3W50i - Getting the most out of it
05-25-2006, 12:39 PM
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3W50i - Getting the most out of it
Greetings All. I am hoping to improve the performance of my 3W50i engine. I am new to gasser class aircraft, and enjoying my 85" QQ Yak. I bought it used, fully equipped (saved like $1400). It has maybe 50-60 flights, never crashed.
Stick with me here... maybe the ideas I am going to suggest will benifit many, maybe they have already been tried. But, a little more background on my situation first.
I have been running an NX 23x8 prop, Amsoil 100:1 on 87 octane. I have completely rewired electrical and re-plumbed the fuel system with a 3-line tank setup. I was having severe issues, been fighting with hard starting and tuning for weeks, and just recenly discovered the little tiny filter screen buried in the carb body, which was clogged badly. So far, that has resolved the bigger problems. I also discovered a cracked Reed Cage and a matching wear point on one of the Reed Valves, new replacement parts will be here this week. The Velocity Stack also has a big chunk broken off, new one of those due also.
So, I think I have a little more tuning to get it right, and maybe the new parts will resolve more of my dilemma. I am still getting a burbbling/sputtering midrange in the air. Seems that if I lean out the low screw any more, I start having unstable idle issues with fade and surge, along with poor transition.
The top end it running pretty smooth, but I am only turning the 23x8 at 6050 rpm WOT. I have heard some reports that the 3W50i should turn that prop as much as 6800+ when all is well. I fly at ~3000 ft ASL. Plane is ~15 lbs AUW dry. I have the stock 3W "Pitts" style muff.
1st Question: What should be my goal top rpm?
I ordered an NX 22x8 and 22x10 to try, but that is a stop-gap measure. I am an novice-intermidiate 3D flyer, and tinkering with IMAC. Not hardcore on anyting, just enjoying the newness of the giant scale world and the pleasures of flying a really stable and highly acrobatic bird. I want to advance my 3D skills, and I am fairly dissapointed with mediocre vertical pullout perfomance.
Anything obvious I can do here to improve performance?
The motor has the rear-draft carb. The inlet is inside the motor box. I fly with several very experienced giant-scale freestyle, 3d and IMAC pilots... so I get a lot of "opinions" on my situation. The engine seems to run differently in the air, as compared to static. I am concerned about feeding the carb with a consistent pressure and airflow. I note that the only large frontal inlet is directed over the head, as you would expect. However, that air passes over the head, and the muffler, to feed the carb. My next question is probably obvious.
If I made an effort to direct/channel another separate frontal inlet airflow into the engine box area, would you expect better performance?
Would you expect better consistency with performance at different speeds with a cold-air feed?
I will check the inlet vs. outlet area ratio to see if I am getting the 3:1 the book recommends. I kinda doubt the exit area is big enough.
Your comments are appreciated. Sorry for being so long-winded. Just wanted to get all the facts out there so we don't have to banter back and forth before you have the whole picture. Thanks!
Stick with me here... maybe the ideas I am going to suggest will benifit many, maybe they have already been tried. But, a little more background on my situation first.
I have been running an NX 23x8 prop, Amsoil 100:1 on 87 octane. I have completely rewired electrical and re-plumbed the fuel system with a 3-line tank setup. I was having severe issues, been fighting with hard starting and tuning for weeks, and just recenly discovered the little tiny filter screen buried in the carb body, which was clogged badly. So far, that has resolved the bigger problems. I also discovered a cracked Reed Cage and a matching wear point on one of the Reed Valves, new replacement parts will be here this week. The Velocity Stack also has a big chunk broken off, new one of those due also.
So, I think I have a little more tuning to get it right, and maybe the new parts will resolve more of my dilemma. I am still getting a burbbling/sputtering midrange in the air. Seems that if I lean out the low screw any more, I start having unstable idle issues with fade and surge, along with poor transition.
The top end it running pretty smooth, but I am only turning the 23x8 at 6050 rpm WOT. I have heard some reports that the 3W50i should turn that prop as much as 6800+ when all is well. I fly at ~3000 ft ASL. Plane is ~15 lbs AUW dry. I have the stock 3W "Pitts" style muff.
1st Question: What should be my goal top rpm?
I ordered an NX 22x8 and 22x10 to try, but that is a stop-gap measure. I am an novice-intermidiate 3D flyer, and tinkering with IMAC. Not hardcore on anyting, just enjoying the newness of the giant scale world and the pleasures of flying a really stable and highly acrobatic bird. I want to advance my 3D skills, and I am fairly dissapointed with mediocre vertical pullout perfomance.
Anything obvious I can do here to improve performance?
The motor has the rear-draft carb. The inlet is inside the motor box. I fly with several very experienced giant-scale freestyle, 3d and IMAC pilots... so I get a lot of "opinions" on my situation. The engine seems to run differently in the air, as compared to static. I am concerned about feeding the carb with a consistent pressure and airflow. I note that the only large frontal inlet is directed over the head, as you would expect. However, that air passes over the head, and the muffler, to feed the carb. My next question is probably obvious.
If I made an effort to direct/channel another separate frontal inlet airflow into the engine box area, would you expect better performance?
Would you expect better consistency with performance at different speeds with a cold-air feed?
I will check the inlet vs. outlet area ratio to see if I am getting the 3:1 the book recommends. I kinda doubt the exit area is big enough.
Your comments are appreciated. Sorry for being so long-winded. Just wanted to get all the facts out there so we don't have to banter back and forth before you have the whole picture. Thanks!
05-25-2006, 06:19 PM
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RE: 3W50i - Getting the most out of it
First of all, your octane rating is too low. It should be at least 88 or 89, but to be safe, I always run 92 octane. You will increase 2-300 rpms if you increase the gas octane.
Personally, I am not a fan of 100:1 mixes. With 2 strokes, more oil means a better sealing ring (there is only one) and more power. A by product of more oil is better lubrication and a longer engine life. Try a 50:1 mix with an oil designed for 50:1 like Belray Mc-1 or Mobile or even Amsoil dominator. Also, Pennzoil air cooled give good performance.
RPMs change with prop brand so it is hard to predict. A bolly 22 x 8 should give you in the low 7K rpms.
airflow to carb: All you need is a small opening in the fuse to allow air to the carb. Consistant runs are helped by "still air" in the fuse. RPMs are limited by prop load, not availability of air.
Hope this helps
Elson
Personally, I am not a fan of 100:1 mixes. With 2 strokes, more oil means a better sealing ring (there is only one) and more power. A by product of more oil is better lubrication and a longer engine life. Try a 50:1 mix with an oil designed for 50:1 like Belray Mc-1 or Mobile or even Amsoil dominator. Also, Pennzoil air cooled give good performance.
RPMs change with prop brand so it is hard to predict. A bolly 22 x 8 should give you in the low 7K rpms.
airflow to carb: All you need is a small opening in the fuse to allow air to the carb. Consistant runs are helped by "still air" in the fuse. RPMs are limited by prop load, not availability of air.
Hope this helps
Elson
05-25-2006, 07:05 PM
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RE: 3W50i - Getting the most out of it
Never had a 3W but for some comparison both of my DA 50's are turning the NX 23-8 at 7060 R's with the stock exhaust..I had up to 7100 but I backed off a bit..Amsoil 80:1..regular gas (89 octane)..one has 25 gallons the other has about 5..Again never having a 3W I would think you should be around 6900 R's..Was thinking about trying the Penzoil but so far I like the Amsoil
05-25-2006, 10:29 PM
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RE: 3W50i - Getting the most out of it
First of all, your octane rating is too low. It should be at least 88 or 89, but to be safe, I always run 92 octane. You will increase 2-300 rpms if you increase the gas octane.
That's good to know. The guy that sold the plane to me said DON'T run anything more than 87 octane. Yet, I see the engine manual says use 89 octane, and doesn't say not to use 92. Good tip, 200-300 rpm gain is huge!
Personally, I am not a fan of 100:1 mixes. With 2 strokes, more oil means a better sealing ring (there is only one) and more power. A by product of more oil is better lubrication and a longer engine life. Try a 50:1 mix with an oil designed for 50:1 like Belray Mc-1 or Mobile or even Amsoil dominator. Also, Pennzoil air cooled give good performance.
Are you saying that a richer oil mix will improve compression, and possibly improve performance as a result. That's cool, I like treating my engine well - and - boost the power too
. The guy that sold it to me said the 100:1 was the only way to go... seems like didn't know much.Seems everyone is saying pretty much what I expected, I should prop for ~7000 rpm, even if I have to go down on size?
05-26-2006, 04:53 AM
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RE: 3W50i - Getting the most out of it
Hi,
There is a huge debate about oil in this forum and everybody has an opinion. Some swear that 100:1 is the way to go, others would not be caught dead running such a light oil mix in their engines. About a year ago, I ran an extensive oil test to mimic the severe engine running conditions that fit my application. Geistware had the results and pictures saved on his web page. That test convinced me not to run amsoil at 100:1.
Elson
There is a huge debate about oil in this forum and everybody has an opinion. Some swear that 100:1 is the way to go, others would not be caught dead running such a light oil mix in their engines. About a year ago, I ran an extensive oil test to mimic the severe engine running conditions that fit my application. Geistware had the results and pictures saved on his web page. That test convinced me not to run amsoil at 100:1.
Elson
05-26-2006, 10:48 AM
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RE: 3W50i - Getting the most out of it
I am from the school of conservative... if running a thinner oil mix has a downside or is questionable about adequate protection, then it's a risk I choose not to take. I would rather take the path that is proven to provide the best long-term protection.
I have heard the heavier oil mix tends to foul plugs faster, but that is a small price to pay to significantly extend the life of the motor and improve performance too. I can afford to change a $3 spark plug regularly... I can't affort to burn up a $600 engine when I fly at high altitude and high desert temperatures in the summer.
I have heard the heavier oil mix tends to foul plugs faster, but that is a small price to pay to significantly extend the life of the motor and improve performance too. I can afford to change a $3 spark plug regularly... I can't affort to burn up a $600 engine when I fly at high altitude and high desert temperatures in the summer.
05-26-2006, 08:07 PM
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RE: 3W50i - Getting the most out of it
Hi,
Most of my research fleet which flies at wide open throttle for 30 min at a time burns 40:1 oil mix. The 6 planes which tow very draggy samplers at wide open throttle burn a 25:1 oil mix. At the end of the year, the cylinders get removed and carbon gets scraped off. Not a big deal but the engines don't fail under heavy loads and use.
Hope this helps
Elson
Most of my research fleet which flies at wide open throttle for 30 min at a time burns 40:1 oil mix. The 6 planes which tow very draggy samplers at wide open throttle burn a 25:1 oil mix. At the end of the year, the cylinders get removed and carbon gets scraped off. Not a big deal but the engines don't fail under heavy loads and use.
Hope this helps
Elson
