By Ken Rand (EAA 30184)
6171 Cornell Dr.
Huntington Beach, CA 92647
In our continuing effort to improve the performance and utility of VW powered aircraft, Rand/ Robinson Engineering has added an electrical system to its KR-2 ... and now, turbocharging. The turbocharger size and scroll were chosen to see if we could eliminate the need of a waste gate. The whole thing was taken over to Revmaster for pipe bending and dyno runs. The only modification to our prototype, N4KR, was to close off the hole in the bottom of the cowl where the right two exhaust pipes used to come out. The prop pitch was set to give 2700 rpm at 30 inches manifold pressure. This is about 65 inches pitch. An interesting bonus is that the engine runs almost silently.
Normal take-off procedure now is to push the throttle in to get 28 inches manifold pressure. This will increase by itself to 30 inches as the airplane accelerates through 100 mph. The KR-2 leaves the ground at about 50 mph in about 300 feet. Normal cruise climb is about 800 ft./min. at 140 mph indicated ... beginning with 3100 rpm at 30 inches manifold pressure at sea level. There is very little playing with the throttle as it goes up in altitude because as air pressure decreases, rpm increases which brings up the manifold pressure. Going through 14,000 feet the rpm will increase to 3500 and the manifold pressure will decrease to 25 inches. Leveling off at 14,500 feet shows 3600 rpm and 26 inches manifold pressure after the airspeed stabilizes at 170 mph indicated, or about 217 true airspeed. Fuel flow is slightly over 4 gallons per hour at this setting. Momentarily pushing the throttle all the way in shows 35 inches manifold pressure which means that cruise power (25 inches) is available for another 10,000 feet. Power was backed off before stable airspeed could be made at that power setting. During the Sun 'N Fun Fly-In in Florida timed runs were made between Melbourne and St. Petersburg at 14,500 feet. The average time was 22 minutes for about 210 mph ground speed.
N4KR has two 14 gallon wing tanks and one 10 gallon forward tank. This gives over 9 hours endurance. Let's see, Chino to Oshkosh is 1900 miles and in a jet stream it probably could be done in less than 7 hours. Hmm, both airports are on 118.5 ...