Does GM REALLY want to phase out the Volt?

That's the point. EPA uses 33.7 kWh (maximum possible) of energy equivalent from gasoline to calculate MPGe. Combustion engine cannot extract all of the possible energy from it. Therefore, the same standard should be held with the wind to calculate MPGe.

Volt has one planetary gearset so it only have one (mechanical) mode. You'll need two or three planetary gearsets to get two or three modes with the "theoretical" mechanical efficiency advantage it described. I said "theoretical" because 2-mode hybrid with 2 planetary gearset does not show any gain from HSD, including the highway. It has proven to be more complex, expensive and slow sales.

In CS mode when Volt's gas engine does NOT engage, all the power will have to go through the generator and take conversion loss. The reason Volt is rated 37 MPG is because gas engine cannot be clutched into the planetary gearset and transfer 69% of the torque all the time, like HSD. That describes transmission shortcoming/inefficiency.

Volt BSFC is comparable to GenII 1.5L engine, maybe slightly worse. Majority of the 5 MPG loss has to be from the transmission conversion loss. Do you have an idea of the percentages when Volt ICE is clutched/de-clutched in CS mode?

 

That doesn't make sense to me.

You want to factor in the energy remaining in the wind passing by the turbine that wasn't used to turn the blade?

I could see this argument if you were leaving energy in coal or oil or some other non-renewable finite resource, but to compare that kind of efficiency with the near limitless power from the sun seems ridiculous.

The energy "left on the table" not captured by the turbine doesn't cost anyone anything. It sounds like if I built a car that ran 100% on rainwater that you would say its not efficient because I can only catch a small portion of the rain.

 

Agreed. More transmission options allow for more efficient coupling of motive power to the wheels. In a simple transmission you add more gears for better matching. With multiple prime movers you need some sort of clutching or combining mechanism, and the more complex designs allow for more options.

The Prius HSD trades flexibility for simplicity. It is about the simplest possible mechanical transmission, but you pay for that with reduced efficiency as you move away from its sweet spot, where a larger percentage of the power is transfered through the electrical path.

As hybrids become more commonplace, I expect more complex transmissions will be the standard for full range hybrid vehicles. HSD works fine right now, but eventually the designers will want to squeeze out that last little bit of efficiency.

The possible exception is if something revolutionary occurs in the area of electric motor efficiency. That could happen, but it's a long shot.

Tom

 

Cruising around 60 mph consumes about 200 Watt-hours per mile. City traffic at low speed however with stop and go, also consume about 200 Wh/mi.

0-60 mph acceleration for Volt consumes 120 kW in 9 seconds (600 times faster). If Volt uses gas engine to filter out every situations that consume more than 200 Wh/mi, the 10.6 kWh available energy from the battery can go 53 miles instead of 35.

You maintain the ICE fresh by using it periodically when you need to. It extends the battery range and it's life. Your recharge finishes faster because you need less electricity. Public charging station becomes more effective and can serve more plugins.

Using the right fuel at the right time achieves synergy. It is what Prius PHV is all about. Volt doesn't have synergy drive but stubbornly tires to be an EV to the point it becomes a battery powered gasoline carrier.

 

You are confused. Wh is not even the correct unit for cruising. W is the correct unit. Further unless you think people will shuffle a vehicle away from chargers you are wrong there too.

 

The key to this discussion is anticipation. The control system in a car does not know in advance where and how the car will be driven. It can only know what has happened and make guesses about future use. These guesses are based on the anticipated use of the vehicle.

With a PHEV, if we know in advance how it will be driven we can gain efficiency by tailoring the use of the gas engine. If we know that the trip will be entirely within the EV limits, we can skip using the ICE. If we know that the trip will substantially exceed the EV limits, then it makes sense to run the entire trip as a hybrid, optimizing the use of the ICE.

It makes no sense to argue about which method is more efficient without defining a given trip profile. The Volt has two trip profiles at present (mountain and normal); perhaps future PHEVs will have a larger number to allow better optimization.

Tom

 

Got it off a power graph from some EV conversion site. The rpm was the motor's rated rpm.

I realize there many configrations of motors and this site wasn't clear on the type in the graph. I should try to erase it from my mind, and it wasn't needed for the point that heavy demand like acceleration is going to lead to reduced fuel efficiency with either propulsion type.

I guess a power plant could be used that is more efficient under those conditions. The ICE would likely be at less efficient in the lower bands where it will spend most of its time.

 

And it will need to use gas to go 53miles instead of 35. (And it can do 53 without gas in the summer with a good driver

Funny how you complain about 14min of charging then talk about charging more often and using public charging. Find on, parking and plugging in takes time. 14min of extra charging overnight takes nothing.

Yep using the right fuel at the right time is good, glad you are starting to see the light. The right time for gas is only on long trips where charging does become impractical (cannot drive for 50min, stop to charge, repeat). Any other time, there is real need for gas as plugging in overnight is the better fuel. It does mean carrying the engine for the small fraction of time one needs it, but then most people carry a spare tire (or fix-a-flat now) and extra seats in their car, but that is the price to pay for using one car to provide the right fuel at the right time.. (Your alternative to use the right fuel is a BEV, but that is limited in other ways).

 

The standard for MPGe dos not care if the source is wind or not, just as the standard for MPG does not care if the source is tar sands or light texas crude. Those are standards about HOW EFFICIENT IS THE VEHICLE, not the production of the energy that goes into it.

It has ne planetary gear-set and separate gears/clutches to engage the engine to the generator and indirectly to the engine. Its not the same a older 2-mode model with two planetary, but the added gearing provides a mechanical advantage allowing the engine to be used in closer to 6th gear type ratios for the HW. No need keep it geared so the ICE can provide lots of torque.

The Volt is rated 37MPG because when using EPA testing methods that is what the total system gets. Therea are many factors that go into the overall lower rating including its increased weight (which you love to harp on), larger wheels, increased drag, smaller engine, less efficient engine cycle, ...

I've not seen any reports on that the fraction of time its clutched when in CS mode. My guess it depends very much on the drive cycle.

 

Totally agree! (The Volt/Ampera in Europe get a "HOLD" mode which engages the ICE at the current SOC level. Its in the car but current government regulations keeps us from getting it in the USA. (My read is that it is allowed, but if provided then must be used in EPA testing which would then render the volt a standard hybrid because it does not use the battery when in hold mode).

If one will eventually use the ICE, then letting the operator control when would be better as they can better project the future needs.

HEAR US EPA --- let users control when to use ICE vs Battery, and don't presume worst-case for testing.

 

As has been pointed out, recharge time is not the most important consideration. Range depletion is the more important consideration. The ideal is to minimize use of the gas engine. (Which is why I prefer a pure EV: It has no gas engine.) Since most charging is done at home, at night, when time is abundant, whereas gassing up requires a stop at a gas station, speaking in terms of recharge times is misleading. We should look instead at how much of the battery's charge is depleted in a given driving scenario. (And even that does not matter if you have enough range that the ICE is not needed. Or if you are driving a car without an ICE.)

In the numbers above, where at 65 mph one minute of driving takes 17 minutes to recharge, that's only about 4 miles of driving for an hour's charging. Whew!!! I get about 30 miles of driving for an hour's charging. Even my little Zap Xebra got about 10 miles of driving for an hour's charging. Four miles for an hour's charging sounds like 120 volts at 15 amps and that's pretty worthless unless you're charging a very small pack overnight or all day at work, in which case charging time (as above) is an unimportant consideration.

I say 42.

 

Watt is power. Watt-Hour is the rate of power consumption. Volt would require about 15 kW to maintain 60 mph cruising but about 200 Wh (per mile) rate of consumption.

 

Yes watt is a unit of power.
No watt-hour is not rate of power consumption, watt-hour is a unit of energy.
"Rate of power consumption" is meaningless. Power is rate of energy consumption, so rate of power consumption would equate to "rate of rate of energy consumption"

[ame]http://en.wikipedia.org/wiki/Kilowatt_hour[/ame]


Scientific units have specific meanings and it's best to adhere to them, otherwise discussions get even more confusing than this one already is. I'm not sure why I'm still reading this thread!!

 

Has anyone hacked this yet for the Volt? The early gen2 Prius didn't have a EV button, but there was an aftermarket part that let a user activate it through the cruise control. Or you could just get the button, run the wire though the dash and simply plug it in to the computer module.

The failure of two-mode in the market isn't necessarily a failure of that hybrid system. GM choose to mate the system to their 6L V8. My guess is that it was to maintain a high tow rating. The system did raise a combine mpg of 15/16 to 21, and the city from 12/14 to 21. For a large truck or SUV that is a big improvement. Cost is an issue, but comparitively equipped, the hybrids aren't a huge chunk of cash more for the price of the vehicle. A base, 2wd, no frills Tahoe costs as much as a Volt. GM is also still selling them. So they can't be a complete sales failure.

Another tidbit for the refueling time discussion. The diesel pumps at truck stops pump two or more times faster than gas pumps. Would it an acceptable arguement that a VW TDI is more efficient than a Prius because it can refuel faster?

 

It excludes the miles when the gas engine is running. 53 miles are the miles with gas engine OFF. If we include gas miles, it'll be more than 53 miles.

Perhaps you missed the point about using public charging station responsibly. When you use electricity to carry the gas engine and gas tank and charge at the public charging station, you take that opportunity away from BEV.

Prius PHV uses electricity only when it makes sense, responsibly. So what if it charges at the station for 3 hours, after an hour of city driving? Why should Volt occupy 10 hours of the charging station for wasting it in 15 mins high speed driving? See the drift?

I disagree with your Hummer SUV mentality. You may be okay but it is not okay for a compact car to weight more than a Equinox SUV. A car supposed to carry people and necessary safety hardware. Not using the on-board gas engine is like a Hummer owner not using it for it's intended purpose but instead for grocery shopping.

For you, the right fuel is electricity because you have access to renewable wind energy. Majority of Americans don't because average electricity has 69% fossil fuel and renewable makes up only a few percent.

 

Clearly, less of the gas engine torque makes it to the wheels whether the gas engine is engaged or disengaged (zero in this case).

I suggest you take back your accusation that my understanding is flawed in post #162.

It won't be a standard hybrid due to the HOLD button. Prius PHV has it with the EV/HV toggle.

GM is afraid that HOLD button will make it a blended plugin hybrid. It defeats the vast amount of money invested in EREV campaign.

 

No, the recharge time is the direct consequence from the "not a drop of gas usage" during full acceleration and high speed driving on EV, red herring. The point was, yes you can do it but here are the consequences.

Gas and diesel fuel are used in the same manner.

 

I agree with sticking with the standard.

300 Wh is using 300 watts for an hour. If you use 120 kW in 9 seconds, that's also 300 Wh. Both were consumed at different rate. That was what I meant in the reply. Thanks for pointing it out.

I corrected the previous posts as I meant Wh/mi.

 

Under the US06 cycle, the Volt spends 58% with the gas engine mechanically connected, 16% in series mode with gas engine, 21% with engine off and using one motor, and 5% with engine off and using two motors combined.

US06 includes a bunch of starts and stops at the beginning and end of the test cycle with accounts for the time spent without the gas engine mechanically connected. The output split works well under lower load conditions so it is usually engaged during continuous highway cruising but at speeds under 35 mph and during significant acceleration the Volt disconnects the mechanical linkage so the large electric motor can drive the car.

 

Not yet.. its on my and a few others to-do-list. But messing with the Volts controller is a risky business so we are moving slow. I'm working o nthe engine-running-due-to-temp first (its more annoying for me)