This covers all DZ engines the 140DZ, 160DZ and the 170DZ. Even much of this stuff applies to the 170DZ CDI engine as well.

 The YS DZ engine seems to be a bit of a mystery to many of the guys that have flown YS for years. The reality is its very similar in how it works. The biggest thing is the engine now gets RAW fuel direct to the intake valve and this can make the engine act funny when you get the mixture too rich. Before the Dingo engines the problem was lean runs and we always set them up slobbery rich at first. The Dingo doesn’t like this, as anyone that has had success with it can attest.

This is going to be a two part series on the DZ engines. What to do when you open the box, how to install it and setup the linkage, header install, mufflers, and finally a long explanation on how the pump, and engine interact and HOW it actually works.

Opening the box:

The engine is inside a little plastic bag. Usually there is a little oil residue in the bag. This is not oil that was put on the outside of the engine to protect it. This is the oil that Yamada Japan put inside the engine when they built it. So guess what you need to lube it up. I recommend using Mobil 1 synthetic 0W-20 oil all synthetic and fairly thin oil. The first place to put a little oil is inside the cam gear area. The DZ motors only get oil to the bottom end of the engine from what blows by the piston ring. This is why the Heli fuels work the best. These fuels have very thin low viscosity oil. This oil will migrate past the ring easier and will also help to carry the heat away.

 Back on track we need to oil the cam gear and also the lower end of the engine. Like the connecting rod and disc valve and all those moving parts inside. They will get oil on that first run but it might be 30 seconds into the run before they get really wet and lubricated properly. Its easy for us to do it when the engine in hand. I put just a few drops in the carb. Also remove the cam gear cover. It has two little screws on the side of the engine up front at the base of the pushrod tubes. With a small amount of oil on the cam and inside turn it over slowly. If you put too much oil in it you will have trouble starting it. You will need a big heavy duty starter to get it to fire if you use too much oil.

Again the reason for this: Any of the oil put inside the engine by Yamada has migrated to another spot  or just plain dried up. When was your engine assembled? You don’t know….it could be a couple months or a year since it was built.  Making sure the cam has a little lube prior to the first run will insure it doesn’t get damaged on that first run. Many guys call me up and say I blew a cam gear in 25 flights or 50 flights. They don’t believe me when I tell them they really damaged the cam on the first run and it took 50 flights to actually fail!  By the way anytime the engine has been sitting in the box or out of the plane I usually put a little oil in on the cam gear. Since I started this back in 2003 I have not had one cam gear failure. That is many many 140DZ, 160’s along with a couple of 170’s also.

Next thing to check is pull the valve cover and check the tappet clearances. They should be set about 0.002”-0.004”. I find the factory doesn’t always get these set the best. I run mine as tight as they will go and still have the valve closed. You can wiggle it and feel some gap but it is too small to measure. If you can tell what you are doing you don’t need a feeler gauge to check it. If you are a sledge hammer mechanic that can break and anvil with a rubber hammer, PLEASE use a feeler gauge. Its very important the valve closes. If it doesn’t the piston could hit it and cause major damage to the engine. Really the only thing you will notice with the tappet clearances too loose is that top end power will be slightly reduced. Not major but a little. The clearances don’t really affect idle, transition much just the top end power. This just means the valve is not staying open as long. So it’s not getting as big of charge before the valve closes and it makes the Boom. While you have the valve cover off, check and torque the head screws. They do not get tightened by an 800lb gorilla but they need to be tight. If they are not, loosen each one a little maybe 1 turn from snug and then tighten in the crossing pattern like Dad taught you when changing a tire on the family sedan. Anytime you remove a part like the valve cover clean the mate surface with denatured alcohol, clean the o-ring or gasket with the same alcohol, and assemble this part dry. This will ensure it doesn’t leak. Once the head is tight replace the valve cover with the gasket aligned properly. Again tighten slowly and alternate between the screws. DO NOT over tighten these screws. It can warp the valve cover. Years ago it was common of lap the mate surface on the valve covers. This doesn’t hurt and if you need instructions on this contact me. Today the YS gaskets are much thicker and this is not really required unless you over tighten the cover and get a little twist or warp in it. This lapping the mate surface will correct minor over tweaking. The engine is now ready to run. Wait until you have your final linkage stuff setup before you bolt it in tight.

 Installing the engine in your model.

I’m a firm believer in using a nose ring. I don’t like the mounts that don’t need a nose ring. They are too stiff and too big and heavy for my tastes. In addition the forces on the thrust line of the engine in corners and such are best handled with a nose ring. I can always tell when flying a model that doesn’t use a nose ring. This ring is to aid in keeping the thrust line in the right spot. For the same reason I choose the mounts Merle makes with the shear axis limiter in the middle. This keeps the two disc plates of the mount from sliding against each other and allows them to only rotate. Some guys have trouble with the Aluminum beams only catching the rear two holes in the mounting lugs. I use a good “T” handle to tighten them, and always use blue locktite. I also will clean the bolts with alcohol before I reinstall them. This ensures the locktite will hold. Make sure the engine can rotate in the nose ring. It should not be binding in any way but should be tight with no slop but a slip fit. YS sometimes machines this front bearing housing to different diameters. Some of the nose rings will be very tight on a given engine and the next engine it’s a slip fit. A dremel tool drum sander can lightly remove the material on the O-ring inside the nose ring until it fits properly. Replacement O-rings can be had at places like Ace Hardware, or you can find a specialty o-ring shop. Take in your old one and they will match it up. Less than $1 and you are good as new.

Another good mount is the YS mount. I’m trying one out for the first time this year and I like it so far. It is lighter than a Hyde mount and seems to work every bit as well. The price is a higher, and there may be some maintenance required but I’m trying it for now. For simple and effective Merle’s mounts will not let you down. In my opinion they are the best around. The YS mount requires a little more work to keep it up and functioning properly. If you know how to work it and understand it it is as good as Merles mounts. Its lighter and has a smoother idle vibration on the airframe. If you just bolt it on and forget about it. The results will be not so good after many many flights and will make things worse in the long run.

 Throttle Control:

Throttle Linkage is very important to the way the engine delivers its power. The DZ has the best power band of any of the engines currently out there for pattern work, and to use this band of power and really tell how good it is you need a good linkage setup. I find guys using sloppy, poor rod material, tiny foamy servos, with flexi linkages and wonder why it dies at idle when they enter a spin. It only happens sometimes but does happen. Well the answer is often found in the linkage. I choose a good precise servo for the throttle. It doesn’t need to be a digital with 100oz of torque but does need to be a precise servo. My opinion is the small micro servos for foamies are not as precise as a good coreless or digital servo. I don’t go for the smallest servo I can get and still move the pushrod.  Some folks swear off the digital because of the vibration and the extra work the servo must do to maintain its position when the linkage is bouncing around. Regardless of this I choose the JR 3421SA for my throttle. I have run them since 2002 and they are perfect servos for the application. I also use a small 0.043” music wire pushrod. It runs directly to the throttle arm and has no funny angles, no bends, and connects straight to the throttle arm. For the Throttle arm connection I use a ball link, the type that has a bolt through it. Not the ones that just snap on. These can fail, and my experience is taken from the Helicopter guys. A good ball link with a bolt through it is used.  You can choose your thread size… I solder a brass solder link to the end of the music wire. I will sand the music wire end with 100grit and clean it with alcohol, then use a good flux and solder joint. For Ball links I use the ones with a 2mm bolt through the ball. When removing the engine a pair of ball link pliers removes the “yoke” from the ball and the engine comes out leaving the linkage intact for the engine to go back in the same spot…no throttle changes. For easy adjustment I use a Tettra style EZ connector on the servo side. These Tettra ones are cool because they have a little nut that screws on the bottom and they won’t pop off the servo arm\wheel. The pushrod runs through a nylon pushrod guide tube and is support at the firewall and back at the servo. If it’s a long run I’ll maybe add a support in the middle.

 Geometry of the throttle linkage is also important. If setup properly only fine tuning is needed on the throttle curve.  I zero out the throttle curve or any expo you may be using on the throttle. I make sure the Travel adjustment is 100% each side, and sub trim values are all zero. Make sure any Throttle cut features are turned off, and any aux trim functions like the Volume controller on the 9Z Futaba radios are turned off. I then move the throttle servo mid throttle. This can be verified in the throttle curve function of the radio, it can also be verified using the servo monitor feature of the radio and various other ways. If your throttle stick in exactly the middle position doesn’t give the same middle position on the servo monitor or the “Out” value in the throttle curve menu then you have something else going on like a mix, or condition or something. If there is nothing programming wise then it could be a bad TX stick pot….

 With the servo at it “neutral” or middle position, attach the servo arm 90degs to the pushrod. This will make the servos travel above and below ½ power be balanced and symmetrical. I use a Standard JR round servo wheel and the outside hole. The hole with a line back to the servo output shaft center and the pushrod form the 90 deg angle. By the way this hole for those of you that choose other brands of servos is about 12mm from the center of the servo shaft. If the servo splines don’t align at this 90 deg point with one of these outside holes perfectly then rotate the servo wheel 180degs and use a hole on the other side. JR and Futaba servos use a spline that has an odd number of teeth on them. So rotation of the arm or wheel 180degs will give alignment “1/2” tooth off.

Next thing I use the furthest outside hole on the black YS throttle arm. This makes the arm 15mm from the middle of the throttle arm screw to the pivot point. If you’ll notice this is slightly less than a one to one ratio, servo wheel to throttle arm. So we are going to use the best possible resolution from our good quality precise servo, remember a foamy servo don’t cut it here in the precision world. It may make the linkage move but you want as fine of control over your power as you get with ailerons or elevator. The servo arm\wheel is now attached so its symmetry is equal above and below the ½ stick position, but we need to match up the throttle barrel to it. It is impossible to know exactly where ½ throttle is from looking at the barrel so I make sure the arm goes from full closed to full open and look at the angles of the throttle arm. Make them equal angles left and right of vertical. If your throttle arm points up in relation to the engine (not the plane) then you will be about 10:30 and 1:30 on the face of the clock. Loosen the throttle arm screw and tighten it with the arm in this magic spot that makes the angles of full open and full closed the same. It’s probably going to change a little in a minute but this where to start. Once you have these angles balanced then you are ready to attach the linkage and get ready to tighten the “ez” connector screw.  The TX end points should setup around 100- 125% each way. Depending on the engine some will be right at 100% and other will be up at the 125%. This really depends on which engine you have….Some of mine have a little more movement on the throttle barrel than others. I would start at 125% both end points for the throttle. Now move the throttle arm back pegged against full throttle. Tighten the EZ connector screw. Now with throttle trim in the middle run the stick to idle, all the time watching to see if it is over traveling and binding on the closed side. If it is binding you adjust the Travel volumes (EPA or ATV) to a lower number like both at 115% and try it again. What you want is on the DZ there is a small “V” cut in the throttle barrel. The engine should be very close to a good idle with this “V” as the only hole exposed as the barrel is rotating closed. The small hole will be only the size of a pin head and you might need a flash light to look in and see the mark on the barrel. The key now is to make small changes in ATV or Travel Volume and resetting the ez connector so that the servo at full throttle pulls the throttle arm TIGHT against the stop at WOT and only allows this small pin head size hole at idle with ATV values matched at the same number. This is simple and will only take you a couple iterations to get it right. Once you have this set properly….You MUST reduce the Full throttle ATV by about 10%. So in a perfect setup you would have the ATV values be 115% at WOT and 125% at the idle position with the pin head size hole and throttle trim in the middle. Again you may be 100% at full power and 110% at idle.  The purpose of this 10% less is because your motor mount will stretch a little when it goes to full power. You don’t want the linkage to be holding the engine, and you don’t want the throttle barrel to start to rotate back past Full open.  This over rotation can make the engine go lean, especially on older engines like 120’s and pressurized 140’s. So setup is with it at the physical stop and them reduce the ATV by 10% to make sure its not over rotating as it travels and there is a little room for the motor to move forward when the mount stretches. Don’t worry you are not going to be losing power by closing the throttle barrel by 10% servo travel. When the motor mount stretches you will get most if not all of this travel back, and also the last little bit of travel of the barrel really has little effect of top end power anyway.  If you setup the linkage with this kind of geometry then it is likely that you not need any throttle curve at all. If anything I usually step up the curve a bit coming off idle so the engine will come up quickly off idle for stall turns and things. Basically I make the 10% stick position equal about 20% out, and the 20% stick position give about 30% out to the servo. This makes for a little hotter throttle coming off idle but then it goes straight from there.

Headers and Mufflers:

 The idea of the copper washers is to give a different metal that expands at a different rate than the aluminum when hot. If you tighten the header up and compress the copper enough, when hot the copper will keep the bushing nut tight. The aluminum will expand more than the copper and will pinch it tight, and since the copper is a softer metal the connection will get tighter as it heats up. The head will expand and the header will expand but the copper is in the middle expanding less than the aluminum. If washers were aluminum they would expand the same as the header and head, and the joint will actually loosen. Think of an imperfect surface that has tiny bumps and ridges from machining the parts. With similar metals any little gaps or microscopic voids in the joint will expand the same when hot. With a different metal in between like the copper these voids and gaps will get even smaller and the header will stay tight.

 Getting back to the bushing nut bottoming out in the exhaust port of the engine, the extra washer will take up that extra 1 turn of thread that is short inside the head. What happens is we want as many threads on the bushing nut as possible yet not all the engines have the exact same thread depth. The extra washer is thick enough to equalize the thread depth issue. Plus the added benefit is that a thicker piece of copper will allow for a tighter connection. Normally you would put one washer on the bushing nut and one between the head and header. This is the one inside and one outside trick. I install (2) copper washers on the bushing nut then slide it inside the header body. Since it is inside it doesn’t affect the spacing of the header away from the head, and is hidden. This system when properly tight will not leak at all. So if you are getting leakage, stop and check it. Running it loose will damage the header. Then it will never seal and it will never stay tight. The bushing nuts will auger the body of the header and it will be time to order a new one.  If you have trouble keeping it tight and leak free, run the engine for about 5mins on the ground. While everything is HOT re-tighten the bushing nut. This will solve 99.9% of the stubborn headers. The other ones need you to inspect the header body for damage on the mating surface. Minor damage can be fixed with a dremel tool and steady hand. While more extensive damage requires a new header.  This header system I have used since 2003 and been the absolute best header I have ever owned. We have refined the header over the last few years to a point where it is nearly bullet proof.

 In the muffler area there are lots of choices. The CF pipes work, and some guys like them, The Hatori 821 short pipe is probably my favorite now. It is simple and easy to use. Central Hobbies now sells a Viton O-ring that can be used to connect the NMP header to the Hatori 821 muffler. This system is extremely good and I have run it or variations of it (long version 699pipe) for about 18months. The O-rings last about 100 flights and then they start to leak a little. It’s not a big deal and it’s a 5 min task. I don’t run header braces and I think in 4 years I have had a header come loose twice.

 How does the Dingo fuel system work?

The Pump on the Dingo can be thought to control the pressure of the fuel. However what it is really doing is playing with a bypass loop or kickback loop on the fuel.  When the pressure in the line to the Needle Valve and throttle body is high enough the extra fuel not being used will go back through to the supply from the tank. The diagram was taken from the YS Doctors’ Website in Japan. He did a better job of drawing the diagram so I want to give the proper credit. I just labeled the parts and pieces

Diagram of the Pump Assembly thanks to the YS Doctor Site in Japan.

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 loop is internal to the pumps body and has a couple of check valves. The pressure control line or Bypass Loop is really like a “Pop Off” valve in Boiler system. When pressure gets high enough to push the diaphragm back against the crankcase pressure the bypass opens and fuel short circuits back to the pump inlet. Basically if it was Electricity it would be a short circuit. The pump adjustment screw controls the pressure inside this bypass line. The more spring tension on the diaphragm the higher the pressure needs to be before it will open the bypass. Again it’s running off the pressure differences inside the engine similar to the demand regulator on the pressurized engines but this time it’s allowing the fuel to bypass the needle valve and injector line and short circuit back to the inlet of the pump. This keeps the pump happy as its always moving the same fuel even if the engine is running at idle. At low RPM the demand would be low and the pressure would be high in the injector line so the excess fuel would open the bypass and “kickback” to the inlet of the pump. The pump has no idea the engine is at full power or idle it is just pushing the same little drip of fuel each time it cycles. Some is being bypassed back to the inlet and some goes to the injector. Think of Electricity the bypass line has a resistor inline; the adjustment screw is adjusting the restriction. The higher the restriction the more that goes to the injector for combustion and the lower the restriction the more fuel that goes back to the front of the line and to get pushed by the pump again. 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 bypass loop or pop off valve. 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.  Running at full power the injector is using all the fuel it can get, the pressure in the injector line is low and the bypass stays closed more. When at Idle the fuel demand is low so the pressure in this line will be higher and more fuel will be heading back for another push from the pump.

 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.  This is tough to think about because we think in terms of needle valves and more fuel means richer and less fuel means leaner. The metering is on the bypass so more bypass means less fuel for the mixture. Less bypass fuel means more fuel is going to the combustion and its richer mixture setting on the engine. A lean situation means that the pop off valves are opening sooner and staying open longer allowing the bypass to happen instead of sending the fuel up the injector. 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 mixed 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. Or an extreme case is the HS needle is closed down so far that the pump pressure is trying to squirt a jet of fuel through but it’s just building too much pressure. I have seen it burst fuel lines or push them off the carburetor.

Now let us take a big step backward. Setting of the motor. We are talking about raw fuel up in the head of the engine. Not fuel air mixture like in a 140FZ sport or any of the other YS pressure system motors. So when you are 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 engines operate are similar to that of a Diesel. Temperature and pressure with a little catalyst from the glow plug make the explosion. 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. When slowing the engine down now the heat is much much more critical. The engine needs that heat to make its big boom. However you are at idle not making the heat and the extra fuel is slowly smothering the fire. After a long idle and you throttle up quickly the fuel demand goes up and it dumps a big gulp of raw fuel into the injector. The result is like smothering the fire. As the RPMS increase the fuel gets there almost instantly, due to the fact the pump is tied directly to the intake valve pushrod. When the RPMS jump up the pump is pushing more drops per minute, and the throttle barrel has a metering slot in it that opens up and allows more flow, which means the pop off pressure on the bypass is satisfied. The big problem is the temps don’t come up as fast as the fuel floods into the chamber so the fire just washes away. This right here is why guys say the DZ engines use so much fuel. They are running the pump pressure too rich. The extra fuel that goes into the engine gets turned into smoke. This transition throttle work is where we fly pattern. Not at full throttle and not at idle. We are always opening and closing the throttle barrel. If you mixture is not efficiently working it is wasting fuel. Only a little drop here and a little drop there, as the heat comes up and the engine starts to use the fuel to make power.  I fly a 20oz tank and regularly get about 14-15 mins per flight if I want to. We as modelers tend to err on the side of a rich mixture. The DZ has a very responsive system and doesn’t like this really rich setting.

By the way this responsive system 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 ratio for the bypass loop and the injector line are all messed up. The pump still pushes the same volume but now less of this volume is fuel and that makes the engine not get a 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 amount of heat to make the boom and not get too much.

 On the Dingo mixture settings are just like all the other YS engines.  To know 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. It could be rich on the Pump and or rich on the HS. The pump and the HS are related as I explained above.

 The Pump when 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.

 When the engine is going through the first 10-20 flights it is not uncommon to have a dead stick in there. What is happening is one of two possible things. First the motor is breaking in and there is less heat. Just like I explained above the gate opens up and fuel rushes in but there is not enough heat to deal with it and the plug just gets wet and the fire goes away. If you think about it this is what happens on all glow engines. Less heat means the setting that once was good for mixture is now too rich and the engine doesn’t clear out. On the Dingo this can mean a dead stick do to the fact that raw fuel is rushing into the head. Next option: The plug is bad. As the engine breaks in like all engines there are little bits and microscopic chunks flying around inside of that engine. If these hit the glow plug they will burn a hot spot in the coil and the plug now doesn’t have its normal catalytic reaction. So it’s easier for the fuel to put the fire out. This is also a symptom of an engine that has been running for a long time well and now doesn’t want to idle. The plug is probably the only change needed. Then the idle usually smoothes right out. Depending on your choice of fuels and so on this could be as soon as 50-75 flights and it could be 100-150 flights. I make it a habit to change the plug before contest and get 2-3 flights on it before the event.

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

I added some information regarding tuning of the YS pressure regulator. Most of the engines the regulator is factory set.  Most YS engine problems are a result of dirty fuel systems, poor choice of fuel….

The next biggest cause is operator adjustment of the regulator. The YS tuning page I have here is an effort to educate the new modeler to YS engines and how they work.  These engines are unique in the modeling world.  Other 4 stroke engines on the market tend to be different in the tuning and break in. YS engines do to their fuel delivery system offer a unique advantage in power, performance, idle and consistency.

The trick is learning the little tell tale signs of it being lean, or rich. Often you can’t set them with your ear. We modelers do that all the time and sometimes our ear needs a little recalibration.

I’m going to be tearing down a  YS 170DZ in the next few days and will post the complete details along with photos as requested by Kirk.

Thanks for coming to the site.

Merry Chrismas

Troy

At the bottom of each post there is a Balloon comment icon. If there are no comments it will say no comments on this post. Click on it and you can leave a comment for a post. For now its OK to ask a YS question in a YS post or a JR question in a JR post.

I get the comments and and can either respond in that post essentially making it a thread or I will write a new post for the day in the Blog.

I’m learning with you guys on this, however I am interested in comments. I want to know what questions to answer. If you have a question by all means leave a comment on a given thread and I’ll get it answered and we’ll continue the growth of Patternflyer.com

Thanks,

 Troy

There seems to be some questions regarding the YS 170DZ CDI engine. Lots of misinformation is out there regarding this engine.

Here is the scoop on the engine. First off I have been testing it now for about 9-10months.

To begin with there is NO power difference between the two engines. Top end RPM is the same for the same prop and fuel regardless of Glow plug or CDI on Spark. The one thing that the engine does do is provide a better transition and more grunt down lower in the throttle curve over the glow version. This means that you are not having to get as high into the throttle for a given pull on the model. The result is it acts like more power…in that the power band is lowered on the engine. At 50% power the engine is making more on Ignition than it is on glow.

The Fuel is still Alcohol, while the engine will run and transition better on lower nitro fuels, you are giving up power from the 30% to lower your nitro content.  Many have run 20% nitro content and it works very well. I have played with 20% nitro also.  However lots of people do this already on the glow engines. The higher nitro helps the engine run a little cooler and also makes them slightly easier to tune properly. I hope this answers the nitro question. The engine is easier to tune on lower nitro with CDI over glow but you are not going to get the power. I have run mine on 10% nitro and it tunes fine and transitions excellent, but it is not the power we are used to. More testing is going on now. Also oil content of the fuel is a critical issue with tuning. I don’t think 10% nitro and low oil is going to work in the current configuration. I’ll explain why below.

Oil Content, This is where lots of folk that don’t know about the engine are telling folks about it on the internet. Too Much speculation is around. This is the scoop from somebody that has run it and knows what it likes and doesn’t like.  The original YS 170 CDI I flew last winter (January) was not capable of the low oil content. This engine used the exact same fuel as the glow guys. I ran Cool Power 30% heli Performance and also Cool Power 30% Heli LS blends in that engine. Yamada then made several changes to the engine. I’ll explain it a bit how the thing is working and the changes so people can understand. Suffice it to say some new parts are in an engine to allow the low oil content.

Let me explain it this way. CDI doesn’t in and of itself allow low oil content. But CDI with some new engine parts does. I’ll talk about oil more in a bit…but the parts are not the same…CDI is one thing and CDI with low oil is another. Right now the low oil is a CDI thing but many of the test engines are not low oil even though they may have CDI on them. This is testing stuff….So bear with me on this I’ll explain.

The CDI system is more efficient and uses the fuel better. The mixture doesn’t need to be sloppy rich in the mid range to keep the engine from detonating. In fact the engine doesn’t detonate. On glow you have a chemical, pressure and heat reaction. As you load the engine down too much it builds heat. The higher heat means the combustion goes off to early. Remember Compression didn’t change, the catalyst in the glow plug and the heat from the plug didn’t change, and the mixture didn’t change so the higher heat caused by the high load and low RPM means a ignition that happens too soon when uncontrolled like with a glow plug. On your car they call this “Ping” or Knocking. I call it pre-ignition or detonation. Anybody that has gotten a YS lean and thrown a spinner knows the hollow loud sound of this. It’s dangerous for the engine and can break pistons like some have posted on the Internet. Usually the cause of this piston failure is detonation not a flooded condition. However the Flooded or kick back can aggravate this problem. Usually if the detonation that causes those things, can also cause Valve seats being pushed out of the head and other issues from detonation. Detonation is bad and hard on parts. One thing about Nitro content here: Lower nitro required smaller props to keep the rpms right to not overload the engine and heat it up. This is on glow plug as the lower nitro doesn’t make the power and the bigger prop makes the engine work too hard. This makes more heat! People run higher nitro to keep the RPM where it makes the engine happy on the larger prop. On the CDI we can load it down further and get the lower RPM the engine doesn’t complain as much as it did before. Also tuning is easier in one aspect with the CDI. This is why some of the prop choices that are being used. We are turning 19-11’s at 7200-7300 20-10’s and wide blade 18-11 and 12’s at really RPMS too low for a normal 170DZ. Below 7500rpm.

Back to the CDI: The Spark is timed off the rear disc valve of the engine. A small magnet is placed there and a pickup sensor reads as this magnet passes a certain point in the rotation. The timing of the engine is set by the actual rotational position of the crankshaft. It doesn’t pre-ignite as the spark controls the fire and timing is always right.

What does this do for us? First off it means you lean the engine way down. The engine is making more efficient use of the fuel. We were running 20oz tanks. I can get about 12-13mins on Glow plug with that tank full of 30%. CDI allows me to use the same tank and get about 16-17mins out of it. This is NOT the double flight time that some are speculating or claiming but it is significant. I can fly a complete P-09 and F-09 and about 2-3 maneuvers before landing. What I have done is gone down to 12-14oz tanks and can still get through the F3A P-09 or F-09 and work on some other figures…about 10 min flight times on 12oz of fuel. This all depends on how much throttle you are using.

How do we get this longer flight time…First of all the ignition system is more efficient which means its not over rich in the midrange just to keep the top end happy. You can lean the midrange out and keep the detonation problem away because of the spark. This also makes more power in the midrange…more raw grunt here in the middle.

The low oil content will also affect the engines mixture. If you are running say 23% oil and switch to a fuel that has 10% or even 5% oil the mixture will change. Can the parts of the engines take that low oil content? Well yes and no. Standard parts like we have had on the 140-160 and first 170DZ’s CANNOT. However when you put a special crank, and some new lifters on the cam, and maybe a few other parts here and there it can run on lower oil content.

Big Benefit is NO smoke trail.

On Oil content there is lots of testing to be done. Some guys are using anywhere from 5% oil to 12.5% oil content if the engine is capable of the low oil mix. We need to give a big thanks to Cool Power fuels for making up some different fuels for the guys to test out. This testing needs to be more extensive. YS doesn’t want to hand an engine to a customer and say go run 5% or 7% oil in it. Then at 150 flights the engine shoots craps. The idea behind the CDI is to make it more reliable, easier to use and give some other benefits too.

For the record I have run 5% oil in my two engines since June and no issues at all. Some folks have had issues with this lower oil content and are playing with 10%. Usually the problem is not engine longevity but tuning issues. The Needle valve while becoming very easy to set with CDI, becomes hard to set when you start to run really low oil contents like the 5%. Who knows where this is going to end up, perhaps new needle valves or pump assemblies. This is the reason for the testing. Everybody is thinking its out in 2 months….That is not what is happening right now. Perhaps a small run of engines to get more and more guys testing them, but I think full production is still a logically down the road thing. This is something new and we the guys flying it are learning how to handle it. It’s different at this point. Is it better? Yes….when it has a problem is it worse? Well perhaps. The people that are running the engines now are learning them and in some cases what you thought you knew is now changed.

So to conclude The CDI gives some big advantages:

·         Super Low idle 1400rpm Great with big props for slow downlines. 19-11 APC Ignition prop.

·         Lower sound profile (deeper sound) but meets the sound rules because it turns the 19-11 at 7200-7300rpm

·         On low oil content no smoke or 10% oil very little smoke

·         Fuel economy

·         Better Grunt in the mid-range

Disadvantages right now:

Weight, the CDI adds about 4.5 oz to the model. The CDI also tends to make model Nose heavy. If you run separate battery for the CDI it can add up to 7-8oz to the weight of the model and this weight is all ahead of the CG.

We are testing the CDI system running off the RX pack. I flew my model this way at the NATS. Euphoria Bipe with CDI on a 1320mah 2 Cell lipo and you can get 4-5 patterns out of it before charging. Yes we are pulling about 250-300ma per flight. This is because not only are the servos working but the Spark is also coming from this battery too. Various ways to run this system off the same battery pack. Right now it seems 2.4ghz technology allows you to do this no problems. I have heard of issues with 72mhz and the CDI system running off the RX power. For me DSM2 fro JR and Spektrum has been bullet proof and I am running the Ignition directly out of a port on the RX. I caution against this….It’s not tested yet. But so far I know several of us are doing it.

I hope this dispels some the myths and misinformation regarding this engine. I have run all the various versions and have learned the little things about it. So to me its easy to a new person grabbing it the 170DZ CDI might be a big learning curve. It works great and I am very pleased with its performance. I’m with Bill Cunningham I think it’s the only way to go. Have there been some speed bumps? YES, will there be some more? Probably

Troy Newman, Team YS

Pattern guys,

This forum is setup to ask questions so if at any point you have a comment or a question please let me know.

I know this was promised to a couple guys. Sorry for the delay. As the Commercial says Life comes at you Fast.

My buddy Robert and I installed a DEPS system in a  Focus 2 model. I have received tons of email on the subject with guys questioning can it be done and they want some photos. As with everything the DEPS system I use today on all my models has evolved. I install it a little different than when I originally wrote the articles about it several years ago. Today I no longer build a latter system outside the model and try to install it. I keep the two balsa sticks separate and get everything fit into the model. Once you have everything in straight you can install small cross members to support the pushrod stick. This is done use a little of the ship in the bottle technique. This is the same method I use to install the DEPS system in any model even the expensive OXAI planes like my Euphoria are running this elevator pushrod system. Below are some photos of the install.

One note before we get going. I have been using the Teflon sleeve material from CST on all my DEPS installs lately. I have explained in other write ups about the differences between the Teflon sleeves and the nylong hard sleeve material supplied with the DEPS kit from Central Hobbies. For me I know how to not wrap the thread too tight on the sticks…so I use the Teflon version. It does require you to purchase extra sleeve material but it allows for a smaller exit in the fuse side. I also think it provides a little better friction free movement. However the stock sleeves with the DEPS system do work and I have used them many times before. I prefer the Teflon sleeve material now.

Important Note this is Roberts’ model and he did most of the work.

You have to mount your elevator servo. We chose a location to allow for the elevator servo on its side and easy access to the center servo arm screw. The servo was oriented so that a Phillips screw driver could remove the servo arm screw from the Aileron servo lead hole in the fuse.

Next the location of the servo connection for the elevator pushrodsystem is marked on the fuse side.  With elevator control horns and stab installed you can then pull a string to get the side view or elevation view of the pushrod location. Since everything must be straight line from the servo to the elevator horns a string can be pulled between the two points and align the side view or elevation line. I use some tape and a Sharpie to make the approximate exit location. At least this gives us the elevation line. You have to sight down the control horns and think in 2D at this step. We will get to the 3D part and find the exact point where the pushrods will exit the fuse side in the next step.

Just make the string froma  side view pass through the end of the elevator control horn and use masking tape to secure in place at the rear of the model.

We know the exit point from experience is going to be close to the Front of the LE of the stab. Probably about 4-5″ in front of it from a experienced guess. We just don’t know the exact location yet. So I mark a extra long area with masking tape. To keep my thread line I mark this area with a sharpie marker. Now I have the thread line or elevation line marked on the fuse side.

The Next step is to get the “V” distance or the spread of the pushrods at the rear of the fuse. This is done with the Fuse upside down and we are going to pull another string line. This time from the fuse center up at the servo to the Elevator control horn. The actual location up front in the center of the fuse is about 5inches or so behind the actual servo. This is where the pushrod balsa sticks are going to come together to form the apex of the “V”

I place a small tube over the top of the elevator control horn…and tie the string off to it. This case its a Fiberglass Dave Brown Pushrod. I have a few of them now that I don’t use this system for Elevator control. Now pull the string to the servo center location and use Masking tape to hold it in place.

Using a piece of Card Stock…in this case a JR servo card, I align the edge of the card stock with the very point the string “exits” the fuse side. I tape the card stock in place and transfer this line to the side of the fuse and make it intersect with our elevation line. Sharpie markers work great as Denatured Alcohol will remove them from most painted surfaces and Ultracote.

This is now the center of our exit slot. And we have the elevation line will show the angle the pushrod will exit from the fuse. Its important at this stage to realize the pushrod will exit the fuse at a very very shallow angle. This means the slot in the fuse side will be fairly long. Oversizing this slot is not a problem but you don’t want to get carried away. Normally this slot depending on the thickness of the fuse sides can be about 3 inches.

Now the tedious part. Cut the slot and trial fit the pushrod sticks in place. You have a line to mark the cut and a center of the exit is the vertical mark. I use a dremel tool to start, then fine tune the slot with a 1/8″ round file.

Test fit each pushrod on its balsa stick to make sure the pushrods path is through the 2 points in space. Servo arm connection and elevator horn connection. This is the important part and will take some trial and error. If the pushrod binds or bends as it exits open the slot further in the right direction to get a straight shot. Use the small 1/8″ diameter round file to open the fuse sides.

A trick to this fitting and installation is to slide the solid CF rods in the slots from the rear of the model. Then inside the model slide the balsa sticks and sleeves over the top of the CF rods. Carefully you can inch the balsa sticks and sleeves over the top of the CF rods and push them back though the exit slot in the fuse side. This can get a little tedious install it try, pull it out file a little more material away, then try it again.

Another Note: my balsa sticks have a sanded tapered end where they will meet inside the fuse. This keeps the the pushrods from binding as they enter the teflon sleeves. The photo below shows the sticks before installation.

Once you have the pushrodina straight line from the center meeting point to the elevator control horns. You can now do the same measurements and transfer the slot location and length to the other side of the Fuselage. You will notice the further aft you push the balsa sticks the more binding that can occur as the pushrod tries to bow out at the rear. So lengthen you slot, until the pushrod guide tubing passes through the fuse side as if the fuse side was not even there. This means the slot will look excessively long. However once the pushrod is installed in it it will look normal as the pushrod and sleeve will fill the gap for the most part.

At the same time as the pushrodsare fitted for both sides I locate a balsa cross member. In this case I just used 1/4″ x 1/4″ balsa Up front to hold the pushrods at the right elevation to hit the servo arm correctly.

The 1/4″ square balsa cross member is attached with medium CA for now. If you misalign it you can always pop it out  and reinstall. In the photos below the Pushrod sticks are not glue in place. They are just sitting on the cross member.

 Once everything is installed properly and you have a straight line for each pushrod, it is time to glue the balsa sticks/pushrod assemblies into the model. Don’t worry about any other supports at this time. You have the front support above and the slot at the rear of the fuse. For now this is enough support. Once the balsa sticks are glued in place we can add a center support to hold the “V” from bowing in the middle.

Use a slow set epoxy and some microballoons to make it thick like toothpaste. Place some epoxy on the end of each aft end of the push balsa sticks. And slide the sticks one at a time in place. A slow setting epoxy is great as it gives plenty of working time. I use BVM Aero Poxy for this task. Tony Frakowiack turned me onto this stuff about 5 years ago and its awesome stuff. Working time is about 40mins or so.

Also use some epoxy to attach the sticks to the front 1/4″ sq cross member support. Let the whole thing cure over night. I get a little brave and can do all the next steps at one time….I glue it all up and get it aligned, make my supports and everything so that I only wait one night for the epoxy to cure and the pushrods are all glued in. Experience is the key with this…I don’t recommend it to somebody trying it the first few time. Let the balsa stick get glued in place. Once cured they will be easier to work with for addition cross member supports and hooking up the CF pushrods to the servo and the elevator control horns. If you try to do it all at one time you might get a little over loaded and screw it up. So take your time and let the epoxy cure. Its not like the contest is tomorrow morning.

Coming back to the install the next day and install at least one mid-span cross member.  I glue this cross member to a small balsa stick or another section of pushrod material…You can use anything.  Tack glue the cross member to it with some medium CA. I use the Purple Bob Smith CA. I like the Bob Smith stuff the best. Its always available from the LHS, and I like the tips better than other brands.  They are pointed and allow for a fine accurate distribution right where you want it. Some of the other brands have a wide tip or a shorter tip and these make it more difficult to get in a tight spot. Again you can use your choice of CA. My local Hobby Shop always has the fresh Bob Smith CA. I hate the old CA. It doesn’t kick off right and is tough to work with. So I buy smaller bottles and keep it fresh. Costs a little more in the end but lack of frustration also is worth a  price to me.

The idea is a handle to to guide the cross member back to the right location. Glue the cross member in place with some epoxy and once cured, the “handle” gets a little twist and it breaks away leaving the cross member glued in place properly. Use an epoxy brush on a stick to reach back into the fuse and get some glue where its needed.

 Now your DEPS is installed. You just need to attach it to the servo and to the elevator control horns. At the servo connection I just use some thread and thin CA to attach the solid rods to a center pushrod tube. This will geta  titanium fitting and attach to the servo. Its inportant to do the servo connevtion first. Once its all attached and working properly tackle the elevator control horn ends.

 I now use Central Hobbies 1/8″ pushrod tubes with 2mm titanium ends for the elevator side connection. The Small solid pushrods will slide perfectly inside the 1/8″ pushrod tubes. Also these tubes are more rigid and can span larger distances without a problem. JB Weld works great and I attach the 2mm pushrod ends to the 1/8″ CF tubes at the same time I glue the 1/8″ tubes over the top of the solid CF rods.

Below are some more photos of the install. 2mm Titanium ends are used with 1/2 the threads cut off. This also makes the system more rigid as there is less threaded area to possible work harden and fail. Shorter exposed threads makes it stronger. I use the 2mm becasue this is the smallest or Finest adjustment. This is important in setting up your mechanical system. A 4-40 thread you will find very course and 1/2 turn is too much…when making small fine tuning adjustments mechanically.

 NOTE: Be sure to have at least 2″ of solid pushrod that fits inside the 1/8″ tubes.

 Here is an older photo I have of the 1/8″ pushrods from Central Hobbies installed over the top of the solid CF DEPS pushrods. This was from a model a few years ago. I now install these longer and leave only about 2″ of the DEPS solid rods exposed from the exit of the Teflon sleeve and I will trim the excess Teflon sleeve back to about 1-2″ from the exit of the fuse. This means the maximum exposed distance of the Solid 0.070″ CF solid rods is about 4-5″

Some people complained that the too long of exposed distance was a problem. I suspect they were over engineering things a bit. I have run the models with 12-15″ of exposed 0.070″ pushrod and you can’t feel any issues with it. However as an Engineer I feel using the 1/8″ tubes on the exposed section makes a stronger and more rigid connection. That is why I do it now.

SO there it is…..Feel free to ask questions.

Troy Newman