Engine quits when vertical
10-08-2002 | 06:24 AM
#1
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From: North Saanich,
BC, CANADA
Engine quits when vertical
I'm new to the use of gassers in RC aircraft.
The engine I'm running is a 45cc (I think the displacement is correct) conversion. During ground testing the engine will quit after about 10 seconds if I hold the aircraft vertical. Is this a carb Hi-Lo mixture adjustment problem? If not what else could be the source of this type of engine behavior.
Additionally, the engine response to throttle movement in the midrange is unsatisfactory. When the engine is running in the midrange throttle setting it only takes about 1 or 2 clicks on the throttle stick to make the rpm jump from 4000 rpm to almost 7000 rpm. Is this normal?
How do I correctly determine the volumetric displacement of the engine? I beleive that it's 45cc but judging by the fact that it turns an 18X8 prop at 7300 rpm, I suspect the displacement might be smaller than 45cc.
Is it possible that the low top end RPM could be the result of the carb intake is too small for the engine? The intake diameter is 11mm. I spoke with Terry from CH ignitions an he mentioned that his 46cc Poulan engine has a carb intake diameter of 14mm. I'm considering purchasing a different walbro carb with a larger intake diameter. Is this worth a try?
Cheers,
- Marc.
The engine I'm running is a 45cc (I think the displacement is correct) conversion. During ground testing the engine will quit after about 10 seconds if I hold the aircraft vertical. Is this a carb Hi-Lo mixture adjustment problem? If not what else could be the source of this type of engine behavior.
Additionally, the engine response to throttle movement in the midrange is unsatisfactory. When the engine is running in the midrange throttle setting it only takes about 1 or 2 clicks on the throttle stick to make the rpm jump from 4000 rpm to almost 7000 rpm. Is this normal?
How do I correctly determine the volumetric displacement of the engine? I beleive that it's 45cc but judging by the fact that it turns an 18X8 prop at 7300 rpm, I suspect the displacement might be smaller than 45cc.
Is it possible that the low top end RPM could be the result of the carb intake is too small for the engine? The intake diameter is 11mm. I spoke with Terry from CH ignitions an he mentioned that his 46cc Poulan engine has a carb intake diameter of 14mm. I'm considering purchasing a different walbro carb with a larger intake diameter. Is this worth a try?
Cheers,
- Marc.
10-08-2002 | 11:03 AM
#2
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From: Tampa, FL
Engine quits when vertical
Well first the engine quitting in vertical is the high end. you have it too lean. But don't mess with that since your low end is not adjusted right. First what type of engine is it? I will give you a brief low down to setting the mixture:
First you have to adjust the low end. Unlike glow engine the low end on gas effects the top end. You can actually have the low end very rich and the high end very lean and the engine will run but not very good.
Reset low and high to factory setting if you know them
If not open the low and high end 1 1/2 turns after you close them completely.
Start the engine and let it warm up and then idle at 1000-1500 rpm. Quickly move the throttle to 2500-3000 rpm. JUst like glow if it quits the engine is lean. If it saggs or popps then comes up you are rich. I would try to get the low end as lean as possible.
Once the low end is set work on the high. Lean the engine until you get peak rpm and then adjust 200 rpm rich of peak.
That should fix your problem
Chris
First you have to adjust the low end. Unlike glow engine the low end on gas effects the top end. You can actually have the low end very rich and the high end very lean and the engine will run but not very good.
Reset low and high to factory setting if you know them
If not open the low and high end 1 1/2 turns after you close them completely.
Start the engine and let it warm up and then idle at 1000-1500 rpm. Quickly move the throttle to 2500-3000 rpm. JUst like glow if it quits the engine is lean. If it saggs or popps then comes up you are rich. I would try to get the low end as lean as possible.
Once the low end is set work on the high. Lean the engine until you get peak rpm and then adjust 200 rpm rich of peak.
That should fix your problem
Chris
