bjr_93tz

OMG [X(]

So......many.......words.....to...........read.... .......

Must....find........busier...... job......

Landed the last flight of the day yesterday afternoon with the fuel line empty to the fill point. I swear that if the engine didn't cut with the throttle it would have only run another 5-10 seconds. Never run it that close before, and is a testiment to the pickup capability of the YS foam clunk.

apereira

Hello Brett,

Yes, I do understand the principle and that's why I mentioned the pressure differential , all I'm saying is I really doubt it can be cavitation, not denying the pump damage, which I attribute to be a pump adjusted on the lean side on very hot days, a pump can be on the lean side but and the top end of the engine can be on the rich side.

The thing is, I don't think is right to say there's a design problem causing cavitation and damaging the pump, that's an affirmation, which is really hard to prove in this specific case, and the reason is there are many many people who don't have that problem even on similar operating conditions, that's all.

Bob,

I think you are right with what you summarized as the necessary improvements, but I do not belive in the cavitaion assetment and that's because I do understand the principle and the values of the variables are too small, some negligible, and I guess you might agree with me in that you will keep believing is cavitation and I will not, so maybe is better to leave the way it is, because we both think we are correct!



Yamada has always made improvements based on previous engine versions, so they pretty much are an evolution of the previous design, I mentioned before even the 160 pump and the 170 looks the same, they are completely different on the inside, and the change was done so the engine could operate in hotter environments, and nobody made a comment, so I wonder if people knew that, the 175 pump is an evolution of the 170, and so on with the next engine, Amram is retrofitting the 175 pump on the 170 and it will be very interesting to know what the engine performance will be(can't wait), and I know Amram will share the information soon.

When a design change is made, they have to evaluate the operators, not just the engine, and that's why are several 175's out to be tested in different conditions, but those who get this engines are really experienced on YS, and sometimes things like the problem in this thread will not happen to those people and the design will not be compensated for certain situations. The fact they take so long to get an engine out clearly demonstrates their commitment to the product, I don't think that anybody realizes the complexity of the market better than the Yamadas, they don't want to loose more ground to electric, but electric is way much simpler and pretty much foolproof, even though I so Jason S. have dead stick in a competition we had in Colombia during practice, I thought I will never see that but it can definitely happen.

Let's see what the new data will provide,

Regards to all

P.D. This is a great thread, we disagree in certain things and still remain respectful to everybody, I wish more people could do that. Hope to see you guys some day in the field like in the USA 2011 worlds, we will need beer for that!!

Wasson

Hello Apereira,

Your sentiments are spot on.

I enjoyed the discussion and I too hope that we might share a beer some time.

I also hope that Dick's thread will have been of interest to many YS users and that we might all come to benefit from it some day.

Best of luck to you, to YS and to all their other customers

Kind regards

Bob

protectedpilot

Good points, Mike. Me, I just LIKE a piston engine in the airplane. Feels like the difference between a machine and a toy, to me. Personal opinion only, keep the flames back, guys! I'll grant it takes a bit of experience to run glow; most of the guys here SHOULD have acquired the skill set by now. And I just put in my third set of bearings on my primary planes motor, this year. Of the other two motors, one needs a bearing set now, and the third is a new rebuild. Fourteen cases of fuel in 100deg+ weather. The motors do better on the Cool Power 30% Heli, it seems. Apprx 500 flights. 'Prolly woulda done better if I'd used the Cool Power from the first.

I'm an electronics tech by trade, but I'll bet you that I'm better at rebuilding YS engines than I am at rewinding motors, repairing lipo batteries or putting the smoke BACK in to speed controllers. Stuff like that, the only solution is to throw more money at it. Which is much, much simpler than learning what is wrong and addressing the problem, like Dick is doing, here. Kudos, Dick.

protectedpilot

[quote]ORIGINAL: Wasson

Adrian,

''I don't think you have to specifically put fins onto the pump area just to cool them''

I think we might have to disagree on that point.

I accept that good cooling and venting arrangements are essential. And I also accept that the pump faces directly forward into the airflow. However even a small increase in pump operating temperature may be sufficient to trigger cavitation. I think that may be why the problem of eroded valve seats is affecting some YS170’s (especially the CDi’s) when it was never really an issue with YS160’s. It would also explain why:


Reading the thread, and having watched a FEW CDI's go through their paces, am not sure CAVITATION is the issue. Cavitation happens when the liquid flashes to the vapor phase, and then collapses back to the liquid phase. Primarily a centrifigal pump phenomenon. These pumps are a type of positive displacement. Cavitation is, as reported, tremendously erosive. Nearly as erosive, and more likely the problem, is flashing without re-entrainment. Less fuel passes the nozzle in the vapor phase, hence the lean condition. Higher pump pressures would effectively raise the BP of the liquid, however, masking the problem. The evidence of cavitation is a near sand-blasting effect, whereas flashing looks like the metal has melted streaks cut in it.

Brian

pattratt

My Feedback: (1)

Thanks for the Kudos Protectedpilot

Quick update on my testing.

I am up to 30 flights on the returned engine from Richard. With the exception of the plug problem the flights have been near perfect as relates to engine performance. With few exceptions these flights are 15 minutes plus in duration, Cool Power 30% LS, APC 19x11, 98 to 100 degree days, and forced air cooling between flights! The big difference I have seen so far is that I barley hit the spinner with the starter and the engine fires and runs with authority and smoothness. I pretty much have to attribute this to the immediate forced air cooling between flights. The "Lasko" high volume fan I am using has the engine back to ambient in about 5 minutes. I am guessing now that the pump is never "dry," thus not experiencing wear, I will get to the 50 flight mark. At 50 flights I am going to call Richard and see if he will give me the OK to go to the APC 19.5x11.5 prop! I have the new plugs but I do not want to introduce a new variable until I finish this 100 flight test. If the current YS plug should fail I will install one of the new ones to start a life cycle comparission.

On a different subject I now have about 75 flights on my Valiant and I am really getting back into the saddle with P-11. I am planning on attending the Dallas event although it will be a one day event for me as I have not even gotten through F-11 once without having to "bail out" of at least one maneuver and most times two!!! Oh well, maybe next year.

Dick

cdodom

Pattratt

what difference do you actually notice between the 19.5 x 11.5 and the 19 x 11?

Thank you,
Chris

pattratt

My Feedback: (1)

Hi Chris

The aircraft maintains a slower and much more constant speed in all attitudes of flight with a lot less active throttle management from me. The other thing I notice is that even though the aircraft is slower, control surface authority feels stronger. As an example, in the figure M 1/2 roll the rudder has more authority at the bottom of the half loop! This difference is fairly substantial. The prop just allows me more time to evaluate and make proper corrections "during" the manuver. At my age I need all the time I can get!! LOL

Dick

papaone

Hi

CPLR Used APC 20x10,5 PN last french championship.
Claude

apereira

Hello Claude,

Did he used that prop on the 170CDI or 175CDI?

Regards

Dave Harmon

Mike Harrison gave me a APC 20x10.5PN several months ago to try out.
I liked it better than the APC 19x11.

So....I bought several of them for use on the 170CDI and it works great.
It lowers the workload on the throttle and the engine turns the same rpm (7300) on the ground as the 19x11 using CP 30% Heli fuel.
It's possible for me to overspeed the airplane using the smaller props if I lose concentration for a moment....the 20x10.5PN reduces this tendancy considerably....at least for me....meaning that if I get distracted from the throttle it takes longer for the airplane to start flying me.
The downlines are much slower especially if you take advantage of the lower idle speed available when using the CDI.
I set mine to 1500 rpm.

Yesterday, Brian Young flew it and he thought it was a bit slow in the up lines. I did not think so but I certainly respect his opinion.

papaone

Hi Apereira

He used APC 20x10,5 PN on 170 CDI.
He has the 175 CDI but he didn't use this engine.
Claude

riot3d

I have been using the 20x10.5 PN for two months now, it runs cooler than the 18.5x12 WPN.

Adrian

cdodom

Can you run the 20 x 10.5pn on a regular glow non CDI engine?

Dave Harmon

I don't see why not......just use 30% nitro fuel.
I know some guys use CP 20/20 Pro Pattern and it works fine for the smaller props but the flight performance is much better with the 20x10.5pn.
What I mean is that the pace of flight is much better, the throttle is easier to control, the uplines arn't quite as fast, the down lines are slower etc etc.
BUT......if you stay on full throttle on a flat line seems like the speed of the airplane is just as high as before......

cdodom

What does "PN" stand for? Is there any difference between the "WPN" props and "PN" props?

Sorry for all the questions.

thank you ,
Chris Odom

riot3d

Don't know exactly what the "PN" is stands for, the shape between the wpn & the pn is different. The wpn is wider in both the main blade & the tip, & the shape of the pn looks just like the normal APC.

I'm using the 20 on both cdi & regular 170. On 20% heli is about 7,000, on the 30% is about 7,100 to 7,200, more than enough for both the P & F.

Adrian

Dave Harmon

'PN' is pattern narrow.....'WPN' is wide pattern narrow.

EDIT:.....from the APC site....the 18.5x12WPN hub is .22 larger in diameter and .100 thicker than the 20x10.5pn.

grcourtney

My Feedback: (1)

Chris

The overriding factor is engine rpm. If you load the engine to much you will build heat. If you are running to small a prop the rpm will be to high rods like to break on the on the high end. What I suggest doing is running a known prop, 170 dz non cdi optimum prop is an 18x11 tach the engine this gives you a baseline rpm. Now swap props and balance the rpm deviation for what you are looking for in the air I.E. constant speed verticle up and down lines etc . I wouldn't deviate more than about 300-400 rpm. a 170 dz cdi is a 19x11. This is how I determined How to shape my props when I was running the 160's optimum for that motor was the 16.5x 12w it gave an rpm of about 8400 I then took the bolly 18x12 and reshaped the tips and shortened the props to get within that rpm range. The reason I used the bolly is it gave me great down line breaking and very good up line performance. It was what I was looking for at the time, I tried the 18x10 but it just didn't have the vertical pull I felt I needed but it did break well n the down lines. the 18x11 and 18x10w I just felt like the rpm was not there for me to get longevity out of the motor.The 16.5x12 just didn't break in the down lines worth a poo for me. I know the bolly props aren't as efficient as the apc's but they struck a balance of what i felt I needed.Now the Bollies are not readily available anymore so I have moved past them when deciding prop selection. If you keep this in mind when swapping props to find your comfort zone you will get the life we are looking for as well as that pull, speed and and breaking out of the DZ's. Right now I find the19x11 good for me on the cdi version of the engine.

That's my thought process on the prop selection on these motors many other methods work but that's how I do it. Hope to see tou in Huntsville in a couple weeks.

gary

pattratt

My Feedback: (1)

Hi All

Quick update on my testing.

I am up to 40 flights on the returned engine. I had another plug failure again giving symptons very similar to a pump-ware failure. Uphon inspection I found that I was running the engine way too "rich" causing the plug to foul due to carbon build up. I cleaned the plug and the engine ran great again. I am running the engine "rich" in an attempt to keep it cool which negates any advantage to running the LS [low smoke] fuel. At this point I can not change to the regular 30% Heli as I have over two cases of the LS left to use. I talked to Richard about going to the 19.5x 11.5 prop if I could get 7000 rpm or more leaning the engine out some. He told me he had sent the factory several of the 19.5x 11.5 props for evaluation several weeks ago and would call to get some follow up from them and get back to me.

Currently Bryan Hebert is running the 19.5x 11.5 on straight 30% Heli and turning a min. of 7200 rpm with good sucess and he is "not" using forced air cooling between flights. I will hit 50 flights with the current setup before the upcoming long weekend at which time I am going to go to the 19.5x11.5 prop and lean for a min. of 7200 rpm maintaining the other parameters. [LS fuel & forced air cooling between flights]

Hopefully I will have some good results to report uphon reaching the 75 flight mark in a couple of weeks. At that point I would have 25 flights over what I have done in the past!

Dick

bjr_93tz

Just a question on the subject of regulators.

Should there be oil in the tube from the crankcase to the regulator? I noticed mine was about half full of oil and when I pulled the diaphram cover off it was totally full of oil.

I assume that the reg diaphram needs to see fluctuating crankcase pressure for some reason, surely being full of oil doesn't help?

pattratt

My Feedback: (1)

If the fuel in the pump housing evaporates due to high heat all that will be left is oil. I'm not sure this is what has happened with your pump.

Dick

bjr_93tz

No pattratt, this is the clear tube running up from in front of the camgear housing. It's the spring side of the diaphram that is full of oil.

I was having a bit of trouble with a misfire in the midrange that I couldn't tune out, that I didn't have when running the engine upright in my test bed, so I flew the Aries around upside down for a few minutes and the misfire went away after a while. I later found the tube and reg full of oil. I've cleaned it out and will try it later?

Wasson

Brett,

If you can PM me your E Mail address, I will send you a copy of an article published in Microsoft Word format (.doc) that may be of some help in explaining the operation of the pressure reference line (The red line in Fig 2 of the Document).

Basically, the purpose of the line is to ensure that the regulated delivery pressure from the fuel pump rises as the crankcase pressure rises and vice versa.

It is fairly normal for the line to contain a mixture of vapour and liquid. However any small head of liquid is likely to have a negligible effect on the reference pressure that is transmitted to the spring side of the diaphragm.

Hope this helps

Regards

Bob

PS:
Would have attached a copy of the document to this post but it would appear that RCU does not support Mircosoft Word attachments. I think that a copy of the article, "A Guide to the Operation of YS Fuel Control Systems" may still be available under "Articles" on the Home Page of the GBRCAA Web Site http://www.gbrcaa.org/

topiwala

Thankfully I've caught onto this thread, however, seems everyone posting has had issues after some hours of running. My new 170dz CDI hasn't even successfully started. The pump is definitely not pumping. With throttle full open, and fuel manually forced up to the regulator, cranking the engine doesn't produce any transition of fuel to the check valve injector. I have only ever successfully got the thing to fire up when I've actually manually forced fuel up to the injector. But the engine will stop as soon as that fuel is drawn. Well I've done all I can with it. It will be on its way to MR YAMADA for a look.