I have 29 flight hours and 70 hours total time on the engine.

 

Water Cooling

Water cooling is good with max temps around 185F in climb and 160F in cruise. During let down water drops to 140F or lower. OAT at take off has been 70-80F. I have 780 cu in of water radiator with the air making a 360 turn through the radiators and cowl. The inlets have been enlarged from 21% to 26% of core face in an attempt to help the oil to water exchanger transfer more heat. It worked but not well enough. I still have an oil cool deficit.

 

Oil Cooling

The oil to water exchanger is limited to 43F of transfer. Oil pan temps on climb-out can reach 262F. Moving the muffler to the belly and a new heat shield by the oil pan had no effect on oil pan temps during flight. It may have had a positive effect on taxi ground cooling but I will have to wait until next summer and 100F+ to verify. The larger radiator inlets have improved the oil temps slightly. With OAT’s between 70-80F I can maintain full power climb-out at 105 mph \ 1350 - 1000 fpm to 4500ft. Oil goes to about 226F. Lowering manifold pressure or the nose lowers the oil temp. Once airspeed increase to 140 mph oil temps drop to about 190F. I ordered half size oil / air exchanger from Techwelding and it’s going on the nose under the front motor mount.  After this addition my cooling system should handle a 20B. (in a couple of years)  My large Mocal oil to water exchanger and at least 650 cu in of radiator should handle a 180-200 hp rotary aircraft.

 

Eaton MP62 Super Charger

The MP62 is perfect for the RX8 but not an aircraft. I found a new MP90 at a reasonable price and will be swapping it out early next year. Redline for the MP62 is 16K rpm. I usually run 7000 motor rpm for the first minute of climb and start reducing the prop speed from there. With a 2:1 pulley ratio that’s 14K rpm on the supercharger. This produces 38” MP. I have been cursing at 5800 rpm with the SC at 11,600 rpm. The MP90 will produce the same CFM at 8K rpm as the MP62 at 14K. Redline on the MP90 is 14K.

Should be a lot less stress on the blower and allow me to normalize above 10K ft.

 

Water Injection.

Without an intercooler and 4-5#’s of boost, intake charge temps would increase 120F. I have been running 93 octane with no sign of detonation. But it’s been a nagging concern. Looked into an intercooler but the pressure drop does not seem to be worth it below 7 psi. So I build a circuit that reads the 0-5V output of my EFIS MP sensor. The circuit is tuned to turn on a relay at 33” MP. The relay turns on a small inverter, that turns on a 230 psi expresses machine pump and solenoid. The whole system draws less than 3 amps. The pump, water jug, two solenoids and inverter weighs less than 5 pounds empty. I made the pump and water jug removable and are located the baggage compartment. The second solenoid and switch controls a nozzle on one of my radiators. Insurance for a 105F+ day and a half mile uphill taxi. I had to shut down during taxi one time last summer. Don’t want to repeat that experience. The ramp temps must have been 115F.

Both the radiator and manifold nozzles are 100CC \ min. Water is injected directly after the supercharger and drops the intake charge to about 15F over OAT. I have been running an overly rich fuel mixture during climb 11:1 but I am now comfortable leaning back to 12.5:1 with the water injection. Of course I constantly monitor the manifold temps. I get 5-6 climb outs on a gallon of water. The manifold nozzle may be too large. I plan to test a 80CC\ min with the next supercharger. I also have a leak around one of the water solenoids that I need to fix.

 

Oil \ Air separator.

 

Added an aircraft oil to air separator. It works. The vented catch can I using was only redistributing the oil around the cowl. No more chasing oil leaks that I didn’t have. 

 

Two exciting events. I had a -4 fitting stress fracture on the line feeding the gearbox. This happened in flight. I had spilled oil installing the oil separator and wrote off the smell to that. I was close to Dennis’s and decided to drop in for a visit. Much to my surprise I had about a cup of oil down the side of my cowl. I have two 6” x 3” exits on the top of my cowl. I added these last summer in an attempt to improve taxi cooling. Remember the half mile up hill taxi? I had convinced myself the exits would also provide an early indication of any leaks. No one drop of oil on my windscreen. The oil on the cowl seam was from the flywheel slinging it against the side. Dennis assisted me with the replacement and ordered a strict 30 minute flight restriction to get me back to Lockhart. The fitting was also supporting my oil pressure sender and really needed to be steel. However the flight restriction was extended to 5 hours after a BBQ run to Llano was instigated. That’s the picture Mark S. posted with the three rotary’s a couple of weeks back.  On the flight back to Lockhart I experienced a small manifold leak shortly after take-off. A small amount of fuel did make it to the windscreen. Reducing manifold pressure stopped the leak. The manifold has now been welded. It was braised before.

 

Still not happy with my EC2 tuning. I have a strange area of addresses that I can’t make happy. It is taking to much attention during different phases of flight. A trip to Shady Bend may be in order next year. Tracy may need to take a look at this one.

 

 

Bobby Hughes

RV10 Super Renesis