For my first trip of the Untold EV & Cleantech Stories project, I wanted to take an EV along. My 40 kWh LEAF doesn’t have sufficient range to make it across the country, as a number of Electrify America stations are too far apart for it at highway speeds. My original plan was to borrow an EV from a manufacturer to review along the way, but logistical issues led to the vehicle being unavailable. I ended up with borrowing a hybrid as my cleanest option this time.
I was originally disappointed that I wouldn’t have a full EV to review, but the Sorento Hybrid Kia lent me turned out to be a really neat vehicle that gives us a peek at Kia’s future electrification plans, as well as a look into how hybrids are changing and improving.
Older Hybrids Relied A Lot On Being Small & Slippery
The biggest difference between today’s new hybrids and most early hybrids is the size of the electric motor. Early hybrids were largely a gas-powered vehicle with a small electric motor-generator that’s meant to collect up regenerative braking energy and dispense it a bit here and there to improve the efficiency of the vehicle. Combined with the ability to eliminate idling and inefficient low-speed engine operation, the results were generally dramatic.
These early vehicles were almost all small vehicles built to be as efficient as possible, though. The Toyota Prius, the Honda Insight, and others got a lot of their efficiency by being small, having low drag coefficients, and low weights. When this early hybrid technology was applied to larger vehicles, like the Chevrolet Tahoe, city fuel economy drastically improved, but overall efficiency was still around 20 MPG, which is far less impressive.
The Sorento Is A Big Vehicle That Gets Small Vehicle Efficiency
Compared to GM’s experiment with hybrid SUVs a decade ago, the Sorento Hybrid is positively impressive (though obviously not as impressive as an EV). It’s a 4,000-pound vehicle with 6 seats (available with 7), plenty of horsepower and torque, and a boxy shape like people would expect from an SUV. Despite all this, it ends up with 39 MPG city, 35 highway, and 37 combined. In my testing, the vehicle actually achieves these numbers.
Those are all better numbers than I achieve with my Volkswagen Jetta, and even slightly better than a Chevy Volt I used to own. Running down the highway at 80 MPH, the Sorento Hybrid does better, despite being larger, heavier, and more powerful. To be fair, a Sorento is a lot smaller and lighter than the truck-based Tahoes were, but it can still tow small trailers and carry a lot of people or cargo. In other words, it’s no Prius. It’s leaning a lot more on the efficiency of its drivetrain than it does on general efficiency.
Nothing proves this more than the initial drive I took from Phoenix to Flagstaff. Despite being one of the steepest, most grueling drives in the continental United States, the vehicle still managed to get 26 MPG going up Interstate 17. This same drive overheated my Nissan LEAF in 2019, and it’s common to see people stuck on the side of the road along that route. Arizona DOT even puts up signs recommending that people turn their air conditioners off.
Bigger Electric Motors Mean Better Efficiency
To figure out how Kia was getting such great efficiency, I kept a close eye on what the vehicle was doing over 2000 miles, and learned a lot.
The first thing I noticed was that the Sorento would often operate in EV mode off and on at nearly any speed. Even at 90 MPH, the gas engine would periodically shut off and the vehicle would push along with excess battery power it needed to burn off. This was more common on downhill stretches and on level ground, but could happen on some uphill stretches.
This kind of electric power at highway speeds wouldn’t be possible without a much bigger electric motor than the previous hybrids, which the Sorento hybrid has. It only has 60 horsepower at 2000 RPM, but that’s more than enough for highway cruising all on its own. Where it’s more impressive is torque, with just under 195 lb-ft on tap. This relatively large hybrid electric motor let Kia use a tiny (for this vehicle size/weight) 1.6L GDI motor, producing 177 HP and roughly the same torque as the electric motor. Total system power isn’t 400 lb-ft of torque, as the electric motor does its best at 2000 RPM while the gas motor does its best at 4500. Combined, the maximum is 227 HP and 258 lb-ft.
Readers are probably going to remind me that all of the power ultimately comes from that 1.6L gas motor, as this is not a plugin hybrid. It manages to get unnatural efficiency, even on the highway, by optimizing its use of the gasoline engine, doing something similar to the “pulse and glide” technique hypermilers use to squeeze bigger efficiency out of the older hybrids. That’s how the vehicle I tested got such good efficiency on the I-17 climb.
When cruising on the highway, the electric motor actively drags the gas engine down a bit to improve the engine’s brake-specific fuel consumption. In this mode, it uses more fuel than it would just pulling the car along, but it uses less fuel per unit of power produced, and stores this excess energy in the battery pack. When it reaches the next uphill, it can expend this excess energy to help the gas engine climb the hill without revving up. Or, if it encounters a downhill or flat segment, it can shut the gas engine off entirely for short periods and drive on EV power alone.
In other words, the car runs the gas engine only when it can run at its most efficient for power generation plus driving, and then runs the electric motor to assist or entirely drive the vehicle at nearly any speed.
The result is that it can get great mileage even on the highway, where most small-motor hybrids don’t gain any advantage.
The bit of important future insight we can gain from this is that Kia isn’t playing the typical shell game many manufacturers are playing with hybrids. They’re serious enough about electrification that they aren’t messing around with crappy small-motor hybrids in an attempt to greenwash their vehicles and avoid building EVs. Instead, they’re building up toward going all in on EVs.
From the Sorento Hybrid, we can see that the company left room for a plug in the fuel door, and left room for more battery in the upcoming plugin hybrid version. From what I can tell, every Sorento, even the gas ones, are set up to allow for this instead of trying to cram batteries into the platform. Because the company put the legwork in, its electrified crossovers deliver dramatically better mileage than the gas versions with very little power loss, which will lead to more people actually buying them over the gas version, and it won’t hurt the company if more people buy the hybrid and PHEV versions.
Finally, there’s the EV6, which is a serious EV built on a dedicated EV platform, so we know the company isn’t just playing hybrid greenwashing games.