Engine tuning?
01-07-2010, 09:40 PM
#2
Senior Member
My Feedback: (15)
Join Date: Sep 2003
Location: va beach,
VA
Posts: 715
Likes: 0
Received 0 Likes
on
0 Posts
RE: Engine tuning?
That depends on what engine you are talking about, but I think most 2 cycles start with the high speed needle 2 turns out. You always get the high speed needle adjusted before messing with the low speed adjustment. After the engine is broken in well I use my trim on my radio to set the idle I want and to shut the engine down if need.
01-07-2010, 11:11 PM
#4
Senior Member
RE: Engine tuning?
Basically tuning most all engines is about the same. To begin engine must be broken in by running (preferrably on the bench). Depending on engine this can be done in just a few tankfuls. This though will differ if it's a ringed engine which will take far longer. Once broken in start by leaning high speed needle to get max rpm then back off a bit. Next bring it to idle, it should run fine but if not you may have to adjust low speed needle. Do this with only slight adjustments. If there is an improvement readjust the high speed needle again since low and high do interact to a degree. If all is well now go from idle to high and see what it does. should do fine but if it quits low is probably too lean. If gurgles and hesitates going to high, low is too rich. You want a oerfecly smooth transision. Usually all this is not difficult but does take some practise to define what needs doing. Once you think you have it right then put in plane and check there could be needing slight readjustment due to tank location etc. final test is when running at full throttle carefully raise nose straight up if it leans some open high speed slightly .
01-08-2010, 01:28 AM
#5
Senior Member
Join Date: Sep 2009
Location: berlin, NL, BHUTAN
Posts: 603
Likes: 0
Received 0 Likes
on
0 Posts
RE: Engine tuning?
Generally speaking, close the main needle and open it 2, or 2 and a half turns. Be careful when closing the main needle as closing it too hard can damage internal parts and you'll have real problems, you may have to buy a new main needle if it gets damaged.Start the engine and keep a close eye on the temperature. I usually keep the temp around 190 and 210 degrees. Buy a temp gun, It'll be worth every penny. The temp should never read 250, 230 atthe most if you wantthe engineto last.
Run several tanks through the engine whilekeeping an eye on the temp. The quicker the throttle response, the more it's being broke-in, or running-in as some call it. As you notice the engine being broke-in, give theengine full throttleand turn the main needle clock-wise until the highest rpm is reached and immediately turn the main needle counter-clockwise until you hear a decrease in rpm, that tells you it hasthe right air/ fuel mixture.
Next, give the engine full throttle andpoint the aircraft upward and downward 30 degrees and listen for increases, or decrease in rpm. Slight decreases, or increases is ok, if the engine stops running, the low speed set screw on the carberator needs to be adjusted richer, or leaner, thats all....
Keep in mind, engines run richer on a stand still, or on the ground, because of prop pressureand run leaner in the air,.Stay on the rich side until you gain experience.
Run several tanks through the engine whilekeeping an eye on the temp. The quicker the throttle response, the more it's being broke-in, or running-in as some call it. As you notice the engine being broke-in, give theengine full throttleand turn the main needle clock-wise until the highest rpm is reached and immediately turn the main needle counter-clockwise until you hear a decrease in rpm, that tells you it hasthe right air/ fuel mixture.
Next, give the engine full throttle andpoint the aircraft upward and downward 30 degrees and listen for increases, or decrease in rpm. Slight decreases, or increases is ok, if the engine stops running, the low speed set screw on the carberator needs to be adjusted richer, or leaner, thats all....
Keep in mind, engines run richer on a stand still, or on the ground, because of prop pressureand run leaner in the air,.Stay on the rich side until you gain experience.
01-08-2010, 08:02 AM
#6
Senior Member
My Feedback: (1)
Join Date: Sep 2004
Location: FrederickMD
Posts: 2,114
Likes: 0
Received 0 Likes
on
0 Posts
RE: Engine tuning?
Buy a temp gun, It'll be worth every penny. The temp should never read 250, 230 at the most if you want the engine to last.
High speed needle settings vary as well depending on temperature, altitude, humidity, etc, but in my experience 2-2 1/2 turns is extremely rich. Most of my engines have ended up between 1 and 1-1/2 turns out. Your setting will be determined by starting the engine, warming it up, setting the needle to peak RPM and then richening it until you hear a slight drop (200-500 rpm if you're using a tachometer).
After a few tanks, you'll begin adjusting the low speed needle, and this is where you tell the difference between someone who knows how to tune and engine and someone that doesn't. Throttle transition is the real test you're looking for on the low speed, because that's the performance you're looking for. You can tell if you're close with pinch tests at low speed, but good transition and smooth, low idle are more sensitive, in my experience.
With the plane warmed up and the high speed needle set as previously described, bring the throttle down to your lowest reliable idle. Listen carefully for the next 30-60 seconds. Does the idle speed increase or decrease while your waiting? If it does, you're slightly off, but you can't really tell which direction yet. Punch the throttle to full. If the engine hesitates or burbles, then spins up to full throttle, you're low end is rich. If it hesitates and then dies, you're low end is probably a little lean. Make a SMALL adjustment to the low end (1/8 turn or less) and repeat this procedure, including resetting the high speed needle. If after 3-4 adjustments (1/2 turn total) you're not seeing any improvement, return to your original setting and go the other direction. Go a full turn if necessary this time, but again, if no improvement, return to the original setting. Keep working this way until you get a smooth transition, and a steady, low (2500 rpm or less) idle speed.
Brad
01-08-2010, 09:01 AM
#7
Join Date: Dec 2001
Location: Upplands Vasby, SWEDEN
Posts: 7,816
Likes: 0
Received 3 Likes
on
3 Posts
RE: Engine tuning?
Hi!
You set every engine by ear! simple as that!
That's how racers do it that way as well as sport fliers. There isn't any better (exact) way of doing it!The human ear (and brain) is wonder full thing.
If you cannot hear 100-200rpm difference ...you can use a tach.
A temp gun isn't used at all for setting engines. They are however sometimes used in R/C car racing for checking head temperatures.
You set every engine by ear! simple as that!
That's how racers do it that way as well as sport fliers. There isn't any better (exact) way of doing it!The human ear (and brain) is wonder full thing.
If you cannot hear 100-200rpm difference ...you can use a tach.
A temp gun isn't used at all for setting engines. They are however sometimes used in R/C car racing for checking head temperatures.
01-08-2010, 12:43 PM
#8
Senior Member
Join Date: Sep 2009
Location: berlin, NL, BHUTAN
Posts: 603
Likes: 0
Received 0 Likes
on
0 Posts
RE: Engine tuning?
ORIGINAL: bkdavy
Where in tarnation did you get this spec from? I've never seen anyone use a temp gun on an airplane, mostly because with a prop spinning between 11,000 and 13,000 RPM its darn near impossible to get a correct reading.
High speed needle settings vary as well depending on temperature, altitude, humidity, etc, but in my experience 2-2 1/2 turns is extremely rich. Most of my engines have ended up between 1 and 1-1/2 turns out. Your setting will be determined by starting the engine, warming it up, setting the needle to peak RPM and then richening it until you hear a slight drop (200-500 rpm if you're using a tachometer).
After a few tanks, you'll begin adjusting the low speed needle, and this is where you tell the difference between someone who knows how to tune and engine and someone that doesn't. Throttle transition is the real test you're looking for on the low speed, because that's the performance you're looking for. You can tell if you're close with pinch tests at low speed, but good transition and smooth, low idle are more sensitive, in my experience.
With the plane warmed up and the high speed needle set as previously described, bring the throttle down to your lowest reliable idle. Listen carefully for the next 30-60 seconds. Does the idle speed increase or decrease while your waiting? If it does, you're slightly off, but you can't really tell which direction yet. Punch the throttle to full. If the engine hesitates or burbles, then spins up to full throttle, you're low end is rich. If it hesitates and then dies, you're low end is probably a little lean. Make a SMALL adjustment to the low end (1/8 turn or less) and repeat this procedure, including resetting the high speed needle. If after 3-4 adjustments (1/2 turn total) you're not seeing any improvement, return to your original setting and go the other direction. Go a full turn if necessary this time, but again, if no improvement, return to the original setting. Keep working this way until you get a smooth transition, and a steady, low (2500 rpm or less) idle speed.
Brad
Buy a temp gun, It'll be worth every penny. The temp should never read 250, 230 at the most if you want the engine to last.
High speed needle settings vary as well depending on temperature, altitude, humidity, etc, but in my experience 2-2 1/2 turns is extremely rich. Most of my engines have ended up between 1 and 1-1/2 turns out. Your setting will be determined by starting the engine, warming it up, setting the needle to peak RPM and then richening it until you hear a slight drop (200-500 rpm if you're using a tachometer).
After a few tanks, you'll begin adjusting the low speed needle, and this is where you tell the difference between someone who knows how to tune and engine and someone that doesn't. Throttle transition is the real test you're looking for on the low speed, because that's the performance you're looking for. You can tell if you're close with pinch tests at low speed, but good transition and smooth, low idle are more sensitive, in my experience.
With the plane warmed up and the high speed needle set as previously described, bring the throttle down to your lowest reliable idle. Listen carefully for the next 30-60 seconds. Does the idle speed increase or decrease while your waiting? If it does, you're slightly off, but you can't really tell which direction yet. Punch the throttle to full. If the engine hesitates or burbles, then spins up to full throttle, you're low end is rich. If it hesitates and then dies, you're low end is probably a little lean. Make a SMALL adjustment to the low end (1/8 turn or less) and repeat this procedure, including resetting the high speed needle. If after 3-4 adjustments (1/2 turn total) you're not seeing any improvement, return to your original setting and go the other direction. Go a full turn if necessary this time, but again, if no improvement, return to the original setting. Keep working this way until you get a smooth transition, and a steady, low (2500 rpm or less) idle speed.
Brad
01-08-2010, 12:47 PM
#9
RE: Engine tuning?
Hi, F-18.
The age of your engine also makes a difference.
If too new, the internal parts are too tight and fine-tuning is useless. At that stage, the engine needs to be broken-in, in order to achieve the proper clearance among those parts. Only after that period, the engine will hold any tune setting.
If too old, the compression may be insufficient, due to ware out piston-cylinder, or the old gaskets, carb’s barrel and o-rings may be letting extra air into the crankcase. Any of those things are able to drive any carburetor tuner crazy.
If your engine is not too new or too old, you should be able to tune it properly, using a new glow plug, new fuel, and checking the condition of the needle’s seals, the proper fuel plumbing (no air leaks nor fuel restrictions), as well as the tightness of all the bolts.
Regarding the best method, I have seen pilots using their ear, tachometers, thermometers, saliva, and even their fingers (not recommended for more than one try) for tuning engines. With some experience, you will find what works better for you.
The bottom line is obtaining a proper combustion thru a balance between fuel and air that is good for idle, transition and max rpm’s. That is a fine balance that is difficult, but not impossible to achieve, if all the engine’s parts and fuel are working properly. The jigsaw that you have to play with are the low and high needles, nothing else. That is why having the rest of the parts working with you and not against, is so important, especially when you are learning.
Some people learn by experimentation, some luckier people are taught by more experienced tuners. Don’t hesitate to ask for help, if you fly with experienced pilots. Regardless the method they use, their experience is priceless.
If you don’t have that opportunity because you fly alone, here you have some good references:
http://www.scootworks.com/rdrc/ then click on engine tuning and on glow plugs
http://www.mecoa.com/faq/carb/needle_aero.htm
http://www.rc-airplane-advisor.com/m...ne-tuning.html
http://www.flyrc.com then click on sample articles then click on tune_your_engine_1.
http://www.holdfastmac.com.au/howidlemix.html
Regards!
The age of your engine also makes a difference.
If too new, the internal parts are too tight and fine-tuning is useless. At that stage, the engine needs to be broken-in, in order to achieve the proper clearance among those parts. Only after that period, the engine will hold any tune setting.
If too old, the compression may be insufficient, due to ware out piston-cylinder, or the old gaskets, carb’s barrel and o-rings may be letting extra air into the crankcase. Any of those things are able to drive any carburetor tuner crazy.
If your engine is not too new or too old, you should be able to tune it properly, using a new glow plug, new fuel, and checking the condition of the needle’s seals, the proper fuel plumbing (no air leaks nor fuel restrictions), as well as the tightness of all the bolts.
Regarding the best method, I have seen pilots using their ear, tachometers, thermometers, saliva, and even their fingers (not recommended for more than one try) for tuning engines. With some experience, you will find what works better for you.
The bottom line is obtaining a proper combustion thru a balance between fuel and air that is good for idle, transition and max rpm’s. That is a fine balance that is difficult, but not impossible to achieve, if all the engine’s parts and fuel are working properly. The jigsaw that you have to play with are the low and high needles, nothing else. That is why having the rest of the parts working with you and not against, is so important, especially when you are learning.
Some people learn by experimentation, some luckier people are taught by more experienced tuners. Don’t hesitate to ask for help, if you fly with experienced pilots. Regardless the method they use, their experience is priceless.
If you don’t have that opportunity because you fly alone, here you have some good references:
http://www.scootworks.com/rdrc/ then click on engine tuning and on glow plugs
http://www.mecoa.com/faq/carb/needle_aero.htm
http://www.rc-airplane-advisor.com/m...ne-tuning.html
http://www.flyrc.com then click on sample articles then click on tune_your_engine_1.
http://www.holdfastmac.com.au/howidlemix.html
Regards!
01-08-2010, 01:33 PM
#10
My Feedback: (2)
Join Date: Jun 2004
Location: Sailing in the Eastern Caribbean
Posts: 4,047
Likes: 0
Received 1 Like
on
1 Post
RE: Engine tuning?
If you have have the instructions they are pretty accurate. if not download them here [link=http://www.evolutionengines.com/ProdInfo/Files/Evolution_60_Engine_Instruction_Manual.pdf]CLICKY[/link]
This engine has a needle valve that was designed to be insensitive in other words you can not go too lean or too rich to start. So if you are used to something like a MDS where one or two clicks makes a difference you need to get used to making a 1/4 turn adjustment. At least that is how I found it to work.
Perhaps you could explain in more detail what the problem is?
This engine has a needle valve that was designed to be insensitive in other words you can not go too lean or too rich to start. So if you are used to something like a MDS where one or two clicks makes a difference you need to get used to making a 1/4 turn adjustment. At least that is how I found it to work.
Perhaps you could explain in more detail what the problem is?
01-09-2010, 01:49 PM
#11
Junior Member
Join Date: May 2007
Location: Earth
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
RE: Engine tuning?
ORIGINAL: Moms Mistake
Generally speaking, close the main needle and open it 2, or 2 and a half turns. Be careful when closing the main needle as closing it too hard can damage internal parts and you'll have real problems, you may have to buy a new main needle if it gets damaged. Start the engine and keep a close eye on the temperature. I usually keep the temp around 190 and 210 degrees. Buy a temp gun, It'll be worth every penny. The temp should never read 250, 230 at the most if you want the engine to last.
Run several tanks through the engine while keeping an eye on the temp. The quicker the throttle response, the more it's being broke-in, or running-in as some call it. As you notice the engine being broke-in, give the engine full throttle and turn the main needle clock-wise until the highest rpm is reached and immediately turn the main needle counter-clockwise until you hear a decrease in rpm, that tells you it has the right air/ fuel mixture.
Next, give the engine full throttle and point the aircraft upward and downward 30 degrees and listen for increases, or decrease in rpm. Slight decreases, or increases is ok, if the engine stops running, the low speed set screw on the carberator needs to be adjusted richer, or leaner, thats all....
Keep in mind, engines run richer on a stand still, or on the ground, because of prop pressure and run leaner in the air, . Stay on the rich side until you gain experience.
Generally speaking, close the main needle and open it 2, or 2 and a half turns. Be careful when closing the main needle as closing it too hard can damage internal parts and you'll have real problems, you may have to buy a new main needle if it gets damaged. Start the engine and keep a close eye on the temperature. I usually keep the temp around 190 and 210 degrees. Buy a temp gun, It'll be worth every penny. The temp should never read 250, 230 at the most if you want the engine to last.
Run several tanks through the engine while keeping an eye on the temp. The quicker the throttle response, the more it's being broke-in, or running-in as some call it. As you notice the engine being broke-in, give the engine full throttle and turn the main needle clock-wise until the highest rpm is reached and immediately turn the main needle counter-clockwise until you hear a decrease in rpm, that tells you it has the right air/ fuel mixture.
Next, give the engine full throttle and point the aircraft upward and downward 30 degrees and listen for increases, or decrease in rpm. Slight decreases, or increases is ok, if the engine stops running, the low speed set screw on the carberator needs to be adjusted richer, or leaner, thats all....
Keep in mind, engines run richer on a stand still, or on the ground, because of prop pressure and run leaner in the air, . Stay on the rich side until you gain experience.
I gave you 5 stars for an excellent post.
