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Engine basics => Engine set up tips => Topic started by: kevin king on August 04, 2021, 10:07:22 AM
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Hi all, not exclusive to the RJ67, but how do i get more 4 cycle and less 2 from my engine??
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Hi all, not exclusive to the RJ67, but how do i get more 4 cycle and less 2 from my engine??
More nitro, more pitch, or a larger venturi. Shortening the pipe, or increasing the compression will also do it but you will get more boost/break.
If you just want to move the operating point more toward the 4, the easy way is to add nitro.
Brett
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Thanks Brett!
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Kevin, I use 15% Bryons Heli fuel( no longer available). I add about 3 ounces of Castor. I use the stock Venturi. I run it on the ground adjusting until it quits cycling back and forth 2-4 then just slightly richer to launch. This is on a muffler for SE or header muffler for RE. If you want it will slightly break in some maneuvers. If you don't like that adjust slightly ( very slightly) richer and it will mostly run in a 4 cycle. I use about 5 ounces of fuel for the pattern .
We are at 1,400 feet elevation, it will use more lower altitude. I will try Powermaster 15% Heli fuel soon, it has 23% Oil all low viscosity synthetic.
The 67 runs much better with the 15% and is easier to needle. I believe you have the same prop I have ( Brian Eather 12.5x5.3) three blade slightly under camber etc. You can take some pitch out to slow lap time down or add a little it needed. Due to the long stroke of this engine it does not wind up to much if you keep the pitch down. Mine does not break into a 2 cycle much when I get it right just beeps occasionally on some maneuvers.
When I say set it richer I am taking about very, very small needle adjustments 1/16 inch or so at a time until you get what you want .
The key for me has been letting it run on the ground until it warms up a bit then making sure it does not break into a 2 cycle or any hint of it on the ground then set it just slightly richer past that. ( How much richer depends on you) Hope this helps. A Fellow flying buddy is using a RO Jett 76
RE using same fuel same adjustment etc runs the same as my 67 . Plane is 68 ounces hauls it fine. Not sure how many head gaskets as it has been a long time since I changed anything it runs so consistent I don't mess with it.
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Thanks Walter!
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Walter, what was the oil content in the Byrons heli fuel before you added the 3oz of castor?
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21% by Volume
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21% by Volume
Walter - did you try the same volume, but synthetic? Adding castor makes me start looking for the crock pot.
Brett
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The Byrons Heli Fuel was all low viscosity synthetic , I added 3 oz degummed castor to the all synthetic fuel.
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The problem i have is once i get a nice four cycle setting, my lap times are to slow. I need to do more testing though. The prop i was using was was a 3 blade Bolly 12.5" with a 6" pitch. Once i get some higher nitro fuel, i will do more testing. Brett i understand your dismay of people not wanting to run some engines the way they were intended. For me, the tone of the engine throughout the flight is very important. I will never be a top level competitor, so i am willing to give up *some* performance to get there. My usual goal is just to have a nice looking plane with a non irritating engine run while still having the ability to fly a competitive pattern. Kevi n