46.5 MPG using Volt gas engine

[saghost]

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]

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]

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.

[doggydogworld]

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.