What does the HHR & Solstice have in common?
 

The 2LT which offeres a 2.4 ecotec engine is also the same engine to be used for the new Pontiac Solstice (very Similar)

From Pontiac Web Site
2.4 liter Ecotec DOHC
Prowess without a perplexing learning curve pens the definition of Solstice's engine. Its all-aluminum, 177-horsepower, longitudinally mounted 2.4 liter Ecotec conveys an assured politeness at low speeds, and, at high revs, another realm of potency entirely. Variable-Valve Timing (VVT) alters the typically fixed relationship of intake and exhaust camshafts to dispatch 90 percent of its peak torque throughout an enthusiast's range from 2200 to 6200 rpms.

Harnessing airflow with four valves per cylinder and upping the size of those valves means better engine breathing and higher output across the spectrum.

It's the same engine, but since the Solstice is RWD the packaging and tuning is a little different. The HHR feels sluggish by comparison, but that's because the HHR is heavier and has a smoother clutch and transaxle.

The Solstice will be getting a 2.0L turbo ECOTEC next year, hopfully they'll bolt the Cobalt SS Supercharged engine/transaxle in the HHR next year.