RCU Forums - View Single Post - How well did your YS run after sending it in for service?
Old 10-08-2007, 02:32 PM
Troy Newman
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Join Date: Dec 2001
Location: Goodyear, AZ
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Default RE: How well did your YS run after sending it in for service?

If the piston/cylinder or ring is scored, the engine will have excessive blow by. This blow by puts already hot, partially burnt charge down below the piston, and down where the next charge is being prepared by the super charger system.

This blow by is mostly oil, since oil doesn't burn as well as nitro and methanol, the next charge is super rich in excess oil that is already hot. The next time charge enters the top and does its thing. Now the some of the excess oil flashes off making the excess smoke, from too much oil in the fuel...and you get an very incomplete burn due to the leaking past the piston and ring, and the in combination with the excess oil it doesn't want to burn as well.

If the regulator was not stopping the fuel because the plunger was not seating the the excess fuel would make the engine rich. Very rich, but it would not change the amount of oil that is getting burnt. It would pump excess nitro-methanol, and oil in the same ratio tot he engine....So the engine would tend to smoke a bunch at idle or mid throttle as the engine is trying to burn too much fuel. But at the High end you could likely needle it down far enough to get the mixture correct for full throttle.

On the blow by side of things...the engine will act like its rich because its not burning correctly due to the leakage past the piston, and its also combined with the excess oil from the last charge that doesn't burn well. So the needle gets set leaner to clean up the "sounds rich condition" but in reality you are just restricting the amount of nitro and methanol even more. Now add in that oil from the blow by and charge is now even higher in oil content and it makes things worse and worse....

If you regulator sticks open then the excess fuel will flood out the glow plug. Leaning the high speed can help at full power. When the piston-ring is leaking the excess heat will not put the glow plug out but there becomes lots of oil to lube the engine but not enough fuel, so the engine starts to burn the oil, and gets hotter and hotter trying to keep up.

Troy Newman
Team YS