46.5 MPG using Volt gas engine

16732 Views 30 Replies 20 Participants Last post by MIKECELI, May 22, 2014

Steverino

Discussion Starter · Jun 30, 2012

I am getting 46.5 MPG on gas, not 37 MPG. That's a pretty huge (25%) difference!

I had one of those infrequent, long drives yesterday. Destination was 52 miles away, mostly expressway driving at 55 MPH in D with cruise on (I use cruise as much as possible). The battery delivered 50 miles and the gas generator kicked in 2.2 miles from arrival. Was able to add 11 miles of charge during my visit using the 110v charge cord. The 52 mile return trip was almost all gas, highway with AC on ECO. Result? Mileage in Prius territory: 46.5 MPG

Oh, tires at 40 PSI

So 50 miles from the battery and 46.5 MPG from the gas engine. I continue to be impressed with the Volt. The Volt is one of the few (only?) vehicles that delivers better than EPA rating estimates in my experience.

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tboult

· #2 · Jun 30, 2012 (Edited)

Congrants.. with a little lighter foot, (or if you did not need AC), you might have made the 50+50 club.
http://gm-volt.com/forum/showthread.php?13991-The-50-50-club-(50-miles-on-a-charge-50-MPG)

the 37MPG is blended city/highway average. EPA highway is 40mpg.
I beat EPA in my previous car, but not by much. In the Volt my EV mode average is way better (46 average (including winter) vs 35 EPA).

Bob_Livonia

· #3 · Jun 30, 2012

Somewhat off topic, but going through notes from a recent cruise, the cruise ship has two 25 megawatt gas turbines, producing 11,000 volts, driving the electric propulsion system. They didn't say what kind of battery they use, but they store energy and can power the essential stuff should the turbines go down until the 11,483 BHP backup diesel generator could kick in. But the gas turbines are much more efficient than the diesels, I am told. Oh yes, fuel consumption is 160 metric tons a day.

saghost

· #4 · Jun 30, 2012

Yup. I did a ~220 mile trip a couple weeks ago that's almost entirely freeway, and by running in cruise at the (mostly 55, 65 for one 40 mile stretch) speed limit, I got 46 battery miles and 47 mpg. Amazing what happens when you slow down.

Steverino

Discussion Starter · #5 · Jun 30, 2012

tboult said:
Congrants.. with a little lighter foot, (not if you did not need AC), you might have made the 50+50 club.
http://gm-volt.com/forum/showthread.php?13991-The-50-50-club-(50-miles-on-a-charge-50-MPG)

Haha. Yes, I suppose I could have went the (still legal) 50 mph, but I did not want people to think of the Volt as a moving roadblock or PO the truck drivers.

In a related note, driving a Volt I tend to notice how many drivers are reactive rather than anticipatory. A common example are drivers who accelerate into a stop light and then hit the brakes hard. The light was red, cars are stopped, they are just not thinking much ahead.

saghost

· #6 · Jun 30, 2012

Getting your head out in front of the airplane is something they taught us in flight school - and of course you have to be further ahead of bigger faster airplanes. It's appalling how few people ever seem to learn it on the road. Maybe we need to have it taught in driver's ed classes? I tend to watch a quarter mile or so of traffic flow when I can - it's prevented a few accidents over the years.

ClarksonCote

· #7 · Jun 30, 2012

Nice, I went on a 375 mile trip recently over lots of hilly terrain.

Got 47MPG with my electric miles counted, and 42MPG on gas only. Mostly driving 73MPH.

Very pleased.

saghost

· #8 · Jun 30, 2012

ClarksonCote said:
Nice, I went on a 375 mile trip recently over lots of hilly terrain.

Got 47MPG with my electric miles counted, and 42MPG on gas only. Mostly driving 73MPH.

Very pleased.

At that high speed, that's awesome! Driving in that speed range through the WV mountains in November, I got 37 mpgcs on the trip shortly after I bought the car. (still impressive, but not nearly the same.)

ClarksonCote

· #9 · Jul 1, 2012 (Edited)

saghost said:
At that high speed, that's awesome! Driving in that speed range through the WV mountains in November, I got 37 mpgcs on the trip shortly after I bought the car. (still impressive, but not nearly the same.)

Thanks. There were also some stretches at 50mph, and a few cities where traffic was crawling.

I've made the trip before and usually only manage 38-40mpg on gas only. That's usually traveling around 76mph on the interstate, and in colder weather.

This trip had tires at 42psi and temps around 90.

Skotty

· #10 · Jul 1, 2012

I average about 36 to 37 mpg going 70 mph.

I average about 40 mpg going 60 mph.

I have yet to experiment with 50 or 55 mph, as I'm not willing to drive that slow on roads where the speed limit is 65 or 70. There really is no even slightly decent route for me to take on slower speed limit roads. But maybe I'll figure something out someday where I can go this slow to gather some more data.

Sometimes I get anomalies (not counting stormy weather, where lower mileage is expected). Perhaps related to wind? I don't know. But I once got over 43 mpg going 65 to 70 mph. And a couple of other times I got around 33 mpg going 70 mph.

All of my drives are over 100 miles in CS-mode, so the duration/distance is good for collecting data. All of these drives are almost entirely spent at a steady speed with cruise control active.

I sometimes wonder if mileage would be better if I drove more like a trucker, slowing on the uphills and speeding up on the downhills, but I haven't tested it. I believe trucks do this mostly due to heavy loads where they can't easily maintain speed on uphill stretches, but I could see there being an efficiency improvement from it as well as you could keep the engine load more consistent.

In the future, I hope Chevy can increase CS mileage of the Volt, but I could see it not being a priority, so it's not something I really expect. One of these days I will fix my commuting nightmare, after which I probably won't care much about CS mode mileage anymore.

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saghost

· #11 · Jul 1, 2012

Skotty said:
Sometimes I get anomalies (not counting stormy weather, where lower mileage is expected). Perhaps related to wind? I don't know. But I once got over 43 mpg going 65 to 70 mph. And a couple of other times I got around 33 mpg going 70 mph.

I sometimes wonder if mileage would be better if I drove more like a trucker, slowing on the uphills and speeding up on the downhills, but I haven't tested it. I believe trucks do this mostly due to heavy loads where they can't easily maintain speed on uphill stretches, but I could see there being an efficiency improvement from it as well as you could keep the engine load more consistent.

Wind is absolutely a factor, and can be a big one, especially if you're already going pretty quickly.

The technique you describe is frequently used by hypermilers in more conventional cars - they call it driving with load (DWL). I'm not certain how it'll work out on the Volt, with all of the behind the scenes things the car is up to.

sinnombre

· #12 · Jul 1, 2012

I've only used two gallons on the generator . The first gallon yielded 43.3 mpg on a rainy day in moderately heavy traffic coming from Dallas to Fort Worth . The second gallon yielded 38 in mixed city / highway driving .

This calculates to more than 40 mpg and beats the wife's 2012 Civic that averages 31-32 mpg and can achieve 39 mpg only @ 60 mph with no traffic .

tboult

· #13 · Jul 1, 2012

saghost said:
Wind is absolutely a factor, and can be a big one, especially if you're already going pretty quickly.

The technique you describe is frequently used by hypermilers in more conventional cars - they call it driving with load (DWL). I'm not certain how it'll work out on the Volt, with all of the behind the scenes things the car is up to.

Driving with should definitely help the Volt when on ICE (and probably with EV). In DWL, the goal is to limit how often the car is in high-load (required torque) and high-RPM combinations which are generally very poor BSFC. The volt's BSFC (if what we've seen is correct) allows high torque only at low RPM. It is more complex since at high speed load torque the Voltis likely to be in two-motor ER moded, which is its most efficient use of the ICE, and if you increase the load it may switch to one-motor ER mode, making the impact even greater. But at the same time one does not want DWL to drop speed so much that it disengages from two motor ER, so its not always better.

CD/EV mode does not have a BSFC, but still inefficiency grows with current demand so it too should benifit from DWL. Driving slower on the highway will be more efficient. DWL expands on that concept a little to recognize that downhill can be a go a bit faster with less added energy (gravity helps) so you can have a slightly higher overall average speed but still keep the speed down on the most demanding sections.

I do DWL as my dominant mode of driving and on ICE, I used to mix it with MM games so its harder to analyze. More recently I've just done in normal CS mode, and I know on my best MPG days (50+50) I was DWL.

In the Volt the Cruise Control, can make DWL easy. If am taking the back roads to work, I set CC at 42mph (speed limit is 45), and then just let it drive. The downhill sections (much of the way to work) will generally coast up to 55mph with most of the trip at or above the 45limit. But on the multiple uphill sections (its rolling hills), it naturally slows down a bit and then accelerates back down the next hill.

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doggydogworld

· #14 · Jul 1, 2012

Bob_Livonia said:
But the gas turbines are much more efficient than the diesels, I am told.

Not true. The massive gas turbines used in power plants top out around 35% efficiency. Small turbines like Captstone's 25 kW model are more like 25% efficient. The Volt's ICE hits 36%, a Prius ICE is about 40% and one of VW's TDIs can do 44%. Large marine diesels have been measured at 55%.

The most efficient thermal powerplants combine gas turbines with a steam bottoming cycle. GE's best combined cycle powerplants are 60% efficient. I doubt your ship used combined cycle turbines, but I know nothing about cruise ships so I could be wrong.

Turbines vibrate less, are quieter and can burn cheap natural gas instead of expensive diesel. They also work well in CHP applications which might apply to a cruise ship, especially in colder regions.

Elemental

· #15 · Nov 5, 2013

Steverino said:
In a related note, driving a Volt I tend to notice how many drivers are reactive rather than anticipatory. A common example are drivers who accelerate into a stop light and then hit the brakes hard. The light was red, cars are stopped, they are just not thinking much ahead.

I noticed this before buying a Volt riding a motorcycle. In fact, if you look deeper you'll see this is how many people live their entire lives like this, not just driving. It's SO FRUSTRATING being smarter then most people.

Steverino

Discussion Starter · #16 · Nov 5, 2013

Elemental said:
I noticed this before buying a Volt riding a motorcycle. In fact, if you look deeper you'll see this is how many people live their entire lives like this, not just driving. It's SO FRUSTRATING being smarter then most people.

Well, it's certainly driving smarter, but you don't have to be a brainiac to do it.

StElmosFire

· #17 · Apr 14, 2014

Yep, SLOW DOWN is a great help.
I got a "how quick can you get here" call. 67.5 mile trip
Batt 44 mile charge 75-80 mph mostly highway/interstate. Actual BEV = 32 miles 64 mpg.
Next call-out, Batt 44 mile charge 45-55 mph ECO mode. Actual BEV = 49.5 miles 142 mpg.
It sure pays to watch the speed and Climate settings.

VoltGuy2014

· #18 · Apr 14, 2014

That proves that most drivers are not a brainiac.

The government issue license to everybody, including incompetent drivers.

Steverino said:
Well, it's certainly driving smarter, but you don't have to be a brainiac to do it.

Billtphotoman

· #19 · Apr 14, 2014

At the other end of the spectrum I was on the 130 tollway last weekend and with the cruise set at 85 (the speed limit), the ICE warm and the AC running intermittently I averaged 30.5 MPG over about 33 miles. I had a slight cross wind and the terrain was gently rolling hills. On a couple of the hills the ICE was running full power.

Cheezmo

· #20 · Apr 14, 2014

I'm in the top 6% for MPGcs (38.87) on Voltstats (https://www.voltstats.net/Stats/Details/1611) probably because most of my gas driving a 300 mile drive from Dallas to San Antonio and back steady highway speeds 60-75mph. Wind absolutely is a huge factor as one trip with a strong north wind I got 44mpg going down and 36 coming back at otherwise similar speed/traffic conditions. Although not a big factor on this trip you also have to take altitude changes in to account.

When I see people reporting 50mpg+ mileage on long trips I really have to wonder because that is nowhere near my experience and there shouldn't be a lot of variation at highway cruising speeds. All I can figure is slow driving, complete avoidance of any climate control, big tailwinds, or overall downward elevation changes.

For me, in normal weather, 38-40 is about normal for long flat trip in the 65-70 mph range.

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