YS Tuning Tee
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Dhmodels http://www.concentric.net/~dhmodels/rc.html The setup is a Tee in the intake runner which faces directly rearward---this is then attached to a length of light ,thinwall 1/2" dia lightweight silicone rubber tubing --approximately one foot long which has a stopper in it's extreme end.-This simply rests along some portion of the airframe and is tied in place. The YS engine produces a positive pressure in the intake tube when it reaches about 5000 rpm as I recall--the pressure builds quickly at that point and depending on the size of the tube (plenum) will reach approximately 5.5 psi. I have proven that IF the plenum is in the system, a rpm gain of 300 rpm is the minimum boost at approximately 9000rpm.--when the plenum is blocked off the engine looses about 500 rpm--BUT adjusting the fuel mixture produces some recovery --about 200 RPM. Conversely - if the plenum is opened --at that time --the engine will pick up some speed BUT will be running lean and require that the mixture be richened to bring up the maximum power. It also appeared that some further work could cause a mild tuning effect in the setup - I did not continue the tests but simply used the engine in this form for about a year. Very strong runner -- NO problems except that the tube wore a little in the O ring seal areas. I used a quality 5 LB pressure gauge for all tests and am satisfied that the rework was worth doing. The engine was a std big valve engine (preceding the air box design.) IF some rework to the head was done to feed the rocker cover from the Tee and if the head was reworked around the intake valve to allow flow through a series of shaped holes (like on the 1.4 engine -- the engine should breath better yet and even though the measured pressure in the tube would drop, the power (torque) should come up even more -- this is to be my next test setup.
Dick Hanson
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