Images from the public unveiling of Piper's new single-engine PiperJet at the AirVenture 2009 show in Oshkosh, Wisconsin, this week reveal a new tailpipe design for the Williams International FJ44-3AP turbofan engine.
....the Oshkosh version (right) appears to be shorter, with less up-tilt, but with a top-hat extension on the top side.
Could this be a Coanda effect modification that Piper had revealed it was working on with Williams last year?
If so, the top hat would likely tilt upward at during high-power situations, causing the engine's thrust to bend upward, thereby reducing the downward turning pitch moment caused by high-thrust line of the tail-mounted engine. Piper had been spending much time and energy trying to minimize such pitch changes to make the aircraft pilot-friendly, particularly in high-thrust situations like go-arounds.
Below is the video of the PiperJet taken by my colleagues at FlightGlobal at the Oshkosh show this week, showing the tail pipe and other details of the PiperJet in much more fidelity.