pattratt

My Feedback: (1)

Hi Jim
Yes right up to the point the regulator screw was bottomed out and the engine leaned out in a vertical and kicked off the prop & Spinner!
Dick

pattratt

My Feedback: (1)

Hey Mike
What you are describing as far as the limitted flight time is one of the major draw backs I see to electric. I tried to fly this evening but continue to have issues trying to keep th engine rich enough to not go lean on the long vertical up lines. Did not work and kicked off another spinner and broke the cheek cowl again! I am pretty sure this pump is a gonner! I borrowed a fan to use between flights but did not get a chance to use it!! I know one thing, it's got to get better!!
Dick

MAVROS

Hi all,
I am not an expert on YS engines but just wondering how much oil content are you using in these troublesome 170 cdi ?
It seems to me that the high temperature you are experiencing may be the result of insuficient oil leading to an overheating and cavitation of the fuel inside the pump .
May be that is why the pumps dont last.....

regards

MAVROS
AUSTRALIA

Wasson

That's 2 votes now for cavitation. Thank you Australia!

I think that Adrian also makes an excellent point about the pump on the original prototype YS140DZ having to be re-located. I think that he is also correct in assuming that this may have been done to lessen the problems associated with overheating.

It makes me even more convinced that one of the root cause of the problem may be cavitation. And that the solution may lie in fitting cooling fins of some kind to the regulator/poppet valve assembly.

If Yamada have not already done so, I would implore them to give this a try. It shouldn't cost too much money to modify 1 or 2 engines on a trial basis, and it shouldn't take too long to find out if it works either.

It is also worth noting that the damage caused to the worn valve seats that I have inspected has a pockmarked appearance. This is highly typical of cavitation damage.

Regards

Bob Wasson

riot3d

I don't think you have to specifically put fins onto the pump area just to cool them. I believe anyone who flies a glow plane with either a chin cowl or a bvellypan already will have an opening right at front where the pump is located, no one will be flying a plane with a totally enclosed frontal area. As much as cooling the pump is important, it is also essential to ensure the rest of the engine runs cool as well - the valve cover area, the cylinder - that's why they have cooling fins along the side of the engine.

In addition, it's real important to install foam to redirect cool air onto those specific area. Otherwise, even though, the pump may get direct cold air, the rest of the engine will still be hot. Thus, will still contribute to "vapor lock".

I know it's very frustrating to have engines that is not operating correctly. It may be a hassle to either put a cooling fan, or, even take the bellypan off on a hot day. However, if those steps actually work and you still enjoy operating a YS, then I believe those are just minor sacrifices. Otherwise, if you think going electric will give you a more peace of mind, then that's not a bad idea as well. After all, this is suppose to be a hobby that brings us enjoyment, not headache.

Adrian

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:

# Propeller load is a significant factor in the equation and why YS are advising that the RPM should be kept above 7,300. More load means more heat generated, which in turn means higher pump operating temperature and a higher chance of cavitation.
# Relocating the pump position of the original YS140 Dingo was enough to solve the problem (at least initially).

No matter how effectively cooling air is directed over the engine, cooling fins on the regulator body could only help with keeping the temperature down and thereby reducing the chances of cavitation. They would also help the heat to dissipate more quickly from the regulator/poppet valve assembly on completion of a flight.

The photographs in the attached link show just how destructive the effects of even a small amounts of cavitation can be - http://www.google.co.uk/images?hl=en...=&oq=&gs_rfai=

In the process industries, even when exotic steels are employed in a pump or valve body, the erosion that is caused by cavitation can eat the metal away in no time. When that metal is an alloy (as in the case of the YS poppet valve seats), it might as well be cheese. Even a very small amount of cavitition could give rise to the pockmarked valve seats that many YS170 users have experienced after relatively few flights.

Anything that can be done to reduce the pump operating temperature could only be worthwhile. Larger cooling fins on the main crankcase would also help in reducing heat transference but at the expense of much more weight, not to mention the higher development costs associated with a new crankcase mould.

Regards

Bob

PS:
Even without the heat transferred from the main engine casing, the pump would still run hot due to the energy used for pumping. That is why YS have fitted separate fins to the pump cylinder. Additional fins on the regulator body would help to dissipate the heat from that part of the pump (i.e. the regulator/poppet valve ssembly) where cavitation seems to be doing most damage.

MAVROS

Hi again from downunder..

Mate I would try increasing the oil content first.

regards

MAVROS AUSTRALIA

M.Kimbro

My Feedback: (5)

Maybe there is a pin HOLE in the fuel line somewhere between the tank and the engine.  Or perhaps inside the tank, depending on how long you are able to fly. 
If possible post some pictures of your installation.  So we can see what you are up against, the problem could be looking right at you and you just don't see it.  A second pair of eyes might do the trick.  

Matt

Wasson

G'day Mavros,

"Mate I would try increasing the oil content first"

Here in the UK, most of the YS 170's that have suffered damage to the pump valve seats have been running 22% oil.

How high would you suggest we increase it ?

Bob

pattratt

My Feedback: (1)

Hi All

I receive my original engine back from Richard with a new pump, front seal, and correct rear plate gasket.

I made 8 flights this afternoon and the engine ran perfectly. All the fuel settings were back where they should be. I am doing some testing for Richard on the pump and dropped back to the 19x11 prop and I agreed to use a fan between flights. I flew with as little as 10 minutes between flights and had absolutely no starting issues. I don"t think today was a good test as relates to heat as we had rain early and the temps were in the mid to high 80's. THE REAL TEST WILL BE AFTER 40 TO 50 FLIGHTS IN 100 DEGREE HEAT!!

I have also learned that YS is making some design changes to the pump diaphram and to what I call the pump body plunger. I am not sure if these changes are going to allow what I call "normal operation" or not, meaning being able to run in the heat back to back flights without having a cooling fan between flights? I would preferr to run the 19.5x11.5 prop, but for now Richard wants me to keep engine rpm's above 7300. I do not have the ground clearence on the Valiant to run a 20x10. I am still using the 30% LS fuel for this test. Hopefully this winter I will have over a 100 flights and can try to run the 19.5x11.5 and lean the engine out to make the 7300 rpm. I may be dreaming here. LOL

I will post more results as they become available.

Thanks to all who have provided input to this thread.

Dick

Wasson

Dick,

That’s good to hear. I hope your rebuilt engine gives you many trouble free hours of flying.

It is also encouraging to learn that YS are considering some design changes. I wish them well too.

In the meantime, I have fitted one of my engines with some additional cooling for the pump valve body. It takes the form of some brass strip, filed and bent to act as a heat conductor. I have bent the strip in a way that should also help to channel more cooling air over the pump assembly. It is very Heath Robinson and because of the imperfect contact between the brass strip and the pump body I would not expect it to do nearly as good a job as some proper fins machined into the poppet valve housing. Nevertheless, it should help to keep the operating temperature of the pump assembly a few degrees lower. Only time will tell if it slows down the erosion of the valve seats.

In examining the pump assembly more closely, I also noticed that there is at least 2 mms gap between the rear of the fins on the pump cylinder and the front of the main fins on the engine crankcase. This would allow YS to increase the diameter of the fins on the pump cylinder from around 15 mms to around 17 mms if they chose to do so. I believe this would also help with reducing the pump operating temperature and the speed at which the pump assembly would cool down between flights.

It will be interesting to see what final form the official YS modifications take.

Regards

Bob

arnstein

The YS 1.70 engine are marvelous engines and a result of excellent engineering, and in pattern one of the few options besides electric. Let us hope that there also in the future will be alternatives to electric, and YS remains one of them, competition benefits everybody. As for any products there are always room for improvements, this is shown by the continous improvements done by YS.

I think it is important to get a grip on why some of us experiences some issues operation the YS 1.70, it could be that this is entirely due to improper tuning of our engines. This was said in a recent conference I attended:

If a customer buys a product and does not have any problems with the product there is a 50% chance he buys it again. On the other have is a customer buys a product gets problems, but the problem is being taken care of, there is a 80% chance he buys the same product again.

As Bob pointed out cavitation most likely occure within the pump, whether this lead to erosion of the valve seats on a properly tuned engine, I do not know. Cavitation occurs if the liquid pressure falls below the vapor pressure (I think methanol is the most critical ingredience in the fuel wrt vapor, vapor pressure data for methanol obtained from Wikipedia):

Methanol
P in mm Hg	1	10	40	100	400	760	1520	3800	7600
T in °C	-44,0	-16,2	5,0	21,2	49,9	64,7	84,0	123,5	138,0
T in °F	-47,2	2,8	41,0	70,2	121,8	148,5	183,2	254,3	280,4

The normal pressure (sea level) is about 760 mm Hg, from the table we see that the vapor pressure is 65C/150F. So vapor will form inside the fuel system, causing vapor lock at this temperature. For methanol the vapor pressure is highly non-linear with temperature as the graph attached shows.

In my opinion this explain why fans are used in Japan and elsewhere to keep the pump temperature below at least 65C for a successful restart also low fuel temperature is beneficial. On a warm day in Norway (25C/77F) I manage to start the engine again within only a few minutes, however, it runs rough for a few seconds until the fuel cools the pump and all vapor dissapears. Was not able to find any data on vapor pressure for fuel, might be different?

As already referred to by Bob I modified the pump with steel valve seats and furthermore I changed to the "low oil" configuration (crank, cam followers and sub needle). This season the engine has run perfectly and very consistent so far (knock wood). My experience is that these engines runs even if they are tuned outside of the "sweet spot", without experiencing any dead stick. The difficulty in tuning these engines, in my opinion, is the strong interaction between the pump pressure and the HS needle. What is really important is to have a clean transition thru the mid-range. Can this be the reason why some of us, myself included, run in problems and the experts do not?

Just a thought: What about making a video on how to tune these engine similar to what Bert and Bobby has done in their SmackTalkRC Episode #1 ?

Regards,

Arnstein

pattratt

My Feedback: (1)

Bob & Arnstein

Great information! I hope YS will be monitoring this thread as there is a wealth of information coming out of it. I know Richard Verano does.

Thanks again.

Dick

amram

Dear All
I find the last posts of Bob & Arnstein very interesting and helpfull.
I am in touch directly with Yamada san and as Dick has informed, YS have modified the pump. It is targeted to be released with the 175DZ.
I was informed by Yamada san that modifications are as follows:

- We modify the diaphragm. It has a better response to regulate the mixture.
- We modify the seal of pump too. The seal material is changed to copper.

I have one 175 modified pump on the way for testing. I hope to get it next week and I will inform the results.
Weather in Israel is extremely hot so we shell seeing the difference right away...

Thank you to all who made this tread so valuable for YS users.

Regards
Amram
F3A Israel

apereira

Good to hear all engines are working out, in the mean time, I found the instructions on Richard's page to be be different to those that came with my CDI engine, it looks to be a revision, in the instructions it says the engine maximum RPM's should not be lees than 7000, so 19.5 prop should not be used or a prop with similar RPM's, it also talks about the high temp in the pump, if you have it then ignore it, but it's better to check it out.

http://www.ysengines.net/manuals-dow...170cdi-YSP.pdf

About the cavitation, I really don't think (not saying is not) is a cavitation problem as the pump pressure is not high enough and there's many soft parts that can absorb the fluid hammering (sorry, on this one I don't know the English term for this effect in hydraulics), it could be the fuel breaking down as the Nitromethane and oil are kept mixed together by the methanol, so if the methanol breaks down the nitro and oil will separate creating the air in the pump without this been cavitation.

Best regards to all

pattratt

My Feedback: (1)

Amram and others who have experienced the same heat related pump problems with the CDI version.

What type of fuel are you using?

I am using Cool Power 30% Heli LS

Thanks
Dick

amram

I am using Cool Power 30% Heli 22% Oil

Wasson

Aperiera,

In your last post you say “I really don't think (not saying is not) is a cavitation problem as the pump pressure is not high enough”

Cavitation is less likely to occur at higher pressures because liquids are prevented from boiling as pressure rises. That is why water will boil at a lower temperature as you climb a mountain, and at a higher temperature as you come back down again. Higher pressures and lower temperatures both help to reduce boiling and thus cavitation.

Cavitation is most likely to occur when pressure is reduced (as it is across the seat of a valve) or when the temperature is increased (which is why it is so important to reduce pump temperature).

As Arnstein has already mentioned in his last post, methanol (the major constituent or fuel) boils at 64.7 degrees C at normal atmospheric pressure. Nitromethane, the next most significant constituent boils at between 100 and 103 degrees C depending on its purity. The remaining oil in the fuel will have a higher boiling point still. Without doing tests, it is difficult to know at what temperature the fuel mixture is likely to start boiling. It would certainly be above 64.7 degrees C as Arstein has indicated, but it is still likely to be less than the levels of pump temperature that are likely to be achieved when the ambient temperature is high. That is why it is so important to do everything possible to reduce pump temperature, especially in that part of the pump where pressure is being dropped across the poppet valves.

I accept that there will be a small amount of hydraulic damping due to the regulator diaphragm, but it is likely to have little or no effect in respect to cavitation.

In summary, I believe that the reliability of the pump could be vastly improved by:

# Adding cooling fins to the poppet valve enclosure
# Increasing the diameter of the existing cooling fins on the pump cylinder
# Changing the material of the poppet valve seats from alloy to brass or steel (As Arnstein has already done)
# If necessary, changing the diaphragm material to cope with higher temperatures.

The first 2 of these modifications steps would also help the pump to cool down more quickly in between flights. And the good news is that none of the modification should add too much cost to the price of a new engine.

Regards

Bob

Torben Parsberg

hey
a great trĂĄd.ther are made here.
I also have trouble with 2 org.170 cdi low oil
the one I have in my Euphoria, has run 30l fuel 12.5 30% mixture
the problem is after 10 15 seconds at full throttle, lean itself out and go hard
and if I give it a couple of clicks on h needle, then turn it some CDI "farts" ;-)

I bought this little 5g delicious case from Robbe, the meter, Max and Min temp.
and stores them,
on my two flights today have been the max of 85 87 degrees
here som pic

Wasson

Hello All,

I have had a very helpful E Mail from Naohisa Yamada. I’m sure that Richard Verano will also have been active behind the scenes.

Yamada san is very well aware of the high temperature issues with the current pump design. He has carried out tests that have indicated that the temperature peaks after 8 minutes (he didn’t say whether this was 8 minutes after starting or 8 minutes after landing). He also acknowledges that when the temperature peaks, the engine can become difficult to start.

Yamada san has replaced the bottom plastic pump cap with an alloy pump cap and has found that this lowers the operating temperature of the pump and also speeds up the rate at which the pump cools down after flight. He has also experimented with fitting stainless steel valve inserts into the pump body to help prevent premature wear of the valve seats.

As Amram has already mentioned, YS are also intending to fit a re-designed regulator diaphragm to the next generation of pump in order to make the setting easier to adjust.

Yamada san has not yet tried increasing the diameter of the existing cooling fins on the valve body or fitting new cooling fins on the pump body housing, but he acknowledges that these modifications might be also be worthwhile. His E Mail also includes the statement “The carb temperature must be down too” though I am not sure whether this points to the need for better insulation (slightly thicker paxolin?) between the crankcase and the carburettor body.

Yamada san was about to leave for the European F3A Championships in Austria when he wrote, but he said that he would start doing some further work on the re-designed pump as soon as he returned to Japan.

It is YS’s intention that the new pump should be available on the forthcoming YS175.

I thanked Yamada san for his very full and very helpful reply and suggested that it would be good if the redesigned pump was also available as a separate item for retrofitting to existing YS 170 glows and YS 170 CDi’s. I also said it would be helpful if the new YS175 CDi was available as a glow version as well as a CDi !

In summary, I think that Yamada san is well up to speed with our concerns and is adopting the usual meticulous YS approach to improving and refining his product.

Hope this helps

Regards

Bob

pattratt

My Feedback: (1)

Bob

Thanks for update.

I was aware of most of this info but but did not share everything here on RCU as this is going to make it pretty hard for YS, Richard Verano, and other world wide distributators to sell their remaining stock without the availability of the new pump and knowledge of the introduction of a new and more powerfull YS DZ 175 CDI. This is a tuff situtation for both the consumer [who is having problems related to design] and the manufacture [who is trying to fix the problem without damaging his current product line].

All

Update on my returned engine from Richard.

I had 13 very perfect runs over the weekend when late Saturday I began having the same surging problems and by the end of the day could not get the engine to run at full throttle and the more I tried to adjust it out the worse it got. All of these runs were with 19x11, 30% LS, high volume fan between flights, 95 to 100 degree days, and no adjustment to the engine mixture prior to it running bad again. the exact same symptons as before, only this time it was at the 14 & 15 flight count!

Sunday morning I asked Ron Barr to bring to the field several other types of fuel including some 20% & reg 30%. No joy, same problem. I had received in Saturdays mail the new pump from Richard and was ready to pull the engine and put the new pump on when I decided to try one more thing even though I was convinced it was not going to be the problem. I had installed two new spark plugs in trying to trouble shoot the engine prior to sending it to Richard so I new the plug was new. Well, by now you guessed it! I changed the plug and the engine ran perfectly for five more flights Sunday.

So I am back on track with testing to see how many flights I can get with cooling between flights, running the 30% LS, & 19x11 prop. By the way, after running the 19.5x11.5 I am not happy with the running the 19x11 but will for the test. As soon as I get to 100 flights with no problems, I am going to switch to the 19.5x11.5 as I need to do this while we we still have at or near 100 degree days. Not sure if or when this will occur.

Does anyone have an alternate source number for the YS spark plug? Central charges $24 for a single plug plus shipping and handling. That's over $30 bucks a pop that in the open market should cost no more than $5 to $10 depending on quanity!!

Dick

apereira

Very good news for sure, even though I do not suffer from the problem, any upgrade or improvement will always be welcome, it's like software, we usually can't stop installing upgrades.

I think is of most importance to note as you did, the fact YS is working continuously on their products, it takes time, but they want to be sure it works, Onda had the 175CDI at the worlds but did not fly his byplane, so we could not see it running.

As your commented before in relation to my post, please note that cavitation occurs in centrifugal compressor like those you referenced when the inlet fluid flow is slower than the exit and the differencial pressure, where cavitation or surging can occur, in this case the fuel flow is very low inside the pump, so the fluid speed is not enough to create cavitation.

One thing to consider is the amount of tiny air bubbles coming from the foam clunk, those are the bubbles wearing the seats, and that's the reason for the check valve/vent on top of the injector, to extract this bubbles before goes into the injector.

Very good and constructive thread this is.

Best regards

Wasson

Dick,

You make an excellent point about the selling of existing stock. I was in 2 minds about whether to share the information for that very same reason. However Yamada san did not say that the information was confidential and the news about the YS175 is freely available on the main YS Japan Web Site. http://www.yspower.co.jp/en/engine/index.html

I was also conscious that a large number of YS 170 users (not all) were having pump problems, and that if the problem continued, it was likely to hasten the speed at which existing YS users thought about converting to electric. (You said as much yourself in one of your earlier posts). Once users had made that initial investment and converted, there would be a good chance that they would stick with electric, whether YS brought out a YS175 or not!

On balance I considered that it would not be doing either YS or their distributors any favours if even more YS customers were to become frustrated due to acknowledged problems with the existing pump design. I though it would be better for all concerned if the full picture was shared with users, rather than causing any further damage to Yamada’s reputation.

Yamada have traditionally adopted a meticulous approach to product development and I was careful to emphasise that point in my post. Good reputations can take a very long time to establish and a very short time to destroy. If history has taught us anything, it is that manufacturers who are open and honest with their customers (as Yamada san has been on this occasion) stand to benefit in the long run. I hope that the same happens here and that Yamada will go on from strength to strength.

I also hope that they will make any modified parts available for retrofitting to existing YS 170 and YS 170 CDi’s. Because of the difficulty in getting the design of a highly specialised small volume product right first time, I would not expect a small company like Yamada to provide a conversion kit free of charge. I can’t speak for other customers (perhaps they would make their own views known), but I would be more than happy to pay for the new parts if I knew that they would make my engine more reliable. Unexpected engine cuts on a $2,000 F3A model are something best avoided.

Aperiera,

Cavitation is not restricted to centrifugal compressors (or pumps). Cavitation and surging are also two different phenomena.

Cavitation can also happen when the pressure is dropped across a valve seat. I accept that it is more likely to happen when bigger changes in fluid velocitity are involved, but it would only take a very small amount of cavitation to cause the type of damage that users have experienced on YS’s existing YS alloy pump seats.

Regards

Bob

PS:
I thought that the main reason for the foam clunk was to remove air bubbles from the fuel line. I do however accept that it is not unusual for tiny bubbles to be present in the fuel feed line to the engine. These would add to the number of small vapour bubbles caused by cavitation. I also understood that the main reason for the black check valve fitted to the fuel injector was to stop fuel running back towards the carburettor. On the early YS 140 Dingos, this sometimes caused a short lean run when the engine was throttled up after a long downline.

DagTheElder

Hi,

Plugs for YS DZ 170 CDI


http://www.ngk.com/more_info.asp?AAIA=&pid=2722

Regards

pattratt

My Feedback: (1)

Dag

Thanks for info.

That at least gives me some spec. to work with here in the US. There price would be worse after shipping!
Dick