One of the year’s most eagerly awaited releases provides more questions than answers.
Wayne Gerdes - CleanMPG
- Oct. 8, 2010
2011 Hyundai Sonata Hybrid - A promised 40 mpg highway rating is just around the corner
Hoffman Estates, IL -- At the annual Midwest Automobile Media Association
(MAMA) Fall Rally, a perfect confluence of weather, manufacturer reps, new automobiles and Midwestern based auto journalists came together to experience the Automobile manufacturers latest wares in a quick get to know you, let’s go for a ride type manner.
The MAMA Fall Rally was held for the second year at the Marriott Northwest in Hoffman Estates, IL with the presiding MAMA President, Jim Jackson introducing high level exec’s from both Nissan for the morning presentation and Kia exec’s for the lunch presentation.
What is a MAMA Fall Rally
While not a week or longer test drive that most automobile journalist’s are used to, the MAMA Fall Rally provides all in attendance the opportunity to experience, albeit for a very brief period, over 65 brand new vehicles from a variety of manufacturers for both drive impressions and no holds barred side by side comparison drives. Even reps from one manufacturer were able to experience the vehicles provided by another (trust me, this happens a lot more than you may know
) in order to improve both the knowledge base and provide feedback to their respective design teams to improve upon their own employers automobiles. You know, the ones you and I will drive in the future.
With the Rally in full swing, we had the opportunity to take out the 2011 Hyundai Sonata Hybrid for our own quick, get to know you drive and without further adieu, we bring you the 2011 Hyundai Sonata Hybrid with its “Direct Hybrid Blue Drive Architecture”.
2011 Hyundai Sonata Hybrid
While the EPA figures have yet to be officially announced, Hyundai has promised that the 2011 Sonata Hybrid sedan will be the most fuel efficient vehicle in its class with an EPA highway rating of 40 mpg. With our experience in the non-hybrid during the 2011 Hyundai Sonata “Challenge” - One day, 1,000 miles and just one tank of gas…
drive event proving the Sonata to be the most fuel efficient midsize car on the highway in all of North America, could the addition of a hybrid drivetrain prove to be even more spectacular?
Let us attempt to answer that very question.
2011 Hyundai Sonata Hybrid Technical Details (the mumbo jumbo)
The 2011 Sonata Hybrid uses what Hyundai calls its “Direct Hybrid Blue Drive” which in more understandable nomenclature is a full parallel hybrid system. And from the tech presentations, the Sonata Hybrid can be driven in fully electric drive mode at speeds up to 62 miles per hour or in a combination of gasoline engine and electric modes at speeds far south of the PSL on any highway in North America. In addition, the car like all hybrids incorporates Start/Stop which shuts the engine down and eliminates idle fuel consumption.
Li-Po Battery Tech
The lithium polymers cells used in the Sonata Hybrid were developed by LG Chem, the same company fitting out the 2011 Chevrolet Volt and the upcoming 2012 Focus BEV. The chemistry is a manganese spinel that supposedly provides a good balance between power density, energy density and thermal stability. Thermal stability is critical to ensuring durability and avoid at all costs, a thermal runaway resulting in a car that burns to the proverbial ground. According to LG Chem, Manganese spinel Li-Po cells have much lower expansion rates than standard Li-Ion chemistries used in other automobile applications and are thus able to go through tens of thousands of charge cycles without having to use a heavier, liquid cooling system.
The Sonata Hybrid’s 1.4 kWh Li-Po pack weighs 95.9 pounds versus the Camry Hybrid’s 1.6 kWh NiMH pack at 114.6 pounds. In addition to the 17 percent reduction in mass, the Li-Po battery is 40 percent smaller in volume and is stated to be 10 percent more efficient.
The Li-Po battery also has less self-discharge and will hold a charge 25 percent longer than a NiMH battery common in today’s Toyota, Lexus, Ford, Mercury and Lincoln hybrids.
2011 Hyundai Sonata Hybrid Drivetrain Layout
The Hyundai Direct Hybrid Blue Drive powertrain is configured with a unique architecture unlike any on the market today. In contrast to the power-split hybrid systems such as those from Toyota and Ford, Direct Hybrid Blue Drive uses a Transmission-Mounted-Electric-Drive (TMED) layout where the motor is separated from the transmission. According to Hyundai, this offers the ability to mix different sized motors and transmissions for future larger and small vehicles to use the same hybrid system.
The Sonata Hybrid incorporates a 30 kW (40 HP) motor to provide full hybrid capability including electric drive at reported speeds up to 62 mph.
- The Sonata Hybrid uses a slightly modified "conventional" step-ratio automatic transmission that debuted on the conventional 2011 Sonata is. For the hybrid application an external, electrically driven oil pump has been added to provide the hydraulic fluid pressure needed to keep the clutches engaged when the Sonata is in idle stop mode.
Traction Motor and Clutch
- The Sonata Hybrid’s 30 kW traction motor is hard-coupled to the input of the transmission and completely replaces the torque converter. A multi-disc clutch pack sits within the inner circumference of the traction motor and is used to de-couple the motor from the 2.4-liter Theta II inline-four cylinder engine for idle stop and electric drive modes. This layout allows the entire package along with a torsional damper to fit within virtually the same volume as the traditional torque converter.
Separating the motor from the gear set has several functional advantages including the fact MG1 in a Toyota HSD or Ford eCVT system spins backwards at upwards of 10,000 RPM while doing no work in a forced glide at 62 mph and why maximum electric drive speed in most other hybrid applications is limited to speeds of 47 mph or less.
Another downside of a power-split systems that we are all familiar with is that all of the power has to drive both MG1which provides power to the battery, spins up the engine from start and maintain it spinning in a power balance above the max EV speed when not using any fuel AND MG2 which powers the car under EV mode or when demand for additional power beyond that provided by the engine is demanded.
The Hyundai Solution
- The hard-coupling of the 40 HP traction motor to the transmission input reduces its rotational speed and the use of the clutch to completely decouple the engine and motor allows the Sonata to drive electrically at speeds up to 62 mph without spinning up the engine.
- The Hybrid-Starter-Generator (HSG) is a 8.5 kW starter motor-generator that is belt-driven off the engine operating at the same 270 volts as the electric traction motor and the Li-Po battery. Its purpose is only to start the engine and charge the hybrid battery when SoC is below a given threshold.
- A low-voltage DC to DC converter steps down the 270 volt output of the Li-Po battery down to 12 volts needed to charge the standard Pb-Acid battery and power all of the vehicle accessory systems.
- One of the benefits of a hybrid drivetrain is the ability to recover kinetic energy lost “when braking is necessary
” and store it in the included traction battery for later use.
Electric Power Assisted Steering and A/C
- The 2011 Sonata Hybrid like all 2011 Sonata’s uses an Electric Power Assist Steering (EPAS) system that provides boost only when it is needed. This reduces the overall parasitic load compared to an engine driven hydraulic assist. Because the EPAS is independent of the engine it also provides assistance when the engine is not running such as during idle stop or electric drive mode.
The Sonata hybrid also features an electrically driven A/C compressor so that climate control can be maintained during engine off driving. Like power steering, the electrically driven A/C compressor allows for more precise on-demand control reducing the overall load on the powertrain, cutting fuel consumption.
Atkinsonized 2.4L Engine
- Like all full hybrids to date, because the traction motor provides a maximum 151 Lb-Ft of torque from 0 RPM, an Atkinson cycle was incorporated into the 2.4L engine. The Atkinson cycle’s compression stroke is shorter than the expansion stroke which reduces pumping losses and improves the overall thermodynamic efficiency of the engine. The improved efficiency comes at a cost of low-end torque response which the traction motor more than makes up for when demanded improving overall power and torque response vs. the conventionally powered Sonata from which the engine is based.
- The conventionally powered Sonata is already the lightest car in the mid-sized/large car segment and with the small Li-Po battery pack and small MGSets, the Sonata Hybrid tips the scale at just 3,483 pounds, 197 and 237 pounds lighter than the Camry and Fusion Hybrid respectively.
- The Sonata hybrid features two independent liquid cooling circuits with a standard high temperature circuit used to manage engine temperatures at up to 190 degrees Fahrenheit and provide passenger compartment heating needs.
A second low temperature cooling circuit is incorporated to manage the temperature of the hybrid starter-generator and the power electronics. The low temperature circuit utilizes an electric pump to circulate the coolant along with a separate heat exchanger to keep the electronics between 86-95 degrees Fahrenheit.
Minimal coasting losses
- The 2011 Sonata Hybrid features a re-shaped front and rear fascias with a deeper air dam, extended rocker panels and lower drag wheels allow the air to flow around the body with less resistance. The drag coefficient for the Sonata Hybrid is an exceptionally low 0.25 that matches that of the 2010 Prius.
2011 Hyundai Sonata Hybrid Short Distance Driving Impression
(with an absolute emphasis on the hybrid drivetrain)
The 2011 Hyundai Sonata Hybrid’s (HSH's) drivetrain was driven over a very short 9.9 mile city/suburban route earlier this week. The 20-minute route had just one short stretch of country road about 2.5-miles long w/ a PSL of 55 mph so the Sonata Hybrid was not allowed to show its stuff as we would normally do. And 9.9 miles is barely enough time to figure out how to reset the aFCD let alone figure out how to drive the darn thing
Additionally, this is a pre-production prototype with the latest flashes being performed to bring the regenerative braking to the latest Hyundai internal build specs just the day before. Some of the internal panels were smooth aluminum looking plastic which actually looked really slick by comparison to the textured pieces we will see on the production cars.
It is a full hybrid and with a SoC above 75%, you can really get into it before ICE engagement from a stop. Think Prius and Ford Fusion Hybrid (FFH). I sat in with a journalist and he was driving like most journalists do, two feet on both pedals at the same time
Anyways, I reset his aFCD as he pulled out of the lot and watched him pull a disappointing 33.x mpg when he had completed the 9.9 mile loop.
My turn… There may be a small bug in the reset of the aFCD as I could not reset it from MFD screen for over a mile on the fly whereas I reset it for the previous journalist as soon as I got in the car from the same screen??? Once reset from the dash vs. MFD and burned off SoC to about 60%, it was time to figure out how to drive it…
-- First, gentle like we all drive. The ICE would not shut down unless I came to a stop at the many lights and stop signs along the route. The SoC built up to what appeared to be 90% and the ICE continued to run and shunt the spare power to the Li-Po pack. After about 1.5 miles of this, I figured out how to get it to glide. It is a more forceful pull from the accelerator pedal to get the ICE to shut down vs. a Prius, Toyota Camry Hybrid (TCH), HS 250h, Ford Escape Hybrid (FEH) or FFH by far. You have to almost allow a hard regen to occur and then reapply to get the ICE to come off. Also, the instrumentation has absolutely no threshold bar or indication so you have no idea when the ICE will kick on or off. The flowery displays are pretty but not that informative including the lack of a tach.
Fortunately when the ICE does shut down, a green EV indicator appears in the central dash to the left of the speedometer. This display is all there but the mimic in the MFD shows only a hair thin sliver of silver (current mimic) coming from the pack and nothing from the engine. There is another indication in the MFD screen for ICE-On and Off but it is not intuitive or informative given it is to small vs. the large graphic with hair thin lines running from engine to wheels to pack and tranny… I really only needed another 30-minutes or so with the screens in the various modes to make them a second nature glance but the HSH was in demand all day long with probably over 30 of the 70 journalists on hand taking a stab at it.
Ok, we know how to evoke glide, now can we maintain it? The answer is a resounding yes! I only reached 53 mph on the 55 mph PSL section and when pulled back to allow some regen, wait for the 6-Speed AT to transition, EV display is up and a placement of the gear selector into N, the ICE stayed shut down and we had a pure glide. Wheewww, I thought I would never get there
Unfortunately, the 6-speed AT transition is about a second or two from ICE-On and 6-speed AT connected to ICE-Off and the 6-speed AT disconnected. That is a long time while you are bleeding off speed waiting for the fuel saving glide to occur.
Pulling away from lights and signs in EV is a no-brainer and especially with a high SoC. But, even though you have a high SoC, the Sonata Hybrid’s propensity to run the ICE is very strong and it is not a good situation for high FE around town. No matter how gentle, at around 20 to 25 mph or so, the ICE simply wanted to come on and for no good reason from the indications I was presented. Hyundai/Kia have used Press Launches to change both HW and SW before the actual OEM dealership showroom models reach us so I suspect they may be looking for input from the Journalists on what the HSH can and cannot do and what they should change or fix before it reaches production status next spring. In any case, there is a problem with a high SoC area in that the ICE wants to come on when it is not needed and thus allowing the TCH/FFH to best the HSH around town. As it was setup, it would probably never see 60 mpg around town whereas the TCH can easily be pushed to 70 mpg and the FFH well into the mid 80’s…
Again, this is a SW fix more than likely and something the Korean engineers need to get on right away.
-- When you have just 2.5 miles, a steep uphill with a stop sign for entry and a hard 90 degree corner onto a barely 2 lane country road at the end, there is not much time. Once I had figured out how to evoke an EV/Glide at speed, it was simply a matter of transition time from ICE-On to Off that will make or break the car. I thought I may have a little EV to play with at 50 mph but apparently not even though the car is spec’ed for a 62 mph EV/Glide. I simply did not experience it. Glide yes, EV, no. Not really a big deal because using EV at that high a speed is a lossy solution at best anyway but I would like to have glide with minimal intrusion of the 6-speed AT or the hybrid system getting in the way. It was not seamless and fighting that 1 to 2-second transition was a SOB to put it lightly.
I also was not SG-II equipped (I forgot my camera, hat and SG-II on the table when I left for the rally in the morning
) so a rate and range was an absolute guess and I only had the feel of the ICE-On in the car in an attempt for optimization.
In any case, I could evoke a glide at the speeds necessary but it was a painful transition and the aFCD was climbing fast after I finally got into a “Best Guess” rhythm with just two cycles vs. thousands like we normally would have time for in a press vehicle over a week. After ~ 6-miles, the aFCD was only at 38.8 mpg. After ~ 8.5 miles, the aFCD was up to 43.8 during this starting from a standing stop, EV to ~ 20 mph, ICE-On during accel to 53 mph, evoke a glide which saw speed drop to 49 mph rather quickly during the ICE-On to ICE-Off N-Glide transition, glide down to maybe 45 mph, fire the ICE back up, reaccelerate back up to 52 to 53 mph and one more time cycle the car for the glide down to about 20 mph for the 90 degree corner ahead.
Again, not much time but doing the calc’s from ~ 6.0 miles and 38.8 mpg to 8.5 miles out and 43.8 leaves us with ~ .0394 gallons consumed over 2.5 miles yielding just 63.41 mpg over the highway stretch. The regen to the 90 degree corner at the end probably left SoC at or ~ equal to where it started at the uphill stop sign and entry onto the 2.5 mile stretch of road… Elevation differences across the 2.5 miles of road were unknown but there was a descent and a climb though the section and we are talking about a suburb of Chicago here so nothing more than 20’ at most. There is a lot more to be had once optimized but the section was simply too short, not really a good test and I did not have my notepad with me as I left it in the car prior and was trying to remember these numbers in my head before I got my notepad back. It was really a rushed day as you can tell
The 9.9 mile drive ended at 49.3 mpg so there was some optimization for the last stop light to stop light city portion as well but with the limited time, it was the best I could do. A poor overall showing, yes but again, with the time we had, the Highway portion looked promising and to move from the mid 40 range to high 40 range in the last 1.5 miles tells you something far beyond the final tally. That last section was well over 100 mpg but I was consuming SoC to drive the last mile and ended up with an ~ 55% SoC final.
All said, I was a bit disappointed in Hyundai’s optimizations for ICE-On to ICE-Off transitions taking so long but the car is still not a production ready vehicle. By the time it reaches the public, it will be even better. Will it touch a TCH or FFH around town? Not imho the way it is currently setup. Will it reach the level of a Sonata with a stick while going advanced on the highway? Maybe but we’ll need some time to figure that one out too. Will it reach the 62 mpg the FFH allowed on 90% highway drive from Dearborn to Milwaukee and back? That too remains to be seen. I think it has the capability but we just need more time as the short drive impression did not provide anything but more questions.
-- Regarding the seating comfort and all of that, it is just like the regular Sonata. Leather seats like the limited were nice, cup holders, ambient lighting thanks to the LED, two sun roofs for both front and rear… It was a nice car inside with all the room we have all come to enjoy. The Ventilation man control (he is still hard for me to stare at as I think he is staring back at me
) appears to have a top button (his head) that forces air to the top vents only. I did not remember the Sonata GLS we drove having the man’s head control enabled for any ventilation so that may be an addition or maybe I did not notice his head worked as a control in the GLS we drove from central WI to NY City this past summer.
2011 Hyundai Sonata Hybrid - Early Conclusions
With all the tech posted above, Hyundai, like every other manufacturer likes to embellish the positives in order to make their car stand out. Given this was such a short drive; I have more questions than answers. I cannot say whether it is capable of besting the all-out 2011 Hyundai Sonata with a stick effort from the Midwest to the East Coast or not? I can say without hesitation however that it can be driven to very high Fuel Economy without all the work, concentration and gyrations which is exactly what a hybrid should do for the average driver.
Also I do not know if the somewhat lengthy hesitation through the ICE-On to ICE-Off transition and AT decoupling will hold from pre-production to production or not? I also really do not have an idea if the 2011 Hyundai Sonata Hybrid can best the Toyota Camry Hybrid or Ford Fusion Hybrid in the real world. Right now, I would say the Toyota and Ford have a distinct advantage around town whereas on the highway, it is going to be a lot closer than the manufacturer prognostications or EPA numbers would suggest.
We complete a more thorough conclusion when we actually get behind the wheel and push the 2011 Hyundai Sonata Hybrid for some maximums while circling a large city, state or possibly even crossing the country because 9.9 miles of experience on a preselected course is a lot different than 300 to 3,000 miles on roadways that we decide to drive as everyone knows.