YS 140DZ Fuel System

Mon Dec 2 13:29:49 AKST 2002

"is the pipe between the regulator and the bearing housing there to pulse the regulator or to bleed fuel off to lubricate the bearings or both?"

Answer....The regulator is no longer a pressure regulator it is actually a pump that's working mechanism is a diaphragm. The screw in the front control the spring tension on the pump to meter fuel flow. Older style YS motors actually have a regulator that regulates pressure of the fuel supply. I think you mean pipe as the fuel line running from the pump bottom to the fitting on the front bearing housing of the case.....The fuel line running from the bottom of the pump to the case is to allow lubrication of the bearings and the some to the worm gear on the crank that drives the cam gear. The intake pushrod tube (has the heat sink on it and is attached to the pump) drives the pressure differentials on the pump....These pressures change as the engine is running and since above the pump is one pressure and below the pump is a different pressure the pump is uses this to move the fuel..The control screw meters the amount in a course adjustment. The cam gear and followers also get some lube via the inside of the pushrod tube on the intake side...The cam follower on this side has a tiny hole in the bottom of it on the side that allows oil to seep into this chamber.  

"The pipe from the carb to the head must be the fuel supply (hence Direct Injection), Yes If this is so is ant fuel drawn into the crank case to lubricate the bottom end?"

Answer. The fuel leaves the pump and heads for the carb....but not fuel mixture with air occurs here...It only goes through the needle valve and the exits the body of the carb. The "pipe" I think you're refering to is the fuel line that heads up to the top of the head from the rear of the carb body. This is raw metered fuel. It has been metered through the needle valve for proper mixture adjustment but is not mixed with air yet....The traditional carb is really only an air valve now and not a carburetor. This means that NO raw fuel or mixture of fuel and air is going through the bottom of the engine to cool it. Instead blow by is cooling the bottom end of the engine. Yes the oil that slips by the piston and is un-used in combustion creeps by the piston and ring to cool the bottom end....Any excess oil is then sent up the metal intake tube to the valve cover. As the intake valve opens the fuel mixes with the oily air as when it goes into through the valve. Now this is why:

#1 the motor likes Heli fuel with thinner oils. The reason is the oil must creep by the piston and lube the bottom end.....Now one of the main reasons the motor was "late" to market is the fact that this cooling of the bottom end was very setup dependant. Many of the early engines did not cool well. This was fixed before production. The orange insolator keeps the fuel from getting hot while being metered in the needle valve. The Carb body then stays cool to keep the air coming in cooler. Also the rotor is covered with a teflon type coating to require less oil to lubricate it through its motion.
The crank shaft has a ring seal on it to separate the bearing area from the rear of the motor as it gets most of its lube from the front fuel line to the case.

#2  The engine doesn't like to run rich because the raw fuel is injected right into the combustion chamber. If the mixture is too rich the fuel can't mix with the air properly and it puts out the fire....Or gives incomplete burn and the motor runs very rough.

#3 The engine produces so much power because the fuel going into the combustion chamber is cold. Look at what the drag racers do they have cooling systems on their fuel.....If the fuel gets run through the motor via a couple chambers here and there the fuel will heat up and not be as effective when it hits the big boom.

#4 The thinner oil excess from the bottom of the motor is traveling up the intake tube and is getting burnt...This is giving that white smoke....I have found the smoke really only gets excessive when the motor is really humping up near full throttle....When its running hotter...If it is cool and running say at half throttle all the time the smoke is minor.....If its smoking a ton down there you are too rich......Too lean means it will sag on an upline just like a sport motor...

Now this all being said....If you dump fuel into the carb which is now an air valve it will travel the route and eventually go through the intake valve and burn just like the oil...But this fuel is traveling with the air and getting to the same place....

This is truly a revolution is design that is very very efficient. The OS fuel injected system is a fuel injected carburetor.....The fuel mixes with the air right in the same spot as it would with a normal spray bar...The needle valve and spray bar in those cases is just replaced with a electric solenoid that pulses the fuel into the carb to mix with the air....The YS is truly a Injected fuel system. Look at when cars started having the Fuel injection systems...power and economy increased. Well if the OS RX and the FI make the exact same power and get the same economy....Now the DZ gets its power over previous versions because its benefiting from the the direct injection of the cold fuel....just like a modern day fuel system on a car. No its not electronic but it is mechanically doing the same things.   

Because of the radical change in technology comes some minor procedure things to make the motor operate to its best...If you try to stray from these little idiosyncrasies then you will not have good success with the motor...But everybody that I have talk to and seen follow the rules and treat engine properly has come to love it....Those with problems are not listening to the rules or not setting things up properly.  

The engine seems to have a timing that like torque and big props....On the ground many of the props in the proper load range run close to the same RPM but in the air they really are different and to motor responds different. The best props we have found are the 16.5-12W APC this is superb for high elevations and windy conditions..... the 17-12 APC is a great prop also but up here where I fly at 6000ft it is just a little too much load...and during high winds I liked the 16.5-12W better....These props are both able to run in the noise limits for messing around the 16-12 APC works like a missile but is too much speed and noise. DON't run the motor up in the 9000's it is not timing wise setup for these higher Rpms....Keep it above 8000 and below about 8800 these two props above do just that. The 16-12 will push to top of the 88700-8800 the 16.5-12W is a good one in the 8400-8600 and the 17-12 reaches the 8100-8200 range....depends on your style of flying the plane.....Planes really dictate the prop selection not the motor.. A heavier plane will like the smaller diameter with its quicker acceleration the lighter planes will like the bigger diameter as they can accelerate the light planes quicker....

I hope this helps understand what's going on in the motor...This knowledge lets you know why the heli fuel is used and why the motor doesn't like rich mixture.

Troy NewmanGet more from the Web.  FREE MSN Explorer download : http://explorer.msn.com
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