Tuned pipe length check - in flight
10-26-2022 | 07:35 PM
#26
Thanks heaps Will!!
that helps a lot. What rpm’s are you pulling as well? I might drop my aluminium head shim then!
I’m currently running 15% nitro, 20% cool power blue oil, aluminium shim, os8, Bolly EQ63 pipe, 510mm from piston face to first baffle (following bend of header), Bolly 12.5x11.5W prop, around 10,300 rpm but I’m not sure if it’s getting hot at that. True piston/liner set too.
mine didn’t like the 13x9 apc, but thinking pipe may have been too short?
that helps a lot. What rpm’s are you pulling as well? I might drop my aluminium head shim then!
I’m currently running 15% nitro, 20% cool power blue oil, aluminium shim, os8, Bolly EQ63 pipe, 510mm from piston face to first baffle (following bend of header), Bolly 12.5x11.5W prop, around 10,300 rpm but I’m not sure if it’s getting hot at that. True piston/liner set too.
mine didn’t like the 13x9 apc, but thinking pipe may have been too short?
10-27-2022 | 07:37 AM
#27
My Feedback: (121)
Two questions:
1) why did you put the head shim in?
2) what do you mean by ‘did not like’ referring to the 13x9 prop? Wouldn’t or couldn’t get on the pipe? The engine rpm dropped noticeably when going vertical? Difficult to set the needle?
Your pipe length seems quite reasonable, you can check by pulling the pipe out another 12-13mm and see how the engine runs. The prop load for a 12.5x11.5 versus a 13x9 is about the same. If the pipe volume is slightly smaller then a slightly longer setting may be required. What is the diameter of the pipe. I have several Bolly pipes, but they are all for 120 or larger displacement engines. I just flew the airplane with the 13x9 prop 2 days ago and the engine ran great. You can also try running the engine with the pipe 12-13mm shorter. If it runs fine on the ground, you should be able to fly it. If the engine sounds lean in the air, land.
one final thought: if the engine has a lot of flights on it, check the needle. I started having problems with an engine and discovered there was an asymmetrical grove worn into the needle. I replaced the needle and the engine ran perfectly.
please keep me posted.
will
1) why did you put the head shim in?
2) what do you mean by ‘did not like’ referring to the 13x9 prop? Wouldn’t or couldn’t get on the pipe? The engine rpm dropped noticeably when going vertical? Difficult to set the needle?
Your pipe length seems quite reasonable, you can check by pulling the pipe out another 12-13mm and see how the engine runs. The prop load for a 12.5x11.5 versus a 13x9 is about the same. If the pipe volume is slightly smaller then a slightly longer setting may be required. What is the diameter of the pipe. I have several Bolly pipes, but they are all for 120 or larger displacement engines. I just flew the airplane with the 13x9 prop 2 days ago and the engine ran great. You can also try running the engine with the pipe 12-13mm shorter. If it runs fine on the ground, you should be able to fly it. If the engine sounds lean in the air, land.
one final thought: if the engine has a lot of flights on it, check the needle. I started having problems with an engine and discovered there was an asymmetrical grove worn into the needle. I replaced the needle and the engine ran perfectly.
please keep me posted.
will
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TheEdge (10-27-2022)
