Troy Newman

I run the fuel line external of the model so I can clamp it down or plug it off. This keeps it from flooding. It only floods quickly when you pump fuel into the tank and allow it to run unrestricted to the pump on the engine. We tend to not run an enclosed setup on other engines like we do on the YS motors. But take an OS46 and put a "T" in the supply fuel line to fill the tank with. Guess what you will flood it too.

Just put a couple of rubber grommets in the cowling. Run the fuel line out one grommet. Then back in the other grommet. Cut the line and install a fuel filter here. This is where you fill up. Use some hemostats or a K+S style clamp like in this photo to close the line to the engine. When the tank is full keep the supply line close until time to start.

If you follow the diagram I posted above or something similar to this photo you will not have problems with flooding.

Troy

rcstavros

Troy, is there a good reason to use this way of plumbing for other YS engines like the 110FZ or the regulator in these engines prevents flooding during filling ?

Stavros

Troy Newman

The way the pressure fuel systems work in all the other YS engines prevents flooding. The DZ engines are different.

The normal YS Engines NON-DZ style, The way the regulator works is a a demand pressure regulator. If the engine is running then it has a demand from one side. A suction or a pressure difference. This causes the plunger to open and fuel to flow. If the engine is sitting not running then there is not pressure difference and the regulator is closed by the spring tension that is controlled by the adjustment screw. More tension on this syruping means that the pressure difference must be greater to open the plunger. This is LEANER the more pressure difference needed to open the plunger means that less fuel will make it past. The less force on the spring means the plunger opens easier and the engine will richen up as more fuel passes. This is all you are doing when turning the regulator screw is adjusting the force of that spring.

So if your carb drips fuel after the engine shuts off, then the plunger is not closing or not right away. This could be dirt or debris in the regulator or it could be the force on the spring is not high enough and the you need to dial the screw in to increase the force on the little spring.

OK back to the question at hand....Non DZ style motors will not flood because there is no pressure difference on the regulator to tell it to open. SO it stays closed and no fuel flows.

On a DZ motor the pump is a positive displacement pump. This pump can have fuel under pressure pushed past it. Since the pump is attached to the intake valve push-rod mechanism depending on where the engine is on its timing cycle you could literally fill the entire inside volume of engine with raw fuel. It would be "Pickled" or totally locked up. Raw fuel both top and bottom of the piston, raw fuel in the cam gear area and under the valve cover. This is a messy situation and I have seen it happen more than once. It usually take removing the glow plug and just cranking and cranking to remove all the fuel from the engine. A real pain the back side. So pitch the line, plug the line do something so it doesn't flood. The Direct Injection system is a really powerful attribute. However by its nature the pump and system can flood. If you take the precaution about plugging or pinching off the line it will not flood.

Of note. This is done not only during fueling should you have the line plugged but also after its fueled and sitting in the sun. The temp will rise and pressure will build in the tank. This will cause the fuel to siphon into the engine and do the exact same thing.

Troy Newman
Team YS Performance

JPal101

My Feedback: (32)

Troy that was great. I now not only understand completely the workings of the FZ and what to look for and know what to do if I do see drips out of the carb but also how the fuel pump works on the DZ. But, still one more question remains. I assume the adjusting screw on the pump (DZ) is to regulate the pump pressure but how do you know when it is correct?

Troy Newman

On the Dingo just like all the other YS engines. A rich setting will maintain an RPM for a few moments say 2000-2300 and then start to fall off slowly. Another sign of being rich on the pump is dead sticks at idle or after a long idle and throttle up the engine quits. This is usually rich. Could be rich on the Pump and or rich on the HS. The pump and the HS are related and I’ll explain it below.

The Pump too lean will detonate or surge in the midrange. A throttle up and backfire in the mid range is too lean. I set the idle down low ( 2000-2200) and watch the rpms. If they surge up and up down about 200-400rpm this is too lean and you need to richen it. I tend to set the pump lean as I can get without detonation in the throttle up or surging at idle.

The Pump on the Dingo can be thought to control the pressure of the fuel. Again what it is really doing is playing with the bypass loop or kickback loop on the fuel.

The pump basically supplies the same volume of fuel every time it cycles. There is a bypass loop or I have heard it called a kickback line. This bypass line is internal in the pumps body and has a couple of check valves or really they are like a "Pop Off" valve in Boiler system. This Bypass goes from the outlet of the pump back to the inlet of the pump. Basically if it was Electricity it would be a short circuit. The pump adjustment screw controls the pressure inside this bypass line. Again its running off the pressure differences inside the engine similar to the demand regulator on the pressurized engines but this time its allowing the fuel to bypass the needle valve and injector line and short circuit back tot he inlet of the pump. This keeps the pump happy. He is in there just pushing fuel. Pushing the same little drip of fuel each time he cycles. Some is being bypassed back to the inlet and some goes to the big boom. Think of Electricity the bypass line has a resistor in it the adjustment screw is adjusting the restriction. The higher the restriction the more that goes to the BOOM and the low the restriction the more fuel that goes back to the front of the line and gets pushed by the pump again. The more restriction in this line the higher the pressure on the pump outlet side needs to be to push fuel through this bypass line. So when you tighten the screw CW rotation, you are putting more force on the spring which is putting more force on the diaphragm. The diaphragm controls two little check valve or pop off valves. If the pressure in the outlet of the pump is big then the pop off valve opens and allows the fuel to bypass. If the pressure is lower in the outlet of the pump the pop off valve stays closed until the pressure is higher.

The pressure in the outlet of the pump is changing every time the intake valve on the engine opens. The pump can be thought of as a piston that is always pushing the same volume of fuel. The spring tension on the diaphragm tells the pop off valves when to open and when to close. So if you turn the pump in to apply more pressure on the spring then the "pop" off will happen at a higher pressure in the pump outlet line and close sooner. This means more fuel in the injector line and less in the Bypass line. In plain old NASCAR American redneck talk, she gets a bigger gulp of fuel to the engine when less is being bypassed. This also means on the other side that less of the fuel is going through the bypass or kickback line.

A lean situation means that the pop off valves are opening sooner and staying open longer allowing the bypass to happen. So in relation more fuel is bypassing and the engine is getting less fuel to combust.

The High Speed needle valve controls how big the hole is the fuel is being metered through. So it is also affecting the pressure in the pump outlet line. This is why on the DZ motors the HS needle and the pump pressure affect each other. Really the screw is adjusting the bypass line and the HS is adjusting the size of the opening the pump is pushing through. A richer setting on the pump means the hole could be small but I'm going to get as much in there as I can for as long as I can. This means that you can set the HS needle and get the engine to run great at high speed even if the pump is way off. Example you have a really rich pump. So your HS needle is closed way down like 1/2 turn open. For High RPMs the fuel to air is getting mixture at the right ratio and all is good but slow the engine down and the high pressure in the pump outlet is pushing just way too much fuel for the idle rpm and the heat generated at idle and the engine goes cold and the fire is killed.

Now let us take a big step backward. Setting of the motor. We are talking about raw fuel. Not fuel air mixture like in a 140FZ sport or any of the other YS pressure system motors. So when you re dumping raw fuel on the piston and there is too much of it the first thing that happens is the temps go down right? Richer means cooling down. However the principles that make our engine operate are similar to that of a Diesel. Temp and pressure with a little catalyst from the glow plug. So if the temp goes down now things are not operating right and you are putting out the fire. So what happens is at full power all is fine because it has lots of heat being generated, and the extra fuel is burning. But when slowing the engine down now the heat is much much more critical. The engine needs that heat to make its big boom. But you are at idle not making the heat and the extra fuel is slowly smothering the fire. So after a long idle and you throttle up quickly is like smothering the fire. As the RPMS increase the fuel gets there almost instantly and the temps don't come up as fast so the fire just washes away.


By the way this is one reason the YS engines have such great throttle response and transition. The two systems the Dingo and the Pressure system always have plenty of fuel there and ready to burn when the throttle body asks for it. On the pressure system its being force fed by the tank pressure. Anyone pulling the pressure line and seeing fuel squirt 10ft across the flight line has seen this. But the DZ does something similar in the positive displacement pump and the bypass loop.

If you think about the pump on the Dingo you will now see why we use the foam fuel clunks with them. Fuel is a liquid and is pretty non-compressible. So the pump outlet pressure is constant up and down as long as the fuel flow is steady with no air bubbles. Now Air on the other hand is a compressible fluid. A little bubble in the fuel line and the pressure ration for the bypass loop and the injector line are all messed up. This makes the pump still pushes the same volume but now less of this volume is fuel and that makes the engine not gets proper drink of the good stuff. It goes lean if only for a split second. Now lean means more heat, and heat means again pressure changes. So it becomes a never ending battle to maintain the right heat to make the boom and not get too much.


So if you made it through this thesis and you understand I did a good job. If I confused you even more then add glow igniter, and flip prop. Turn the HS needle in to make lots of heat and out to reduce the amount of heat being made. Enjoy!

Troy Newman
Team YS Perfomance

rcstavros

Thanks a lot for your complete answer Troy.

Stavros

gra95770

Well Troy that has answered a few more questions I had, unfortunately I had a big backfire and bent both valve stems,so at present waiting for more to arrive,by the way completely my fault

jschwenk

How will a ys 140 DZ compare to a saito 150 4 stroke? Do you need to run with a muffler? Do these Dz engine last as long as a saito?

thanks (I'm thinking about getting one)

Troy Newman

The 140DZ will outrun a Saito 180. The DZ is the direct Fuel injected version of the YS 140 and it has major power over the normal YS 140's The normal YS 140 L, Sport or FZ is equal to the Saito 180 so a 150 Saito is not even in the ball park for power output.

I like the Saito engines they are really good engines. I own a couple of them. The application of the engine is totally different.

The Saito is a very reliable 4 stroke engine. Scale projects, and non High performance applications are the best place for the Saito

The YS engine is a high performance High power output engine that is supercharged.

With the performance comes a little different care and feeding. With proper care the YS engine will last a really long time. I have had 140DZ go over 1000 flights. Now they did get a rebuild during that time. Usually its just new ring and bearings about every 250-300 flights. This is about the same as the Saito for repair work.

The YS engines are more like race car engines, and the Saito is more like a production car engine. Different apllications and different technology. The question on the comercial is does it have a Hemi? Well decide for yourself which one you want or need in the application.


Troy Newman
Team YS

CASTAJ

My Feedback: (4)

dear Mr. newman, i see you are in all techical posts for ys.

i own multiple engines but thisbis my first dz engine, i just fired it up today and it started with 1 flip, really powerfull engine 18-8w apc 8350 rpm. Wow!

but i noticed a constant leaking of fuel at the head nipple, i see some green snot was applied around nipple that enters the head assembly.

is this serviceable?

can this be the source of the leak or just the black check valve? I opened it and it seems fine, clean and good diaphragm.

i hope tobhear your thoughts on this issue.

thanks
jesus castaneda