Prius Plug-in Hybrid Gets Improved 95 MPGe Rating

The most interesting thing to me is the 11 mile range is the blended range, much as I suspected. I think its pretty clear now they are going to have the blended PHEV sticker that was discussed some months ago.

Toyota is likely issuing this new data now to soften the blow when the EPA sticker reads ALL Electric Range = 0 miles.

I think John's comments about viewing the grid charge as an mpg boost are right on. For the first bit of every day's driving it will be the most efficient gasoline powered car on the planet, and even after that its truly impressive.

I am sure you will all really enjoy your super hybrids.

http://priuschat.com/forums/chevrolet-volt/98347-volt-sales-figures-23.html

(See usbs' post 230)

 

It would be incredulous for Toyota to publish numbers for 11 miles saying it used gas and EV, and not actually have used gas. So its not a question of "If" it used gas, just how much.

MPG(e) is defined as (miles travel) / (Total energy sources used). There is no way to computed MPGe for only one of the two sources in a test. If it was 11 miles and 3kw the computation would be 11* 33.705 / 3 = 123.58. That provides an estimated upper bound, but otherwise cannot provide much of a comparison.

We already know that Toyota says it will be 95 MPG(e). Assuming that is what the EPA reports too, then that is the only measure of efficiency for blended mode operations that can be compared to other vehicles. (Well if both gas used and kWr used was simultaneously better or worse then the pair of number could be compared across two vehicles).

 

I think that was to me, for my "if it uses any". I don't think its likely that toyota is using no gas in the tests, in fact I'm guessing it will use a few more drops than you are. But it is not impossible that toyota increased their SOC range to say 70% and got an all electric 95 MPGe. We will know how much gas, if any, when they release the full figures.

 

Hmm using USB's numbers.. it is too close to call if the prius PHV will be the "most efficient gasoline powered car on the planet". Looks like toyota might be able pull that off and reclaim the crown. If the Utility factor is .24, then its overall MPGe would 95 * .2 + 50 * .76 = 60.8. Just a little better than the Volt at 60 MPGe overall.

(Though neither I nor USB could reconstruct the Volt numbers, so there may be a more complex city/highway split in the computation so we'll have to wait for the EPA numbers on that too.

 

Thats why I limited the claim to the initial CD period, nothing that actually burns gas gets anything close to 95 mpge while doing it. (volt only gets the 94 by NOT burning gas).

Point is its a super efficient gas burner, then a really really efficient gas burner; if gas burning efficiency is your goal the PiP will be hard to beat.

 

My own quote from the Volt daily blog on September 2010 sums up the situation: "Those attempting to force an EV perspective on a hybrid are missing the point and causing confusion."

http://gm-volt.com/2010/09/14/toyota-exec-outlines-companys-upcoming-electric-car-offensive/

It was one of many, many attempts to convey the "BOOST MPG" expectation for PHV that ended up falling on deaf ears.

Reading that particular daily exchange of banter reinforces the trophy mentality we've been dealing with for years. In fact, that particular group still thrives on bragging rights.

It sure will be interesting will be when GM finally diversifies. Without anything competitive to offer, something must give. Because Volt has become a halo product and the source of much controversy, there continues to be a chance of the front-wheel-drive Two-Mode plug-in coming to market. The latest model being tested is a Cruze.

And since we know other automakers are also planning to offer their own "blended" plug-in hybrids, it does tend to make sense that GM wouldn't ignore that category entirely. In other words, each must offer something that can be sold in high-volume for a profit.

But while we wait for those offerings, some will attempt to spin "blended" as being a bad thing. There is no stigma. EV isn't necessary. The true goal is to significantly reduce emissions & consumption.
.

 

Biggest reason the Volt will be less efficient (regardless of your oversight) is more mass (3781 lb curb weight for the Volt vs 3165 lb curb weight for the PiP - about 20% more mass). The Volt has larger tires/wheels which we all know hurt efficiency (195/65-15 vs 215/55-17) all else being equal, so I'd wager those 2 things alone account for the majority of any lower efficiency of the Volt compared to the PiP.

EPA doesn't do any estimation of wall-battery-wheel losses - it only measures how much juice goes into charging the car. You are right though - the only thing that matters from our point of view is the electricity that goes into the car from the wall, but it's also important as others have noted to know at what rate the car is charged at since higher rates tend to have higher efficiency due to charging overhead like running cooling pumps. It really would be nice if there were published efficiencies at a couple different rates, though, since it can vary. I have to assume that the testing will be done at the most efficiency charge rate.

 

Those 0 miles are before introducing the EPA 30% reduction? LOL

 

I do suspect Toyota 'tweaked' the system (if this is the right word) to get mpg(e) in the test just above the Volt, on the account of Rcda.
This may be a good marketing decision, after all, we on PC are not a representative sample of the average consumer. The average consumer will probably look at the sticker for mpg(e) ("efficiency") and cost to drive a mile.
If we want to break the magic 3% penetration, this may help (I hope).

 

What's your source for this? As I understand it, MPGe is defined as (miles traveled) / (equivalent energy of one gallon of gasoline consumed).

MPGe can be used with hydrogen, electricity, natural gas, etc. They calculate the amount of the alternative energy source that is equal to the potential energy in one gallon of gasoline, and determine how many miles the vehicle will travel using that much energy. So in comparing two electric cars, it compares how efficiently they use electricity. In comparing gasoline to electric, it's only useful if you compare the cost of one gallon of gas to the cost of the equivalent amount of electricity.

As an aside, the constant Prius vs Volt comparisons are silly: In a trip of 11 miles or less, Prius is insignificantly more efficient (94 vs 95 MPGe is basically a rounding error). In a trip of 11 to 25 miles, maybe more, Volt is definitely more efficient. Past its all-EV range, Volt remains more efficient for tens of miles more, but at some distance, Prius is more efficient. Jay Leno claims he drove his Volt over 13,000 miles on its first tank of gas. Given his commute distance, it's very possible that a Plug-in Prius would have consumed several tanks of gas, and therefore, under those conditions, you could not possibly call the PiP a more energy efficient car.

 

Correct. I was showing that the EV test must be a blended result.

I calculate efficiency for the electric fuel source by using the MPG result from the CS (HV) test. More than good enough for me, although I agree that the approach may introduce an error in accuracy of a couple percent.

 

But were the EV miles you got on the prototype 'blended' (using gas)? Also, what type of driving did you do (was it all low speed driving)?

 

Of course you can -- you just have to understand what efficiency means.

Hint: it is NOT MPG while ignoring the electricity used.

 

The differences seem to be explained by a bigger battery in the prototype.

 

In what I wrote I did not explicitly state that one converts all energy gallons of gas equivalent. But one cannot divide by the energy equivalent of gallon of gas.. as that is a constant. ( I think you ment exactly what I did). Its formalized in http://standards.sae.org/j1711_201006 and reasonably explained in [ame]http://en.wikipedia.org/wiki/MPGe[/ame] and yes it can be used for any energy source -- it moves things into the same space energy.

The general formula is is shown in wikipidiea as




For a plug in using both electricity and gas it would work out to be
MPGe=( (Total Miles)) / (( kWr used) / 33.705 + gallons of gas )


I agree that MilePerFuelDollar is a more meaningful number for most people, though that is about cost (monetary efficiency), not energy efficiency. My sig has them all.

 

You are right, MPG alone is not appropriate. That is whey we use MPG(e).. And Jay is getting an estimated 94 MPGe * 13000 + 20*10 = 92.5MPGe (I used 20mpg for the gas presuming he is getting very poor gas milage as it is mostly maintenance runs).

(To avoid the usual EV-hater comeback about the grid effiecncy and pollution please note that Jay has both a personal wind generator and solar panels http://www.popularmechanics.com/cars/jay-leno/green-garage/4228638
)

So Rebound was correct in saying that under Jay Leno's conditions the PiP is not more efficient.

 

IIRC from an SAE book I have lying around my house somewhere, a rule of thumb relating weight differences to fuel economy is that all else being equal, fuel economy will improve (as a percentage) about half the fractional drop in weight.

E.g., a 20 weight reduction will improve fuel economy 10%.

In the case of the prototype and market PiP, weight went down some 5% (right?), but battery capacity dropped a whole lot more -- from 5.2 nominal to 4.4 kwh nominal = ~ 15%. I am unsure if DoD changed also.

 

No, he is not. A car's electric efficiency has nothing to do with how the electricity was produced.