Engine tuning
03-25-2004, 04:33 PM
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Engine tuning
Guys,
what exactly should I do with a new engine before flying a plane with it. I mean how to tune/tweak it? I haven't bought one yet but I think it is going to be a Thunder Tiger .46 or something very similar. Also, the prop should be balanced, right? How?
Thanks.
what exactly should I do with a new engine before flying a plane with it. I mean how to tune/tweak it? I haven't bought one yet but I think it is going to be a Thunder Tiger .46 or something very similar. Also, the prop should be balanced, right? How?
Thanks.
03-25-2004, 05:06 PM
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RE: Engine tuning
First suggestion is to read the manual for the engine THOROUGHLY! It will be chocked full of very useful info and diagrams that could make your first attempts at tuning the engine much easier. Also, if possible, have someone else with experience listen to the motor and make adjustments if necessary. Just make sure you get them to explain why they did what they did. Learning to start the engine is just the beginning, you must then learn to adjust the needle valve and sometimes be able to distiguish certain sounds from the engine as you adjust. Again the engine manual will be very helpful in this area.
As for prop balancing, if you can't get your hands on a prop balancer, just put a nail, screwdriver, pencil or other object of that nature through the shaft hole and hold it level. If one side of the prop continually drops to the bottom you have two choices. One, either sand off some of the heavy side. Or two, add some weight to the lighter side. I use the second option. The weight is added by spraying layers of clearcoat model spraypaint (available in most WMarts) to the lighter side until both sides sit level.
As for prop balancing, if you can't get your hands on a prop balancer, just put a nail, screwdriver, pencil or other object of that nature through the shaft hole and hold it level. If one side of the prop continually drops to the bottom you have two choices. One, either sand off some of the heavy side. Or two, add some weight to the lighter side. I use the second option. The weight is added by spraying layers of clearcoat model spraypaint (available in most WMarts) to the lighter side until both sides sit level.
03-25-2004, 07:46 PM
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RE: Engine tuning
I agree, read the manual but never tweak the engine. The engine would be adjusted and run at the factory. Just fly it as is. You should not have to adjust it until after many gallons of gas.
03-25-2004, 09:00 PM
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RE: Engine tuning
Wait, what do you mean, do not adjust the engine?? Each time me or somebody else here on the board asks why he needs an instructor, the first answer is always: "An instructor knows how to tune the engine." I assumed that tuning the engine is a must.
03-25-2004, 09:13 PM
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RE: Engine tuning
Sorry, thought you were talking about a gas engine.
For glow engines, yes, you need to adjust the engine.
For glow engines, yes, you need to adjust the engine.
ORIGINAL: kukarzev
Wait, what do you mean, do not adjust the engine?? Each time me or somebody else here on the board asks why he needs an instructor, the first answer is always: "An instructor knows how to tune the engine." I assumed that tuning the engine is a must.
Wait, what do you mean, do not adjust the engine?? Each time me or somebody else here on the board asks why he needs an instructor, the first answer is always: "An instructor knows how to tune the engine." I assumed that tuning the engine is a must.
03-26-2004, 01:19 AM
#6
RE: Engine tuning
I use this method when I was learning and it's a good way to start out learning to tune your engine.
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
03-26-2004, 11:42 AM
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RE: Engine tuning
Dauntae,
Thanks a million -- sounds like good method. I'm a newbie who is getting his first instruction session this Sunday, but I have been playing with my Tower .46 in my trainer, because I feel that being competent in starting the engine and tuning it is as important as the flying side of things. I have gotten the top end all tuned out to the point of being lean when tilted upward, and then richened it back up a tad. I can get it to idle down super low without the glowplug, but open up the throttle to WOT, and it hesitates through the midrange and takes about 5-7 seconds to finally hit max RPM. Once I have it at max, I can back down to half throttle or 3/4 and then back to full without the hesitation. It only hesitates after its sat at idle for a few seconds.
From your instruction above it sounds that it's idling rich to me, am I following everything correctly?
Thanks a million -- sounds like good method. I'm a newbie who is getting his first instruction session this Sunday, but I have been playing with my Tower .46 in my trainer, because I feel that being competent in starting the engine and tuning it is as important as the flying side of things. I have gotten the top end all tuned out to the point of being lean when tilted upward, and then richened it back up a tad. I can get it to idle down super low without the glowplug, but open up the throttle to WOT, and it hesitates through the midrange and takes about 5-7 seconds to finally hit max RPM. Once I have it at max, I can back down to half throttle or 3/4 and then back to full without the hesitation. It only hesitates after its sat at idle for a few seconds.
From your instruction above it sounds that it's idling rich to me, am I following everything correctly?
03-26-2004, 12:13 PM
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RE: Engine tuning
Dauntae: .....
I will probably create a new thread but still... can you describe how to connect and adjust servos on a four-channel
model (BUHOR). All I know now is that ailerons must be level with the bottom of the wing or lean down a little.
Thanks!
03-27-2004, 01:20 PM
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RE: Engine tuning
I would recommend that all glow engines be set rich initially. That way as fuel is consumed, the engine will run leaner and you must have enough fuel flowing to keep it rich. No engine has been damaged from a rich run.
03-27-2004, 07:21 PM
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RE: Engine tuning
i just have one thing to add to dauntea's post. i always run the engine up for a minute or so to get it to opperating temperature. dont just start the engine and start tuning right away.
03-27-2004, 08:17 PM
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RE: Engine tuning
adrenaljunky, did you break in your engine first??? You can not run it peak without first breaking the engine in. when an engine is new, you need to run the engine for a bit to make all the parts wear into each other. if this is not done correctly, you can wear them too much and drastically shorten your engine life. read your manual, it will give you the best way recommended for break in the engine.
sean
sean
04-23-2004, 04:46 AM
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RE: Engine tuning
Dauntae,
I read your suggestion and found it very informative.
However, you did not mention if you were tuning your engine on a full fuel tank or half.
Will it make a difference?
Thanks.
I read your suggestion and found it very informative.
However, you did not mention if you were tuning your engine on a full fuel tank or half.
Will it make a difference?
Thanks.
06-28-2004, 04:42 PM
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RE: Engine tuning
Leave the low speed needle alone when you first fire up a new engine. They are (as a a rule of thumb) fairly close from the factory. Get your high speed needle set first, following the above suggestions. Then set your idle. Close the throttle. Let it idle. If it slows down and dies, it's too rich. Turn the idle needle in a tiny bit. Speeds up and dies, too lean. Back the needle out slightly. Turn it 1/16th to 1/8th turn at a time. Keep it up 'til you get a steady idle. It rarely takes me more than 3-4 tries to get close enough to fly. Then it can be fine tuned a little if it still needs it.
Plus, take your time and run the engine for a bunch of short runs. Two minutes at first, gradually extending them to 7-8 minutes. Let it cool 10-12 minutes in between. Do that cycle as much as twenty times. I know that it's a lot, but an engine heat cycled this way, run a little on the rich side, and fed fuel with 20-22% oil (at least a little of it castor) should never wear out and give you first flip starts every time.
Even the instructions with a lot of engines basically say, run a tank through it and go fly. But they are in the business of selling engines.......Break one in right, and you'll be amazed at how friendly and dependable it'll be.
Plus, take your time and run the engine for a bunch of short runs. Two minutes at first, gradually extending them to 7-8 minutes. Let it cool 10-12 minutes in between. Do that cycle as much as twenty times. I know that it's a lot, but an engine heat cycled this way, run a little on the rich side, and fed fuel with 20-22% oil (at least a little of it castor) should never wear out and give you first flip starts every time.
Even the instructions with a lot of engines basically say, run a tank through it and go fly. But they are in the business of selling engines.......Break one in right, and you'll be amazed at how friendly and dependable it'll be.
06-28-2004, 05:36 PM
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RE: Engine tuning
Thanks for the reply. I hear what you say (so to speak) but I'm fooling around with a new engine and a used carb, so I still don't know what to start with. I'll get there eventually.
06-30-2004, 07:07 AM
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RE: Engine tuning
ORIGINAL: Dauntae
I use this method when I was learning and it's a good way to start out learning to tune your engine.
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
I use this method when I was learning and it's a good way to start out learning to tune your engine.
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
Hi,
may I know where is the low speed needle located in the thunder tiger .46 PRO series engine?
Thanks
06-30-2004, 09:50 AM
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RE: Engine tuning
ORIGINAL: falcon_5
Hi,
may I know where is the low speed needle located in the thunder tiger .46 PRO series engine?
Thanks
Hi,
may I know where is the low speed needle located in the thunder tiger .46 PRO series engine?
Thanks
dano13
06-30-2004, 10:32 AM
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RE: Engine tuning
Just to reiterate what steener said, make sure you let the engine run and heat up to a stable operating temperature before you start futzing with the needles. It's not such an issue on hot days, but particularly in colder temperatures, prematurely playing with the mixture can often lead to misleading behaviour as the engine often hasn't fully warmed up.
That said, take your time and follow Dauntae's excellent instructions and you won't go too far wrong.
That said, take your time and follow Dauntae's excellent instructions and you won't go too far wrong.
08-12-2006, 11:12 PM
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RE: Engine tuning
Dauntae
Thanks for the good explanation of the low end tuning process.
I have a Thunder Tiger .61 GP that has an air-bleed carb.
Most descriptions of this type of carb say to start out with the screw half out or one half of the hole open. This setting doe not seem to work on the TT .61. I checked the specs listed in the Tower website for this motor. The last spec seems to say not leave a gap but have the hole closed. I tried this today and it did seem to improve the idle but it still does not seem to idle too great but at least it does not die on landing approach. I have only been able to get the idle down to about 3500 RPM on idle. Can you add anything to this.
AWL
Thanks for the good explanation of the low end tuning process.
I have a Thunder Tiger .61 GP that has an air-bleed carb.
Most descriptions of this type of carb say to start out with the screw half out or one half of the hole open. This setting doe not seem to work on the TT .61. I checked the specs listed in the Tower website for this motor. The last spec seems to say not leave a gap but have the hole closed. I tried this today and it did seem to improve the idle but it still does not seem to idle too great but at least it does not die on landing approach. I have only been able to get the idle down to about 3500 RPM on idle. Can you add anything to this.
AWL
08-13-2006, 07:49 AM
#20
Senior Member
RE: Engine tuning
One detail that's not been mentioned...............
The first run of the day, ALWAYS, when you get the engine started, go to full throttle and immediately click the needle out until you get a rich run. Then turn it back in to wherever you think it ought to run while warming up. You always want to insure that it's "rich enough" and you shouldn't bet that the setting from whenever it was run last will be good for that day. And you shouldn't bet that the needle hasn't been twiddled with since that last flying session.
It's a good idea to NEVER lean the engine out the first time you touch it. Always turn it out to be sure that slows the rpms. That proves the needle is being adjusted from the safe direction (safe for the engine) and the engine won't start out cold and too lean.
The first run of the day, ALWAYS, when you get the engine started, go to full throttle and immediately click the needle out until you get a rich run. Then turn it back in to wherever you think it ought to run while warming up. You always want to insure that it's "rich enough" and you shouldn't bet that the setting from whenever it was run last will be good for that day. And you shouldn't bet that the needle hasn't been twiddled with since that last flying session.
It's a good idea to NEVER lean the engine out the first time you touch it. Always turn it out to be sure that slows the rpms. That proves the needle is being adjusted from the safe direction (safe for the engine) and the engine won't start out cold and too lean.
08-13-2006, 07:55 AM
#21
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RE: Engine tuning
The engine behavior is not dependent on the type of carb, only the rich/lean mixture. Air bleed carbs can be VERY sensitive to small adjustments. Starting with the hole 1/2 blocked is usually a good place to start.
What fuel and prop are you using? I have a GP-61 using a 13x4 APC, and it turns at 13,000 RPM and idles well around 2750 with Omega 15.
To check your idle mixture, start the engine, then at full throttle, adjust the high speed valve to peak RPM less 300-500 rpm to the rich side. Now reduce throttle to your lowest reliable idle. Let the engine idle for about 30 seconds, then punch the throttle to full. If the engine hesitates, then goes to full throttle, the low speed mixture is rich. If it goes to full throttle without hesitation, your done. If it just dies, your low end is lean. An alternative check is to pinch the fuel line. If there is a slight rise in RPM when you pinch it, your rich. If it dies immediately your lean. If it continues to run for a few seconds without RPM rising, your close. Use both tests.
Now based on your results, you can make a small adjustment in your low end needle. Remember with an airbleed carb, turning the screw out will LEAN the mixture, and vice versa. Make your adjustments in 1/8 turn increments. Then you MUST reset the high speed needle as before and repeat.
Take your time. It might take a few tries to get it dialed in, but once you get it, you'll never have to mess with it again.
Good Luck.
Brad
What fuel and prop are you using? I have a GP-61 using a 13x4 APC, and it turns at 13,000 RPM and idles well around 2750 with Omega 15.
To check your idle mixture, start the engine, then at full throttle, adjust the high speed valve to peak RPM less 300-500 rpm to the rich side. Now reduce throttle to your lowest reliable idle. Let the engine idle for about 30 seconds, then punch the throttle to full. If the engine hesitates, then goes to full throttle, the low speed mixture is rich. If it goes to full throttle without hesitation, your done. If it just dies, your low end is lean. An alternative check is to pinch the fuel line. If there is a slight rise in RPM when you pinch it, your rich. If it dies immediately your lean. If it continues to run for a few seconds without RPM rising, your close. Use both tests.
Now based on your results, you can make a small adjustment in your low end needle. Remember with an airbleed carb, turning the screw out will LEAN the mixture, and vice versa. Make your adjustments in 1/8 turn increments. Then you MUST reset the high speed needle as before and repeat.
Take your time. It might take a few tries to get it dialed in, but once you get it, you'll never have to mess with it again.
Good Luck.
Brad
08-13-2006, 07:59 AM
#22
Senior Member
RE: Engine tuning
awleder,
Try the pinch test and set the airbleed from what it tells you.
First off make sure the hole isn't gummed up.
To pinch test, first run the engine with the throttle open to clear out any excess fuel. Then let it idle about a minute. Adjust the TX setting to get your lowest idle before you do all this.
After it's run at it's lowest idle for about a minute, pinch the fuel deliver line completely. Stop the fuel flow.
If the engine speeds up just before dying, then it was running too rich. With an airbleed carb, to lean out the idle mixture you need more air going through the airbleed. Turn the airbleed screw to open the hole. repeat the test with the new setting.
Try the pinch test and set the airbleed from what it tells you.
First off make sure the hole isn't gummed up.
To pinch test, first run the engine with the throttle open to clear out any excess fuel. Then let it idle about a minute. Adjust the TX setting to get your lowest idle before you do all this.
After it's run at it's lowest idle for about a minute, pinch the fuel deliver line completely. Stop the fuel flow.
If the engine speeds up just before dying, then it was running too rich. With an airbleed carb, to lean out the idle mixture you need more air going through the airbleed. Turn the airbleed screw to open the hole. repeat the test with the new setting.
08-13-2006, 08:04 AM
#23
Senior Member
RE: Engine tuning
Oh yeah, if stopping the fuel flow results in the engine just idling awhile and shutting off suddenly, it's best to richen up the idle and test until you actually get the pinch test to show your setting is too rich. THEN lean that lowspeed back a click or two.
You know how everyone always advises that you run your highspeed needle a couple of clicks richer than the peak rpm setting on the ground? The idea is that the engine is going to run higher rpm in the air and is going to need more fuel when at flying speed. Same is true with the low speed needle/airbleed setting.
You know how everyone always advises that you run your highspeed needle a couple of clicks richer than the peak rpm setting on the ground? The idea is that the engine is going to run higher rpm in the air and is going to need more fuel when at flying speed. Same is true with the low speed needle/airbleed setting.
08-13-2006, 11:08 AM
#24
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RE: Engine tuning
... can you describe how to connect and adjust servos on a four-channel
model (BUHOR). All I know now is that ailerons must be level with the bottom of the wing or lean down a little.
Thanks!
model (BUHOR). All I know now is that ailerons must be level with the bottom of the wing or lean down a little.
Thanks!
08-13-2006, 11:51 AM
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RE: Engine tuning
ORIGINAL: Dauntae
I use this method when I was learning and it's a good way to start out learning to tune your engine.
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
I use this method when I was learning and it's a good way to start out learning to tune your engine.
Here's a scenario: Pilot takes off, plane's engine sounds great. After several minutes of flying, engine seems to lose power, sounds kinda "thin", pilot keeps flying. Engine continues to sag, now full throttle is very weak, pilot now understands that maybe this isn't gonna clear up. Engine dies (what a shock! ), pilot calls for "deadstick" landing overshoots, tears off landing gear, etc. Never seen this at your field, right?
Here's the way that *I* set mixture on non-airbleed carbed engines (90% of the engines out there fit this category, but the theory is similar for air-bleed carbs). First of all, understand that the high speed needle has its main effect from 3/4 to full throttle, and the low speed needle controls everything from idle up to 3/4 throttle. It thus makes sense to me to spend the biggest majority of my tuning time adjusting the needle that controls the largest portion of engine running, right? Also, remember that there is a proper air to fuel ratio (mixture) that allows the engine to run properly. Too much fuel is rich, and too little fuel is lean. We "richen" the mixture by adding more fuel (turning the needle out, or counter-clockwise), and we "lean the mixture out" by decreasing the fuel (turning the needle valve in, or clockwise).
I start the engine give it full throttle, and lean it to it's highest rpm (peak), then richen it by maybe a quarter turn. Then with the glow plug igniter still attached, I slowly close the throttle to an idle rpm. At the lowest rpm that the engine will still reliably run, I then remove the glow igniter. If the engine dies immediately, I know it's too rich, and I then lean out the LOW SPEED NEEDLE by 1/8th of a turn (don't touch the high speed needle). Start the engine again, (and this is important) give FULL throttle briefly to clear out excess fuel, then slowly close the throttle again. Remove the glow igniter, and this time it may run a little longer before it dies, so lean the low speed another 1/8th turn. Re-fire the engine, give a burst of full throttle to clear it out, and slowly close the throttle again. remove the glow igniter and now notice that the rpm DROPPED a bit when you removed the glow igniter, but the engine kept running. We're getting there. It's still too rich, and you'll prove that by opening up the throttle and hearing the engine "blubber" then die. That's because excess fuel has collected in the crankcase during the rich idle, and when you opened up the throttle, the excess was pulled into the cylinder, making it WAY too rich. Supposed you were on a landing approach, and decided to go around, you throttle up but the engine "blubbers" and then dies (another thing we haven't seen, right?). Yep, the LOW SPEED needle was still too rich, allowing excess fuel to collect in the crankcase, just WAITING on you to try to go around so it could "LOAD UP", blubber, and die!
Keep leaning the low speed needle down until it idles well, but now, when you open up the throttle, it HESITATES instead of BLUBBERS. When this happens, you've lean it down too far, so richen it up 1/16th of a turn and try again. You know you've got the LOW SPEED needle right when you can fire it up, remove the glow igniter, and the rpm doesn't change AT ALL, and you can open the throttle up, and it doesn't blubber or hesitate, it just runs!
The final thing you do is re-adjust the HIGH SPEED NEEDLE, leaning it to it's highest rpm (peak) and then richening it up maybe 1/8th turn to give it a slightly rich mixture. We also know that the fuel mixture will change in flight when you point the nose up (harder for fuel to travel uphill) and also as the fuel level in the tank changes. In both cases, a leaner mixture results, so we actually need to set the mixture a bit further on the rich side to account for this. While the engine is running at full throttle, CAREFULLY pick the model up and raise the nose to at least a 45 degree angle while listening to the engine. If the engine sags a bit, then you'll need to richen up the high speed needle 1/16th turn. Try it again, and when you can point the nose up and the engine doesn't sag, but maybe shows a slight GAIN in rpm, you know you've got it right.
Now the engine will be happy, and chances are will reward you with reliable running. If you've got one of the few engines with an air bleed adjustment for low speed adjustment, the theory is the same, just refer to your manual to see how to richen and lean the low speed mixture.
Hope this helped
Dauntae
_________________
I used to think that the world was crazy and I was the only one sane... I now realize I am crazy and the world is sane but that's ok...The world will adjust!!!!
I found this before in a much older thread. I was so impressed with it that I saved it, then ran off copies of it for myself & a few friends that we now keep in our flight boxes so we have it to referr to while at the field & tuning on an engine. Just wanted to say thanks for taking the time to offer up such a detailed report in a way that we can all understand. I really appreciate it!! As I am sure many others do too.
Well Done!