The experimental amateur-built airplane impacted terrain during a forced landing to a field following a loss of engine power on downwind. A post accident ground fire destroyed the airplane. The pilot stated that he was approximately "600 ft above ground ... on a wide down wind airspeed 118 MPH at 2400 RPM, retarded throttle, engine sped up, pumped throttle 2 to 3 times, felt like no connection to aircraft response. Aircraft was slowing down saw an open field, thought I would overshoot, I steepened the decent and decided I could S turn to use it. Then I had to steepen the decent again to maintain airspeed at least as steep as an autorotation as in a helicopter. I changed my field to one right below me. ... Impacted the ground, one bounce, landing gear flattened out, engine stopped, open door exited aircraft, came back 1 to 2 minutes latter to look. A fire had started up front by gasglator, I tried throwing dirt on it to put it out, did not help, so I got out of the way and watched to burn." A Federal Aviation Administration inspector examined the wreckage. The wreckage did not reveal any anomalies in reference to the engine's power loss.