Gen 2 Volt Combine Peak System Output?

The 2016 ELR is based on the first generation Voltec transmission, battery, and motor inverter electronics but aspects of those systems and cabling have been tweaked to allow greater battery output and electrical power flow in general. The 2016 ELR in EV mode can output 160 kW or 214 HP in EV-only driving because of these enhancements. The 2016 ELR's Sport Mode has also been enhanced to allow gas engine startup under hard acceleration to generate additional electricity in series configuration to boost the total output from the big electric motor to 174 kW or 233 HP. Under more sedate conditions with the gas engine running (due to Hold mode or an "empty" battery) the ELR can combine some mechanical torque from the engine together with electrical power generated by one of the motors but because of the way the motors and the engine mechanically connect it needs to drop the mechanical engine path to the wheels in favor of series mode for high output. The 2011-2015 Volt works the same way (but without gas engine assist in Sport Mode) but the Volt is limited to a 111 kW (149 HP) EV capability from the battery and with power output through MG B (both battery and motor are rated up to 149 HP).

I know from discussions a few months back that you were skeptical that the 2016 ELR works this way and is really capable of drawing 160 kW of power from it's battery pack and using it in MG B to put out 214 HP with even a bit more series mode electrical boost from the gas engine and MG A in Sport Mode. You felt that in spite of GM specifications that clearly call out a 160 kW EV Touring Mode you thought that couldn't really be true and the battery must still be limited to be close to the Volt's 111 kW output limit since the ELR appears to use the same battery cells and pack as the 2014 or 2015 Volt. Ultimately, we will know for certain when the first reviewers or owners get in the new 2016 ELR and put the petal to the metal. Or, perhaps GM will put out additional public PR material before then. Anyway, based on various sources of information I'm pretty confident of my interpretation of how the 2016 ELR works.

eigenmeat said:

Based on this video posted by another forum member:
https://www.youtube.com/watch?v=G7IXoZ5g-cw

It seems Gen 2 Volt's gas engine can send torque directly to the wheels. Therefore, in theory both the electric motors and the gas engine can drive the wheels together. Does that mean the Gen 2 Volt can actually have more than 149 peak HP(but obliviously less than 101+149)? Or does GM choose to "crippling" it to a peak of 149HP regardless? I could not fine a combine system output from any online sources.

Other plug in hybrids like the Prius and C-Max all quote a ICE power, electric motor power, and combined power separately.

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The 2016 Volt (and 2016 Malibu hybrid) have a completely new transmission design that no longer has a series mode. Read about it here:

http://gm-volt.com/2015/02/20/gen-2-volt-transmission-operating-modes-explained/

A less technical description with a few additional pretty pictures is available but note that both of these articles are from February and might have some slightly out of date numbers for estimated mpg and EV efficiency etc. This other article can be found here:

http://www.greencarreports.com/news...ws/1096942_2016-chevrolet-volt-powertrain-how-it-works-in-electric-hybrid-modes

In the new transmission design there is always a mechanical path to the wheels for the gas engine whenever it is running. There is one fixed gear ratio mode at speeds above 30-40 mph where the engine has a direct path to the wheels and no electric motors need to be involved although they can assist with power or regenerate power during braking if needed. In that case, the gas engine and electric motor output is completely additive. In theory, the bigger electric motor (MG B) could put out up to its maximum listed peak of 87 kW (111 HP) and that could be combined with the gas engine power which reaches a peak of 74 kW (101 HP) for a total peak of 212 HP for some period at certain vehicle speeds and engine rpms. This peak may be limited in reality by various factors and so far GM only stated a specified peak output of 149 HP.

Likewise, the new transmission's Low Extended Range eCVT mode should have strong capabilities for adding mechanical gas engine output power but some of that engine power gets split over to the MG A to generate electricity which is then used by MG B possibly together with some battery power to drive the final output. Again, GM specifies a peak output of 149 HP. The engine alone has a peak of 101 HP so presumably some battery assist to MG B can fill the gap. Unlike the original Volt and ELR, the big MG B motor cannot provide the full 149 HP (it can only do 111 HP because it was downsized) so the gas engine is being additively used to reach the total combined output.

Finally, the new transmission has a High Extended Range eCVT mode which is used at highway speeds. This mode can also additively combine power from the gas engine mechanically while also splitting some to use one motor to generate electricity to power the other motor plus some additional power from the battery, if needed.

So, the answer is that the gas engine's power (101 HP peak at higher rpms) is already being additively combined with the electric motors to reach the specified peak system output of 149 HP in the 2016 Volt when the engine is being used. When the gas engine is off, the 2016 Volt is able to combine the output power of MG A with the power of MG B to surpass MG B's peak of 111 HP and together produce the full specified 149 HP in EV mode.

If you look at the Prius specs, it appears that it's gas engine output power is completely additive with its maximum hybrid battery output power to create a total system power of 134 HP. However, if you look at the specs for the Toyota Camry hybrid (based on the same general hybrid architecture but with more powerful components) you will see that it's total combined system output is less than completely additive. Likewise for the C-MAX or Fusion hybrid. The 2016 Volt specs don't call out "total system power" as a separate line item but elsewhere it implies a maximum output of 149 HP.

The 2016 Malibu hybrid specs give the transmission's total power output as being 182 HP while the gas engine peak HP is 124. That implies a battery and electric motor assist of 58 HP (43 kW). GM does not publish the peak power output of the Malibu's hybrid battery but there is reason to believe it could be as high as 84 HP (60 kW) so the Malibu may also be less than totally additive or at least may be taking a somewhat conservative use of their Hitachi battery pack. Or maybe it isn't using Hitachi's highest power hybrid cells.

By comparison with the 2016 Malibu hybrid, the 2016 Volt does seem to be limiting itself from additive engine and battery power to a somewhat greater degree. Is that an artificial marketing limitation soon to be lifted by a Chevy Volt SS model? Or maybe Chevy has one last surprise left to spring on us with the regular new Volt. It is notable that GM has released EV performance specs for 0-30 mph and 0-60 mph but still hasn't released any performance specs when the gas engine is running. They have released some technical graphics and engineers have made some vague statements that have tended to imply that performance with the gas engine on is roughly about the same as EV mode performance. We should know the real answer soon.

Please don't devalue the Gen2 Volt without testing it first! You remind me of Aesop's fable about the fox who couldn't grab a bunch of grapes, so he called them "sour grapes". I wish I could bet against you personally that the 2016 Volt will be much better than any prejudgement you have.

"It's complicated and may vary, especially between generations" is usually the best answer for a Volt...

You're absolutely correct about how the planetary system works. But the motor is designed to run at the full speed of the Volt, so that's not really a consideration. The same amount of energy has to come from someplace, either way, and for most people, energy from the wall costs less than energy from the tank. So the real win is "don't use gas if you can help it and get back home with no range left ever". That kind of leans on "Just use up the range, sometimes CS will come on" as the most consistently good plan for efficiency. Sometimes you'll lose an the ICE will start on the last hundred yards, but that'll be rare enough to not really matter. in comparison to the number of times you'll get home having used no gas at all when habitually kicking on Hold Mode for a while would have used up a pint unnecessarily.

Jaar819 said:

I am a physicist/electrical engineer who has designed inverters and know that motors have operational bounds, in both speed and torque.

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Well, then, you obviously know better than anybody that's bothering to answer your question. What's YOUR answer? You're not going to get many arguing with you unless WoT comes back.

The 2018 volt has an upper speed limit slightly in excess of 100mph, I believe. As you continue increasing in speed towards that limit, there are two ways of doing that, one in cd mode, the other in cs mode. The running rpm of all the motors seems to me to be quite different in those two cases. My question has to do with the RELATIVE efficiencies between the two modes for speeds beyond 70 mph. Below that speed, I am sure gm has algorithm somewhat optimized. Above those speeds, perhaps there is a legal issue gm is staying out of. In any case, as evident in this forum, many of us volt owners purchased the vehicles partly for the novelty of owning it, and are curious about it on different levels.

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I don't know the absolute efficiencies above 70 MPH between the two modes. Go test 'em. I've already given my REASON for not knowing: I don't care. The relative efficiency between CS and CD at 80 MPH is never going to matter to me because it's going to be buried and tamped down by the efficiency of driving 65 MPH instead and the stake through its heart is what matters more is how much it's going to COST me rather than rarified efficiency. And right now, for me? Wall miles are cheaper. By a lot. Gas costs 50% more easily vs wall miles on average. Throwing in just the cost of oil changes adds a penny a mile to gas costs. So for me, it's ALWAYS beneficial to bet on not using the engine. I don't care by how much, whether it's 40%, 50% or 60% cheaper to use wall miles, because that's never going to result in a change of how I need to operate the vehicle. I just need to run it to CS and let it do its thing.