Tarno carb operation

An RCU thread about the Tarno Carb and instructions. It has some comments of users.

https://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/8359997-tarno-carburetor-instructions-setup.html

A few comments:

"Look closely at Paragraph 3 on the Tarno 1/2A Carb factory instructions and you'll see that they highly recommend adding a Cox muffler that is "essential for reliable idling and noise reduction".
This also appears on the Tarno.09 Carb instructions.
This leads me to believe that the Tarno carb design needed additional exhaust back pressure to create a consistant Air/Fuel ratio for a smooth transition from idle to WOT rpms.
It probably worked best with cylinders that had little or none Sub Port Industion.
I have not had time to try out a with and without muffler test yet but hope to shortly.
Lack of muffler back pressure or low back pressure from a Cox/Ace Throttle ring is probably the reason that 50% of the opinions of the Tarno Carb say it's junk and the other 50% who installed it a muffler said it was great."


"The Cox muffler is a power robbing POS. The Cox muffler by itself brings you down to 3/4 throttle. What is needed is a muffler with an expansion chamber. Finding a strong running non SPI P/L set might be a tall order. After satisfying these first 2 conditions, any decently made throttle valve should do the job nicely."

@Cribbs74 wrote:Thanks guys,

Looks like I have some bench running to do. I’ll try multiple configurations and tach each for best performance. I’ll choose the highest rpm with the best idle.
Ron

Hey, Ron. If you want to throw in another variable, there's the Cox throttle muffler. Also used on the Medallion .049 RC.

With some clever linkage, this might work. Since there's no exhaust port on this one, tweaking the muffler spring may help
maintain  some combustion chamber heat(low idle).  
If you want to pursue this, I'll send you one. I have a Tarno TD carb, but I'm lazy of late.
Bob

@Cribbs74 wrote:Thanks Bob,
You are too generous. Let me see with what I can do with what I have on hand first. I may have the right combo.

Lots of unexplored avenues here, Ron. Glow plugs, pressurizing the tank, back pressure, cylinder height/ sub port induction, fuel
mix, etcetera, etcetera, etcetera(King and I reference) https://www.youtube.com/watch?v=1JHH6iwgIek
I might try a few defined possibilities, but the combinations are endless. There might be a magic potion, and I hope one of us comes up with it.
I'm basing my next thesis defense on it. PHD here I come!
Dr. Bob