mastering low throttle on 4 cycles?
07-12-2006, 04:40 AM
#1
mastering low throttle on 4 cycles?
I fly warbirds and have found that very reliable low throttle is my friend yet I can not master this tuneing skill. regardless of my engine size or brand but for those interested I fly Saito , Magnum and OS 4 cycles .
Most recent example is a magnum 52 . 1)Radio is set correctly with full range of throttle control , start engine , advance throttle on radio to full , engine is giving me about 70% , adjust high speed valve inward -increases RPMs but not to max , try opening high speed rpms start to decrease so neither direction gets me the desired results , is it time to adjust the slow setting needle valve ? Tank set up is accurate , OS plug is fresh , engine has about 12 tanks thru the engine ect ect . If i go below the midway setting on the radio engine wants to quit vs where it should be -a slow decending speed to idle to stop (in that order is what I am trying to achieve . [&o]Pleae help its the last stage of my learning curve in the realm of flying warbirds . I have mastered the take offs , landing , flying now in about 10 birds but the skill set is still difficult based on lack of accurate throtle control .
I dont want to take the nest step to Saito 180 until I really feel good in the smaller sizes
Most recent example is a magnum 52 . 1)Radio is set correctly with full range of throttle control , start engine , advance throttle on radio to full , engine is giving me about 70% , adjust high speed valve inward -increases RPMs but not to max , try opening high speed rpms start to decrease so neither direction gets me the desired results , is it time to adjust the slow setting needle valve ? Tank set up is accurate , OS plug is fresh , engine has about 12 tanks thru the engine ect ect . If i go below the midway setting on the radio engine wants to quit vs where it should be -a slow decending speed to idle to stop (in that order is what I am trying to achieve . [&o]Pleae help its the last stage of my learning curve in the realm of flying warbirds . I have mastered the take offs , landing , flying now in about 10 birds but the skill set is still difficult based on lack of accurate throtle control .
I dont want to take the nest step to Saito 180 until I really feel good in the smaller sizes
07-12-2006, 04:53 AM
#2
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RE: mastering low throttle on 4 cycles?
Nothing like an onboard glow for a reliable 4 st idle. Esp with an inverted engine.
http://www.rc-float-flying.rchomepag...ti/switch.html
Set it so it comes in below 1/3 throttle and everything gets easier to set up.
Just do not forget that you have a live engine when turning it over below 1/3 throttle without any external glow clip!
http://www.rc-float-flying.rchomepag...ti/switch.html
Set it so it comes in below 1/3 throttle and everything gets easier to set up.
Just do not forget that you have a live engine when turning it over below 1/3 throttle without any external glow clip!
07-12-2006, 06:32 AM
#3
RE: mastering low throttle on 4 cycles?
Even if you have an onboard glow, you must have the low end set correctly.
You need to have a small access hole in the side of the plane, so you can reach
in there with a long thin hobby screw driver and get to the low speed adjustment.
Get the engine running, and warm it up good.
Leave the glow starter on the engine. With the engine running at a fast idle, reach
in there (carefully) and adjust the low end mixture screw until the engine is
running as fast as it will run at that throttle setting. Run the engine back up to
full throttle and set it. You want to run it up so the engine isn't "loaded up",
If the engine is "loaded up", it will throw off your attempts to get a good idle setting.
Now come back to idle. Don't worry about setting the engine for the slowest
possible idle just yet. Ultimately you want a good reliable idle, and you do not
want the engine to quit on you. You may have to adjust the idle screw a little
from this setting, but do it with 1/8 turn of the screw at a time.
You always want to end up with the mixture just slightly rich. This will ease
in starting the engine, and will keep it running better when the engine is hot
....as opposed to a slightly lean idle mixture where the engine is more likely
to die out. If the engine idle is slightly rich, it should have a decent reliable
transition from idle to full throttle.
Now, this is where an onboard glow system can be of benefit as an insurance
policy. But keep in mind, the engine has to be set correctly in the first place.
If the engine is set too lean, it will die out....remote glow or not. If it is set too
rich, it will run a little longer before it dies out, but it will still die out.
If you use a fuel like PowerMaster 20/20 YS/Saito mix you will get a better idle
than with the 10 or 15% nitro blends. I use the 20% in my Magnums, YS, and
OS four strokes. The Saito's like it too. This higher nitro gives a slightly better
edge, and makes tuning the engines easier too, because they really perform
with the 20%. I always add some castor to the 20/20 fuels as well. This helps
the engines run cooler. Lately, I have just bought the 15% PowerMaster fuels,
and bumped the nitro up to 20% with some straight nitro. It is much cheaper
this way, and I don't have to add the castor oil, it is already in there.
No matter what anyone says, the engines will idle better and perform better
with the 20% nitro.
The OS "F" type plug is still the best plug for all the fourstrokes, and it will give
the best idle as well. There are a couple other plugs that come close, but the OS
is still the best bet. You want to stack all the odds in your favor, to get the best
possible idle.
FBD.
You need to have a small access hole in the side of the plane, so you can reach
in there with a long thin hobby screw driver and get to the low speed adjustment.
Get the engine running, and warm it up good.
Leave the glow starter on the engine. With the engine running at a fast idle, reach
in there (carefully) and adjust the low end mixture screw until the engine is
running as fast as it will run at that throttle setting. Run the engine back up to
full throttle and set it. You want to run it up so the engine isn't "loaded up",
If the engine is "loaded up", it will throw off your attempts to get a good idle setting.
Now come back to idle. Don't worry about setting the engine for the slowest
possible idle just yet. Ultimately you want a good reliable idle, and you do not
want the engine to quit on you. You may have to adjust the idle screw a little
from this setting, but do it with 1/8 turn of the screw at a time.
You always want to end up with the mixture just slightly rich. This will ease
in starting the engine, and will keep it running better when the engine is hot
....as opposed to a slightly lean idle mixture where the engine is more likely
to die out. If the engine idle is slightly rich, it should have a decent reliable
transition from idle to full throttle.
Now, this is where an onboard glow system can be of benefit as an insurance
policy. But keep in mind, the engine has to be set correctly in the first place.
If the engine is set too lean, it will die out....remote glow or not. If it is set too
rich, it will run a little longer before it dies out, but it will still die out.
If you use a fuel like PowerMaster 20/20 YS/Saito mix you will get a better idle
than with the 10 or 15% nitro blends. I use the 20% in my Magnums, YS, and
OS four strokes. The Saito's like it too. This higher nitro gives a slightly better
edge, and makes tuning the engines easier too, because they really perform
with the 20%. I always add some castor to the 20/20 fuels as well. This helps
the engines run cooler. Lately, I have just bought the 15% PowerMaster fuels,
and bumped the nitro up to 20% with some straight nitro. It is much cheaper
this way, and I don't have to add the castor oil, it is already in there.
No matter what anyone says, the engines will idle better and perform better
with the 20% nitro.
The OS "F" type plug is still the best plug for all the fourstrokes, and it will give
the best idle as well. There are a couple other plugs that come close, but the OS
is still the best bet. You want to stack all the odds in your favor, to get the best
possible idle.
FBD.
07-12-2006, 06:46 AM
#4
Senior Member
RE: mastering low throttle on 4 cycles?
LDM, don't misinterpret me, but....how did you ever get to warbirds and not know how to tune an engine?
This trinket, that gizmo, different fuels and a variety of plugs aren't what you need. What you DO need is someone (a qualified someone) to SHOW YOU face to face, and hands-on how to tune the engine. It's that simple. Anything else will prove to be a very costly and frustrating path.
So as to avoid going through another 10 planes in your quest to set the idle, I'd recommend that you enlist the aid of a qualified helper at your local field to help you along.
Good luck with it.
This trinket, that gizmo, different fuels and a variety of plugs aren't what you need. What you DO need is someone (a qualified someone) to SHOW YOU face to face, and hands-on how to tune the engine. It's that simple. Anything else will prove to be a very costly and frustrating path.
So as to avoid going through another 10 planes in your quest to set the idle, I'd recommend that you enlist the aid of a qualified helper at your local field to help you along.
Good luck with it.
07-12-2006, 08:30 AM
#5
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RE: mastering low throttle on 4 cycles?
I agree with RaceCity and disagree with Dave (only about the nitro content- Sorry, Dave!)
My Saito 82 idles reliably @ 1900 RPM all day on Wildcat Jet A (10% nitro, 23% synth/castor blend). When warmed up, I can idle this motor for 2+ minutes, and it will still "snap to" when I hit the throttle, even agressively!
I'm swinging an APC 13x4W prop.
I'm using the Saito "SS" plug that came with the engine.
I actually get compliments on how nicely this motor runs.
This should show you that the fuel that you choose (although it should definitely be of high quality) is actually not the primary factor in the performance of your engine. True, higher nitro content will give you a smoother, more reliable idle... and for inverted applications, you could benefit from onboard glow... but tuning is most important. Get with someone who really knows what they're doing, and you will be pleasantly surprised. [8D]
Just a side note- don't expect the motor to be fully tunable until it is completely broken in. And check your valve lash as per the manual. And troll the engine forums here, they are full of good info. Good luck!
My Saito 82 idles reliably @ 1900 RPM all day on Wildcat Jet A (10% nitro, 23% synth/castor blend). When warmed up, I can idle this motor for 2+ minutes, and it will still "snap to" when I hit the throttle, even agressively!
I'm swinging an APC 13x4W prop.
I'm using the Saito "SS" plug that came with the engine.
I actually get compliments on how nicely this motor runs.
This should show you that the fuel that you choose (although it should definitely be of high quality
) is actually not the primary factor in the performance of your engine. True, higher nitro content will give you a smoother, more reliable idle... and for inverted applications, you could benefit from onboard glow... but tuning is most important. Get with someone who really knows what they're doing, and you will be pleasantly surprised. [8D]Just a side note- don't expect the motor to be fully tunable until it is completely broken in. And check your valve lash as per the manual. And troll the engine forums here, they are full of good info. Good luck!
07-12-2006, 09:43 AM
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RE: mastering low throttle on 4 cycles?
ORIGINAL: LDM
.
Most recent example is a magnum 52 . 1)Radio is set correctly with full range of throttle control , start engine , advance throttle on radio to full , engine is giving me about 70% , adjust high speed valve inward -increases RPMs but not to max , try opening high speed rpms start to decrease so neither direction gets me the desired results , is it time to adjust the slow setting needle valve ? Tank set up is accurate , OS plug is fresh , engine has about 12 tanks thru the engine ect ect . If i go below the midway setting on the radio engine wants to quit vs where it should be -a slow decending speed to idle to stop (in that order is what I am trying to achieve .
.
Most recent example is a magnum 52 . 1)Radio is set correctly with full range of throttle control , start engine , advance throttle on radio to full , engine is giving me about 70% , adjust high speed valve inward -increases RPMs but not to max , try opening high speed rpms start to decrease so neither direction gets me the desired results , is it time to adjust the slow setting needle valve ? Tank set up is accurate , OS plug is fresh , engine has about 12 tanks thru the engine ect ect . If i go below the midway setting on the radio engine wants to quit vs where it should be -a slow decending speed to idle to stop (in that order is what I am trying to achieve .
1. Set the high speed at about 300 RPM below max to the rich side. Use a tach to determine this setting. Very few people can accurately set four stroke engines by ear.
2. Go to idle and do the pinch test on the fuel line going to the carb. A four stroke will react quickly to the pinch test and a two stroke reacts slower to the pinch test. Use a pair of needle nose pliers and keep away from the prop! If the engine immediately speeds up and dies, the engine is to rich at the diel setting; if the engine dies immediately, it is to lean at the idle setting. If the engine runs momentarily and does not speed up, it is adjusted correctly.
a. If the engine speeds up and quits the idle is set to rich.
b. Make an 1/8th turn on the low speed needle adjustment. That would be, if I am correct, to the right (clockwise). This moves the low speed needle inward toward the high speed needle valve. Idles adjustments are always done is small increments -- fine tuning.
c. Run up the engine to max and them back to idle. Do the pinch test again. Continue the pinch test and 1/8th turns until the einge does not speed up during the pinch test. Always run the engine up to max after an adjustment. The low speed needle valve controls the idle and mid range acceleration of the engine. Sometimes after several low speed adjustments, the high speed needle needs to be readjusted a bit.
d. If the pinch test makes the engine quit immediately, then it is too lean and needs to be adjusted counterclock wise outward.
e. If the pinch test at idle lets the engine run momentarily without speeding up, then the idle is adjusted correctly.
Magnum engines will not idle as low as Saito engines. Magnum and OS are about the same with that regard. They idle around 3000 RPM, as they become well broken in, they may idle slightly less. Higher Nitro fuel will result in higher RPMs and lower idle RPMs
Have patience, may take several times to get it done. Don't expect a cold engine to idle at its lowest speed, it needs a bit of warm up.
Cheers,
Chip
07-12-2006, 09:59 AM
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RE: mastering low throttle on 4 cycles?
ORIGINAL: flycfii
I have an OS 52 Surpass that idles @ 2400, this is its first season and I expect to get it down to a 2200 RPM reliable idle on the same 10% Jet A by this fall.
I have an OS 52 Surpass that idles @ 2400, this is its first season and I expect to get it down to a 2200 RPM reliable idle on the same 10% Jet A by this fall.
Cheers,
Chip
07-12-2006, 02:12 PM
#10
RE: mastering low throttle on 4 cycles?
Just 2200 RPM idle? I have done better with slag motors. Well so people tell me.
LOL now the wild claims will come in so I will now refrain.
LOL now the wild claims will come in so I will now refrain.
07-12-2006, 02:20 PM
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RE: mastering low throttle on 4 cycles?
Just to add to what Flyboy Dave instructed: Once you find the lowest idle point with the glow igniter attached, remove igniter and listen to engine. If the engine looses rpm, lean your low-end needle 1/6 of a turn, and continue doing so until there is not a drop in rpm. Works like a charm.
07-12-2006, 03:20 PM
#13
RE: mastering low throttle on 4 cycles?
Sorry Fellas....a new modeler wishing to learn will not learn my having someone
tune his engine....I disagree wholeheartedly. It's learning by trial and error, hands
on....that will be the best teacher. Once he has the formula, which I and others
have given....it is only a matter of applying them in practice on his own engine.
It's not brain surgery. Turn the needle one way, and see the result....turn the
needle the other way, see the result....which one was the best way....which way
did the engine run better ? It's not magic. I learned on my own, so can he. So
can most people. I never used a tach for 30 years until I started running speed
engines, and I had to know what they were turning.
Yo, 'Race....
....gimme a break. 
10 planes ???
He needs to turn the screws himself. If another persons adjusts the engine....even if
he explains what he is doing is not the same as experiencing it for himself. I do have
some experience in this area. I was the Leadman and the Instructor in the Power
Production Shop (small engines) in the Air Force for 11 years. I have the training, and
the experience in "training" people.
Trust me, the next time it is time to tune an engine, he won't have a clue what the
"other guy did". When he turns the screw the right way, and the engine responds
favorably....he will catch on quickly.
FBD.
tune his engine....I disagree wholeheartedly. It's learning by trial and error, hands
on....that will be the best teacher. Once he has the formula, which I and others
have given....it is only a matter of applying them in practice on his own engine.
It's not brain surgery. Turn the needle one way, and see the result....turn the
needle the other way, see the result....which one was the best way....which way
did the engine run better ? It's not magic. I learned on my own, so can he. So
can most people. I never used a tach for 30 years until I started running speed
engines, and I had to know what they were turning.
Yo, 'Race....
This trinket, that gizmo, different fuels and a variety of plugs aren't what you need. What you DO need is someone (a qualified someone) to SHOW YOU face to face, and hands-on how to tune the engine. It's that simple. Anything else will prove to be a very costly and frustrating path.
So as to avoid going through another 10 planes in your quest to set the idle, I'd recommend that you enlist the aid of a qualified helper at your local field to help you along.
So as to avoid going through another 10 planes in your quest to set the idle, I'd recommend that you enlist the aid of a qualified helper at your local field to help you along.
10 planes ???He needs to turn the screws himself. If another persons adjusts the engine....even if
he explains what he is doing is not the same as experiencing it for himself. I do have
some experience in this area. I was the Leadman and the Instructor in the Power
Production Shop (small engines) in the Air Force for 11 years. I have the training, and
the experience in "training" people.
Trust me, the next time it is time to tune an engine, he won't have a clue what the
"other guy did". When he turns the screw the right way, and the engine responds
favorably....he will catch on quickly.
FBD.
07-12-2006, 03:31 PM
#14
RE: mastering low throttle on 4 cycles?
I think it would work, if the owner tunes it, and the experianced "help". Tells him what to do and what he did wrong. You don't learn to fly an airplane by trial and error, so I don't think that this is alway's the best training method. In fact the trail and error method gives lots of people weird ideas in their heads from trying to reason why this works or does not work.
07-12-2006, 07:19 PM
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RE: mastering low throttle on 4 cycles?
ORIGINAL: Fuelman
Well FlyBoyDave, I should have been a little clearer.
What I was inferring was that he get tought by a local engine tuner, not have him do it.
Well FlyBoyDave, I should have been a little clearer.
What I was inferring was that he get tought by a local engine tuner, not have him do it.
Cheers,
Chip
07-12-2006, 08:10 PM
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RE: mastering low throttle on 4 cycles?
I too swear by the pintch test. But one more step. Once you get to the point were a good pinch doesn't change the RPM richen the low end about a 1/4 turn. if you don't it'll die on final approch becuase there is less head pressure in the tank
07-12-2006, 08:20 PM
#18
RE: mastering low throttle on 4 cycles?
Fkyboy , Chip , thanks good factual info , i will print this info and go to work . To answer one question "how do you get to warbirds and still are learning to tune low engine throttle" , you coach hockey travel in your spare time (whats left lol ) so you fly alone ,no time for a club , become a damm good flyer and you never call yourself an expert at anything so you are always learning .
Thanks for all the comments , the tips are excellant .Please keep them coming
Thanks for all the comments , the tips are excellant .Please keep them coming
07-12-2006, 09:35 PM
#19
RE: mastering low throttle on 4 cycles?
LDM- what Flyboy is suggesting isn't exactly being on your own with trial and error. You can here and got good advice. Big difference. If you remember what FBD is telling you it will go fine. Just be patient with the low speed needle valve. There is a point where it is just right. You may need quite a few more tanks of fuel burned in the engine before it is totally broken in...which means that you will have to fine tune the settings along the way as it progresses in the break in period.
You should develop an ear for that engine.....
You should develop an ear for that engine.....
07-12-2006, 09:48 PM
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RE: mastering low throttle on 4 cycles?
LDM
One more thing to think about. If you have too large of a prop (either diameter or pitch) than your engine can pull, you will tend to set the high end too rich to compensate. This can make it hard to get a reliable idle. I do not run your engine, so I wouldn't suggest the actual prop size to try, but if all else fails, try a smaller prop just to see what happens.
Sandy T
One more thing to think about. If you have too large of a prop (either diameter or pitch) than your engine can pull, you will tend to set the high end too rich to compensate. This can make it hard to get a reliable idle. I do not run your engine, so I wouldn't suggest the actual prop size to try, but if all else fails, try a smaller prop just to see what happens.
Sandy T
07-12-2006, 10:06 PM
#21
Senior Member
RE: mastering low throttle on 4 cycles?
Another fine suggestion, and another vote for having a local "guru" take a look-see to get you on your way. Too many variables involved in the grand scheme of things to do otherwise.
Gives me an idea though....
Watch for my "Engine Tuning DVD" series....available soon at a store near you. Just like those Sally Struthers things where you can learn high demand, valuable skills like VCR repair...Birdhouse making, and Envelope licking, all in your SPARE TIME, and NEVER set foot in a classroom! There's no need to go out to a bug infested flying field, when you too can become an expert r/c engine tuner in the comfort of your own home, office or car!!!
It's a million dollar idea...
Hobbico? Horizon? The idea is available to you at a very reasonable cost....
<GGGG>
Gives me an idea though....
Watch for my "Engine Tuning DVD" series....available soon at a store near you. Just like those Sally Struthers things where you can learn high demand, valuable skills like VCR repair...Birdhouse making, and Envelope licking, all in your SPARE TIME, and NEVER set foot in a classroom! There's no need to go out to a bug infested flying field, when you too can become an expert r/c engine tuner in the comfort of your own home, office or car!!!
It's a million dollar idea...
Hobbico? Horizon? The idea is available to you at a very reasonable cost....
<GGGG>
07-13-2006, 03:57 AM
#22
RE: mastering low throttle on 4 cycles?
Thanks guys , funny thing there a free on demand vid on DYI with Chris Chinnelli and tuneing engines . My problem is that in the beginging of my RC experience I was told to advoid adjusting anything but the high speed needle valve , the rest is set at the factory .As we all know weather , and many other conditions can effect engine performance so I muddeled my way thru . This is great info , thanks again .
07-13-2006, 08:35 AM
#23
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RE: mastering low throttle on 4 cycles?
ORIGINAL: LDM
Thanks guys , funny thing there a free on demand vid on DYI with Chris Chinnelli and tuneing engines . My problem is that in the beginging of my RC experience I was told to advoid adjusting anything but the high speed needle valve , the rest is set at the factory .As we all know weather , and many other conditions can effect engine performance so I muddeled my way thru . This is great info , thanks again .
Thanks guys , funny thing there a free on demand vid on DYI with Chris Chinnelli and tuneing engines . My problem is that in the beginging of my RC experience I was told to advoid adjusting anything but the high speed needle valve , the rest is set at the factory .As we all know weather , and many other conditions can effect engine performance so I muddeled my way thru . This is great info , thanks again .
---------------
You came to the right place for help, LDM. That was a smart move on your part.
I don't know your circumstances, but having a test bench made of a sawhorse and some kind of specialized mount that will accept varying engine sizes is a good start to mastering these beasts. Even if you have to cart the mess to the field to run the engines. At least the pressure is off in that if you make a mistake, your model isn't crashing. This is where to learn to tune engines. Believe it or not, this practice can become a hobby in and of itself. Plus, once you have mastered things, you can be proud when your engines are running perfectly at the field and everyone else spends all of their time tinkering. Good luck. Oh, a WorkMate works well for this use too and is more portable.
07-13-2006, 08:37 AM
#24
Senior Member
My Feedback: (14)
RE: mastering low throttle on 4 cycles?
ORIGINAL: LDM
Thanks guys , funny thing there a free on demand vid on DYI with Chris Chinnelli and tuneing engines . My problem is that in the beginging of my RC experience I was told to advoid adjusting anything but the high speed needle valve , the rest is set at the factory .As we all know weather , and many other conditions can effect engine performance so I muddeled my way thru . This is great info , thanks again .
Thanks guys , funny thing there a free on demand vid on DYI with Chris Chinnelli and tuneing engines . My problem is that in the beginging of my RC experience I was told to advoid adjusting anything but the high speed needle valve , the rest is set at the factory .As we all know weather , and many other conditions can effect engine performance so I muddeled my way thru . This is great info , thanks again .
---------------
You came to the right place for help, LDM. That was a smart move on your part.
I don't know your circumstances, but having a test bench made of a sawhorse and some kind of specialized mount that will accept varying engine sizes is a good start to mastering these beasts. Even if you have to cart the mess to the field to run the engines. At least the pressure is off in that if you make a mistake, your model isn't crashing. This is where to learn to tune engines. Believe it or not, this practice can become a hobby in and of itself. Plus, once you have mastered things, you can be proud when your engines are running perfectly at the field and everyone else spends all of their time tinkering. Good luck. Oh, a WorkMate works well for this use too and is more portable.