Want a bench dyno to tune small engines? BlackBoxDyno has you covered. Get a large flywheel and switch to Inertia Dyno mode, in Settings, and start pulling!
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Easy Install
Mount the BlackBox to any stable surface
Mount the self-stick magnet on flywheel
Use bracket to position Speed Sensor
Point Sensor at magnet about 1/4" away
Clip RPM Sensor on Spark Plug wire
Secure Ground under valve cover bolt
Run History
Automatically saves your last 10 runs
Shows Date, Time, Speed, HP of each
Tap Center to see any run
Tap ⭐ to Keep any run
Tap 🗑️ to Delete any run
Super Frugal?
I built this inertia dyno with a $75 wagon wheel and scrap wood I had laying around. It is incredibly accurate. The bigger your inertia, the more torque and HP you can run. Inertia comes more from diameter than weight, so I can test up to about 18HP. Watch the video to see build.
Flywheel Size Chart
A good rule of thumb is to multiply your max HP by 20 to get the Inertia you will need.
Say you wanted to test up to 12HP
12HP x 20 = 240 Inertia
Look in the white section of the chart for a number of 240 or higher. Trace up to get the wheel diameter in yellow. Trace left to get the wheel weight in pounds.
A 32" diameter, 275 pound flywheel gives you 244 inertia, so that will work.
Questions Contact: BlackBoxDyno@gmail.com
Once you have a flywheel, this is how to accurately determine its inertia using the weight and string method
Questions Contact: BlackBoxDyno@gmail.com
A quick wagon wheel dyno run
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