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One of the reasons I've heard cited for why GM hasn't used the Voltec powertrain in other vehicles is that they were having difficulty scaling up the power output. Whether or not that is true, I feel that it would be a mistake to approach these hybrid systems solely by focusing on the mechanical output of the internal combustion engine.

 

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I don't see what the difficulty would be. The thing you have to scale up are the electric motors, that's not hard you can build a motor of any size. I don't see why the ICE matters. The performance of an EREV should be entirely based on it's electric drive train, motors and batteries, the ICE is there to run a generator and for no other purpose. The ICE needs enough power to handle average highway cruising, acceleration including including the weight of a towed trailer or boat, should be handled by the battery not the ICE. That would mean that a Voltec Silverado would need a bigger battery than the Volt, maybe 30KWh, plus bigger motors but it shouldn't need a bigger ICE. GM's decision to not electrify it's trucks is probably for marketing reasons not engineering reasons.
 

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Seems the video discusses two different issues. First, the ability to scale up the Voltec architecture, and second, the recommendations to increase the ICE thermal efficiency instead of simply using a larger (and more thursty) ICE if a more powerful Voltec based drivetrain is envisioned.

In regards to scalability, how difficult would it be to make a more powerful Voltec propulsion system for heavier vehicles like SUVs? The second generation Voltec is a parallel hybrid system that has been designed for more emphases on the electric propulsion. This the Volt drives more like a pure electric car than say a more conventional parallel hybrid like the Prius. I don't see anything in the Voltec powertrain that would be difficult to scale up. Motors, inverter and controlling software, no problem. Planetary gear sets and electronically controlled clutches, again no problem since the same components are already used in automatic transmissions used on heavier vehicles. The ICE is certainly no issue, GM has a lot of ICEs that can be used in a more powerful Voltec. Let me give one example, the 2 liter turbo 4-cylinder used in the CT6 Hybrid. Batteries are technically no problem, but cost maybe an issue. Heavier vehicles will place heavier demands on the battery, and batteries are the most expensive component. But battery technology and costs are steadily improving. Let me go out on a limb and say that additional battery capacity required to maintain Voltec range in heavier SUVs and trucks should be easily absorbed by the high profit margins made with these overly expensive vehicles.

In regards to better ICE efficiency, sure no question. An ICE powerful enough for a large SUV but consuming the same as the Volt is desirable. As stated in the video there are a number of things that can be done to improve efficiency, but these things add costs. That leaves GM with the unenviable choice of selling a Voltec SUV at a higher price, so high as to restrict market share, or heaven forbid, reduce profits to pay the ICE improvements. Considering that the average Volt owner makes 90% of his trips on electric only, dumping money on high tech fuel efficiency not used in ordinary ICEs seems like a bad investment.
 

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What I think no one is addressing is the complexity of the Votec system. Sure it's easy to put in a bigger battery or a bigger ICE. That's child's play for GM. The magic is integrating both, and seamlessly switching back and forth. That's an engineering marvel. As you increase the power of the electric motors or ICE, this engineering problem gets more complex. Least we forget, the G2 had a serious backfire problem that it took GM more than a year to resolve. That's the type of thing that can crop up in scaled versions of the Voltec.
 

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Considering that a diesel electric locomotive engine is pretty similar technology on a much larger scale, I doubt the obstacles are technical. I agree it is more likely a marketing problem. Like how many truck owners want a hybrid? Or why should we make a truck that costs 50% more to manufacture and few want to pay more for?
 

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Considering that a diesel electric locomotive engine is pretty similar technology on a much larger scale, I doubt the obstacles are technical. I agree it is more likely a marketing problem. Like how many truck owners want a hybrid? Or why should we make a truck that costs 50% more to manufacture and few want to pay more for?

People are standing in line to pay $75k to $100k for an urban cowboy truck. GM, Ford, etc. has them flying off the showroom floors. What's another $7-$10k?
 

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^ those urban cowboys generally want a big diesel with a 5 inch diameter tailpipe that roars when he stomps the accelerator. He may not be so excited about a hybrid. No way to roll coal in that.
 

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my 2008 Tahoe was hybrid , worked just like the volt up to 25 mph and for about 3 blocks
6 litre motor , the electric motors were in the convention 4wd transmission
gm has had the tech for a while and yes they wanted 20 extra grand Canadian for the hybrid
got that bus down to 12l /100km or 19.6 mpg
 

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^ those urban cowboys generally want a big diesel with a 5 inch diameter tailpipe that roars when he stomps the accelerator. He may not be so excited about a hybrid. No way to roll coal in that.
But, when the Voltec or Tesla version beats them from a stoplight (remember, urban cowboys, not hauling logs across raging rivers in a forest mountain range) their diesel manhood will be a little diminished. They'll have a little d instead of a big d, lol.
 

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One thing commonly forgotten in these discussions is the aerodynamics of the car itself, aside from the electric drive-train. (Ever replace your tires on your volt and lost 15-20% instantly? I have. and with efficient third party tires that are no where near OEM efficiencies.)

Every bit of the car is designed to be as efficient as possible. Take the exact same drive-train and throw it in the same size and weight of a car that does not have the efficiency designs of the volt and you will lose better than half your range. An article that just came out today discussing a car like this, a 1960's Mustang shell with an electric drive-train. It has a 60kWh battery while only getting 125 mi range. http electrek.co/2018/11/14/all-electric-1960s-mustang-charge/ .

Trucks and SUV's have much more air drag than a Volt and these are actually the design principles that need to be overcome. You would likely need a 30kWh+ batter in a truck just to achieve the same mileage a Volt gets. As for the engine, it would have to be bigger for sure. As these vehicles would need to use more energy to get down the road even without consideration of towing or hauling, an engine output can be calculated in kWh just the same as batteries. kWh is not isolated to electricity. If it takes X amount of energy to move the vehicle y amount of miles at a speed of Z, then that energy has to come from somewhere. If the ICE is does not provide X in the time of Y you cant move the vehicle at the speed of Z. Engineers have to account for their being zero energy in battery when sizing for a range extender.
 

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It doesn't share much with the Volt design, but the CT6 PHEV weighs 4500 pounds, has (2) 100kw motors, is paired with a 2.0L turbo 4 (265HP, 295lbft), has a combined output of 335hp and 430 lb ft of torque. It's good for a 0-60 of 5.1 seconds, but it kicks on the gas engine to do it. It will go 31 miles on a charge and up to 78MPH on electric only. I feel like that's scaled up.
 

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My guess is that GM is done with the Voltec drivetrain, it doesn't make sense to invest further in it. The Volt is a transitional EV, it has a gas engine because batteries were too expensive and too heavy, especially so when the Gen1 Volt came out. We are getting to the point very batteries are almost reasonable. The Bolt costs about the same as a Volt, it's range is about 30% less than you would like it to be but you can see that in just a couple of years batteries will have improved enough to give a Bolt a 300+ mile range (the Model 3 is already there and the base LR model was only about $5K more than the Bolt). Assuming that batteries continue making incremental improvements over the next 10 years you will see larger and larger vehicles hitting the good enough range level, 350 miles or so, first at the high end of their price class but then in a few more years at the lower end. So why would GM want to invest in a throwaway technology instead of putting all of their money into the Boltec basket which represents the future.
 

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Discussion Starter #13
It doesn't share much with the Volt design, but the CT6 PHEV weighs 4500 pounds, has (2) 100kw motors, is paired with a 2.0L turbo 4 (265HP, 295lbft), has a combined output of 335hp and 430 lb ft of torque. It's good for a 0-60 of 5.1 seconds, but it kicks on the gas engine to do it. It will go 31 miles on a charge and up to 78MPH on electric only. I feel like that's scaled up.
That's true. I was also speaking from a bit of ignorance regarding Voltec 2.0 (my experiences with the Volt are with the Gen 1). The Gen 2 Volt and CT6 PHEV both have a more connected ICE. With the Volt, at least, it's capable of 100% of it's driving on electricity as long as the battery has capacity.

It's also possible that they just didn't see a big enough reward scaling the Voltec up for larger vehicles. The CT6 PHEV gets what? 25 mpg? At that point, you might as well save the money and go with a mild hybrid.

My guess is that GM is done with the Voltec drivetrain, it doesn't make sense to invest further in it. The Volt is a transitional EV, it has a gas engine because batteries were too expensive and too heavy, especially so when the Gen1 Volt came out. We are getting to the point very batteries are almost reasonable. The Bolt costs about the same as a Volt, it's range is about 30% less than you would like it to be but you can see that in just a couple of years batteries will have improved enough to give a Bolt a 300+ mile range (the Model 3 is already there and the base LR model was only about $5K more than the Bolt). Assuming that batteries continue making incremental improvements over the next 10 years you will see larger and larger vehicles hitting the good enough range level, 350 miles or so, first at the high end of their price class but then in a few more years at the lower end. So why would GM want to invest in a throwaway technology instead of putting all of their money into the Boltec basket which represents the future.
You might be right. I'm interested to see whether GM thinks that hydrogen fuel cell technology will take off. Personally, I think the missing ingredient from the Clarity and Mirai is a plug. Why would you build an electric vehicle with a battery that can only refuel using hydrogen?

An electric SUV/truck with a ~20 kWh battery and HFC range extender seems like a much better use of the technology.
 

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One of the reasons I've heard cited for why GM hasn't used the Voltec powertrain in other vehicles is that they were having difficulty scaling up the power output. Whether or not that is true, I feel that it would be a mistake to approach these hybrid systems solely by focusing on the mechanical output of the internal combustion engine.
I don't question that you've heard that, but I feel like there's really not enough to assess anything in that statement -- "difficult" in a car manufacturer context can by anything from all the way from engineering issues to "we can't get the public to pay more for it". The only engineering issue that's obvious is the matter of shoehorning all the bits into places that are both out of the way and accessible enough to repair.

The real reason to do it is hybrid reasons, though. The Malibu is a great example: the gas versions get EPA ratings of 26 and 30 MPG, and the Voltec-based hybrid gets 46 MPG. That's 50% better fuel economy without even doing a ton of aerodynamic work, AND it out-accelerates the gas siblings. The cost? $4k and some trunk space, which can completely vanish under the floor once you get into the "small to midsize SUV" profile. Okay, it's more of "hybrid" than the Volt is, but that's fine. Start putting that level of "hybrid" into the top trims, and your whole fleet fuel economy flies.

The place where I can see things might actually become difficult (or fun, depending on your perspective) is how to do this kind of thing in a AWD-capable way, and that might be solvable by rethinking power distribution. Maybe there's actually independent systems for front and reat and you get Real Voltec on the rear axel, and the front becomes an induction motor and regen system for seamless switching between 1 and 2 axel propulsion...
 

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That's true. I was also speaking from a bit of ignorance regarding Voltec 2.0 (my experiences with the Volt are with the Gen 1). The Gen 2 Volt and CT6 PHEV both have a more connected ICE. With the Volt, at least, it's capable of 100% of it's driving on electricity as long as the battery has capacity.
Heh. I get that. The Gen 2 is a really different platform when you start digging into the details. It's beyond "complete redesign" and into "complete rethinking from a learned and experienced perspective". The use and blending with the ICE is WAY more of a "cooperative" hybrid system than "series" or "parallel". It's more like "parallel" of the two, but the balanced, equal-sized MGs can combine in a lot of ways that the Gen 1 just can't.

It's also possible that they just didn't see a big enough reward scaling the Voltec up for larger vehicles. The CT6 PHEV gets what? 25 mpg? At that point, you might as well save the money and go with a mild hybrid.
Or twist it more like the Malibu. Severe hybrid but no pretense of trying to keep more than very short EV-only range. Malibu gets good economy, and it's hearty enough for at least some towing. (Half a ton or so. Not bad for a mid-sized FWD vehicle, but clearly not designed for that purpose.)
 

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Discussion Starter #16
The place where I can see things might actually become difficult (or fun, depending on your perspective) is how to do this kind of thing in a AWD-capable way, and that might be solvable by rethinking power distribution. Maybe there's actually independent systems for front and reat and you get Real Voltec on the rear axel, and the front becomes an induction motor and regen system for seamless switching between 1 and 2 axel propulsion...
I'm a bigger fan of a rear induction "pusher" motor. It's in the right position for low-end torque and towing. The front PMAC/Voltec system allows most of the sustained speed driving and regenerative braking to be done with the front wheels (also where you want it).

That layout would be able to enhance both EV and PHEV layouts.
 

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That's true. I was also speaking from a bit of ignorance regarding Voltec 2.0 (my experiences with the Volt are with the Gen 1). The Gen 2 Volt and CT6 PHEV both have a more connected ICE. With the Volt, at least, it's capable of 100% of it's driving on electricity as long as the battery has capacity.

It's also possible that they just didn't see a big enough reward scaling the Voltec up for larger vehicles. The CT6 PHEV gets what? 25 mpg? At that point, you might as well save the money and go with a mild hybrid.
Yeah, it's rated at 25mpg combined, but in reality, my parents have been getting closer to 30. And for retired folks, it's nice to get the first 30 miles on electric, because they don't drive much anymore. It's an interesting car, in that the performance of the PHEV version is better than 2 of the 3 other engine options, and gets significantly better mileage than all 3. It's a completely different philosophy than the Volt... less about energy savings, and more about performance. But this philosophy should translate to larger SUV's and trucks, because those are also more about performance. I just feel, for the people who buy a diesel to tow, the torque of an electric system with a small motor generator to recover some battery when not at peak load, would be ideal, especially when towing in city traffic.
 

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We are not at the end of battery development, we are at the beginning plus the prices will come down as they find ways to get rid of the rare cobalt There's lots of lithium around and it (and cobalt) can be recycled in the 90% and greater range right now. Governments and auto companies are forming conglomerates to spend billions around the world on development and manufacturing. You can only do so much with Voltec and money spent on it has diminishing returns. We are fast coming to the point where batteries will hold enough energy, be cheap enough and charging stations will be fast enough and ubiquitous enough that charging anywhere won't be an issue. Energy will get cheap enough through solar, wind, tidal, hydro that gasoline will be the more expensive way to go even with the subsidized oil industry we have now. With increasing environmental concerns and wearing out of infrastructure raising the cost of refineries, pipelines etc. oil/gas costs will rise. The cost of gas in the US is artificially low (compare to anywhere else on earth that isn't subsidized) and will go up. All this means the end for hybrid and Voltec type of power.
 

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We are not at the end of battery development, we are at the beginning plus the prices will come down as they find ways to get rid of the rare cobalt There's lots of lithium around and it (and cobalt) can be recycled in the 90% and greater range right now. Governments and auto companies are forming conglomerates to spend billions around the world on development and manufacturing. You can only do so much with Voltec and money spent on it has diminishing returns. We are fast coming to the point where batteries will hold enough energy, be cheap enough and charging stations will be fast enough and ubiquitous enough that charging anywhere won't be an issue. Energy will get cheap enough through solar, wind, tidal, hydro that gasoline will be the more expensive way to go even with the subsidized oil industry we have now. With increasing environmental concerns and wearing out of infrastructure raising the cost of refineries, pipelines etc. oil/gas costs will rise. The cost of gas in the US is artificially low (compare to anywhere else on earth that isn't subsidized) and will go up. All this means the end for hybrid and Voltec type of power.
All this is very valid, but I'm not convinced that the timeline is short enough to not allow for another generation or two of Voltec development.
 

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Perhaps the number 1 rule of designing and selling cars is that any car that develops a reputation of being "underpowered" will not sell. this applies to almost every potential buyer. part of the negative press from the nattering nabobs of negativism on gen 1 volts was that the 8.5 second 0-60 time was "low" compared to some other supposedly comparable cars. I'd love to buy an equinox with a voltec power train ( the Vequinox?). but that nagging "underpowered" word would pop up in every review from MT to Green Thumb Cars Daily. I understand the decision, we will have to wait to see what the future brings...
 
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