Here is an Image of the type of DynoJet this project was completed on:-

The original intention was to piggy back the Yourdyno on to the existing speed pick up, which on these older models is a single tooth on a 6" disc that passes through a optical sensor.

The WinPEP software has a drum information screen and gave to following information 

Drum :1 Model: 200

Serial number: 00001XXX

Drum Mass:14.272

Drum Circumference: 4.67

Number of Tabs on Drum: 1  

No units are displayed initially if was though that the drum mass was the mass in Stone giving 90.63Kg when converted. this number is also stamped on the edge of the drum by the starter ring gear. It was assumed also the the drum circumference was in Feet and Inches giving 1.423416M, this was check by wrapping wire around the circumference. The drum diameter was then calculated to be 45.3cm as required for the YourDyno input box.

The Yourdyno allowed the input of 1 notch event thought we know we would not reach the recommended minimum of 200Hz we gave it a go. 

We had a motorcycle that had previously run on a more modern DynoJet so we had an appreciation of what to expect, the first run proved to give some strange result for the bike in question. While it initial appeared to capture the initial power the results gave up, the X scale for the RPM looked correct, the Yourdyno also froze when the log button was selected, (there are some warning about the freezing  issue in the software)

Jostein confirmed that for the drum acceleration to be calculated Yourdyno logic need to see a minimum of 200 0-5V square wave  pulse per second Hz. Instructions for the hall sensor and a download of a file that would produce a suitable 20T wheel can be found on the Yourdyno site here:- Link To Speed Speed Spec

How ever it was decided to continue with the same diameter wheel and optical pick up, an image of the 20T wheel fitted to the DynoJet drum shaft is attached below.

Once the 20T wheel was fitted, the engine RPM to the drum ratio was set in 4th gear, this time the curve produced followed what was expected to be seen in terms of power at the wheel versus engine RPM, unfortunately the HP was significantly less than what was expected. Further runs were completed leaving the verified drum diameter static the mass value was increased until the output curve matched the known curve. The final value for the drum mass appeared to be 580Kg. While this appeared to initially a much higher value than expected a quick calculation of the volume multiplied by the density of steel confirmed that the drum could be close to this value.

The drums construction did not help understanding how it had been constructed, it could have been a solid or looking how the end caps are weld it could have been cylinder. The formula that is being used in the Yourdyno input screen was examined and is the formula to estimate the Mass Moment of Inertia for a solid cylinder.

Without being able to physically measure the dimensions of the drum after research two methods of testing the drum where found.

Method One from the DTech site (The guys at DTech should be thanked here they have some fantastic tools and guides I would like to buy one of the RPM pick up conversion boxes.

Method Two from an interesting home build this method was interesting as there was potential to use the Yourdyno to collect the data to check the inertia value  

20 Tooth wheel fitted to DynoJet shaft and optical Sensor 

After the 20T wheel was fitted more runs were completed, it was not possible to simply test the inertia as per the example shown in the previous posts as it was not possible to wrap cord to the roller and create a vertical tangential pull.

The output from the optical sensor was scoped to see if it was outputting the desired values, while the steady state screen capture was what was expected if only a little high on the voltage when the bike was accelerated the image changed. Unsure what this meant it was decided to move to a hall sensor

The hall sensor that is supplied with the kit was fitted to a different dyno project, the hall senor is wired direct to the Yourdyno with no modification and works fine. What was available for this project was what is commonly known as a Cherry sensor, These sensors have a wide range of input voltages but need a pull up resistor Relative to the input voltage to work 

Cherry Sensor Data sheet

The advantage of this sensor is the threaded exterior body that allows the require gap to be adjusted with ease once a simple bracket had been made. The Yourdyno has an on board pull up resistor and no additional resistor was added and the system seam to work fine see picture below to see attachment. The shielded cable was from a old USB extension cable and handles the 5V supply, signal and shield fine.

Once the speed signal from the drum to the Youdyno was brought in to spec the value that DynoJet has original quoted as being mass was notes as being close to the Mass Moment of Inertia for the guess value for the mass. The value as show in the attachment stamped on to the drum was inputted in as 14.272Kgm^2.

Lots of research found differing answers of what units were used by DynoJet for the value stamped on the drum. I now believe this to be the MOI in SI units.

The environmental compensation factor was set to use the real time values.

Boom the output from the next dyno runs were with in a few percent of the last know WHP values for this bike, overlay of the DynoJet V the YourDyno curves to follow 

Very interesting.

Nice!

Here is a very quick overlay of the scaled YourDyno output screen over the DynoJet results. If through out this process if YourDyno user have seen similar issues and have overcome them in different way I would love to see and here about them. For myself I now have a tool measure the mechanical changes I implement on my bike

I currently have a Inovate LC2 wideband hooked up and also a EGT probe on the K-type input of the Yourdyno

I am sure that once I have the engine RPM pick up up and running that may take a little bit more of the error out of the system when setting the overall engine to drum gear ratio. 

I see other user are asking for a velocity output and I am aware of the issues of Tyre slip and the change in rolling radius effecting the results maybe Jostein is working on that as the changes for plug in come online in the software. 

Please accept my apologies for the low and poor quality of the images I have shown I can not be bothered with quality editing and hope that someone get some inspiration from them 

Todays test was to validate the dyno at higher horsepower the result shown below shoe 117WHP compared to the other previous results of 115WHP.

This now confirm what I need which is a measuring tool to see what the difference the modification I am to make to my machine with some confidence the drift is minor 

Next job is to start using the LC2 wideband both via exhaust port tapping, via the pumped DynoJet sniffed and also via a slip on tailpipe to understand if there are any difference when on the same machine.  I have access to both 4.2 and 4.9 controllers so may look at that as well. The 4.9 controller benefits by not requiring the additional free air calibration button, integrated blink code light and a better methods of communication via serial to modify the outputs for AFR and differing fuel types.