|
Jim, Just thought of one other item.... As the Stihl carb has both a fixed high speed and fixed idle jet the curve is much less pronounced than most of our other setups - here is a sample from my 32cc... as you can see the idle is at about 70% output as the jet is doing a lot of the restriction... you might have to try substantial output pulse to get enough fuel in...
https://cimg2.ibsrv.net/gimg/www.rcu...80fbae285.jpeg |
Chris,
That is most helpful information. Thanks. I will send an email message. Jim. |
Originally Posted by Jim.Thompson
(Post 12811443)
What "bolded" part is that Bert?
Was it on an earlier page? I don't recall using bold, but I am forgetful! QUOTE: No, but in my previous post I reported that I can adjust the solenoid rate by S1 and so achieve the same result. In other words, CH5 output is functioning over the required range. I can hear it changing the sound of the solenoid. END QUOTE To my non-english speaking brain, this comes across as if you hear a continuous change in the sound of the solenoid when you turn knob S1 over the entire range. That is not what you should hear. You should only hear a very minor change ONLY at the extremities of the range, where it stops rattling. You should hear for the main section a constant frequency, constant "loudness" and a constant "character" of the noise, because what you hear, is just the valve clicking on its seat. In the time the valve is either closed or opening, there is no movement, no sound at all. Combined with this earlier remark about the program line you made for Ch 5: QUOTE: Should it provide for full -100 to +100 to provide the range required? In other words, like this: https://cimg4.ibsrv.net/gimg/www.rcu...c700c6f463.png END QUOTE As said before, Ch 5 should have weight 100, offset zero, and I cannot see a reason to use the values you used, but I think this might be part of the issue. |
Originally Posted by Cat 1
(Post 12811454)
Jim, Just thought of one other item.... As the Stihl carb has both a fixed high speed and fixed idle jet the curve is much less pronounced than most of our other setups - here is a sample from my 32cc... as you can see the idle is at about 70% output as the jet is doing a lot of the restriction... you might have to try substantial output pulse to get enough fuel in...
https://cimg2.ibsrv.net/gimg/www.rcu...80fbae285.jpeg Regardless of this phenomenon, which is engine/carb determined, IF the knob S1 would have the proper control range, the engine SHOULD have fired. That is why I think your programming of Ch5 is the issue, and you have misled yourself by accepting the "change of sound" as proof of a full control range. That is why I asked you to use a servo as a simple visual check of having full control range on Ch5, or alternative, confirm with a scope whether the solenoid driver covers the entire range from 0 to 100% dutycycle. Because the mixture not getting into the ignitable range is the only reason I can think of, for the engine refusing to fire. |
Originally Posted by Jim.Thompson
(Post 12811397)
No, I cannot! Good question, this may be steering me towards a solution.
Edit#1: Now I can now get it to shut off when I use the mix line I posted above @ post#2440 when the pot is turned down fully (counterclockwise). I get that; what is missing my end is a workable set up line in the OpenTx line for CH5 to drive the solenoid. If we refer to my CH5 line in my previous post, what should I change to get started? Or, should this latest edit work? Edit #2: We now have tried that without any success. It seems to me, in my comparative ignorance, this is a simple question. Not so? I have them still intact; I read your relevant earlier posts in this regard (on the other thread?) and observed the take home points accordingly. Good tips! Thanks for replying. Edit #3: I should point out that I am about to abandon this project and go back to my simple tried and tested WT668 Walbro clone diaphragm carb. But.........once again........many thanks to all who did their best to assist. Jim. Re-reading this thread, the bolded in the quote above, to me suggests that the solenoid at the time of that test was silent with knob S1 in the outer left position. It does not say explicitly whether the solenoid was silent in the outer RIGHT position, but the programming line for CH 5 as posted, to me suggests it was not. Meaning that the solenoid, limited by the programming of CH 5 only utilised half of its availlable control range. Since Chris' posts suggest that the Stihl carb needs about 70% "opening" at around idle, that would indeed mean that the engine never was able to fire due to too lean mixture. |
Originally Posted by Jim.Thompson
(Post 12811436)
I have just suddenly realised this is a big part of the communication problem...........quite despite your genuine willingness to assist.
This project, as I see it, is probably an OpenTx dependant one. Correct? It is now clear that we are not all OpenTx savvy! Something that I suspected a bit earlier. I cannot blame anyone for not being so, after all, it is almost a hobby in itself. In fact, it could be said that some hobbyists make it their main hobby focus! If we cannot talk Otx and swap mix lines etc. we are (or rather I am) severely handicapped in interpreting what is being posted. This is one of the reasons that I am abandoning this project................... .................If only one of you folks could provide me with a screenshot of a working CH5 line from Otx Companion to obviate many unrelated questions and answers, like some of the above, we would sort this out (I suspect) in one exchange. However, I sense that I am asking too much and may have already stretched good friendships, which is the last thing I want to do. This is another reason I am abandoning this project. Jim. As I mentioned, I have never used Companion to set up OTX, so I can't help you there, however, I did email you pictures of my OTX fuel mixture channel setup way back. Perhaps you can reference those images? Bert's advice on using a servo to verify full range of motion of the fuel channel output is a good one. I've used that technique many times. Good luck, Lonnie |
Originally Posted by Glowgeek
(Post 12811540)
Jim, it's to early to give up. I struggled for a month or more trying to get a Spectrum DX8 to cooperate with this project, only to find that it is incapable of using Servo slowdown in conjunction with a master/slave channel setup. I had to buy a different radio, and chose OTX, which I had to learn from scratch. I thought about giving up on this project several times. Glad I didn't.
As I mentioned, I have never used Companion to set up OTX, so I can't help you there, however, I did email you pictures of my OTX fuel mixture channel setup way back. Perhaps you can reference those images? Bert's advice on using a servo to verify full range of motion of the fuel channel output is a good one. I've used that technique many times. Good luck, Lonnie And in all fairness, my first real attempts back then... yeah, I had a running engine, and I had "promising behaviour" in those engines. But it took at least 2 months before I had the first one "tamed" so far, that I dared say "This is IT".... And then Dave came along, and suggested the atmospheric correction, and it turned out that it could be EVEN better... :( But I can tell this: I will never EVER go back to "analog". No way, |
hi,
i still have bubles and i can get more than 40 % throttle if you have any idea? |
Originally Posted by ronron1
(Post 12811764)
hi,
i still have bubles and i can get more than 40 % throttle if you have any idea. |
Your video is too fuzzy to properly determine, but I would think, the remote needle, being mounted on the backplate of the engine. If that Remote Needle Valve Assembly is made out of metal, the heat from the engine is getting to that NVA, and causing the fuel to evaporate at the pressure drop.
Plase post an as clear and as large as possible detail photo of the remote needle valve assembly and how it is fitted to the rear of the engine. |
hi,
thanks for your answers, here is the picture, as you can see the pipe are made of polyethilene, buble were coming from the valve exit and getting bigger until the engine stopped. https://cimg6.ibsrv.net/gimg/www.rcu...676386a746.jpg |
That metal part is probably close enough to warm up the plastic NVA sufficiently.
Try what happens if you unscrew the two small crosshead screws, and reroute that tubing so it does not pass through the hole in the braacket anymore. The bubbles after the solenoid should be extremely tiny and normally are no problem. |
I've had several OS 46AX and 55AX engines with that remote needle setup. They run great, no fuel starvation problems. Might be worthwhile to check the remote needle valve assembly for leaks ie plug the fuel inlet and pull a vacuum on the outlet. I would also move the fuel tank closer to the engine.
|
Originally Posted by Glowgeek
(Post 12811831)
I've had several OS 46AX and 55AX engines with that remote needle setup.
But yes, a blockage would cause similar issues. |
Originally Posted by 1967brutus
(Post 12811833)
On gasoline?
But yes, a blockage would cause similar issues. |
Originally Posted by Glowgeek
(Post 12811889)
On methanol, but I understand why you asked.;)
|
ok i've shorten the thank tube and now it's bettter i can run it 0 to 100% without any problem , i run a full tank at 50% for today, but i still have buble between valve and needle like you see in picture, i wonder if the tank filter is ok, i'm using this one : https://fr.aliexpress.com/item/10050...yAdapt=glo2fra and i order this one to replace it :https://fr.aliexpress.com/item/10050...yAdapt=glo2fra , thanks for your help
https://cimg8.ibsrv.net/gimg/www.rcu...b371089eef.jpg |
Cut 1/4" (6mm) pieces of tubing and use them as clamps at all the tubing joints in and out of the tank, solenoid, and engine. See if that stops the air leak.
https://cimg2.ibsrv.net/gimg/www.rcu...1ab0d7f5f9.png |
what about electric shrink tube instead?
|
Maybe but I know short bits of the same size tubing works well.
|
Originally Posted by ronron1
(Post 12811953)
what about electric shrink tube instead?
As for the filters: I use exclusively feltclunks similar to this: https://www.justengines.co.uk/shop/a...v=796834e7a283 As for the bubble problem, please unscrew the entire remote needle assembly OFF from the engine and attach it to any COLD part of the testbench (or just for the test, leave it loose, as long as it does not have any contact with hot parts of the engine. |
Originally Posted by ronron1
(Post 12811949)
ok i've shorten the thank tube and now it's bettter i can run it 0 to 100% without any problem , i run a full tank at 50% for today, but i still have buble between valve and needle like you see in picture, i wonder if the tank filter is ok, i'm using this one : https://fr.aliexpress.com/item/10050...yAdapt=glo2fra and i order this one to replace it :https://fr.aliexpress.com/item/10050...yAdapt=glo2fra , thanks for your help
|
Originally Posted by 1967brutus
(Post 12811991)
Electric shrink tubing has barely any tensioning power, and probably won't help.
As for the filters: I use exclusively feltclunks similar to this: https://www.justengines.co.uk/shop/a...v=796834e7a283 As for the bubble problem, please unscrew the entire remote needle assembly OFF from the engine and attach it to any COLD part of the testbench (or just for the test, leave it loose, as long as it does not have any contact with hot parts of the engine. |
Originally Posted by Glowgeek
(Post 12811993)
As the solenoid is not a pump, the tank should be mounted as close to the engine as possible. The centerline of the tank should be mounted very close to the same height as the high speed needle.
On the testbench, only the height of the tank matters, but the distance can be up to one metre (3 ft) without issues, as long as the fuel tubing is "immobilized", |
Originally Posted by 1967brutus
(Post 12812047)
In the final installation, in a plane, this is important.
On the testbench, only the height of the tank matters, but the distance can be up to one metre (3 ft) without issues, as long as the fuel tubing is "immobilized", I'm a stickler for setting up engines on the test stand to emulate, as closely as possible, the setup in the aircraft. I even run them with the same fuel tank that's to be used. Eliminates many factors when trouble raises it's head. |
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