[PodCat]

Its 3400 pounds. And the gen 2 uses (5) Modes of driving the front wheels, one of which is coupling the gas motor directly to the wheels when cruising at a constant speed, then the engine can be leaned out and it's RPM maintained for maximum MPG.
If you are really into tech, here is an excellent explanation, the two electric motors are separated by a clutch and a planetary gear set such that the final drive ratio is infinitely variable.

. GM provides technical details of the Gen 2 Voltec propulsion system used in the 2016 Volt

i read all about the planetary gears with my Gen 1, which had 4 modes — #3 of which was direct coupling of both engine and motor. Never did a deep dive into that for my 2017. For some reason I thought the direct coupling had been dropped but apparently it’s there with an even more efficient version.

 

[oscarw]

I bought a new 2000 Saturn SL base model.

It was manual 5 speed, did not have power steering. At 70mph it got 45 mpg.

It was so aerodynamic on the highway the loudest thing was the radio antenna on the passenger side of the windshield, it whistled.

At a stop i could not hear the engine running, had to look at the tach and see it still was at 800 rpm.
that was a great car, went 180,000 miles before rusting out.

 

[obermd]

i read all about the planetary gears with my Gen 1, which had 4 modes — #3 of which was direct coupling of both engine and motor. Never did a deep dive into that for my 2017. For some reason I thought the direct coupling had been dropped but apparently it’s there with an even more efficient version.

GM learned from the Gen 1 Volt that thermodynamics rules. Thus the Gen 2 Volt spends more time with the gas engine in a direct linkage to the drive wheels.

 

[oscarw]

is that true? The gen 1 cars couple the ICE engine directly to the wheel axles at some speeds?

Ive heard it explained both ways (the ICE engine only spins the generators).... and I dont know who to believe anymore

 

[obermd]

is that true? The gen 1 cars couple the ICE engine directly to the wheel axles at some speeds?

Ive heard it explained both ways (the ICE engine only spins the generators).... and I dont know who to believe anymore

There is one, infrequently used mode in the Gen 1 Volt that couples the gas engine directly to the drive wheels. In the Gen 2 Volt anytime you're above a certain speed and running on gas the gas engine is directly driving the car as this is more efficient than converting to electricity and then to propulsion. What the Gen 2 will do in this case is attempt to run the engine at the most efficient speeds for fuel to power conversion and puts the excess back into the battery via MGA.

 

[hellsop]

It's ... complicated. Basically the primary difference between Gen 1 and Gen 2 drivetrains is that in Gen 1, the ICE is clutched through MGA, to the transmission. MGA can be clutched to the ICE (and generate, or start the ICE, for series hybrid mode), to the ring gear (2 motor drive), or both (power split), which is the confusing "is it directly connected or not?" question. I tend to lean on "it is" but that's a matter of interpretation because MGA is in between them in a diagrammatical way. (Gen 1 depends a third clutch to frame to prevent the ring gear from turning AT ALL, which comes into play whenever MGA isn't clutched to it, as in series-hybrid or 1-motor modes.) Gen 2 has the ICE always connected to the ring gear in the transmission, though a freewheel that prevents either from spinning backwards. When that ring gear turns, MGA also turns, and whether that's happening because MGA is powering it or the ICE is powering it depends on the mode and the arrangement of Clutch 1. So the ICE always turns the ring gear when it's running, which leads people to say "ICE DOES connect directly to the wheels", but there's still the problem that spinning the ring gear doesn't make the wheels go unless MGB (or A, but in practice it's always B) is supplying torque on the sun gear to counteract the turning of the ring gear. And how fast and in which direction MGB turns modulates the speed in comparison to ICE RPM, which is how Gen 2 is capable of power split in low speed as well. ICE has a minimum RPM it can keep running, so if that's faster than the RPM of the wheels should be, then sun gear has to turn backwards to keep it all working. And I'm pretty sure "Hey, can MGB turn in reverse?" was the big insight into the Gen 2 Voltec redesign.

Gen 2: https://www.gm-volt.com/attachments/slide3-jpg.168332/

 

[stevon]

PodCat,

The gen 2 Volt does have an overdrive function, as I understand it as described by GM Engineer Tim Grewe, motor MGA turns faster creating an overdrive speed to the wheels. This keeps the ICE engine rpm down, improves efficiency and keeps ICE quieter as well.

Stephen

There’s so much remarkable engineering on this car that one big plus often gets forgotten: that 42 mpg on regular gas, in a car that weighs 2 and a half tons. That’s a very good number for any hybrid, let alone one so heavy. How the hell does it do that?

I understand hybrids (yes, I know the Volt isn’t really one) getting great mileage in traffic.The regenerative braking and instant torque (alleviating the inefficiency of a transmission) are ideal for squeezing out more power from less. But where’s the advantage at highway speeds? There’s no overdrive or other gear change to optimize RPM’s for the higher speed — one reason EV’s do so relatively poorly on the highway. And the regen is no help since you’re normally not braking. Yet I got 41.1 mpg recently on a 50-miles trip at 70-80 mph — with a cold engine on a 50 degree night when the engine hadn’t even had time to reach peak efficiency. On 500-mile trips I have sometimes gotten more than the promised 42 mpg despite a steady 80 mph.

Can someone explain how this is possible?

I’m wondering if the ugly truth is that powering an electric motor with a gas generator is just inherently more efficient than a typical ICE engine. If that’s true, then why did ICE cars develop the way they did when a gas-powered electric motor — feasible even a century ago — was the better way?

 

[begreen]

I love this car. Our 2018 gets 42-45mpg at 65-70 with mountain mode on cruise control and can get higher on the highway at speeds of 50-55 mph. Terrain and winds will affect this but in general, the Volt has a nice, slippery exterior and a very efficient drivetrain that makes for pleasing gas mileage.

 

[imajoebob]

I'm not an engineer, but I play one on the Internet.

One of the reasons is that, especially in the Gen I version, the engine does not drive the car, except in (ridiculous) extreme situations. The ICE is there to generate electricity, not drive the wheels, except in instances where I want to drive over ~75mph. At that point the motors are not strong enough to propel the car any faster by itself, so the engine finally directly engages the driver wheels to give them the needed boost. I don't know if this is also controlled by a "governor" on the electric motors, but I wouldn't be surprised.

So in 99.9% of driving, the ICE is only an electrical generator. The engine revs based on the amount of electricity you're draining from the battery. So under hard acceleration, the engine will kick up the RPMs. Very noticeable when I first get on the highway and turn on Hold mode. As I'm getting up to highway speed, and then for a short while after, the revs are quite high, and the total kWs it's using is almost maxed out. But it drops down quickly enough.

A simple explanation is that using the engine as a generator is a more predictable and, when designed well, more efficient way of driving the wheels. I expect there's a lot less parasitic loss than through a standard differential on an ICE car. Years ago I thought this Volt scheme was a smart way for the oil companies to stay in business: Electric motors driven by gasoline-powered generators. We'd all be driving them by now, and battery development would still be at about 30 miles range.

By the way, if you know your drive will require using gasoline, switch to the Hold mode for highway driving, then back to Normal for city streets. You get relatively lousy gas mileage at city speeds (I "only" get about 33mpg), and at highway speeds my battery mileage drops by at least 1/3, maybe more. If I know my drive won't completely eat up the battery I can charge it, then I use Normal on the highway. This gets me maximum efficiency from both. 20 miles out of a full charge is still cheaper than 40mpg for gas. It helps that I have a 220V charger and can get a useable recharge in short order. 1 hr= ~13 miles, 2 is ~20, 3.5 for a fill-up, ~37-41, depending on the weather and recent driving habits. I'm not a "range monkey." The car just fits my style of driving. But I'm older and don't drive like I did my 5.0 Mustang GT - 19mpg on a good tankful, but admittedly, 500 smiles per gallon... But, off the line, I can still smoke a jerk in a tricked-out Lexus.

 

[begreen]

My 2017 does not get 42 mpg on the highway unless I'm cruising at 60 mph or less. At actual freeway speeds like 75 mph, it's closer to 38-39 mpg. I attribute this to the fact that I "cheaped out" and didn't buy fuel efficient tires when I replaced them.

Modern cars are awesome. I averaged ~45 mpg traveling mostly at 60-70 mph with Super Cruise coming up from CA to WA state on I5, including the stretch over Siskayou Pass. That said, I have a friend with a Camry Hybrid that has a bit better mileage averaging close to 50 mpg on a trip. It weighs about the same as a Gen 2 Volt.