Throttled TD .09
02-23-2004, 10:00 PM
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Throttled TD .09
Most of us remember the Cox RC .05 and RC .09. This was a refreshing attempt by Cox to give us a throttled engine that included a proper throttle with adjustable airbleed and muffler. I finally got the RC .05 but I found overheating problems along with significantly non linear throttle response. Because of that experience I never did get the RC .09.
With a bit of throttle experimentation under my belt, I decided, last year to give my well used TD .09 the treatment. Pictured is that effort. The throttle is from the MVVS .09 and was provided by www.carlsonengineimports.com . The muffler was custom made. Throttling was quite good with decent linearity. Perhaps I shouldn't have let my experience with the .05 deter me from getting the .09 version.
As it was a pretty much worn out engine, power was down. The donation of a couple of Medallion .09 cylinders by AJ was a most welcome gesture allowing me to experiment with enlarged by-pass ports and altered timing. Not much success with any kind of power boost was the result. One thing that was noted was that compression seal, even though these were new piston/cylinder sets, wasn't all that great. These were fit to fairly loose tolerances and this appears to have been done to minimize the amount of break in required. Myself, I'd MUCH rather have a tight engine requiring careful break in. This usually gives you an engine with superior power and longevity.
Pictured along with the engine is one of two piston/cylinder sets that I obtained that had the ports cut but did not have the final honing done. Thanks to the generous help of AJ, I finally learned how to do piston and cylinder lapping. One set has been lapped for very light drag at the top. Final break in should give me perfect running tolerance. One set (installed) has been lapped to a very tight fit, much as you see on ABC or Norvel engines. This will mimic my experiment with TD .049s that have considerable pinch at the top. Once broken in, they still have a light pinch at the top when hot and when cold will snag if you don't flip the prop through quickly. Much like Norvels.
By taking worn out .049 cylinders, I was able to lap them out to suit .051 pistons. This was done to optimize compression seal for diesel conversions. I never had much luck with Cox diesel conversions but once I had excellent compression seal, I found starting easy and very often on the first flip. That's saying a lot for a diesel.
Yes, the .09 in question here is slated to be broken in on glow and then run as a diesel. I'm anticipating that the throttle bore will be too big so a new barrel is being made with a smaller bore. If throttling is still not up to par, I can still install a Jets two needle throttle.
With a bit of throttle experimentation under my belt, I decided, last year to give my well used TD .09 the treatment. Pictured is that effort. The throttle is from the MVVS .09 and was provided by www.carlsonengineimports.com . The muffler was custom made. Throttling was quite good with decent linearity. Perhaps I shouldn't have let my experience with the .05 deter me from getting the .09 version.
As it was a pretty much worn out engine, power was down. The donation of a couple of Medallion .09 cylinders by AJ was a most welcome gesture allowing me to experiment with enlarged by-pass ports and altered timing. Not much success with any kind of power boost was the result. One thing that was noted was that compression seal, even though these were new piston/cylinder sets, wasn't all that great. These were fit to fairly loose tolerances and this appears to have been done to minimize the amount of break in required. Myself, I'd MUCH rather have a tight engine requiring careful break in. This usually gives you an engine with superior power and longevity.
Pictured along with the engine is one of two piston/cylinder sets that I obtained that had the ports cut but did not have the final honing done. Thanks to the generous help of AJ, I finally learned how to do piston and cylinder lapping. One set has been lapped for very light drag at the top. Final break in should give me perfect running tolerance. One set (installed) has been lapped to a very tight fit, much as you see on ABC or Norvel engines. This will mimic my experiment with TD .049s that have considerable pinch at the top. Once broken in, they still have a light pinch at the top when hot and when cold will snag if you don't flip the prop through quickly. Much like Norvels.
By taking worn out .049 cylinders, I was able to lap them out to suit .051 pistons. This was done to optimize compression seal for diesel conversions. I never had much luck with Cox diesel conversions but once I had excellent compression seal, I found starting easy and very often on the first flip. That's saying a lot for a diesel.
Yes, the .09 in question here is slated to be broken in on glow and then run as a diesel. I'm anticipating that the throttle bore will be too big so a new barrel is being made with a smaller bore. If throttling is still not up to par, I can still install a Jets two needle throttle.
[that would be a great project for you to tackle next].
