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Old 06-15-2011 | 11:37 AM
  #47  
summerwind
 
Joined: Feb 2007
Posts: 3,996
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From: fresno, CA
Default RE: first flight good, second flight BAD.


ORIGINAL: Rendegade

Another weekend, another conundrum it seems.

This time we were flying with two indentical aircraft with different engines, but essentially the same fuel (18% oil (roughly 3% castor) and no nitro.

I was fighting the dreaded NVA bubbles on 'new' 46fx and he was having lean runs with his Enya 40 ss. I should also point out that it was around 10°c and dry.

After a while I suggested he borrow some fuel from a friend (local store bought stuff, I'd say 10% nitro and probably straight klotz from the colour)
he got a nice COOL run with his enya and a much happier engine all round.

This seems a bit counter intuitive to me, I would have thought that 10% would have overcompressed the enya and made it run hot/like a dog. Turns out the opposite is true.

IT then begs the question, is the addition of small amounts, 5% or so of nitro a way of cooling the engine and allowing more fuel to pass through the motor, without adversely affecting the C/R and timing?
when i read that higher nitro improved things i have to ask...........what size props are being used on the engines.

our YS 4 strokes act like this when overloaded, but then run better with higher nitro.