Getting ready for the tests.

There has been much discussion about the engine system and how I have constructed the various elements, but ultimately it is the thrust that pushes the aircraft into the air. Thrust can be measured for a number of conditions and indeed Don Bates' propeller model indicates that for the 64 inch three blade propeller design, described in the pages of this web site, the static thrust, for my configuration, should be 414lbs with a propeller rpm of 4130.

I was concerned that the engine may produce more horse power than the Subaru data had suggested. I suspected that my design for a tuned, and less restrictive, exhaust system would increase power but by some undetermined value in particular at the higher RPM conditions. I elected to fabricate the propeller almost exactly in accordance with the Don Bates model recommendation except that I would continued the blade lengths a further 1.5 inches with the intention of removing the excess as appropriate. The results to date indicate that this was a smart thing to do and even longer blades may have been better still.

Initial power testing has been conducted using the engine with no radiator attached. The cooling system was arranged with the coolant flowing in a closed circuit i.e. the output from the engine's cooling system was connected to the input using a clear 1 1/4" pipe purchased from Home Depot. I used a pre mixed Prestone coolant and a 16 p.s.i. cap on the cooling system. I had been running with this arrangement without the propeller for some weeks to set-up the basic engine conditions and to check the operation of the engine computer (ECU).

The time had come to test the engine with propeller attached. These test were conducted in the middle of the Canadian winter here in Ottawa, Ontario. Outside temperatures were -25 Celsius (-13 degrees F) so the test set-up period was well planned and implemented in the shortest possible time to minimise the personal exposure to the low temperatures.

To expedite the tests the aeroplane was rolled out of the hanger/workshop so that the propeller was just outside the shop leaving the front still in the shop. This allowed the wheels to be just on the concrete which made for quick tests since rolling the aeroplane in any direction was quick and simple. Two 3/4" ropes, tied to the landing gear and a suitably located tree, secured the aeroplane against forward motion. (The infinity retracts give a spacing of approximately 11 feet unlike the stock landing gear thereby keeping the securing lines away from the propeller.)

Test Equipment

A "Grand Rapids" engine information system EIS has been installed to monitor most of the engine temperatures and pressures with a sampling rate of one second. A small buffer amplifier was also used to buffer the voltage from the mass airflow (MAF) sensor. The output from this buffer amplifier was fed directly to one of the auxiliary inputs of the EIS. A simple software package provided means for reading the EIS data using a serial connection to a PC.

A four channel storage oscilloscope was also connected to the following sensors and signals found on the engine. The scope could be triggered at any time by pressing the data capture button on the front panel.

• Channel 1        Cam angle sensor
• Channel 2        Cylinder #5 ignition coil
• Channel 3        Cylinder #5 fuel injector
• Channel 4        Crank angle sensor

Some Video's during an EAA Chapter visit (February 2004)

The following videos were were filmed during the winter months (February) of 2004. Outside temperatures were about -15 degrees centigrade. The Cozy was pulled out into clear air unlike the previous testing which had been conducted under the canopy of the Hanger/Workshop. This created better airflow stability to the mass airflow sensor however the absence of the cowling meant that the mass airflow sensor was directly in the suction path of the propeller and a loss in performance was anticipated.