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Probing Hyundai's Veloster N Performance Powertrain

Theta Data

Richard Fong
Aug 23, 2019

Time truly flies when you stop to consider that Hyundai vehicles have been sold stateside since 1986. Although it started off as a cost-conscious brand, the Korean manufacturer has strived to change consumers' perceptions throughout the years. Things like offering a 10-year/100,000-mile powertrain warranty showed confidence in its engineering. The Genesis Coupe was the company's first foray into the rear-wheel-drive sport compact segment against the likes of the 350Z, Mustang, and Camaro. Hyundai then launched its luxury marque, Genesis, in a demonstration of its capacity for refinement. Hyundai now sets its sights on the performance segment, launching the first of its "N" Performance vehicles in the U.S., the 2019 Veloster N.

Forged in Namyang, Honed on the N rburgring

Hyundai Veloster N 003 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain

Hyundai brought in the former head of BMW's M division, Albert Biermann, to lead the Performance Division of the Hyundai Motor Group. Biermann's vision for Hyundai's performance line is designated simply by the letter "N," representing a duality of meaning: one for the Namyang R&D Center in South Korea where the Veloster N was engineered and developed, and the second for the N rburgring, where Hyundai has a development center at the track, on which it was refined. For the Veloster N, Hyundai chose the 306hp Honda FK8 Civic Type R as its performance benchmark. Hyundai knew it had to step up to compete with Honda's latest sport compact car. Enter the 275hp, turbocharged Theta II-i engine...

Theta Generations

The Theta engine family was introduced in the '06 Sonata. This naturally aspirated, multi-port, fuel-injected engine employed constant variable valve timing (CVVT) on the intake camshaft. In 2009, the Theta II engine was released across multiple platforms. This engine included several block design revisions in order to add CVVT to the exhaust camshaft. The Theta II engine, available both naturally aspirated and turbocharged, was offered across several vehicle platforms. One of the turbocharged versions powered the Genesis Coupe.

Theta II, Turbocharged

The Theta II engine that powered variants of the Genesis Coupe was longitudinally mounted for a rear-wheel-drive configuration. This 210hp engine ('09 to '12) featured a single-scroll Mitsubishi TD04 turbocharger and a hydraulically controlled CVVT on both camshafts. For the '13-to-'14 models, the Theta II was upgraded with a larger turbocharger and electronic wastegate actuator, a new intercooler, and ECU recalibration, raising output to 275 hp.

Theta II-i, the Next Level

Hyundai Veloster N Theta II Engine Veloster Engine Bay Photo 21/21   |   The turbocharged Theta II-i engine mounts transversely and drives the front wheels by way of a six-speed transmission with an electronically controlled limited-slip differential.

The powertrain of the Veloster N centers on its turbocharged Theta 2.0 T-GDi engine, which goes by the designation Theta II-i. This descendant of the Theta II has little in common with its predecessors, other than the fact that it has an all-aluminum long-block, open deck, and 86x86mm bore and stroke dimensions. Designed for front-wheel-drive duty, the Veloster N's Theta II-i boasts a host of enhancements that contribute to its 275hp peak output (N Performance Package). Simply put, this engine is about efficient power production. Incorporating direct injection into the design of this engine ensures optimal fuel atomization. The pistons feature specially shaped crown profiles that reflect the atomized fuel back toward the spark plug for efficient and complete combustion of the air/fuel mixture.

Hyundai Veloster N Theta II Engine Polymer Intake Manifold 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine Valve Plate Photo 21/21   |   The polymer intake manifold features valve plates linked to a valve control module. The plates are partially closed to generate a tumble flow effect at low engine speed and opened completely when the throttle is opened for maximum performance.

The cylinder head design incorporates the direct injection system while also improving the volumetric efficiency. A heat-soak resistant, polymer intake manifold features a valve control module (VCM) linked to valve plates in each intake runner. The VCM closes partially at lower engine speeds to generate a tumble flow effect for optimal atomization of the air charge. As engine speed increases, the VCM opens the valve to permit unrestricted airflow into the cylinders under boost.

Next-Generation CVVT

Hyundai Veloster N Theta II Engine CVVT System 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine CVVT System 02 Photo 21/21   |   The electronic CVVT system adjusts the intake camshaft timing by way of an electric motor instead of relying on oil pressure, as does the CVVT system on the exhaust side.

Hyundai engineers improved the CVVT system for the Theta II-i. Now, a more responsive electronic CVVT (E-CVVT) adjusts the intake camshaft timing, while the traditional hydraulics continue actuating the CVVT on the exhaust camshaft. Why the move to E-CVVT? The electric motor that adjusts the cam offers quicker response and a wider range of timing (compared to the hydraulic system), which, in turn, permits calibration settings that help reduce pumping loss. Since it is electronic, adjusting the intake camshaft timing is not dependent on oil pressure. The exhaust camshaft timing remains hydraulically controlled since it is not as critical for the exhaust cam to adjust as quickly.

Hyundai Veloster N Theta II Engine E CVVT Components Photo 21/21   |   The E-CVVT system is composed of the cam gear cover, the E-CVVT drive motor, and the hollow camshaft it's bolted onto.
Hyundai Veloster N Theta II Engine Intake Cam Timing Cover 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine Intake Cam Timing Cover 02 Photo 21/21   |   The intake cam timing has an adjustment range of roughly 45 degrees from maximum retard to maximum advance.

Improved Induction

In conjunction with the improvements made to the block, cylinder head, and valvetrain, the Theta II-i benefits from a twin-scroll turbo. It spools more quickly and generates boost more efficiently than the previously employed single-scroll units. The enlarged turbine housing does not cause excessive restriction to the exhaust flow while generating boost pressure. An electronic wastegate actuator takes the place of a traditional vacuum-controlled wastegate for more precise boost control.

Hyundai Veloster N Theta II Engine Electronic Wastegate Acutator 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine Electronic Wastegate Acutator 02 Photo 21/21   |   Rather than relying on a vacuum-controlled wastegate actuator and a boost control solenoid, the Theta II-i turbocharger relies on an electronic wastegate actuator.

Cool Under Pressure

While developing and testing the Veloster N, Hyundai engineers demanded the car be capable of running at an open track day without the need for modifications, especially when it comes to combating heat. They went to great lengths to ensure adequate heat management so the Veloster N could take a beating all day without failure or overheating. A key factor was the adoption of a pressurized coolant reservoir instead of a simple coolant overflow bottle, creating a closed coolant circuit. This helps raise the coolant boiling point. An auxiliary electric water pump will continue to circulate coolant through the turbo even after the engine shuts down to help cool the turbo and bearings. To further ensure reliable engine performance under tough conditions, sodium-filled exhaust valves were included in the cylinder head.

Hyundai Veloster N Theta II Engine Hot Bottle Coolant Overflow System Photo 21/21   |   To better manage engine temperatures, Hyundai incorporates a pressurized "hot bottle" coolant overflow, which forces coolant back into the engine once the temperatures begin to come back down.

Uninterrupted Fun Factor

Producing a fun car to drive is one thing-ensuring the fun factor isn't limited is another. The Veloster N feels like a modern take on the sport compact cars of the '90s. In Normal mode, the Veloster N drives like a comfortable, levelheaded commuter car. At the push of a button, switching to N mode, it transforms into a corner-killing weekend warrior. The touchscreen display that, moments earlier, showed you which XM channel you were listening to now relays everything from real-time G-force values to power and torque output and boost pressure. Switch to the lap timer, and you're ready to see if your split times are improving or not. With the N Performance Package, the Veloster N gets its maximum factory output of 275hp and, with it, a lot of fun. An electronic valve opens the secondary exhaust outlet, changing the exhaust note from a hum to a snarl. Coming off the throttle, you get the popping sounds like the late ignition of unburnt fuel in the exhaust-and this is from the factory!

Hyundai Veloster N 002 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain

For the track, the Veloster N can be calibrated to the driver's preference. With all its faculties activated, the electronically controlled limited-slip differential splits the power between the front wheels while the torque-vectoring system helps with yaw through the corners. Together with the traction control system, the Veloster N gives the driver a confident sense of control. With the driver aids deactivated, the Veloster N provides a visceral feedback familiar to those who remember driving before traction control came to be. And thanks to the efforts of Hyundai's engineering team, you won't need to pull into the hot pits mid-session to cool down because the Veloster N manages heat so well. Is it possible to have it all: a "practical" commuter that transforms into a weekend warrior? In the case of the Veloster N Performance Package, at an MSRP of $29,885, it's very possible, as it packs a lot of value and has an engine unlike anything Hyundai has ever engineered or tested previously.

The Inner Workings of the E-CVVT

Hyundai Veloster N Theta II Engine E CVVT System Components 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine E CVVT System Components 02 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain

In order to adjust the camshaft timing while the engine is running, it is necessary to overcome significant centrifugal force. While the exhaust cam relies on oil (hydraulic) pressure to adjust the cam timing, the intake side relies on an electronic system. The E-CVVT is made up of an electric motor that turns a cycloidal drive bolted to the camshaft. This cycloidal drive design functions more quickly and efficiently than oil, which is particularly important on the intake camshaft. When voltage passes through the brushes located in the cover, the electric motor is energized and advances or retards the camshaft timing accordingly.

Hyundai Veloster N Theta II Engine E CVVT Electic Motor 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine E CVVT Electic Motor 02 Photo 21/21   |   Electric motor
Hyundai Veloster N Theta II Engine E CVVT Cycloidal Drive 01 Photo 21/21   |   Probing Hyundai's Veloster N Performance Powertrain
Hyundai Veloster N Theta II Engine E CVVT Cycloidal Drive 02 Photo 21/21   |   Cycloidal drive.
Hyundai Veloster N Theta II Engine E CVVT Cover Photo 21/21   |   Cover
By Richard Fong
19 Articles

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