What Our Members Are Building
Ben Schneider's Mazda Renesis-powered RV-7
By Ben Schneider
My alternative engine installation in my RV-7 is a Mazda Renesis (RX-8) engine built for this purpose by Bruce Turrentine1. The intake, exhaust, and cooling systems are of my own design, though Ed Klepis at Tech Welding welded the intake and fabricated the cooling system from scratch. I prefabricated and fitted all the components for intake and had Ed do the actual welding. On the control side of the intake, I have a Holley throttle body designed for a Ford Mustang coupled to a ram-air filter bypass for use at altitude. The bypass is operated by a Futaba servo (for radio-control models) wired to a potentiometer in the panel. I can open and close the bypass with a turn of the knob.
The 13-inch-by-20-inch radiator (with 2-inch-thick core) was custom made to fit the application. It hangs under the engine with a forward slant. The water inlet and outlet are also at the top end to aid in bleeding air from the system and to keep the lines out of the exiting airflow. The oil cooler is a dual pass cooler made entirely from aluminum and, as with the radiator, both the inlet and outlet ports are at the front end.
I also scratch-built the exhaust but had it welded up by Mike Petersen. Welding is not my forté, so I leave that to the pros. The exhaust is made of .065-inch 321 stainless steel tubing, opting for extra wall thickness at the expense of weight. I started with a scratch-built, 2-inch, three-into-one header system, flowing toward the firewall as it turns down and slightly in. It then passes through a spring-loaded ball joint as it continues down before turning aft under the fuselage. It then increases in diameter to 2.5 inches before attaching to the Aero Turbine muffler, to which a short section of tailpipe is affixed. There are two streamlined tube hangers under the fuselage that are thermally isolated to prevent heat transfer into the aluminum belly. The entire exhaust system has been ceramic-coated and is supposed to be good to 2,000 degrees Fahrenheit. Time will tell.
My wife thought air conditioning would be nice, especially since the brackets were already there for the compressor, but I decided to go with dual alternator and dual batteries for total redundancy instead. Each system consists of a 40-amp B&C alternator and a 17-ampere-hour battery, either of which is capable of handling the entire load of the aircraft under any circumstance. Dual high-pressure fuel pumps feed the fuel injectors that are controlled by a Real World Solutions (RWS) EC2 engine controller. Up front I have a 66" dia by 85" pitch three-blade, fixed-pitch prop built by Craig Catto that’s bolted to a Saber Mfg. prop spacer and is driven by an RDS, RD1C propeller speed reduction unit (PSRU), also from Tracy Crook at RWS.
The fuel system is a return-type system with fuel flowing from each tank through an Andair dual stack selector valve, through the firewall, to the dual fuel pumps, through a Aeromotive fuel filter, a flow sensor, and into a fuel rail. From there, fuel is sent through individual braided stainless lines to each of the four fuel injectors mounted in injector bosses supplied by Simple Digital Systems (SDS).
Off the end of the fuel rail, the return line is routed to the firewall and passes through an Aeromotive fuel pressure regulator. Fuel then flows through the firewall, through a return flow sensor, and back to its respective tank. I also installed a bypass to prevent vapor locking the pumps. It is bypassed from the pressure side of the regulator through a restrictor and back into the return line to go to the tank.
The entire engine installation is hanging on a Conversion Concepts engine mount and is wrapped with a James Aircraft cowl for rotary engines.
I am currently working on the ducting inside the cowling to the radiator and oil cooler. It is poured foam with a fiberglass overlay. Though I have no real data yet, as I have not started the engine as of this writing, I have pretty high hopes for my installation. (Don’t we all?) My concerns with my installation are: 1) I now believe my intake runners are a bit too long for optimum performance and 2) I worry about exhaust heat radiating to the fuselage. I still plan to run the engine as it is and iron out the wrinkles as they develop. I anticipate starting the engine very soon.
1Bruce Turrentine, 3008 Airpark Road, Triple W Airport, Fuquay-Varina, North Carolina, 919-557-6512.