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Discussion Starter · #1 ·
GM released some information on the 2016 Volt powertrain. The range extender is a new 1.5L engine from the new GM small engine family with a compression ratio of 12.5:1.

They comment that the compression ratio is higher than the 10.5:1 of the "standard" version of the engine.

I wonder if the "standard" 1.5L they're referring to is the turbocharged and direct injected version that is supposed to power the next Cruze? If so, the 10.5:1 CR should improve efficiency quite a bit over the current 1.4T.

Source:

2016 Chevy Volt: Bigger Battery, More Motor Power, New Range Extender Engine Details: EXPANDED
 

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If there was ever an application for a turbine engine in an automobile this is it.
 

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I also noted Chevy figured out how to keep emissions down when running regular gas - talk about dropping your cost per mile.
 

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Would the higher compression ratio of the 1.5 Litre Engine ( 12 . 5 to 1 ) Demand a higher Octane Fuel ?
 

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I do not think you 2 Goof Balls have a clue about Physics !
 

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Another real improvement - reduction in the need for rare earth metals. This makes the electric power plant less expensive and more sustainable. Rare earths, while actually very common, are hard to mine and hard on the environment.
 

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Discussion Starter · #11 ·
I do not think you 2 Goof Balls have a clue about Physics !
You're so right Brian. They sooooo forgot to mention that GM is incorporating new wide angle cam phasers that allow near-Atkinson Cycle operation (intake valve stays open later reducing cylinder pressure). That means the DYNAMIC compression ratio, the one that actually matters, can be varied much more than before. Very similar to other engines like the Mazda SkyActive.

Jeez you guys, get a clue would you!!! :)
 

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You're so right Brian. They sooooo forgot to mention that GM is incorporating new wide angle cam phasers that allow near-Atkinson Cycle operation (intake valve stays open later reducing cylinder pressure). That means the DYNAMIC compression ratio, the one that actually matters, can be varied much more than before. Very similar to other engines like the Mazda SkyActive.

Jeez you guys, get a clue would you!!! :)
That also pushes the gas burner far closer to the theoretical limits for fuel efficiency, which is extremely important in the Volt.
 

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It actually surprises me a bit that they didn't tweak the 1.4 in the current Volt to run on Atkinson cycle.

But I guess it was already on the small side for a N/A engine and already reportedly worked hard in hilly regions.
 

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I do not think you 2 Goof Balls have a clue about Physics !
Pre-ignition is much less likely with direct injection, since the fuel is actually injected at the time it's needed in the firing order. Unlike all non-direct injection engines where the fuel is injected before hand so the air/fuel charge has time to reach the cylinder.

I say much less likely, but in reality it should never ever occur.
 

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It actually surprises me a bit that they didn't tweak the 1.4 in the current Volt to run on Atkinson cycle.

But I guess it was already on the small side for a N/A engine and already reportedly worked hard in hilly regions.
I suspect GM had basically blown through their R&D budget for the Volt and they already had a working 1.4 engine.
 
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