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I understand the ICE will have a mechanical connection to the drive wheels under certain circumstance. What are the conditions that make this happen? How can the driver tell when it happens?

TIA
 

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The driver can't tell, basically. There may be a way to derive it from the bus data. The conditions are "anytime the ICE is running and driving is smooth above about 50" for Gen 1 and "anytime the ICE is running and driving is above about 30" for Gen 2.
 

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Others will correct me if I'm wrong on this but it is my understanding that there is a sort-of "assist" mode that pretty much only runs at higher speed (+45mph) and steady driving. Think of it as a sort of "overdrive".

Even when it engages I've never noticed it kicking in.

HOWEVER

If you then need to accelerate to pass, there is a somewhat disconcerting lag while the clutches disengage and the electric motors synchronize. To me it feel a lot like Turbo Lag used to. Once I got used to it I just sort of built it into my driving habits and compensated.
 

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Others will correct me if I'm wrong on this but it is my understanding that there is a sort-of "assist" mode that pretty much only runs at higher speed (+45mph) and steady driving. Think of it as a sort of "overdrive".

Even when it engages I've never noticed it kicking in.

HOWEVER

If you then need to accelerate to pass, there is a somewhat disconcerting lag while the clutches disengage and the electric motors synchronize. To me it feel a lot like Turbo Lag used to. Once I got used to it I just sort of built it into my driving habits and compensated.
This is basically correct - for a first generation Volt.

The OP indicated that they have a 2016, second generation car.

The engine is always connected to the wheels in the second generation, in a fashion that's very similar to a Prius - engine geared to one part of a planetary set, wheels on another, and a motor on the third elegant regulating what happens.
 

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So the bottom line, it will engage when it is optimal to do so, it's really hard for you to dictate when.
 

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I've heard that the very first version, 2011-mid 2012, the ICE didn't connect until you were somewhere over 70 mph, and then only under heavy load or if you were going up a steep hill. I know that in my early 2012 I don't have any of that lag when hitting the pedal to pass at highway speed - it zooms immediately.
 

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I've heard that the very first version, 2011-mid 2012, the ICE didn't connect until you were somewhere over 70 mph, and then only under heavy load or if you were going up a steep hill. I know that in my early 2012 I don't have any of that lag when hitting the pedal to pass at highway speed - it zooms immediately.
You heard wrong.

In fairness, it's a fairly common misconception, likely driven by the exact examples GM chose when they made the initial presentation to the press in the fall of 2010 - the lead engineer walked the press through animations of how the car worked at 30 mph and 70 mph, and despite her emphasizing a couple times that those particular speeds weren't important and were just examples, about half the resulting articles said the engine only connected at 70 mph.

My guess is they chose 70 so they wouldn't have to explain the engine cycling behavior (or be accused of lying later for not explaining it.)

In fact, the engine connects to the wheels at any speed over 35 mph except under moderate to hard acceleration (when the engine is on.)

The design of the transmission means that MG B can't deliver full torque in Power Split mode, because after the gearing it makes significantly more torque than the ICE and MG A combined. That's why the car shifts back to Series under hard acceleration, which may or may not be detectable depending on how abruptly you transition from low acceleration to high.
 

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You heard wrong.

In fairness, it's a fairly common misconception, likely driven by the exact examples GM chose when they made the initial presentation to the press in the fall of 2010 - the lead engineer walked the press through animations of how the car worked at 30 mph and 70 mph, and despite her emphasizing a couple times that those particular speeds weren't important and were just examples, about half the resulting articles said the engine only connected at 70 mph.

My guess is they chose 70 so they wouldn't have to explain the engine cycling behavior (or be accused of lying later for not explaining it.)

In fact, the engine connects to the wheels at any speed over 35 mph except under moderate to hard acceleration (when the engine is on.)

The design of the transmission means that MG B can't deliver full torque in Power Split mode, because after the gearing it makes significantly more torque than the ICE and MG A combined. That's why the car shifts back to Series under hard acceleration, which may or may not be detectable depending on how abruptly you transition from low acceleration to high.
So the bottom line is, drive like a grandpa on the highway with Long acceleration cycles to slowly get up to speed and that might cause you to be in "overdrive" more often. Driving like a jack rabbit like many Chicagoland drivers in rush hour traffic will cause you to more likely disable power split mode. Alternatively, just drive and don't worry about it.
 

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Our 2016 Volt screen will display when our Volt is running on just the gas engine with no assistance from the battery. It will also display when its using assistance from the battery and when the gas engine is running, propelling the car, and charging the battery. I'm sure the 2017 Volt has the same display as well.
 

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For gen2, the is an efficient direct clutch for highway driving. I think >45mph????
Plus there is a CVT connection to the wheels for low speeds, and/or higher horsepower required.
Regardless of which mode, the battery motor is also connected and can add additional power, or generate battery power via regen/momentum.
There must be some mode where the CVT is only connected to the battery motor and not the wheels, cause the engine can run when the car is not in motion.
 

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Our 2016 Volt screen will display when our Volt is running on just the gas engine with no assistance from the battery. It will also display when its using assistance from the battery and when the gas engine is running, propelling the car, and charging the battery. I'm sure the 2017 Volt has the same display as well.
Note that "no assistance from the battery" is not the same as "no assistance from the motor-generators". On average, any time you're in any of the CS modes you're netting out "no assistance from the battery".
 

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For gen2....
There must be some mode where the CVT is only connected to the battery motor and not the wheels, cause the engine can run when the car is not in motion.
Nope. The gas engine is always mechanically connected to the wheels through the planetary gears. If the car is stopped and engine is running it just means that all of that engine output rpm goes to spinning the "battery motor" also known as the generator motor or "MG A". The same thing happens in a Prius which has no clutches. Most of the engine torque wants to flow towards driving the wheels but if the brakes are engaged when the vehicle is stopped then the only gear that can turn and absorb the engine's rotation is the sun gear which is connected to MG A (or MG1 as it's known in a Prius). Like a Prius, the gen 2 Volt and Malibu hybrid (and Cadillac CT6 plug-in hybrid) do not have the series mode which the gen 1 Volt had that allowed the engine to disconnect from the planetary gears and only spin the MG A generator.
 

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Nope. The gas engine is always mechanically connected to the wheels through the planetary gears. If the car is stopped and engine is running it just means that all of that engine output rpm goes to spinning the "battery motor" also known as the generator motor or "MG A". The same thing happens in a Prius which has no clutches. Most of the engine torque wants to flow towards driving the wheels but if the brakes are engaged when the vehicle is stopped then the only gear that can turn and absorb the engine's rotation is the sun gear which is connected to MG A (or MG1 as it's known in a Prius). Like a Prius, the gen 2 Volt and Malibu hybrid (and Cadillac CT6 plug-in hybrid) do not have the series mode which the gen 1 Volt had that allowed the engine to disconnect from the planetary gears and only spin the MG A generator.
The important thing to remember is that when the ICE on Gen 2 is running and the car isn't moving, it just means that the sun gear is spinning "backwards" proportionally. Not a problem; it's designed to do that. But it's a bit of a jump to think how much flexibility there is in a system when you can do things like that, or that you're essentially *braking* that spinning sun gear with MGB to make the wheels start turning from a ICE-turning dead stop.
 
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