Scully

Sorry if these are stupid questions... I am a beginner.

1)Muffler pressure and bubles in fuel line - I seem to get a lot of these going to carb and a lot of foaming in the plastic tank.
Is this normal? It does not seem to affect running a lot, but there are lots of bubles in the fuel line. Any hints please? What I am doing wrong?
My tank is Norvel's BigMig standard CL tank with pressure relieve valve.


2)People here say Norvel RC needs muffler pressure to run well. I tried and found it works quit well (IMHO).
What I don't understand is how when I go to lower RPM engine does not seem to lean out badly. Really muffler pressure should drop a lot so this would result in much less fuel going in...

Is there a danger of leaning out RC Norvel 0.061 too much using carb?

2fast4u

My Feedback: (5)

1) The bubbles are due to vibration. If you balance the prop, that is about all you can do. If you use a regular tank, mounted in the fuse, then wrap it in foam to reduce the vibration and bubbles.

2) The muffler pressure is good for the R/C engine because pressure drops as rpm drops. If you use crank case pressure on the R/C engine it will flood every time you reduce the throttle. With muffler pressure, the tank pressure is following the throttle opening. Full throttle, lots of air into engine, lots of pressure, lots of fuel to engine... low throttle, small amount of air into engine, small amount of pressure, small amount of fuel to engine.

That's the simple version. I hope it helps some. If you are using the engine mount with the tank built into it, then bubbles are just part of that combination. If you can put a separate tank inside the fuse and wrap it in foam, then your bubble problem will most likely disappear. Good luck and have fun!!

AndyW

My Feedback: (1)

As 2fast says, the drop in muffler pressure is proportional to the demands of the engine as the throttle is reduced. Also, the barrel is carried by the threaded portion of the nipple and, as the throttle is closed, the high speed needle is drawn into the nipple, slightly leaning out the mixture. This is always desirable.

On the RC version, I'd be interested as to the idle and top end rpms and how well the throttle responds.

The Norvel tank mount, as with all other plastic tank mounts aren't stiff enough and allow a lot of vibration to be transmitted to the tank. This produces bubbles and as long as the delivery of bubbles is consistent, you're probably compensating for this with the high speed needle.

Scully

Thanks a lot for your replies, great to have some competent advice!

It does look a bit that fuel line going to the bottom of the tank means some bubbles can reach pick-up tube before reaching the surface, but probably vibrations is major factor, as you pointed out. As long as ohter people are happy I am happy to fly like this I am happy too <not too demanding - so far - grin>

I do not have a tahometer (and many other things as well<grin>) - I was doing some EPP gliders and a bit of CL so far.
Tried throttle last night and it did sound and felt like dropping quit a bit... I mean holding model in your hand you can tell the pull and it was probably 3 times less at the lower throttle. As for RPM I don't have a clue... I was runniing 5x3 COx and it was above 15-16,000 probably and went down to may be 5-7? Just a guess though.
The pick up was immediate while drop may be 0.1-0.2 secs delayed (or so I felt)

Once I start flying I can probably get someone to do RPM for me as just now I really need to buy a reciever, servos and power panel...