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Engine basics => Engine set up tips => Topic started by: Paul Allen on November 26, 2016, 02:02:24 PM
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I have a problem with the run of my XLS 36,it appears to drop revs in some manoeuvre's
but picks them up again,may take a lap and a half to pick them back up,it seems to go rich
when it does it,but it may not do it all the time!I am guessing its only a few hundred RPM, but when the
winds blowing its a bit of a worry.
Any ideas much appreciated.
Prop 11 x 4 APC,Thunderbolt 4 cycle plug,11 castor/11 coolpower,5 nitro. 10,000 rpm ground release
0.244" restrictor venturi with PA needle valve,uniflow open to air.
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I have a problem with the run of my XLS 36,it appears to drop revs in some manoeuvre's
but picks them up again,may take a lap and a half to pick them back up,it seems to go rich
when it does it,but it may not do it all the time!I am guessing its only a few hundred RPM, but when the
winds blowing its a bit of a worry.
Any ideas much appreciated.
Prop 11 x 4 APC,Thunderbolt 4 cycle plug,11 castor/11 coolpower,5 nitro. 10,000 rpm ground release
0.244" restrictor venturi with PA needle valve,uniflow open to air.
In manouvers it could go slower by going into a 4 cycle, or going over the hill lean, lean is most common in this situation
and I would open the ventuire up to at least .255 , i put a .260 in the ones I do
Randy
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Randy
I had just finished opening up the venturi to 0.250" when I read your reply.
Will try it tomorrow and see if it improves,I have another XLS which has a 0.253"venturi
but it runs a green bruline filter,the 0.244" venturi only had one layer of pantyhose on it.
Thanks
Paul
In OZ
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Agree with Randy, I'm sure you're launching too close to peaked and sagging lean. Change to a bigger venturi (.272" is good), single layer of pantyhose stuff, maybe more nitro. Any of the above will let you launch richer. If you're not running muffler pressure, put the uniflow inlet into a place out of the slipstream. Be careful you don't run out of fuel unexpectedly. Burning a bit more fuel is usually better, IMO. H^^ Steve
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OK tried motor this morning,opening up the venturi solved the problem I was having,
running in a 2 cycle with no break now. But I had it cutout on one flight after the hourglass?( still had fuel)
Now when you start it, its running about 700 rpm higher then the previous flight without touching the
needle,you have to back out the needle, set it to 10,000rpm then it runs the whole flight OK.
Next restart the same deal and the motor does not seem to follow the needle adjustments
you seem to turn the needle a long way before it drops the revs.
Once again any idea's much appreciated
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More nitro & bigger intake bore! What sort of tank are you using? 7 minute or 8 minute flight time? D>K Steve
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Found backplate gasket leaking oil,the XLS has a clear plastic gasket.
Where it sits on the crankcase had a small nick in the face of the crankcase
this motor was new so must have been there from manufacture.
All good now.