Hyundai's Theta II 2.4-liter Direct-Injection Four-Cylinder: First Look

Today, Hyundai showed off its latest engine, the Theta II, a 2.4-liter, direct-injection four-cylinder with variable valve timing destined for the 2011 Hyundai Sonata. Impressively, they also showed us the guts of a beat-to-hell test unit.

The Theta II 2.4 GDI is, unsurprisingly a 2.4-liter, gasoline direct-injection four-cylinder which makes 200 HP at 6,300 RPM and 186 lb-ft of torque at 4,250 RPM. It produces quite a bit more power than the unit it replaces, and in actuality, makes about as much power as the outgoing V6 with better fuel efficiency than the outgoing four-cylinder. The beating heart of the next Sonata is designed with a lot of well-tested tech all integrated into a tightly-packaged unit — it's actually 10 lbs lighter than the outgoing one.

If you've been paying attention at all to design of direct-injection engines, the Theta II will be fairly familiar territory. Starting with the fuel delivery system, the system builds 2175 PSI of pressure using a four-lobe-cam-driven mechanical fuel pump which feeds a high-pressure rail and then the compact, six hole, direct-injectors. The engine breaths through a dual stage intake manifold with long runners for low end torque and a vacuum assisted, servo actuated valve swaps things over to a short runner for high-speed power. Adding to the fun is a hydraulic variable valve timing system on both the intake and exhaust which can advance timing up to sixty degrees.

Less sexy, but still important tidbits include a floating wrist pin design which reduces friction, oil jets to cool the bottom of the pistons, a coating on the valve buckets called DLC, or "Diamond Like Coating, a super-hard carbon substance designed to reduce cam contact friction and improve wear, a domed combustion chamber (don't call it a Hemi) and a surprisingly high 11.3:1 compression ratio on 87 octane.

Now as to the engine you see above, it's been run through hell and back as a test unit. In order to stand behind their 100,000 mile warranty, Hyundai does some very serious testing on the front end. This engine has been operated for 300 hours at wide open throttle on an engine dyno, so you might excuse some carbon here and there. Tells us they're confident in their product when this was what they chose as their demonstration unit.

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