Engine basics > Engine set up tips

Engine seemingly going richer throughout flight?

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Curare:
HI guys, I've got a bit of a head scratcher at the moment. I've been flying a refurbished ship with a new-ish Moki 51, and its doing a puzzling thing at the moment, which is seemingly going fat, just as I start entering vertical territory.

I'll get through the vertical 8 OK, but the hourglass is hit and miss, sometime's it'll stay on song, and other times it'll start 8-stroking on the lap leading up to it, which means I ususally end up floundering at the third corner for lack of airspeed.

I've tried new plugs, adding and removing head shims, cleaning the NVA, cleaning the tank. The issue is nothing if not consistent.

Any other things I should be looking for?

Oh, the fuel mix is 10% castor 10%Synth and 5% Nitro. Plug is a Thunderbolt RC long, and the prop is a Xoar 12x6.

Cheers
Greg

Lauri Malila:
Is it a profile or is the fuselage built-up?
Of course, the fuel tank may be faulty, but if we assume it and the engine itself are ok, then I'd look at the thermal insulation of fuel tank. L

Dan McEntee:

--- Quote from: Lauri Malila on March 19, 2024, 04:48:42 AM ---Is it a profile or is the fuselage built-up.
Of course, the fuel tank may be faulty, but if we assume it and the engine itself are ok, then I'd look at the thermal insulation of fuel tank. L

--- End quote ---

      Can you expand a little bit on this? I have had experiences in the past where I wondered if the engine was heating the fuel tank and such or not. Some designs make things pretty snug up front. What happens and what do you use for the insulation?

  Thanks in advance,
  Dan McEntee

Brett Buck:

--- Quote from: Lauri Malila on March 19, 2024, 04:48:42 AM ---Is it a profile or is the fuselage built-up.
Of course, the fuel tank may be faulty, but if we assume it and the engine itself are ok, then I'd look at the thermal insulation of fuel tank. L

--- End quote ---

   That's a pretty good guess, but the few times I have seen that happen were with fairly extraordinary arrangements of fuel tank and muffler or header. I think a picture would help immensely.

     Brett

Brett Buck:

--- Quote from: Dan McEntee on March 19, 2024, 10:36:06 AM ---      Can you expand a little bit on this? I have had experiences in the past where I wondered if the engine was heating the fuel tank and such or not. Some designs make things pretty snug up front. What happens and what do you use for the insulation?

--- End quote ---

   Last few times, a 1/16 balsa sheet between the muffler and the tank worked pretty well.

    Brett

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