Volt - 72.9 miles on one charge

While this is a good test to see what the Volt can do under ideal conditions, with variables and extremes eliminated, it doesn't impress me because it's not representative of what can be done in real life.

Pulse & Glide works with internal combustion engines because it has very limited efficiency band, but a battery/inverter/motor setup should have broader efficiency zones that allow constant cruise to beat P&G. His results show P&G is mostly useless or even counterproductive in an EV because resistive losses will increase significantly during the pulse and not average lower than what it would be at constant speed.

So am I surprised that going slower and keeping the same speed yields better mileage? Nope.

If you can take the same Volt and drive it in various commutes and conditions and eek out much more than 40 miles per charge without disrupting traffic, I will be impressed.

 

32 mph. Anybody know what mileage a Gen 3 prius can get at that speed? I bet at least 75 mpg constant.

I agree that the test is interesting but completely irrelevant. The conditions on a public road that would allow constant variation between 25 and 40 are few and far between. Maybe at 3 am?

But it can't be. If I was behind a guy on a non-passing road constantly speeding up to 40 and then down to 25 I'd actually call the police and report that there is a drunk driver in front of me just to get him the hell out of the way.

The test is worth remembering if there is an apocalypse and no cars left and we're very short on fuel

 

Exactly.

The point is that mpg (or range for EV's) isn't a single number, it's always a range. And hypermiling gives the upper end of the range. The lower end of the range would also be helpful: what is the minimum range one gets if one accelerates and decelerates hard, runs at high speeds, has AC on all the time, etc.?? Then you know not only what to expect but also how sensitive the range/mpg is to various driving conditions/styles.

 

The link points out that the range was better with CC on, so varying speed up and down (P&G) apparently doesn't work for an EV, or at least this one.

As for P&G, it's done on non-passing roads only when there is no one behind (which does require learning to watch the rearview mirror closely, something I found hard to do). Even on multilane highways you narrow the speed range if someone is following, especially if traffic makes it difficult for them to switch lanes. There are lots of opportunities to do P&G without impeding other drivers.

That said, sometimes someone sits behind me and ignore multiple opportunities to pass me. Often they're yakking on a handheld cell or texting, but sometimes they are simply unable to figure out how to change lanes and pass. When this happens I resume P&G over a limited range.

I haven't been able to figure out how to do P&G with the Prius, best I can manage so far is to let the speed fluctuate in response to the terrain. But I did it a lot in my previous car, a Subaru, with great results.

 

I agree it gives a range, a lower bound and upper bound for the EV distance you can travel. It's a good test in that regard but that's all it provides.

But as far as being an achievement --- it is not (IMO), because you really can calculate the mileage on paper when you eliminate so many variables and obstacles that stand in the way of achieving good mileage. He might as well have been running on a dyno, it would give the same info.

So the upper bound gives a goal that if one can achieve in real life would represent an actual achievement.

So for instance the MPG figures Mike has at the bottom of his posts, that impresses me because I know that is achieved in real life. Though extreme hypermilers will go to some extremes to squeeze out some MPGs, it still the point to get my rear end from point A to point B.

Otherwise I could drive in circles to increase my mileage and report here some fantastic figures. But I don't because that is a pointless endeavor. I don't drain the battery or drive an extra loop in a parking lot because I know it gives better mileage. At the end of the day if you appreciate good mileage, it's best to know it was achieved during a fruitful activity.

I think we could push > 90 mpg @ average 32 mph in a Prius Gen III using the same conditions this guy has.

 

P&G shouldn't work on a properly designed EV, unless the EV is one designed for high performance driving. Electric motors can have wide efficiency bands. Not so with internal combustion engines, which tend to suffer when running at low power outputs. So with an EV, cruising continuously at low speed minimizes aerodynamic drag and the motor is still efficient. Most ICEs are not efficient at continuous low power levels, so P&G allows for efficient power levels for the ICE while maintaining a low speed for aerodynamics.

Tom

 

Yes, data from my Subaru had convinced me of this. The way I used to drive (80-85mph on the highway) yielded 24-25mpg tanks (measured at the pump). Slowing to a steady 55-60mph raised it to only 27-28mpg (per a calibrated Scangauge, I didn't run a whole tank that way). Driving to Maine mostly highway doing P&G 50-60mph yielded 34mpg for a full tank, at the pump. For reference, EPA highway for it is 25mpg. Subaru Outbacks like the one I had have no aerodynamics.

As a neophyte to the Prius, I wonder if it adds regen when the driving load on the ICE is light in order to get the ICE up to a more efficient power level?

Yes, it's hardly surprising that constant speed works better than P&G for an EV. It's useful to have a range for the Volt at 32mph, lots of the roads in my area are zoned at 25-40mph.

 

I'm over 40 miles predicted (usually 43-45) every single day, driving with traffic at all times (usually 5mph over, speeds from 35-55). By experience, the prediction algorithm is very accurate and my weekly posts of energy usage in the other thread support my assertion.

My personal best observed (that is, I actually traveled that far) of 48.x included a few miles at 70mph, and a bunch at 60.

 

As to stock Volt tires, the recommended pressure on the door frame states max PRESSURES at 35F/37R. He says he's running over FIFTY pounds. Ok, so it's possible. I suppose it's possible you could get even higher than 72 EV miles if you do other proceedures not recommended by the manufacturer ... like use a 90lb jockey for the test ... tear out all the seats - upholstery - headliner - plastic moulding ... only have a few ounces in the gas tank ... etc. For us whacky folks that won't ever go that far, I suppose we'll never achieve 72 EV miles in a Volt. On a more realistic note, 72 EV miles is the WORST I've ever gotten in our Leaf, and THAT was into a 35mph average headwind, climbing to 4,500 feet elevation from sea level, 90 degrees temperature day with the AC on, averaging 50mph ... maxing 65mph in some places of the drive, with tire pressure within the manufacturer's recommendations. Some day it'd be fun to see if I can crack the 135 EV mile range of another Leaf driver ... not that it will have ANY bearing on reality.


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To be pedantic, did you actually GO 72 miles or was that how far you went plus the estimated range remaining? Did you charge 100% or the recommended 80%?

Have you been calculating miles/kWh at the wall? My Volt results seem to be right in there with what I'm seeing reported with the Leaf but I think many Leaf owners are in much hillier places.

In any case, the Leaf range reports support the notion that the EPA numbers are low.

It's still interesting. I don't see any criticism of people posting big Prius MPG numbers. I think Edmunds got 138 in the Leaf on a test track @ 30mph.

 

IMO it's a bit more of a challenge to beat the EPA or achieve the big numbers in a Prius because there's more involved in getting the ICE into the sweet spot (pulsing), then switching to a soft glide, then repeating it, within the flow of traffic patterns, traffic signals and terrain. This is without the benefit of perspective of driving an Volt (I know).

That's not to say it's better. Who wants to do extra work anyways? It's just how the dynamics of the car are.

You're doing a great job at beating the EPA. There's no criticism in that. However the original tester's foot (P&G method) wasn't able to beat cruise control. It's OK because it's the nature of the thing for the Volt to get great results staying at 1 speed versus going up and down on the speed curve and power curve.

But really it's just setting cruise control, or driving slower and accelerating more slowly and coasting to stops. So there's less of a challenge. Though it's cool to go further on less energy.

 

I'm interested in seeing what methods work in the Volt when it gets beyond EV range and goes into CS mode. Will the same steady-speed strategy work best, or will something else work better?

The criticisms in various posts above are unwarranted. The guy in the link in the OP is simply exploring what his Volt will do under different conditions and posting it as interesting info for discussion. After all, he's starting out at 5AM so there isn't much traffic to disturb. As for "it's not real-world", he's simply finding out what works, once he knows that he can decide how much of it he can (or wants to or feels is safe to) incorporate into his daily driving.

 

Motortrend published some charts, which imply pulse and glide will work best in CS mode. We don't really know what the GM software is set at though, so its going to take some experimentation.

 

If you hook an OBDII scanner up to the car in CS mode, you find it runs big throttle openings when running in series mode. I saw 75% at 1500rpm which is basically wide open throttle at low rpm. The engineers have a luxury you guys don't - they can change the load against the engine regardless of driver demand. It's effectively self-managing "pulse and glide" within the constraints of management's desire for a "normal" driving experience for the user (that is: rpm trends higher or lower with driver demand).

I never hooked the scanner up at highway speeds but I suspect it runs pretty big throttle openings there too, simply because it's a little 85hp 1.4L engine. In CS mode, it is possible to get the engine to shut off for as long as a mile @ 60mph but I'm not convinced that gaming it is really going to increase overall efficiency.

I know for a fact that some efficiency was left on the table (see above reference to management) but I don't know how a driver is going to access it.

 

Wide open throttle reduces pumping losses. It's one of the reasons pulse and coasting a non-hybrid is supposed to increase fuel economy. The other is that the engine is in it's most energy efficient curve. An advantage of decoupling the engine from the wheels is to allow the engine to operate more often at that efficient band.

Energy efficiency does not equal fuel efficiency, though. The EE is getting the most chemical energy from the fuel converted into mechanical energy. For a most cars this only happens under acceleration. They need the following coast to see increased FE.

 

"The wall?" ... not certain what the expression means. We calc our miles/kWh by measuring (fluke amprobe) kWh's used to charge, divided by miles traveled. Life time is 5.3 miles per kWh which is almost 2x what the manufacturer SAYS the Leaf will Average - BUT:



As you can see - we're no stranger to P & G mileage techniques. Our farthest tankfull range in our Gen II was in the 720 mile range.

Sorry for not detailing the above mileage calc's. Yes - from 100% charge, 72 miles left us discharged to the point that the warning light was on. We were on electron fumes when we reached our Lytle creek destination. 80% recharge is a manufacturer's recommendation to extend battery life (number of re-charge/discharge cycles) ... which takes 2nd fiddle if you need to maximize range on occasions. We only go 100% recharge about 25% of the time ... so far ... we've only logged about 4,000 ish miles total so far.

 

As in measuring the use from the socket on the wall (wall-to-wheel) instead of the charge drawn from the battery (battery-to-wheel).

Your answer is yes.