Opel Monza Concept, The Next Volt?

Very nice looking.. and a CNG range extender would be great if there were a few CNG stations along the highway or if it could use LPG from a standard tank.

I won't be surprised if the next engine is a 1.0 3-cyl. I can see the advantages of lowering weight even if it does not incease CS MPG. Since many do most driving on EV, increasing that by lowering weight might be more important. But hope they get it up to high 40s or even 50MPG_CS or for some it will continue to suffer from misplaced prius envy.

 

Let's go point by point on a 1L 3-cyl di-turbo gasoline ice for the next volt. It likely wouldn't save much weight. The ford 1L ecoboost weighs 100 kg, about the same as the prius's (sp?) 1.8L Atkinson. Part of the reason for the weight is the use of an iron block that reduces the start up penalty by heating up fast, and the strength of the iron makes the engine very small. This is a good design. If you go aluminum you don't save much weight, certainly much less than 50 kg. If you want to shave weight a great deal can be removed from the rest of the volt. The ice isn't the heavy part.

Advantages of a 1L Turbo versus 1.8L atkinson (these have about the same hp, about 35% more than the current volt ice)
1) smaller volume
2) less start up penalty
3) more efficient at lower power levels (lower friction, lower pumping losses)
4) more efficient at high load low to moderate rpm running the miller cycle
5) broader torque curve for better direct driving of wheels

Advantages of 1.8L atkinson
1) lower cost
2) lower complexity and 4 cyclinders (buyers may prefer this)
3) more efficient at higher power levels

Either ice would make the volt more efficient. I would go the Atkinson route at these power levels and price levels, as buyers might not like the tiny 3-cylinder turbo on a $30,000+ car. Then again bmw is going 3cyl 1.5L on there much more expensive and powerful i8 (I have to question why not a 4cyl turbo?). The battery can cut off the inefficient low power of the Atkinson or high power of the turbo in most cases.

cng is not a good fit for the volt, but a small turbo could efficiently burn cng (filled at home) and gasoline in a bifuel non-plugin vehicle.

 

My bet is on the 1L turbo. A new DI one is debuting in the Opel Adam. It's an aluminum block that produces 115hp in that application. Sounds like the first use of new engine family that will be replacing the ones in the current Sonic and Cruze.
Future Chevrolets to Benefit from Small Gas Engine Family
Opel Adam Gets New 1-Liter 3-Cylinder Turbo with 115 HP

A 3 cylinder engine might have less internal friction than a 4. Beginning with 1 less piston rod. It could be part of the reason the new Mirage does better than the Spark in fuel economy. There are other variables, but we don't have all the details on the Mirage yet.

 

I really don't know what the next gen volt will have. I do know originally they wanted something like this new 1L turbo. There are tradeoffs, and now unlike in the launch gm has the time and money to get the volt designed right. To me the NVH and lower cost of an atkinson 4 cylinder makes more sense in a car like the volt (currently about 62% electric, 38% gasoline hybrid miles in a 3500+ lb vehicle). Say you can get 5% more mpg out of that baby turbo versus an atkinson, but it sounds worse(NVH), will those extra 6 gallons of fuel a year make up for it? Then again gm has made questionable decisions in the past. The engineers should have plenty of time to listen to how the engine sounds.

It will be interesting to see what these new 1L ices do on the epa test, especially on the 5-cycle version. We know they do well on the European tests, but these are quite different from how amricans drive. It is hard to believe a 1L turbo would do much better than a 1.4L turbo on real american roads. The chevy 1.4L turbo does need di though. It would also be nice if it learned the vw cylinder deactivation trick and could run as a 2-cylinder 0.7L engine.