dhal22
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Sleet and rain all day today here, then the cold starts to get serious tomorrow night. At least for Georgia......
Electronic Carburetor/Roto 85 FS Install
- Thread starter TonyHallo
- Start date
Sleet and rain all day today here, then the cold starts to get serious tomorrow night. At least for Georgia......
Snoopy1
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WOW NICE TO HAVE YOU BACK. We have missed you.
dhal22
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TonyHallo
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I had to cut a rather large hole in the engine stand used for the Saito FG61 to get the Roto mounted. When I ran the engine it had quite a bit or vibration in the 3000 - 4000 rpm range. Decided to make a stand for the engine and increase the stiffness. It's mounted and ready for testing.
TonyHallo
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Quick update here on the conversion. The controller wasn't working properly when connected to an additional Smart Port device. I was using an AT-V1 sensor to measure the head temps and the RPM. The solenoid pulses would jump around 600 to 1000 pulses. At idle that was ok since the solenoid pulse is about 4600 at idle, at WOT the pulse is somewhere less than 1000 so the engine would just quit. I started trying different approaches to measure the throttle pulse width from the radio, nothing worked. I played around for a couple weeks before stumbling over the fast that the second Smart port device was causing the problem. Next step was to eliminate the AT-V1 device and move the measurements into the engine controller. That code was added and somewhere along the line it hit that a SBUS input signal would work great so that's where I'm at now. The use of SBUS added another problem that was solved using AI to write the code, the SBUS communicates at 100000 baud rate while the SPORT uses 57600 baud rate. At any rate after a week or so trying different approaches using AI the final prototype controller is built and tested. I was in no hurry since the bench that the engine was mounted to was now holding the Cherokee fuselage for painting. The code also richens the mixture as the head temperatures exceed 290 and continues to richen as the temperature continues to increase, this needs tested.
As far as the engine goes, the carb in the photo above was off a 55 cc Stihl chain saw, on the initial runs it would only idle as low as 1600 rpm, a smaller electronic carb was purchased from a 35 CC Stihl saw, this was run and achieved an idle of 1200 RPM. The engine would purr at 1000 RPM with the original WT962 carb so I wasn't satisfied with 1200 RPM.
For reference the original WT962 bore is 14 mm, the 35 CC saw is 15 mm, and the 55 CC is 18 mm. The carbs are shown below.
Additionally the bleed passage on the 35 CC throttle plate is much larger than that of the WT962. I suspect this has to do with the fact that saw must be running to power the controller in the saw, there is no battery. The solenoid is a normally open device to allow fuel to flow while starting, once started the fuel controller takes over. Note the difference below.
The throttle plate was removed and the passage was filled in with Harris stay bright solder. That where it stands today, once the new controller is built, tuning will continue.
I learned a lot during this project and I can see using the microcontroller for other RC applications. Was thinking about controlling the navigation lights as once example.
As far as the engine goes, the carb in the photo above was off a 55 cc Stihl chain saw, on the initial runs it would only idle as low as 1600 rpm, a smaller electronic carb was purchased from a 35 CC Stihl saw, this was run and achieved an idle of 1200 RPM. The engine would purr at 1000 RPM with the original WT962 carb so I wasn't satisfied with 1200 RPM.
For reference the original WT962 bore is 14 mm, the 35 CC saw is 15 mm, and the 55 CC is 18 mm. The carbs are shown below.
Additionally the bleed passage on the 35 CC throttle plate is much larger than that of the WT962. I suspect this has to do with the fact that saw must be running to power the controller in the saw, there is no battery. The solenoid is a normally open device to allow fuel to flow while starting, once started the fuel controller takes over. Note the difference below.
The throttle plate was removed and the passage was filled in with Harris stay bright solder. That where it stands today, once the new controller is built, tuning will continue.
I learned a lot during this project and I can see using the microcontroller for other RC applications. Was thinking about controlling the navigation lights as once example.