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Discussion Starter #1
I will be taking the Volt on a 500+ mile tour shortly. I am thinking some owners out there have already figured this out and can give me a heads up on best speed.

If you are driving on a long trip and after the initial charge running completely on ICE with mostly interstate (55-65 mph) speeds , is there a speed that is a 'sweet spot' for mileage ?

In my commute I stay under 60mph and will get right around 39-40 mpg running on ICE only. Does anyone have experience with long distance travel where they monitored the fuel usage at different speeds ?

thanks
 

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I would say, go at least the speed limit. Or at least stay the hell in the right lane so people can easily pass you if you plan on being slower than the flow of traffic.
 

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Here is a chart of speed vs power for a 4000 lb Volt with driver with 0.28 cD and 23.7 ft^2 area from with a steady state load of 700 watts (might be high, just guessing for headlights and electronics, this only impacts low speeds): http://ecomodder.com/forum/tool-aero-rolling-resistance.php

Going 55 or 60 is right at what you see, 40 mpg, and at 90 you can probably expect half that.

If you want best gas mileage drive 55 or 60. But driving 70 would save you tons of time. I find I would rather drive 70 and save a lot of time over the gas, but it depends on what you are doing. Often times you can take highways instead of interstates and save both distance and lower average speed (greatly reducing fuel consumption).

This assumes flat ground and no tail winds. I imagine the Volt can do a bit better at speeds above 60 mph (I tend to get around 35 at 70), but depends on a lot of factors.

As a note, you can see the Volt needs about 55 hp to drive 100 mph, which probably explains the genset sizing (55 kW), as this is more than enough to cover that, and if you add in some for headwinds or steep hills and the thing is rarely not going to have enough power (up long steep hills at high speeds is only issue point).

Code:
MPH	Watts		HP	HPAero	HP Rolling	MPG(US)
5	1,022.38	0.43	0.01	0.43		34.3
10	1,370.07	0.9	0.05	0.85		51.19
15	1,768.35	1.43	0.15	1.28		59.49
20	2,242.54	2.07	0.36	1.71		62.55
25	2,817.94	2.84	0.71	2.13		62.22
30	3,519.84	3.78	1.22	2.56		59.78
35	4,373.55	4.93	1.94	2.99		56.13
40	5,404.37	6.31	2.9	3.41		51.91
45	6,637.60	7.96	4.12	3.84		47.55
50	8,098.54	9.92	5.65	4.27		43.3
55	9,812.49	12.22	7.53	4.69		39.31
60	11,804.76	14.89	9.77	5.12		35.65
65	14,100.64	17.97	12.42	5.55		32.33
70	16,725.44	21.49	15.52	5.97		29.35
75	19,704.46	25.49	19.09	6.4		26.69
80	23,063.00	29.99	23.16	6.83		24.33
85	26,826.36	35.04	27.78	7.25		22.22
90	31,019.84	40.66	32.98	7.68		20.35
95	35,668.74	46.89	38.79	8.11		18.68
100	40,798.37	53.77	45.24	8.53		17.19
 

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is it recharging at all while your running on gasoline? As in long stretches of freeway but hit an off ramp and go electric for a bit?
 

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Only in Mountain Mode. In Hold mode it holds the current charge level but does not increase it. In Normal and Sport modes the battery will run down to the lower set point and show "empty". In Mountain Mode the ICE will run until the state of charge (SOC) is about 50%.
 

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is it recharging at all while your running on gasoline? As in long stretches of freeway but hit an off ramp and go electric for a bit?
The engine will add charge to the battery until the buffer is built back up and then shut off and draw down the buffer before turning back on and repeating the cycle. At really high speed or while going up hill the engine will stay on. The Volt is a really smart car. I think the buffer is about 1kw-hr.

Here is info about a trip I took during which I drove conservatively.
http://gm-volt.com/forum/showthread...le-even-when-it-is-not-convenient-to-recharge.
As always, your mileage will vary with terrain, temperature and technique. Of the three you have direct control over only technique. It definitely pays to keep an eye on the green ball for immediate feedback on your own driving technique.

KNS
 

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Discussion Starter #8
Looking at that graph, I guess staying around the 60 mph on the interstates, would be best mpg without being in the way of traffic. I thought I read something about the EV or ICE running more efficiently at some faster speed . but obviously not.
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How to get the most joy long distance with the VOLT is the better question.

I will be taking the Volt on a 500+ mile tour shortly. I am thinking some owners out there have already figured this out and can give me a heads up on best speed.

If you are driving on a long trip and after the initial charge running completely on ICE with mostly interstate (55-65 mph) speeds , is there a speed that is a 'sweet spot' for mileage ?

In my commute I stay under 60mph and will get right around 39-40 mpg running on ICE only. Does anyone have experience with long distance travel where they monitored the fuel usage at different speeds ?

thanks
Hi Rusty,
Here is what I usually do when I go for a long range trip without time constrains. No time constrains! That is important.
I plan my route in advance with Google earth or any other route planner. They usually pick the fastest route from point A to point B.
Once I see, what the fastest route is, I look closely, what kind of roads they want me to take. Usually it is Interstate to max extent. Less travel time due to higher Speed limits on long stretches, but often significantly more miles and less scenic routes.
I usually look for parallel or short cutting highways with higher scenic value and some nice stopping opportunies. Here the speed limits are usually between 55 and 70 MPH. That is a region where the VOLT can be kept just around 40MPG. Check for charging opportunities on the way. A 1 hour lunch break on a Level 2 charger gives you about 10 EV miles extra. PlugShare.com is a good source. Many private EV owners offer their EVSE´s or outdoor outlets. Ask restaurant owners, if you can use their outdoor 120V outlet. I always look for one when I pull into a parking lot and ask the people. Most people are helpful with that. Enter the address on plugshare, if they allowed you to charge.

When I am on the road, I usually switch to Mountain Mode when I see 2 EV miles remaining. If I don´t do that, the car goes into CS mode and the battery indication will be greyed out for the rest of the trip. It stays like that, even if I get a partial charge somewhere inbetween. I try to keep some juice in the battery for the whole trip, so that I can go pure electric whenever I want to. Through towns, at rest areas, on overall long downhill stretches with intermediate ups and downs, in state parks, scenic areas with some stops - you name it. I know that people argue, that you lose efficiency due do to the intermediate battery charging. May be, but I like it much better this way. Just did a 700 miles trip last week and had overall above 40MPG with 4 charging opportunities inbetween. 3 full, one partial.

I make it a game for myself to hit a certain point on my route with a certain battery state. For example, if I approach a town I switch to NORMAL (full electric) mode X miles out, so that I will hit my MOUNTAIN MODE SWITCH ON CUE of 2 EV miles remaining once I exit that town and go back to Highway speed. Sounds silly, but I like it that way.

Regarding HOLD mode, I don´t like it on long distance rides. My experience is, that it will deplete the battery, if you go above 75MP on long trips. It sets the red bar, but it is not very aggressive to keep the battery charge at that mark. Two times I ended up with a completely depleted battery when using HOLD mode. Those were long Interstate rides at 80 MPH or faster with (stupidly self induced) time pressure. Usually not what I do. 32MPG or even less was the result.

I drive the speed limit most of the time and use Cruise control to max extent. I use slipstream opportunities behind semis if the wind is not too much cross and I can keep my distance. I switch between D and L often, whatever is better for the situation. Coasting in D feels more efficient than regenning in L.
If you drive above 65 miles or so at a constant speed, the ICE will connect directly to the wheels via the planetary ring gear. From my experience half of the power comes from the ICE directly, the other half from the MG. I think I can tell, because on my 13VOLT the power gauge suddenly drops by 10 to 15 KW while driving constant speed on level road. And I think I can even feel the clutch engage. I guess that is the most efficient cruising mode once the ICE is on.
I don´t know the exact speed, where this happens. The computer probably uses a bunch of variables to decide, when to engage the clutch. One factor I think, is a certain time at constant power demand above a set threshold speed.

Obviously the speed is the most important factor on energy consumption above 45MPH or so. Answering your question is easy. The faster you go, the lower your MPG will go. So, if time is not a factor, avoid interstates and take highways with lower speed limits.

Enjoy your trip!

P.S. In may I will take a trip along the continental divide from southern New Mexico to Calgary, CAN and back. More than 3000 miles in 2 weeks. Will go any 11K feet pass that is on the way. And avoid Interstates to max extent!
 

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What did you put in for engine thermal efficiency on the model? The horsepower requirements look close to both our empirical data and our assumptions about GM's design requirements, but the mpg results are definitely low - I can average well over 40 mpg in the 60-65 mph range.

The Volt optimizes engine efficiency with its loading regime, and routinely sees something close to its peak of 33% thermal much of the time.
 

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Manual says electric efficiency is optimized 50mph and lower. Seems like 60 or so would be more efficient than 70+. That being said I did a road trip form CT to TN with two passengers and the rest of the car filled with luggage running at the speed limit or a couple over in cruise as traffic and weather permitted. Just left it in hold mode with 75-50% charge and got between 38.5 and 40.5 mpg. As I got out of CT, I seemed to see fewer drivers going significantly faster that the posted speed limit. Of course other places the speed limit was 70mph. I used D almost exclusively for the whole trip.
 

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I say enjoy the drip and please don't give Volts a bad name by driving significantly slower than traffic.
 

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Cruise control can be your friend. ;)
 

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Don't over think it. Just drive and enjoy the ride. Let the car handle the computing.
 

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I can consistently get 50 miles of EV range at 50 mph in warm upper 70s weather with no AC. ari C has demonstrated over 80 mpg driving 20-25 mph in a circle without stopping last Memorial Day.

That said, neither are a good idea if the speed limit is 60-70 mph. Just drive and enjoy, and plug in when you can (Plugshare can help)
 

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Use battery at the lowest speed limits and ICE at highest,

Battery is most efficient from 0-50 MPH. ICE is most efficient from 50 MPH above.

I make a 450 mile trip about 4 times a month. I use battery power from 0-55 MPH. Hold mode ICE above 55 MPH (whatever the speed limit is). I have enough small towns to use up battery power along the way at low speed. If not, I'd stay on battery power for the slowest stretches, even if at 70 MPH.

Don't over think it, and don use Mountain Mode unless you are in the Rockies.
 

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Very interesting, Viking79! I think you worst cased it a bit, which is a good thing in my book, but it does match up fairly closely with what I see. I tend to get around 42 mpg at 62 mpg if the terrain is flat and the temps are between 40 degrees and 70 degrees. When the speed limit goes up from 55 to 65 my speed goes up just a bit to around 65-66 mph and my mpg goes down a bit to about 40 mpg.

I can get around 44 mpg on flat terrain at 50 mph, and I see this fairly frequently since the GM Parkway has a 40 mph speed limit.

My regular setting on AC is Eco 1 or 2 so I don't draw much there and a fair amount of the time (if temps are between 60 and 75 degrees) I just use fan.

My screens kW use rate seems to be a bit higher at lower speeds than this chart but it is right on for highway speeds.
 
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