another darn ryobi post (ryobi performance modification, analysis and comparison)
04-05-2009 | 06:59 PM
#351
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
HEY COMBAT? If you are running "70" to Denver, I would buy your lunch or whatever at EXIT 17. My cell phone is 785 821 4381. After one more trip to the Wound Center in Garden City tommorow, 4-6, I plan on being around. Flathead
Pretty much everything Jack said in the last post is what i would have said also.
I just want to add. A frank bowman ring is not a garunteed gain in power. it could be bubble gum for all I care. if it does not seal it does not seal wiether its a new ring old ring or whatever. there are more variables to a good seal here.
number one cylinder condition. ie is it round? is it scored?
next would be ring gap. larger gap more leakage.
Is the ring flat and seals good to the ring land?
Does the piston ring groves have a bunch of carbon build up preventing compression from getting behind the rings?
so on and so on. i made a used cylinder and used stock two ring piston have a 100 over 100 psi reading with a 13 second leakdown count. thats a pretty damn good seal compared to the 94 over 100 psi and a 3 second leakdown count that i had in my first set up.
Again only way to know what any set up is doing is to leakdown test it.
Again the only way to tell no matter what you do or what or how many rings you have is to do a leakdown test. agin see the leakdown testing in previous posts.
Yes a good seal does help prevent cross contamination of the exshaust and fuel air charge but anything you can do to up compression ratio makes more power. I proved this when i reuduced the base gasket and got a power increaseon the very same piston and cylinder combo. granted it wasent much but it was still an increase.
But from what I have been able to understand from Jennings, port timing and compression are not as important as port scavenging. In other words, how quickly we can get the exhaust out and the fresh new charge in. This is mostly controlled by the area of the exhaust ports and transfer ports and also by the direction and smoothness of the transfer ports. I am sure everyone has heard the term Schnerle porting on our glow engines. This is a reference to a man who came up with one of the best ways to arrange the transfer ports of a 2 stroke engine to bring the charge into the cylinder in an upward direction that then pushes the exhaust out. That is why the transfer ports are set at 90 degrees to the exhaust port, to keep the fresh charge from going straight across the piston and back out the exhaust port.
First, there is not much gain to be had by changing the intake any as a reed type induction is pretty well regulated by the engine anyway. However the larger carb is needed to supply as much as it can take.
Also as far as increasing the exhaust port area, raising the exhaust port timming also deos this to some effect. it had no effect on my engine but the cylinder with greater intake port area ie. the two runner cylinder seems to respond to this mod.
04-05-2009 | 07:33 PM
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Hey I just want to add that I am by no way to be considered an expert on this and do not feel that I am. everything here is my opinion and should be taken as just that. I am merely trying to share the results of my testing and in no way am implying that any test anyone else will do will have these results period. I actually hope others have different results and do find power gains and I sure hope they will share it here just like I have shared my findings.
04-05-2009 | 08:58 PM
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From: Southeastern,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I looked in the plug hole and found that the cylinder has two transfer ports per side. So, from all the experimenting, this cylinder should respond to exhaust port modification. Am I correct on this assumption? Also, from what has been determined. lowering the cylinder by going to a thinner gasket should help some. I found the original gasket to be around .030" thick. I cut a new gasket that is around .015" thick. This should give a slight performance increase, correct?. I have already went to a 11.1mm carb on mine. Another thing that seems to help is a more free flowing muffler. I used the stock muffler with some of the guts removed. I put a single 1/2" id outlet which may not be enough to get the most performance. Has anyone used a Wackerengines muffler on their conversion? If so, what are your thoughts on this muffler? Did anybody modify the stock muffler? If so, what did you do and how did you do it?
If anyone is interested, a guy on Ebay has numerous parts for the Ryobi including a complete gasket kit for the engine. The price isn't too bad especially if you can make a good offer. I got a complete kit from him a while back for around $12 shipped. This is what I used as a pattern to cut a new and thinner base gasket.
What kind of adapter was used in the plug hole for the leak down test and where can it be found?
Thanks
If anyone is interested, a guy on Ebay has numerous parts for the Ryobi including a complete gasket kit for the engine. The price isn't too bad especially if you can make a good offer. I got a complete kit from him a while back for around $12 shipped. This is what I used as a pattern to cut a new and thinner base gasket.
What kind of adapter was used in the plug hole for the leak down test and where can it be found?
Thanks
04-06-2009 | 01:15 AM
#354
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
The clearances seem to be "all over the place" on the Ryobis. You can't just arbitrarily leave out the cylinder base gasket as we do on some engines, because on some it will work out to a workable deck height, and sometimes not. A good minimum piston to head clearance is .015" to .020". On some Ryobis this means leaving out the base gasket completely, and on some you have to make a thinner base gasket because leaving it out completely would result in the piston hitting the head. On the other side of the coin, the last one I did had a deck clearance of .035" with no base gasket. I could have machined some off the bottom of the cylinder to get an optimum deck height, but I just went ahead and assembled it without a gasket and accepted the larger than optimal deck height. It ran pretty well none the less. Once again, as has been noted here before; set your deck height first, and then go after your optimum port timing. The Ryobi seems to like about 150 degrees exhaust timing, and when you lower the cylinder you LOWER the port timing. This is not a good thing, as many Ryobis come stock with a really low exhaust port timing.
As regards to the Bowman ring deal, I have yet to see an engine that didn't respond with more power when equipped with one of his rings. As you mentioned, ring seal is dependant on many factors. Frank's rings seem to seal better under a variety of conditions (and piston positions apparently.) A good leak down test at TDC doesn't necessarily mean that the ring is sealing well for the entire power stroke as your tests have already shown. Once again, just speaking from actual experience, a Frank Bowman ring is just about guaranteed to add some power, especially to a used engine, given that the bore is good enough to seal any ring at all.
AV8TOR
As regards to the Bowman ring deal, I have yet to see an engine that didn't respond with more power when equipped with one of his rings. As you mentioned, ring seal is dependant on many factors. Frank's rings seem to seal better under a variety of conditions (and piston positions apparently.) A good leak down test at TDC doesn't necessarily mean that the ring is sealing well for the entire power stroke as your tests have already shown. Once again, just speaking from actual experience, a Frank Bowman ring is just about guaranteed to add some power, especially to a used engine, given that the bore is good enough to seal any ring at all.
AV8TOR
04-06-2009 | 07:01 AM
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
As regards to the Bowman ring deal, I have yet to see an engine that didn't respond with more power when equipped with one of his rings. As you mentioned, ring seal is dependant on many factors. Frank's rings seem to seal better under a variety of conditions (and piston positions apparently.) A good leak down test at TDC doesn't necessarily mean that the ring is sealing well for the entire power stroke as your tests have already shown. Once again, just speaking from actual experience, a Frank Bowman ring is just about guaranteed to add some power, especially to a used engine, given that the bore is good enough to seal any ring at all.
If you read through the posts again where i did my leakdown tests you will see where i rotated the prop under pressure and could see the condition of the seal all the way through the stroke. remeber i was saying on my first cylinder that the best spot was at TDC but far worse everywhere else?
As far as th adapter that i used if you look at it in the pictures it is an adapter off of a compression testor i had on hand already. it just so happened the quick change end already fit a air chuck i got at harbor frieght.
I was prepared to make an adapter by welding an air chuck fitting to a spark plug after knocking all the ceramic out.
I looked in the plug hole and found that the cylinder has two transfer ports per side. So, from all the experimenting, this cylinder should respond to exhaust port modification. Am I correct on this assumption? Also, from what has been determined. lowering the cylinder by going to a thinner gasket should help some. I found the original gasket to be around .030" thick. I cut a new gasket that is around .015" thick. This should give a slight performance increase, correct?. I have already went to a 11.1mm carb on mine. Another thing that seems to help is a more free flowing muffler. I used the stock muffler with some of the guts removed. I put a single 1/2" id outlet which may not be enough to get the most performance. Has anyone used a Wackerengines muffler on their conversion? If so, what are your thoughts on this muffler? Did anybody modify the stock muffler? If so, what did you do and how did you do it?
If anyone is interested, a guy on Ebay has numerous parts for the Ryobi including a complete gasket kit for the engine. The price isn't too bad especially if you can make a good offer. I got a complete kit from him a while back for around $12 shipped. This is what I used as a pattern to cut a new and thinner base gasket.
What kind of adapter was used in the plug hole for the leak down test and where can it be found?
Thanks
If anyone is interested, a guy on Ebay has numerous parts for the Ryobi including a complete gasket kit for the engine. The price isn't too bad especially if you can make a good offer. I got a complete kit from him a while back for around $12 shipped. This is what I used as a pattern to cut a new and thinner base gasket.
What kind of adapter was used in the plug hole for the leak down test and where can it be found?
Thanks
there is a procedure somewhere to put some solder in the cylinder and smash it with the piston to see how thick this area is. be sure to do this over the wrist pin or the reading wont be right.
On the muffler aftermarket or modified stock the key seems to be as much flow as possible. it is very possible to modify a stock on as it has been done here with much sucsess. the aftermarket ones are lighter and look neater though but a modified stock one will work just as good.
as far as gaskets i just buy then at the local engine shop they are pretty cheap really and i dont think i pay that much for the three gaskets i use carb, backplate and exhaust dosent add up to five bucks where i get them.
I think it is fair to say that you dont need to spend alot of money to make a good running ryobi. there really isnt any aftermarket parts for sale that i have seen that produce anymore power than a good well put together stock setup with a modified muffler and a larger carb. sure an electronic ignition is nice as it stats better and idles better and is lighter but a stock one gives just as good performance.
I cant remeber Av8tor what cylinder are you using as I rember you had gains in the exshaust mod to?
04-07-2009 | 09:50 AM
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From: Fletcher,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
madman75 said: Another thing that seems to help is a more free flowing muffler. I used the stock muffler with some of the guts removed. I put a single 1/2" id outlet which may not be enough to get the most performance.
diceco
04-07-2009 | 10:04 AM
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I take a screw driver, and carefully work my way around the crimp in the muffler, prying it open. The muffler can then be taken apart. After gutting the muffler, I then put JB Weld or silicone on the crimp, and crimp the muffler back together with pliers. Just be sure to leave whatever is in the muffler to prevent it from collapsing when the mounting screws are tightened. Sometimes it is two tubes, sometimes it is a squarish piece with holes in it. If that piece would be restrictive to exhaust flow, I either modifiy it, or leave it out and make up tubes to use in it's place.
AV8TOR
AV8TOR
04-08-2009 | 01:59 AM
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From: Woodland,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
If you don't have the exhaust tube at the bottom of the muffler it will catch the oil in the exaust.
You can also just have a small hole it the tube just above the bottom of the muffler to let the oil drain as the engine runs.
I just used a deep hole saw and drilled out the exhaust tube and cut through the guts of the muffler.
I drilled right next the the outlet tube. So I cut out the outlet tube and made the new larger hole at the same time.
This was done on a Ryobi muffler.
You can also just have a small hole it the tube just above the bottom of the muffler to let the oil drain as the engine runs.
I just used a deep hole saw and drilled out the exhaust tube and cut through the guts of the muffler.
I drilled right next the the outlet tube. So I cut out the outlet tube and made the new larger hole at the same time.
This was done on a Ryobi muffler.
04-11-2009 | 04:22 PM
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From: Fletcher,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
A note on large bore carb replacements and chokes. This may seem obvious..... but maybe not.
I thought I'd recount my adventure with fitting a 12.7mm carb to the Ryobi. It's not quite as simple as moving the butterfly shaft/arm from your old carb and bolting the carb on. On the carb I got, a WA-2, the entrance bore of the carb was way bigger than the hole in the stock Ryobi choke base plate. The carb has a nice bellmouth shaped entrance and in order to make that work to best advantage the hole in the choke base plate needed to be enlarged to the outer diameter of the bellmouth. Now the choke plate itself, the one that moves, was way too small to seal the opening when fully closed. The result; no effective choke.
I cut a piece of thin aluminum from some flashing and fashioned a plate to cover the carb opening, including the area under the pivot. I then glued it to the stock choke plate. I had to cut a scallop in one of the edges to provide an unrestricted opening when the choke was fully opened, which requires more rotation than the stock set up. I dispensed with the stock wave washer and made a shim to take up the slop in the assembly of the choke plate and the carb bolt. I now have a choke that will suck so much fuel from the tank that it will run right out of the carb if I'm not careful, a much better situation than trying to prime a cold engine by squirting fuel in the vicinity of the carb opening or removing the spark plug to prime it!
diceco
I thought I'd recount my adventure with fitting a 12.7mm carb to the Ryobi. It's not quite as simple as moving the butterfly shaft/arm from your old carb and bolting the carb on. On the carb I got, a WA-2, the entrance bore of the carb was way bigger than the hole in the stock Ryobi choke base plate. The carb has a nice bellmouth shaped entrance and in order to make that work to best advantage the hole in the choke base plate needed to be enlarged to the outer diameter of the bellmouth. Now the choke plate itself, the one that moves, was way too small to seal the opening when fully closed. The result; no effective choke.
I cut a piece of thin aluminum from some flashing and fashioned a plate to cover the carb opening, including the area under the pivot. I then glued it to the stock choke plate. I had to cut a scallop in one of the edges to provide an unrestricted opening when the choke was fully opened, which requires more rotation than the stock set up. I dispensed with the stock wave washer and made a shim to take up the slop in the assembly of the choke plate and the carb bolt. I now have a choke that will suck so much fuel from the tank that it will run right out of the carb if I'm not careful, a much better situation than trying to prime a cold engine by squirting fuel in the vicinity of the carb opening or removing the spark plug to prime it!
diceco
04-12-2009 | 06:25 PM
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I had the same problem with the throttle shaft to. the new lever arm on the new carb dosent work with any rc type set up. i tried to change out throttle shafts and they were just different enough that all it did was beat up the butterfly valve.
I plan on trying to make a new throttle shaft with a much longer rod to be able to install a throttle arm in a much better location that will be more usable when i get back with some machining capabilities.
the carb i used already had a nice choke so all the choke modification wasent nessacary and sure makes for a nice install
I should be back in a few days and I can get back to doing some testing lol
I plan on trying to make a new throttle shaft with a much longer rod to be able to install a throttle arm in a much better location that will be more usable when i get back with some machining capabilities.
the carb i used already had a nice choke so all the choke modification wasent nessacary and sure makes for a nice install
I should be back in a few days and I can get back to doing some testing lol
04-12-2009 | 09:22 PM
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From: Fletcher,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Stock muffler mods and performance results: when installed on a modified Ryobi 31cc (reed, transfer port inlet, exhaust port) outlined in previous posts in this thread. Tests were done using an APC 18x8W prop.
Test 1) 7415 rpm 14.3 lbs thrust Stock muffler with inlet screen removed.
Test 2) 7630 rpm 15.0 lbs thrust Stock muffler with inlet screen removed and outlet pipe replaced with 5/8" ID pipe.
Test 3) 7680 rpm 15.1 lbs thrust Stock muffler fully gutted with 0.8" ID pipe.
Somewhat surprisingly there was only a very slight improvement between tests 2 and 3. The baffle in the stock muffler appears to be very restrictive and I would have thought that removing it and installing a big outlet pipe would have given a larger effect than it did. This is consistent with what combatpilot found when he covered one of the two outlet pipes on his aftermarket muffler and found no change in performance. I guess the operation of the two stroke engine ain't that simple, as Gordon Jennings professes in his book.
The first photo shows the gutted muffler and all the parts. The baffle and the small outlet pipe (in the upper right corner of the photo), both are internal in the stock muffler, and are discarded. I made the 0.8" id outlet pipe from a thin wall metal (steel not aluminum) broom handle. The hole sizes and spacing of the drillings in the outlet pipe were arbitrary, but plenty greater in total area than that of the pipe. I opened up the outlet hole in the muffler case to fit the larger outlet pipe and braised it in (second photo). When refitting the two halves of the muffler be sure to shorten the bolt standoffs a little to account for the thickness of the baffle which is not present, otherwise the halves will not fully seat together. It was about .030" in my case. I reassembled the halves using RTV to seal the joint and bent the flange back to secure the halves.
In conclusion; all of the work required to gut the stock muffler has not enough pay-off to make it worth while. You can get nearly the same benefit by just cutting out the stock outlet pipe and replacing it with a bigger pipe without having to take apart the muffler.
The gutted muffler is very loud too. Although I haven't measured the noise level of the muffler as configured in test 2 for comparison, the fully gutted one as tested in test 3 measured 104 db at 10 ft distance. Admittedly this was in a test stand resting on saw horses on a concrete slab and no more than 20 feet away from a brick wall. It may have been a little quieter installed in an airplane on a grass field. The AMA guidelines are 96 db for an airplane sitting on a concrete runway and 94 for a grass field.
diceco
Test 1) 7415 rpm 14.3 lbs thrust Stock muffler with inlet screen removed.
Test 2) 7630 rpm 15.0 lbs thrust Stock muffler with inlet screen removed and outlet pipe replaced with 5/8" ID pipe.
Test 3) 7680 rpm 15.1 lbs thrust Stock muffler fully gutted with 0.8" ID pipe.
Somewhat surprisingly there was only a very slight improvement between tests 2 and 3. The baffle in the stock muffler appears to be very restrictive and I would have thought that removing it and installing a big outlet pipe would have given a larger effect than it did. This is consistent with what combatpilot found when he covered one of the two outlet pipes on his aftermarket muffler and found no change in performance. I guess the operation of the two stroke engine ain't that simple, as Gordon Jennings professes in his book.
The first photo shows the gutted muffler and all the parts. The baffle and the small outlet pipe (in the upper right corner of the photo), both are internal in the stock muffler, and are discarded. I made the 0.8" id outlet pipe from a thin wall metal (steel not aluminum) broom handle. The hole sizes and spacing of the drillings in the outlet pipe were arbitrary, but plenty greater in total area than that of the pipe. I opened up the outlet hole in the muffler case to fit the larger outlet pipe and braised it in (second photo). When refitting the two halves of the muffler be sure to shorten the bolt standoffs a little to account for the thickness of the baffle which is not present, otherwise the halves will not fully seat together. It was about .030" in my case. I reassembled the halves using RTV to seal the joint and bent the flange back to secure the halves.
In conclusion; all of the work required to gut the stock muffler has not enough pay-off to make it worth while. You can get nearly the same benefit by just cutting out the stock outlet pipe and replacing it with a bigger pipe without having to take apart the muffler.
The gutted muffler is very loud too. Although I haven't measured the noise level of the muffler as configured in test 2 for comparison, the fully gutted one as tested in test 3 measured 104 db at 10 ft distance. Admittedly this was in a test stand resting on saw horses on a concrete slab and no more than 20 feet away from a brick wall. It may have been a little quieter installed in an airplane on a grass field. The AMA guidelines are 96 db for an airplane sitting on a concrete runway and 94 for a grass field.
diceco
04-14-2009 | 08:32 PM
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Hey im back lol. I got tons of work to do before im back to testing. I cant wait to get started again. on my way back I stopped in goodland and had a great visit with Flathead. Thanks for lunch by the way. I learned a bunch looking at his engines and talking to him about all this. He brought it to my attention that I really do need to call frank bowman and talk to him bout rings. I think there are some things to experiment with there.
Dieco thats some pretty interesting results. it looks like increasing the flow helps but it also looks like there is a point that no matter how much bigger you make the outlet it wont flow anymore and will hit a top end. I am wondering is this is due to the volume of this engine just wont flow anymore and hence at a certian point a larger exshaust outlet wont help. I do remeber when I was playing with motorcycles in colorado and i had built my own exsaust pipe for an old 73 suzuki that i could not find an exhaust pipe for anywhere. It would run like crap till i started welding washers over the outlet reducing the size and it ran better with each reduction in size till i reached a point where the reduction was detrimental. just a little larger than this point is where i stopped at and the thing ran great. I think what was happening was the reduced size gave it just enough backpressure so the fuel air charge would be somewhat held in the cylinder and not follow the exhaust out the port. Objects in motion stay in motion principal. this dosent seem to be the case with the ryobi however as you can keep opening up the exhaust and it dosent seem to increase power. except when you open up a stock muffler as they sound pretty restrictive. once the point is found where increasing the exshaust opening has no affect reducing it has a detrimental affect so i dont think the principal i found on the motorcycle applies.
Dieco thats some pretty interesting results. it looks like increasing the flow helps but it also looks like there is a point that no matter how much bigger you make the outlet it wont flow anymore and will hit a top end. I am wondering is this is due to the volume of this engine just wont flow anymore and hence at a certian point a larger exshaust outlet wont help. I do remeber when I was playing with motorcycles in colorado and i had built my own exsaust pipe for an old 73 suzuki that i could not find an exhaust pipe for anywhere. It would run like crap till i started welding washers over the outlet reducing the size and it ran better with each reduction in size till i reached a point where the reduction was detrimental. just a little larger than this point is where i stopped at and the thing ran great. I think what was happening was the reduced size gave it just enough backpressure so the fuel air charge would be somewhat held in the cylinder and not follow the exhaust out the port. Objects in motion stay in motion principal. this dosent seem to be the case with the ryobi however as you can keep opening up the exhaust and it dosent seem to increase power. except when you open up a stock muffler as they sound pretty restrictive. once the point is found where increasing the exshaust opening has no affect reducing it has a detrimental affect so i dont think the principal i found on the motorcycle applies.
04-20-2009 | 03:14 PM
#364
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
ORIGINAL: combatpilot
Jack i dont think its so much what piston you use or what mods you have done to it. no matter what mods or what ring gap or how many ring ect ect if it wont seal its no good. Only way to know how your set up is is with a leakdown testor. I think i would even say that no matter what ring and piston combo you have if you test it with a leakdown testor with a .023 orfice and get a 100 over 100 reading with a 13 second time from valve close to 0 psi leakdown count then your gona get a stock motor with a larger 12.7 or 11.1mm venturi carb close to or around 7500 rpm.
It seems these are the most important factors.
#1 a cylinder ring combo with as little leakage as possible and
#2 a larger carb
eveything else just dosent seem to work I know others have had some gains in increasing the port timming and that just hasent been the case for me and i had done that mod twice with two different cylinders. the gains others got from this mod i think are on cylinders that are very different from mine. i know for sure your using the two runner per side and getting results close to mine with this mod so yes it probably works on that type cyl. on mine nope no cigar lol.
I started out today to do the rest of my testing. I had my engine all ready to go with the port mods and test ran recorded 7530 rpm with a static thrust of 14 lbs 2 oz. so absolutly no change there.
Next i converted to the electronic ignition. when test ran it seem to lose rpm and performance. this puzzles me greatly. I had the timming set to 28 degrees advanced as I understand how to set the timming. i degreed in 28 degree advance and set the sensor in the middle of the magnet. when test run i was getting 7280 rpm and 13 lbs 2 oz thrust.
I was able to gain back some of the power by hand tunning the timming and testing retime and test and retime and kind of adjust for performance. best i could get was 7440 rpm @ 13 lbs 13 oz thrust.
Even though the electronic ignition seemed to lose power it was so easy to start. just a light flip and man it was off and running. this thing also has a great advance curve so at idle the timming is retarded to where the idle is so smooth. yo can idle so low you can darn near count the prop blades go by. SERIOUSLY the idle and starting was drastically improved and this was worth it right there.
From here im pretty much done testing this engine. It is more than adequate for the plane im gona put it on and its getting nice out so its time to go fly.
I am gona start another conversion that can be tested on further.
With the set up I currently have there is something limmiting this engine to or around the 7500 rpm range. no matter what I do other than the making sure I have a good cylinder to ring seal and providing all the compression i can get and a larger carb nothing else works in any tangible gain in power. I dont know if there is something holding back this set up or if it has just plainly reached a point to where there is no more to get out of this engine with this CC range. it seems the only way to get more power from here is more CC.
I did check the port volume on the two runner cylinder and it has a volume with the two runners together of 2 ml. so that would be a 4 ml port volume altogether. sorry got no way to convert this to cc.
The cylinder witht the one runner port has a capacity of 2.6 ml so that would be a total port volume of 5.2 ml. interesting that my cylinder has the larger ports but yet it dosent repond to the port timming modification.
I dont know what else i can try. I do however think that if i take a stock ryobi and get it to have around a 13 second leakdown count at 100 over 100 reading and put a 12.7 mm venturi carb on it it should run around 7500 rpm. I guess this will be where i will start when I do my next test engine. I will know that alll the mods discussed here so far will do nothing to improve this number and from there i need to go new directions.
Man, that's very encouraging.
So, to make a Ryobi develop a bunch more power:
Get bigger 11.1 or 12.7mm carb
Fix single ring pistons with a better piston ring (ala Frank Bowman?) THE TWO RING PISTON NEEDS NO MODIFICATION
Get after market free flow exhaust or modify stock muffler with bigger outlet pipe.
YOU ARE MOST OF THE WAY THERE!! Right??
Those are pretty inexpensive and painless mods.
So, to make a Ryobi develop a bunch more power:
Get bigger 11.1 or 12.7mm carb
Fix single ring pistons with a better piston ring (ala Frank Bowman?) THE TWO RING PISTON NEEDS NO MODIFICATION
Get after market free flow exhaust or modify stock muffler with bigger outlet pipe.
YOU ARE MOST OF THE WAY THERE!! Right??
Those are pretty inexpensive and painless mods.
It seems these are the most important factors.
#1 a cylinder ring combo with as little leakage as possible and
#2 a larger carb
eveything else just dosent seem to work I know others have had some gains in increasing the port timming and that just hasent been the case for me and i had done that mod twice with two different cylinders. the gains others got from this mod i think are on cylinders that are very different from mine. i know for sure your using the two runner per side and getting results close to mine with this mod so yes it probably works on that type cyl. on mine nope no cigar lol.
I started out today to do the rest of my testing. I had my engine all ready to go with the port mods and test ran recorded 7530 rpm with a static thrust of 14 lbs 2 oz. so absolutly no change there.
Next i converted to the electronic ignition. when test ran it seem to lose rpm and performance. this puzzles me greatly. I had the timming set to 28 degrees advanced as I understand how to set the timming. i degreed in 28 degree advance and set the sensor in the middle of the magnet. when test run i was getting 7280 rpm and 13 lbs 2 oz thrust.
I was able to gain back some of the power by hand tunning the timming and testing retime and test and retime and kind of adjust for performance. best i could get was 7440 rpm @ 13 lbs 13 oz thrust.
Even though the electronic ignition seemed to lose power it was so easy to start. just a light flip and man it was off and running. this thing also has a great advance curve so at idle the timming is retarded to where the idle is so smooth. yo can idle so low you can darn near count the prop blades go by. SERIOUSLY the idle and starting was drastically improved and this was worth it right there.
From here im pretty much done testing this engine. It is more than adequate for the plane im gona put it on and its getting nice out so its time to go fly.
I am gona start another conversion that can be tested on further.
With the set up I currently have there is something limmiting this engine to or around the 7500 rpm range. no matter what I do other than the making sure I have a good cylinder to ring seal and providing all the compression i can get and a larger carb nothing else works in any tangible gain in power. I dont know if there is something holding back this set up or if it has just plainly reached a point to where there is no more to get out of this engine with this CC range. it seems the only way to get more power from here is more CC.
I did check the port volume on the two runner cylinder and it has a volume with the two runners together of 2 ml. so that would be a 4 ml port volume altogether. sorry got no way to convert this to cc.
The cylinder witht the one runner port has a capacity of 2.6 ml so that would be a total port volume of 5.2 ml. interesting that my cylinder has the larger ports but yet it dosent repond to the port timming modification.
I dont know what else i can try. I do however think that if i take a stock ryobi and get it to have around a 13 second leakdown count at 100 over 100 reading and put a 12.7 mm venturi carb on it it should run around 7500 rpm. I guess this will be where i will start when I do my next test engine. I will know that alll the mods discussed here so far will do nothing to improve this number and from there i need to go new directions.
04-20-2009 | 06:54 PM
#365
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From: Branson,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
One thing I think also hasn't been considered is spark plug. In testing my converted 22cc Poulan, I tried a different plug and gained 400 RPM. This result may be unique to my engine but I think you can't rule anything out.
04-21-2009 | 09:05 PM
#367
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From: Fletcher,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
captinjohn.....
Photos 3 and 4 look like a custom reed valve set up.... but are they made for the Ryobi?? I don't quite see how they would fit into the back of the crankcase.
diceco
Photos 3 and 4 look like a custom reed valve set up.... but are they made for the Ryobi?? I don't quite see how they would fit into the back of the crankcase.
diceco
04-21-2009 | 09:35 PM
#368
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Start looking here http://home.wanadoo.nl/pereivers/ryobimods.htm Good luck. Capt,n
04-21-2009 | 10:52 PM
#369
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
One thing I think also hasn't been considered is spark plug. In testing my converted 22cc Poulan, I tried a different plug and gained 400 RPM. This result may be unique to my engine but I think you can't rule anything out.
Start looking here http://home.wanadoo.nl/pereivers/ryobimods.htm Good luck. Capt,n
More on reed & intake. Also ways to mount a Ryobi. Capt,n
Sorry im not trying to beat you up or be an a hole. i just hate seeing others here being mislead and waisting there time on bullcrap mods that have no net gain and no proof or testing numbers to back it up. Im sorry but it seemed to help just dosent cut it if im gona spend my time and money and build one of these mods.
The Frank Boman piston ring, a good strait cylinder, exhaust at about 150 degrees with the right oil (like Pennzoil for Air cooled engines ) at a 32-1 ratio should give tou a good running engine. Also right prop for the airplane you are going to fly. Just because you get higher RPM,s from a certain prop.. it does not mean it is the best one for the airplane you fly. I do wonder how many different tests you made using the same ring??? Also it takes more time for a used ring to seat back in to give best performance. Thanks Capt,n
The 150 degree timming mod dosent garuntee anything either. some engines respond others dont and the numbers are on here to prove that. I have my suspicions as to why some respond and others dont but i havent had time to try it yet. i need to get my machine shop set up before i can continue.
Why would it matter how many test was made on the same ring? I can see this on an engine where the ring is not pinned like on a 4 stroke. on these engines the ring is pinned on and will go back in the exaxt same position where it came off. again if a leakdown test is performed you will know exactlly how your seal is anyhow.
04-21-2009 | 11:08 PM
#370
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I just want to add and again im not trying to be an a hole or insult anyone and I am sure im gona come off here as arogant and an a hole but this site http://home.wanadoo.nl/pereivers/ryobimods.htm is one of the prime reasons this thread was started. he does give some datta but makes no sense at all to me anyhow. From what i have seen he dosent have a single engine turning over 7000 rpm. guys here are getting good 7500 rpm results with not much mods at all and darn near stock engines that are well set up. mines turning 7400 rpm with a dynathrust 18-8 and his is only turning 6400 with a 18-6 dynathrust prop. 2 deg less pitch and it still wont turn over 7000 rpm. hmmmmmm interesting huh.
04-22-2009 | 10:31 AM
#372
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From: Fletcher,
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RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
ORIGINAL: captinjohn
Start looking here http://home.wanadoo.nl/pereivers/ryobimods.htm Good luck. Capt,n
Start looking here http://home.wanadoo.nl/pereivers/ryobimods.htm Good luck. Capt,n
The date/update on his page dates back to June of 2001. There may have been a lot of design/re-design work done by the factory on the motor since then that would make the newer ones perform that much better. I have no performance experience with the older Ryobi motors but just from looking at the piston/ring design it is clear that there is a great improvement from the old single ring piston to the newer two ring piston. BTW pereivers mentions nothing about pistons or rings on his page.
We know nothing about the ambient conditions prevailing during his tests but even if they were vastly different than the conditions of our tests it would only be several hundred RPM and not a 1000 RPM difference.
pereivers mentions exhaust back pressure as being a detriment to the motor's performance and mentions that he's using tuned pipes, but other than that doesn't say much about it. In his photo there is the header of what looks like a tuned pipe. I wonder if his pipe design is what has made his motor perform so poorly. Jennings accounts clearly that if you mess up the design of the pipe you'll cause the motor to perform worse than with a properly configured one, and by inference maybe worse than a modified stock muffler!
Maybe his tach was not working correctly. There is only prop speed data and no thrust data to cross check the RPM data.
diceco
04-22-2009 | 08:22 PM
#374
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
Boy...you guys that do not know Pe R. and what his background is, you better go back and read everything you can find about Hopping up a Ryobi engine. There has been many other Real good posts & threads hopping up this engine. I can tell you have not even scratched the surface on what can be done with this engine and many other engines. I suggest get some reading done before you Tell us a Guys tack must be off. Sounds like you tack my be off and that is not all thats may be off!!! Lord...have Mercy! Also do not expect me to look up any data on this engine. I will not baby set anyone not willing to take the time to dig up data ...do it youself!
Capt,n
Capt,n
04-22-2009 | 08:30 PM
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From: springfield, MO
RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
You failed, that is how you come across .......
Oh god here i go again (somebody stop me lol)
It is curious that pereivers performance RPM numbers are so far below what we are getting.
The date/update on his page dates back to June of 2001. There may have been a lot of design/re-design work done by the factory on the motor since then that would make the newer ones perform that much better. I have no performance experience with the older Ryobi motors but just from looking at the piston/ring design it is clear that there is a great improvement from the old single ring piston to the newer two ring piston. BTW pereivers mentions nothing about pistons or rings on his page.
We know nothing about the ambient conditions prevailing during his tests but even if they were vastly different than the conditions of our tests it would only be several hundred RPM and not a 1000 RPM difference.
pereivers mentions exhaust back pressure as being a detriment to the motor's performance and mentions that he's using tuned pipes, but other than that doesn't say much about it. In his photo there is the header of what looks like a tuned pipe. I wonder if his pipe design is what has made his motor perform so poorly. Jennings accounts clearly that if you mess up the design of the pipe you'll cause the motor to perform worse than with a properly configured one, and by inference maybe worse than a modified stock muffler!
Maybe his tach was not working correctly. There is only prop speed data and no thrust data to cross check the RPM data.
diceco
The date/update on his page dates back to June of 2001. There may have been a lot of design/re-design work done by the factory on the motor since then that would make the newer ones perform that much better. I have no performance experience with the older Ryobi motors but just from looking at the piston/ring design it is clear that there is a great improvement from the old single ring piston to the newer two ring piston. BTW pereivers mentions nothing about pistons or rings on his page.
We know nothing about the ambient conditions prevailing during his tests but even if they were vastly different than the conditions of our tests it would only be several hundred RPM and not a 1000 RPM difference.
pereivers mentions exhaust back pressure as being a detriment to the motor's performance and mentions that he's using tuned pipes, but other than that doesn't say much about it. In his photo there is the header of what looks like a tuned pipe. I wonder if his pipe design is what has made his motor perform so poorly. Jennings accounts clearly that if you mess up the design of the pipe you'll cause the motor to perform worse than with a properly configured one, and by inference maybe worse than a modified stock muffler!
Maybe his tach was not working correctly. There is only prop speed data and no thrust data to cross check the RPM data.
diceco
