On January 31, 2015, about 1445 central standard time, an experimental amateur-built Rotorway Exec 162F, N162RB, landed hard during an emergency autorotation near Seadrift, Texas. The pilot and his passenger were not injured. The helicopter was substantially damaged. The helicopter was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Port Lavaca, Texas, about 1420.The pilot said they were flying at about 300 feet above ground level and were returning to Port Lavaca after a 25 minute sightseeing flight. The LOW ROTOR RPM horn sounded and the engine had lost power. The pilot entered an autorotation and picked a landing spot. He arrested the rate of descent but the helicopter had too much forward speed to set down vertically. As he maneuvered the helicopter into some tall heavy grass about 8 feet above the ground, the main rotor speed decelerated below the minimum safe rpm. The pilot said the helicopter was still moving forward at high speed and, as such, it landed hard, tearing off the landing gear. According to the pilot, the stock Rotorway engine had been highly modified. An after-market Full Authority Digital Electronic Control (FADEC) system, designed specifically for the engine, had been installed. The FADEC system consisted of two separate and redundant Engine Control Modules (ECMs). On one occasion, the engine failed to start after the pilot had made a brief flight. He determined that there was a fault in the No. 1 ECM. Both ECMs were sent to the manufacturer for examination and testing. No problems were identified and they were returned to the pilot. He made four additional uneventful flights, totaling more than 3 hours, before the accident flight. After the accident, the pilot examined and tested the ignition system since the manufacturer was no longer in business. With both ECMs on, the engine was started and ran normally. When the No. 1 ECM was switched off, the engine continued to run on the No. 2 ECM. When the No. 1 ECM was switched back on, the engine quit. The only way the engine would start was to turn on the No. 2 ECM and leave the No. 1 ECM off. Every time the No. 1 ECM was switched on, the engine would quit. The pilot switched the wiring harnesses and established that the problem followed the No. 1 ECM. He determined the fault lay solely in the No. 1 ECM.