dry and 1 wet) plus a PSD. With the right combination of clutches engaged, the gas engine can output power directly (mechanical path) to the wheels. The last we heard, it will not use that mode to avoid Prius patent.

The fact that Toyota referred to the Volt as "series hybrid" was, I assume this direct power output mode will not be used in Volt. Otherwise, Volt would become a series-parallel hybrid just like Prius.

15-20% hit could be due to the conversion loss nature of the series hybrid. Volt ICE is said to run on Otto cycle. Atkinson cycle of PHV Prius has about 15% efficiency advantage but with larger displacement (1.8 liter vs. 1.4 liter).

I have to say nothing is conclusive because there isn't enough information and there are too many variables.

 

The bottom line is I wouldn't believe any estimates of the volts efficiency until we get it in public hands.

For your questions though the first gen volt
1.4L Otto range extender with some but not optimized for efficiency battery charge and discharge.
There is a real mechanical path but it is not used to provide direct power from ice to wheels according to gm. The generator motor is used sometimes for regen braking and for supplying power, but the software does not apply ice power while it is doing these tasks.

 

Actually, the Volt has no clutches and no mechanical connection from engine to wheels. The engine is just a generator.

I can't understand why GM chose to put in a low efficiency otto cycle engine (maybe 28% peak efficiency) when they could have easily put in a higher efficiency atkinson cycle (35% efficiency) engine. Presumably the Gen2 Volt will address this?

 

IMHO - the problem with the Volt is the serial Gas-to-Electric.

Gas is a very POOR choice for making electricity, the RPM is too high, you need gearing to make good torque.

Within the same space, a small Diesel / generator system, would have boosted efficiency tremendously. But GM wanted to re-use an existing engine and the plant that makes the small engine - a bad compromise.

I have a trucker friend that has a small generator that taps into his 250g diesel tank, that he uses when he parks at night in a truck stop w/o electricity. Costs him peanuts in fuel to operate, not noisy, and provides plenty of juice.

In any case, going from Kinetic energy to Potential energy to Kinetic again is a major loss. At least the Prius uses Kinetic to either move the car or recharge the car, or both.

The only thing better than the HSD, technology wise, is an efficient diesel generator or turbine generator, again, purely for torque.

Then again, this is just a G1 car...

 

Then again, this is just a G1 car...
That is most important thing to remember
Everything has to start at a G1 and hopefully gets better

 

This is my source. What is yours?

I also don't understand as well. Atkinson cycle produces less emission too. I was hoping they use HCCI engine when I heard of the Volt back in 2007. I still hope it happens in Gen2 Volt.

 

Prius was once Gen1. It was priced at $19,995. It got bigger, faster and better. The price remained about the same (considering inflation).

Volt Gen1 is priced at $41,000. Will Gen2 be less expensive? If it is, Gen1 owners are screwed with their resale value. Leasing is best with the Volt.

Perhaps, Gen2 Volt may make sense for those looking for ownership.

 

Yea, this is especially puzling as in the Volt vehicle architecture, the Atkison configuration does not require variable valve timing...

 

Thanks for the link. Based on my understanding, using Google translate, I think he is comparing the efficiency of the vehicle when it is operating purely as a hybrid (EV range excluded). The Prius operates as a normal Prius HSD, with 51mpg. Whereas, the Volt operates as a series hybrid, with ~40mpg.

If we factor in the EV range, with the Volt using zero drops of gasoline during the first ~40 miles versus the Prius PHV getting ~13miles, we should be able to create a graph in which the two vehicles cross (or use a polynomial).

13+51x = 40+40x ===> x=2.45

13+51(2.45) = 137.95 and 40+40(2.45) = 138

So, if you drive less than 138 miles between charging, you are better off with a Volt.
If you drive more than 138 miles between charging, you are better off with an HSD.

Feel free to correct my math and/or refine it.

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Rybold, you cannot tell from the article if CD, CS, or combined fuel economy is being talked about.
""הפתרון שמציעה שברולט עם הוולט, פחות יעיל מהגרסה הניתנת לטעינה של הפריוס ב-15% עד 20%", הוא אומר, בהתייחסות לבחירת היצרנית האמריקנית בשיטת הנעה שונה, שבה מנוע הבנזין משמש באופן בלעדי לטעינת הסוללות, ואינו מניע את הגלגלים."

The Toyota rep says "Chevrolet's Volt solution is 15 - 20% less efficient."

 

"by 15% to 20%," he says, referring to the American manufacturer to select a different propulsion system, in which the gasoline engine used solely to charge the battery, and drives the wheels."

You might be right, but I tend to believe he is referring to the series-hybrid versus the HSD here.

 

maybe that's the Scottish version


clett
Senior Member

Join Date: Jul 2005
Location: Scotland


Seriously though ... can ANYONE make sense of CAFE mumbo jumbo?!? Some charts show Honda with the highest fleet mpg average, while (laughable) GM is higher on others ... while Lotus is higher on still other charts.

First - read back over 2004-2007 cafe mpg & you see that over-all average fleet mileage is FAKED!! You find GM's and other's land barges being made to run on flex fuel that NO one virtually uses. Why? It's got poorer mileage! The math permits only the gasoline portion to count towards mileage. So if you ran a 50/50 flex fuel mixture (1/2 gas 1/2 alcohol), the fake formula lets you claim that you doubled your mileage. So the 14mpg land barge thus gets 28mpg because it only burned 1/2 a gallon of gasoline. The 50/50 mixture is simply for explanatory purposes, but it lets you see how bogus the formulas are due to B.S. manipulation.

Second - Manufacturers don't have to count their land barges (big SUV's, pickups, etc) into their fleet formulas. Why? Just because they weigh over 6,000 pounds?

Sadly, every manufacturer is panicked about higher mpg standards if ALL their products get equal weight, and they historically fought hard to keep CAFE standards at status quo. Doesn't that say volumes? Even now, California's oil lobby is fighting to over-turn legislation that will require a tax that'll raise fossil fuel prices, with the money going to renewable fuels development. The oil lobby is spending TONS in fear add campaigns to overturn this legislation, claiming how the weak economy will loose jobs and everything will collapse if we don't overturn the renewable legislation. It's nearly impossible to fight their multi billion dollar lobby. As for the Volt? Why doesn't GM act with true transparency, IF in fact its mpg is decent in CS (charge sustain) mode. IS the Volt 15% less efficient than the Prius' traditional HSD? Man, that'll be one of the biggest acts of pulling the wool over the public's eyes that GM has ever pulled off. I hope it's not true.

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