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On 8/24, there was a home page (not forum) post named "Pure Series E-REV – In Search of the Holy Grail" which concluded that Volt's power split mode was likely more efficient than a pure series hybrid powertrain setup, even if the pure series setup can be run at the engine's most efficient RPMs. See
http://gm-volt.com/2012/08/24/pure-series-e-rev-in-search-of-the-holy-grail/

In reading the responses to that post, I didn't see any discussion of the implications for the "mountain mode" games that some Volt drivers play in order to maximize CS MPGs, where drivers will engage mountain mode after the battery's depleted to try to force the ICE into a higher (and presumably more efficient?) RPM band, with the extra energy going into the battery for later use. At first blush, it would seem that such mountain mode games aren't worth it if power split mode is more efficient than pure series hybrid, especially if the Volt ICE stays within about 6% of minimum SFC anyway. What are your thoughts? George? Walter?
 

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Generally, I'd agree, whenever converting energy, there is a loss, usually a significant loss from the conversion. Then there is mountain mode. I'd actually say it's far more energy efficient in gas mode going up hill, and the car's design going downhill in electric seems superior. I did the gaming thing (lots of moutains here in Colorado). I squeezed 100 miles from a charge plus recharging in mountain mode by toggling at what I believe were good tradeoff points between mountain mode and gas. I managed about 58 MPG over a 250 mile trip on one charge. So, yes, there appear to be ways to time regeenrative braking, down hill, up hill, etc., but give me electric all the time - wonderful.
 

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Whenever I travel beyond EV range I engage mountain mode during the highway portion of the trip and use my TomTom's reading of distance to destination to estimate when to disengage it so that I use no more gas than necessary. The few times that I used mountain mode to add charge to the battery seemed to use more gas than when I remembered to engage mountain mode early enough in the trip.

KNS
 

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As an early proponent of MountainMode games, I now realize that the real gains I was getting were not really from putting it in higher RPMs, but really from using it in the highway conditions (when the power-split can work well) and saving the battery power for the stop/go traffic at the other end of the trip. Basically using it as a poor-2011 owner's Hold mode. There are a few threads that show that using it earlier while still on the highway, or while on higher-load parts of the trip even if off highway, and saving battery for stop/go is better.
 

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As an early proponent of MountainMode games, I now realize that the real gains I was getting were not really from putting it in higher RPMs, but really from using it in the highway conditions (when the power-split can work well) and saving the battery power for the stop/go traffic at the other end of the trip. Basically using it as a poor-2011 owner's Hold mode. There are a few threads that show that using it earlier while still on the highway, or while on higher-load parts of the trip even if off highway, and saving battery for stop/go is better.
Right, any mountain mode gaming "gains" are really by shifting the use of the ICE in time to more efficient conditions for the ICE, and shifting the battery to conditions more conducive for electric operation (and longer durations of the ICE not starting up).

In the general case, for the average user, they should only use Mountain mode for very large mountains, or to maintain their battery charge for city driving when there's first a lot highway driving (and they don't have hold mode). Even then, I'd generally recommend everyone to just use Normal or Sport. That maximizes battery use over a full trip on the whole (it's not often the driver successfully ends their destination during mountain mode games with zero battery miles), and minimizes inconvenience/extra work for the driver.

In short, Just run the Volt in Normal/Sport as it's intended for to maximize savings and pleasure. That's why the original Volts didn't come with a Hold Mode to begin with, it's only legislation in Europe involving zero emission city centers that made that mode attractive.
 
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