another darn ryobi post (ryobi performance modification, analysis and comparison)
#201
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Wow... Cool!
I assume you've got a two ring piston, yes?
I've had trouble getting a steady reading on my tach. It normally jumps around plus or minus 40 rpm. I'm not sure how much of this is instability of the motor itself or whether the tach is not getting every pulse of the prop blade. When I test it on a 60 cycle electric light bulb it's dead on. The APC prop is gray, a pretty neutral color, so maybe the sensor has a hard time picking it up against the background. Maybe if I took a black marker and colored it up it would help. I'll have to try that! The tach I've got is a "GloBee" from Tower Hobbies but I'd bet all the R/C marketed tachs are basically the same.
diceco
I assume you've got a two ring piston, yes?
I've had trouble getting a steady reading on my tach. It normally jumps around plus or minus 40 rpm. I'm not sure how much of this is instability of the motor itself or whether the tach is not getting every pulse of the prop blade. When I test it on a 60 cycle electric light bulb it's dead on. The APC prop is gray, a pretty neutral color, so maybe the sensor has a hard time picking it up against the background. Maybe if I took a black marker and colored it up it would help. I'll have to try that! The tach I've got is a "GloBee" from Tower Hobbies but I'd bet all the R/C marketed tachs are basically the same.
diceco
#202
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I appreciate all the hard work everyone is doing here to come up with the best combo and/or ideas for the Ryobi. But I want to make something that is very important clear. The very first thing one should do before modifying an engine is to make sure it is in perfect shape to begin with, especially as regards to the ring seal. I have personally seen engines gain over 600 rpms with just a ring change, and even more so with the Ryobi in the case of those that do not have rings that overlap the retaining pin. Once again, the recommended ring gap in other, similar engines is .003" which is about the width of a piece of paper! It is just basic good practice when modifying engines of any type to get a good seal on all important parts before starting with modifications. Then you can get a good, honest baseline to work with, and go from there. Without a "given" of a good ring seal, all the results and comparisons you all are getting will be "all over the board" and not realistic/significant.
Just my input here....
AV8TOR
Just my input here....
AV8TOR
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I appreciate all the hard work everyone is doing here to come up with the best combo and/or ideas for the Ryobi. But I want to make something that is very important clear. The very first thing one should do before modifying an engine is to make sure it is in perfect shape to begin with, especially as regards to the ring seal. I have personally seen engines gain over 600 rpms with just a ring change, and even more so with the Ryobi in the case of those that do not have rings that overlap the retaining pin. Once again, the recommended ring gap in other, similar engines is .003" which is about the width of a piece of paper! It is just basic good practice when modifying engines of any type to get a good seal on all important parts before starting with modifications. Then you can get a good, honest baseline to work with, and go from there. Without a "given" of a good ring seal, all the results and comparisons you all are getting will be "all over the board" and not realistic/significant.
I've had trouble getting a steady reading on my tach. It normally jumps around plus or minus 40 rpm. I'm not sure how much of this is instability of the motor itself or whether the tach is not getting every pulse of the prop blade. When I test it on a 60 cycle electric light bulb it's dead on. The APC prop is gray, a pretty neutral color, so maybe the sensor has a hard time picking it up against the background. Maybe if I took a black marker and colored it up it would help. I'll have to try that! The tach I've got is a "GloBee" from Tower Hobbies but I'd bet all the R/C marketed tachs are basically the same.
I think it's more likely an inertia problem. The reed has got to change direction 7000 times a minute. That's over a hundred times a second! I bet with so little spring force on the reed it's lagging behind in getting back down to the seat as the crankcase pressure builds up on the piston's down stroke. In fact it may be still on the way up as the crankcase pressure turns around from negative to positive!
As for the newer style cylinder with four transfer runners, I believe there are huge gains to be made by smoothing out the entrance to the transfer ports. The flow coefficient, and thus the effective flow area, of those ports just has to be abysmal with those blunt facing surfaces facing the flow. I not only bullet-nosed the web separating the two runners but also matched the outer edges of the ports to the crankcase so nowhere are there forward facing steps in the flow path. I bet you are right about the difference in cylinder volume (compared to the older cylinder, ie compression) but I'm not sure how to improve that situation with my setup. The only other cylinder I've got is the one with decompression slots.
I got the parts from ajonr today. I got one of the engines with the small crank case and shrouded reed valve. I am so excited about this engine as i think its got lots of potential. Thanks anjor i cant wait to play with all this.
I think after i am done with this engine in the test peramiters i have laid out i think im gona do it again with a whole new set up and see if the results are simmilar or repeatable. I am about to get into some areas with engine that i have never seen done on the net before. not saying its never been done just saying i havent seen it so it should be interesting.
#204
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I wonder if an automotive inductive style tach would work better. You know, the kind with a pickup that clamps on to the ignition wire.
diceco
diceco
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Thats not a bad idea. I havent seen one of those units in a while but i bet i could find one at a auction. Im just not sure it would work with a single cylinder.
#206
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
combatpilot said: I though of this to but the rubber reed valve you could open by merely blowing on it. it had no spring action whatsoever.
diceco
edit: OH, SORRY. I MISSED YOUR POINT! You saw no change from stock to modified clamp plate to waist cut reed, right? Gee I don't know what's going on then. Maybe there is some distortion of the reed or a sideways twist or something on the reed with a bean hole in it.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I think your overlooking the pressure differential created by the pistion travel. I think this force is far greater than any exerted on the reed valve. The fact that the rubber valve has no spring action proves this. granted it will have more mass therfore there will be more inertia energy to overcome to get it to stop change direction and go back to the seat. so what is this force if its not spring action in the reed itself. it has to be pressure differential.
The reeed valve has no effect on the transfer phase of the the cycle. this cycle starts as soon as the piston opens the transfer port and ends when the tranfer ports are closed by the piston. the only way to change the timming of this cycle is to change the intake port timming. I think what you are talking about is the lower end compresion cycle. true if there is a lag it in effect lowers the duration of the lower end compression cycle. this in turn creats a lower pressure differential and there will be less pressure energy to force or transfer the air and gas mix through the ports and into the cylinder during the transfer cycle when the transfer ports are open.
The reed needs to reverse directions and get back down and close off the intake port so the transfer phase of the cycle can start. If it lags a bit there won't be as long a duration of transfer and performance will suffer.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
edit: OH, SORRY. I MISSED YOUR POINT! You saw no change from stock to modified clamp plate to waist cut reed, right? Gee I don't know what's going on then. Maybe there is some distortion of the reed or a sideways twist or something on the reed with a bean hole in it.
Yea i dont know whats going on here either. tell ya what i will mail you a waist cut reed and you mail me the bean cut reed and we can each try these and see if we get the same reults again. I am wondering if it would be worthwhile for you to do your test again. I had done my reed valve twice and got two different results to.
I have my suspicions as to why there is no change in performance.
At this rate i just cant see what a y manifold with a two reed set up would do.
Yea i dont know whats going on here either. tell ya what i will mail you a waist cut reed and you mail me the bean cut reed and we can each try these and see if we get the same reults again. I am wondering if it would be worthwhile for you to do your test again. I had done my reed valve twice and got two different results to.
Again in my first testing of test #7 reed valves
stock valve RPM 7050
modified reed valve 7410
rubber reed valve 7410
Second testing of test #7 reed valves
stock valve RPM 7410
modified reed valve 7410
rubber reed valve 7410
stock valve RPM 7050
modified reed valve 7410
rubber reed valve 7410
Second testing of test #7 reed valves
stock valve RPM 7410
modified reed valve 7410
rubber reed valve 7410
At this rate i just cant see what a y manifold with a two reed set up would do.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Read some of this site on the reeds.They are useing differant designs.
http://rcshowcase.com/html/faq.html
Look at the rotary reed valve
http://rcshowcase.com/html/faq.html
Look at the rotary reed valve
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
i just bought a tach from princess auto today. they had one on sale for $20, so i couldnt pass it up. i think that this type will be more accurate, cause i need to attach reflective tape to the prop. It says that the readings are +- 1 rpm and the max range is 8 meters. I wont have time to run the engine again til tomorrow, or monday. I will have a helper with me, so i hope to get a good video for you guys. I contacted frank about a ring (single ring piston) so i will probably be getting it in the mail in a couple weeks or so.
#211
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
combatpilot said: Yea i dont know whats going on here either. tell ya what i will mail you a waist cut reed and you mail me the bean cut reed and we can each try these and see if we get the same reults again. I am wondering if it would be worthwhile for you to do your test again. I had done my reed valve twice and got two different results to.
combatpilot said: The reeed valve has no effect on the transfer phase of the the cycle. this cycle starts as soon as the piston opens the transfer port and ends when the tranfer ports are closed by the piston. the only way to change the timming of this cycle is to change the intake port timming. I think what you are talking about is the lower end compresion cycle. true if there is a lag it in effect lowers the duration of the lower end compression cycle. this in turn creats a lower pressure differential and there will be less pressure energy to force or transfer the air and gas mix through the ports and into the cylinder during the transfer cycle when the transfer ports are open.
12.7 mm carb on the way. I'm already wondering if my exhaust system needs opening up. The 1/2'' EMT (electrical metal tubing) stinger has no more area than a 12.7mm venturi. You'd think the total exhaust exit area should be greater than the carb inlet area.
diceco
#212
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
andrew66 said: i just bought a tach from princess auto today. they had one on sale for $20, so i couldnt pass it up. i think that this type will be more accurate, cause i need to attach reflective tape to the prop. It says that the readings are +- 1 rpm and the max range is 8 meters.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I've heard that you don't want to turn a Ryobi much more than 7000 rpm static
The issue with the reeds maybe as I read on another web site. The reed system becomes less efficient with the increase in RPM. This would be similar to "valve float" in a 4 cycle engine at a high RPM. So maybe a stiffer reed with stronger impulses to open and close it with increased RPM is the answer to more horse power. HP generally increases with RPM.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
just bought a tach from princess auto today. they had one on sale for $20, so i couldnt pass it up. i think that this type will be more accurate, cause i need to attach reflective tape to the prop. It says that the readings are +- 1 rpm and the max range is 8 meters.
12.7 mm carb on the way. I'm already wondering if my exhaust system needs opening up. The 1/2'' EMT (electrical metal tubing) stinger has no more area than a 12.7mm venturi. You'd think the total exhaust exit area should be greater than the carb inlet area.
That should be more than enough for the outlet of the muffler. mine has two half inch tubes and you can cover one up completly with no effect at all. Did you remove all the baffling inside also? In all reality 7200 rpm isnt that far off from what im getting with the same modifications. that bigger carb should put you up or above the 7400 range where im at.
Wow.... +-1rpm! I never see a digit in the "ones" column on my tach. How is this tach different from the ones we buy from the hobby store that would make it more accurate?
The issue with the reeds maybe as I read on another web site. The reed system becomes less efficient with the increase in RPM. This would be similar to "valve float" in a 4 cycle engine at a high RPM. So maybe a stiffer reed with stronger impulses to open and close it with increased RPM is the answer to more horse power. HP generally increases with RPM.
The rotary valve is interesting but i just dont think it will work on the ryobi engines as there is no practical way to mount or drive it.
I don't know how true this is but, I do know, my wife loves to run our Weed Eater ( w/Ryobi engine) with about 2"- 3" of line sticking out of the cutting head. That engine has to be turning around 10,000 RPM and let me tell you, she don't care that it has a throttle. She runs it like this until it runs out of gas. Believe it or not, our wackers will last for several years, I haven't had one throw a rod yet.
#215
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
My modified Ryobi turns an 18 x 6 prop at 8500 rpms, and it has the stock reed valve so I don't think that is a limiting factor. I am going to put a larger prop on it, because I have heard of Ryobis blowing up when run this fast. When looking at that stamped steel rod, I am rather amazed that they hold up at the recommended 7500 static rpms. 7500 static will unload to 8000 plus in flight anyway.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
i will get pics of the tach later tonight. I think it is more accurate b/c it has a laser that hits the reflector tape (sticks to the prop) and it measures the rpm from that. It says it has 5 digit read out. This tach is normally around $60.00, thats why i didnt hesitate to buy it. lol
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
i got a pic of my tach. The brand is power fist. Just for the hell of it, i put a reflector on my fan in the house to test, and it works beautifully. It wont pick up a reading unless the laser beam hits the reflector. And it reads down to 1 digit.
here are the pics
here are the pics
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Man that was good deal for 20 bucks. did they by chance have another lol?
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I have a referance test engine working now.
A very clean stock single ring piston,large case long shaft,with a small 8mm carb that was also cleanned up,and a 2 runner port head.It has about 5 for compression.I was working with the EI,so there was no mag. and coil to mess with.I think the timming was about 15 degres BTDC.A Zoar 18x6 for the prop.I was getting abound 7100 rpms at full throtle and was idleing down to 2500rpms.The gas was 91 octane and 40:1 oil mix.I was running open exhast to see how bad it was burnning the fuel.Yea, a little loud !!
About 62 sunny little to no wind and dry( around 30%)
If anyone else is running the XYZ EI ignition that you got from China, check your magnet before you glue it into the hub. It is picky to N or S to trigger it.Hook it all up and pass the magnet up to the hall sensor to get the right side up.
A very clean stock single ring piston,large case long shaft,with a small 8mm carb that was also cleanned up,and a 2 runner port head.It has about 5 for compression.I was working with the EI,so there was no mag. and coil to mess with.I think the timming was about 15 degres BTDC.A Zoar 18x6 for the prop.I was getting abound 7100 rpms at full throtle and was idleing down to 2500rpms.The gas was 91 octane and 40:1 oil mix.I was running open exhast to see how bad it was burnning the fuel.Yea, a little loud !!
About 62 sunny little to no wind and dry( around 30%)
If anyone else is running the XYZ EI ignition that you got from China, check your magnet before you glue it into the hub. It is picky to N or S to trigger it.Hook it all up and pass the magnet up to the hall sensor to get the right side up.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
thats good to know about the magnet. sounds like your making progress. I worked on my test stand a little more today and should be ready to get back to testing soon.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I was planning to get a static thrust reading but the batterys were dead in the scale.I was getting dark, and needing to get cleanned up.There is always tomarrow.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Yea i had to quit working today early cause my wife wanted some attention today. So i got to go ridding all over the country. She didnt know it but i was secretly looking for weedeaters lol.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
they had a few left, but were going fast. Sometimes they list these items online, but its hard to find them, cause the stock varies from store to store. Maybe searching powerfist would turn something up? but i doubt that they will be on sale for as low as at princess auto.
Looks like the weather might be crap for full scale flying tomorrow, so i will probably get a chance to run the engine so i can post a video with rpms. My buddy just got back so i might have a camera man, if he isnt busy tomorrow.
Looks like the weather might be crap for full scale flying tomorrow, so i will probably get a chance to run the engine so i can post a video with rpms. My buddy just got back so i might have a camera man, if he isnt busy tomorrow.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
The Radio Shack magnets DID work fine .ie-the XYZ EI.I was also using 6volts with no problem.
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I got to run my engine today. It went well i guess... My miracle tach decided that it wouldnt work in the cold. wouldnt pick up any reading at all. I brought it home, and tested on the fan, and it works fine. Only difference is that its 20C in the house, and 3C outside. They state that the operating temp is 0-30C and a max RH of 80%, so i guess thats probably why i was having troubles. But for now, im finished testing this engine, until it gets warmer, and the 18-8 prop gets here. I now have about 3.2 hours on this engine, running 87 octane fuel and castrol grand prix motorcycle oil mixed at 32:1.
here is the link to the video from today: http://www.youtube.com/watch?v=RjF6PusJxUU
here is the link to the video from today: http://www.youtube.com/watch?v=RjF6PusJxUU