Does GM REALLY want to phase out the Volt?

That's my point. They both take hit under those conditions.

The other is that the charge time to replenish the current of a heavy acceleration event isn't of concern to the owners of plug ins. The Prius PHV, with the smallest pack, still has a charge time of over an hour. 14 minutes added on to an hour plus charge time isn't a big deal if you're watching TV, working, eating, or sleeping during that time. Taking time out of your commute to pump gas is the inconvience.

The heavy acceleration will lower the EV range, but it will also lower the gas tank range of the ICE.

Calculating the charge time do to a particular driving maneuver is nitpicking.

 

Well since I plug in and it recharges overnight, 14min is nothing. If I arrive home with battery left, which I do every day, the added 14min is not even a split second for me, its nothing at all.

Even if I had to recharge at work its trivial. (I don't recharge at work as I don't have to and then don't know the power source).

Time to generate even 1/4 cup of gasoline is a long time-- nature takes millions of years.

Your understanding seems flawed. More ICE torque exists at the wheels in the Prius split because it has to, that does not make it more efficient. The whole point of the power-split is that in many operational ranges the ICE has too much torque, so putting more of that on the wheels does not improve efficiency. And in other regions the ICE does not have enough, so the EVs provide the gap. The Torque from the electric motors torque is more efficient at low speeds and low-loads, even with conversion losses, ICE torque at high speed and high-load. The compound-split, with two gears between the ICE and the wheels, can use either mode, depending on which is more efficient. The real advantage the Prius has here is its 1.8L engine which is more efficient (but bigger/heaver than the Volt 1.4L), but allows more efficient (in BSFC terms) production of torque in the ideal region for 55-65mph ICE-based loads. In other words, its not the transmission, its the engine. That is also part of why the earlier 1.5L prius did not, on average, do as well in MPG even though it used the same transmission design.

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That makes no sense.. and even if it did, its not true. the ICE and MGb spin in the same direction in the Volt.
The following image shows how things connect in both prius and Volt



The Sun gear and ring gear move in the same direction.. so ICE and traction motor spin the same direction.


You might want to watch the video's on the Volt power train at (especially at 5:00-6:00 in the video)

 

That's just one example of when using gas is beneficial. If you drive fast (85 mph) on the battery, every minute of driving requires 40 minutes of recharging. At 75 mph, every minute requires 24 minutes. At 65 mph, every minute requires 17 minutes.

For high power and high speed, it is better to use the gas engine rather than lugging it around like a dead weight. It cuts down the refueling time, the need for expensive high voltage charger, extend the battery life, properly maintain the gas engine and eliminate the need for premium gasoline.

 

PHV offers a toggle button, allowing you to take advantage of the engine and save EV for later.

That will come in handy both for hard acceleration and for winter heating.

Volt's approach of forcing EV and excluding driver input is a scarifice, a missed efficiency opportunity.
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Even if its the top decile, since I'm not at the top of that group, I cannot be that exceptional. I'm not like
Marc whose stats for the first year were
Total Miles 18310.03
EV miles 17121.48
Apparent MPG 603.09
Gallons used 30.36

That is exceptional!

Or Dave and his wife (ecosister) whose pair of volts are charged from PV with stats of 97 and 95% EV, which just blow mine away

https://www.voltstats.net/Stats/Details/63
https://www.voltstats.net/Stats/Details/323

I may be above average, but I'm not exceptional. Realistically, though, if I could get away with 97% EV driving I'd be in a BEV.

Don't know where you live, and so we are not likely Neighbors. But my gas is mostly tar sands and I get no choice about it. If you live east coast, its more likely Venusan + Middle east. If Tx or CA.. well maybe your gas is a bit cleaner.

Why MPG(e).. because I can choose to be that efficient and be green. If one cares enough to buy a "green" car, might as well fill it properly with green electrons and hence (e)! If you don't like MPG(e), and just want to burn gas, and measure MPG, that is your choice.

 

The electric drivetrain is still more efficient when merging. It isn't missed efficiency opportunity. When it is cold enough the volt runs the ICE. You want a button though, that's cool I guess. I certainly don't mind.

 

This misses the broader point of why we have gearing in any car. We have gearing to match the power characteristics of the engine to the propulsion needs of the vehicle. Since we insist on doing inconvenient things like driving at different speeds and climbing hills, we can't use one fixed gear ratio and call it good. We need some way to vary the effective gear ratio between the engine and the wheels. This is the purpose of the power split device. It provides a method to vary the effective gearing while still allowing for some torque to be mechanically coupled.

Tom

 

Those are vehicle efficiency without the fuel production included. Those MPGe would rock bottom if you include fuel production efficiency of 39%.

You are the exception because you use wind powered electricity without carbon footprint. However, wind generators have 20-40% capacity factor so your total energy efficiency isn't 85 MPGe as claimed.

 

Something I hadn't realized until today when I was reading further on power-split hybrid transmissions is that GM appears to have the earliest patent which most closely describes what people think of as the Prius transmission.

Yes, Toyota has many patents beginning with US 5907191 filed on June 18, 1997 but it turns out that GM had already filed for and received US 5888588 titled "One-mode, input-split, parallel, hybrid transmission". GM's patent was filed on February 17, 1995 and issued September 24, 1996. The first Prius went on sale in Japan in 1997.

GM's patent describes a very Prius-like transmission (alternative embodiment 3) and several other variants. The engine hooks up to the planetary carriers and the smaller MG hooks up to the Sun gear, and the larger MG and the output to the wheels hook up to the Ring gear just like the Prius using a single planetary gear and no clutches.

Occasionally I see claims here that Toyota's patented HSD somehow causes GM to choose inferior designs for patent avoidance reasons. I noted the other day that GM has been selling bus and truck hybrid transmissions since 2003 that include an input-split path along with a compound-split path as part of a 2-mode transmission and hadn't been sued yet by Toyota. However, I hadn't realized GM's first patent along this design space was for a Prius-like one-mode transmission or that it went back to the mid-90's and proceeded Toyota's Prius transmission patent (at least as filed in the US).

Specifically, see column 11 on the PDF document page 19 with the sub-header "Description of a third alternative embodiment":

Patent US5558595 - One-mode, input-split, parallel, hybrid transmission - Google Patents
http://www.google.com/patents/US5558595.pdf

Notice how Toyota's patent included prior art citations to GM's patent but GM's patent does not cite any prior Toyota patents.

Patent US5907191 - Power output apparatus and method of controlling the same - Google Patents

 

Before calling out someone on flaw understanding, I suggest you read the document you provided in your post #131 (specifically page 19). 72% of Prius ICE make it to the wheels. Do you know many percent for the Volt?

The gearing is optimized for the most frequent power range. Over and under-supply of torque gets compensated by the electric motor.

At very high speed, Prius gas engine does oversupply torque and about half of the power goes through re-circulation to reduce the ICE torque. Even with that, it beats Volt's CS highway MPG by 20% (48 vs. 40).

Even the Gen II Prius with 1.5L ICE (came out in 1995?) gets 45 MPG on the highway. What is the BSFC for Volt's gas engine? We can compare it directly and that should answer where the inefficiency is.

 

You missed the point...

It's more efficient to use the EV for cruising than it is for merging.

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I would add more practical, on top of that.

 

Why? I would contend it is the opposite.

 

It always boils down to the same thing anyway.

Volt has a heavy dependency on the battery-pack. Making it smaller to offer an affordable model doesn't work well... efficiency plummets and that doesn't trim enough from the price.
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This statement doesn't seem to jive with basic hybrid car theory where the motor supplements the power and torque the engine sacrificed for efficiency. Situations like merging.

While there is merit to the blended approach of 'you got it, use it', the Prius PHV has a smaller battery and much shorter range. I think the battery also has a slower rate of discharge than the Volt's. The blended approach probably has some degree necessity to it do to these limitations.

Here is something I've been wondering about. If the blended approach is the best in terms of efficiency, why offer an EV mode? Those of us that got to play with the EV mode in the non plug in know using it too much can lower fuel economy, and after market plug in kits greatly reduce gas use with an EV mode. Why not just have the ICE kick in at lower speed, like 47mph, and the car just uses electricity for propulsion at lower speeds if the charge is available.

Charge times are a red herring. The Volt driver isn't going to be shivering out in the cold for another 14 minutes.

What is the hang up with premium gas? US premium is regular over in Europe and Japan. We'll never get a fully tuned Skyactiv-G, and other advance tech engine, with the improved performance and efficiency because of it. Premium fueled engines are, all else being equal, more efficient than a regular fueled one. The Atkinson cycle is efficient because of the long expansion/power stroke. Premium just allows it to be longer. The cost per mile is roughly the same. If the goal is to burn less total fuel, shouldn't we be using premium?

For the energy in, motors are most efficient at 75% rpm, and engines are at around 70% load. Which doesn't necessarily mean most efficient for distance traveled at those points. Heavy acceleration with either one will drop average 'tank' fuel economy.

 

75% of what? The maximum RPM as limited by drag in the motor? The RPM right before the motor explodes due to centrifugal forces? 75% of the cost of the motor? Honestly, where do you come up with a figure like that?

Electric motors come in a wide variety of types and configurations. Even with my background in electrical engineering and all of my theoretical knowledge of motor design, I wouldn't begin to understand how you could produce a single figure of merit like that. Perhaps if you state which motor you have in mind and what defines 100% RPM. Even then we would need to know the load characteristics.

This line of argument is getting silly. I suggest we get back to arguing over how many angels can dance on the head of a pin. I say 17.

Tom

 

Thanks, tom. I do understand, and your logic is fine but missing the point that the simple the simple input-split model in the prius has a smaller range of potential splits than a compound-split. (like a 3 speed vs 6speed range). Its a big part of why a prius cannot go above 62mph in EV mode.. the speed needed cannot be reached without overdriving the other EV motor. The compound split allows the EV motor to drive at full speed/power or the ICE or any combination.

 

Put another way, it's better use of the electricity supply available.

Look at the big deal being made about driving faster than 62 mph. The goal isn't absolute purity and you still get a substantial MPG boost anyway.

Of course, I have 4 different routes to work. 2 of them have a maximum speed of 55 mph. So, I don't see what difference going faster makes. And during the peak of rush, traffic slows down on the 70 mph route.
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Do you have any idea what you are talking about.. Capacity factor is not even related to the efficiency of the power used. (It is related to the cost effectiveness, but that's why its still more expensive than using old dirty coal-based electricity)

The net capacity factor or load factor of a power plant is the ratio of the actual output of a power plant over a period of time and its potential output if it had operated at full nameplate capacity the entire time.

So yeah.. wind does not extract all the possible energy it could and does not produce power at its nameplate capacity. But it still produces lots and lots of clean energy.. So much that in 2010 25Terawatts, of wind power were idled. (See 25 TWh of Wind Power Idled in 2010 in US – Grid Storage Needed | CleanTechnica)


Even if what idled was nameplate, assuming 20% capacity factor, that means that in 2010 wasted wind capacity, was 5 TW. Since Volts get more than 2.5m/kWh, so that is enough to drive Volts 13 Trillion (yes with a T) miles. So explain again why its more efficient to use Gas, when wind energy is just being idled.

And its not just Colorado.. wind energy can be purchased in the majority of states. With many state's REC tracking in many states you can even select the type of renewable energy you want.

 

I read the whole document, did you? Nothing, on p19, compares the efficiency. (its a backup slide). Page 10 of http://www1.eere.energy.gov/vehicle...w_2010/veh_sys_sim/vss010_rousseau_2010_o.pdf
concludes that dual-mode compound allows more efficient "electro-mechanical power path" and improved "Electro-mechanical capacity"


The volt's ICE->wheels depends on the mode. Of course most of the time, the ICE is not engaged at all so the EV motors can be more efficient in EV mode.

In CS-mode the power split its 69%. You can see calculations on the split at

Solving the Volt

Don't have a definitive BSFC for the Volt. There is a hypothesized (but not confirmed one) in this thread
VOLT MPG estimate using BSFC maps

The best BSFC operating point is about 235g/kWr, and that is narrow, most of it is at 240 or higher. As I recall the 1.5L in the Prius had large region below 230 (best at about 225).