Update
Geoff sent me some further info and updates on his plane:
"Have been doing a lot of flying over the past few months as the weather has been perfect?cool, calm and clear days?beautiful.
I have fitted out the rear seat with a full set of instruments and controls so the RV8 can be flown from the back seat?very interesting!!!! Anyway in the process when we calibrated the rear airspeed indicator, we discovered the front one was under reading by 10-12 knots. We did 4 way speed runs and the GPS data confirmed the rear airspeed indicator was spot on and the front one out!!! The upside is that we discovered our cruise speed is actually 160 knots @ 4200RPM..approx 2200 prop rpm for a throttle setting of 49% as shown from my MoTeC data logger. We are suffering in top end speed seeing only 185 knots flat out this due to a lack of prop efficiency. Climb performance is fabulous, seeing 3000 fpm @ 89 knots, with one POB and 120 litres of fuel and 20 kgs ballast on the rear seat.
Today (21/07/18) we were two up( approx 160 kgs), 90 litres of fuel and comfortably still climbed @ 2500 fpm @ 90 knots.
The fuel burn sits at 28 litres per hour (7.4 US Gallons)in cruise.
My MoTeC data logging confirms that cooling issues are non existant. The log line is almost dead flat from takeoff to landing!! Inlet air temp usually sits @ approx 10 Deg C above ambient, rising to 51-55 Deg C at 160 Kpa boost on takeoff and climb then very quickly dropping back in cruise. Again today, doing touch and goes the coolant temp never exceeded 83 deg C and oil and gearbox temps were all well within spec. EGTs were 1380 ? 1450 f and afr all below .95 lamda. Cannot fault the engine or airframe. Very happy so far.
Very hard to say if the underwing rads have affected performance much but even if they have, it is minimal and the trade off is effective and reliable cooling. The figures all mirror what I have seen in the summer months so I am confident I have solved the cooling issues that have plagued the Suby installations for years!!
I think someone asked how I had routed the cooling lines from the motor to the rads and back again. I routed the coolant pipes under the fuse to avoid the main wing spar cross member and brought them up behind the pilots seat and routed them out to the rads on the wings. I used 22mm OD 6061 alloy tube and formed silicon hose bends and straight sections to link everything together.
After a lot of research I found that 1 Sq ft of Rad surface was required to cool 100 hp in free air and that placing the rads in a duct improved the cooling efficiency considerably and also the specific shape and length of the duct had a dramatic effect on cooling performance. I designed the ducts to take advantage of the above criteria. The rads themselves I constructed as two rads in one, having a double pass from front to back. This allowed me to minimise the rad frontal area but effectively doubling the surface area exposed to the airflow. The actual surface area is approx. 2.5 sq ft.
The oil is also cooled by the engine coolant passing through an in line heat exchanger so the rads are doing double duty.
If anyone wants more info, feel free to drop me an e-mail. I have kept a comprehensive log of what I have done, made templates etc of the parts, brackets, for the cooling system and have an extensive list of all the parts necessary to construct the system. I also made very good moulds for the inner and outer ducts (8 incarnations until I was happy?just over a years work!!!!)"