Guys,
I'm working through a setup issue on my El D with a Fox 35. The engine holds a fast 4 cycle (with blips to 2) in level flight and wingovers but when doing the 5 inside or outside loops (or 3 eights for that matter) it will break to a 2 cycle and hold until returning to level flight then it goes back (within 1/8 lap) to the 4 cycle. The speed in the maneuvers is slightly faster then in level flight and I would like to get it to do the classic 10 - 2 break to keep a more constant speed (in this case a little slower) through maneuvers.
Details - Fox 35 iron p/c, upright mount, 9.5x6 old TF prop, uniflow tank with pinched outside corner (GMA style), 5%_28% oil Sig, Sig plug, ST NVA, launch rpm 9100, lap time level 4.8 on 60' C to C.
The one area that I am thinking about is the NVA - being a standard ST 51 spraybar it is 0.151" diameter, the normal Fox spraybar is 0.125", this cuts the venture open area down by almost half. I have read that it should not make that much difference, after seeing the numbers I'm not sure I buy that, but for now it has enough pulling power for this ship. One thing I found that I'm not sure of the effect is that I installed the spraybar with the hole pointing forward across the venturi just below sight level (about where the hole would be with the 2 hole Fox spraybar). I'm wondering if that position is causing some slight airflow differential down the venturi that reduces fuel draw on the round maneuvers and if pointing straight down would get more consistent fuel flow and a better break?
I don't get to fly until Thursday so rather than try something that takes up flight time and may or may not work I though I'd ask if anyone has had this condition and how did you correct it?
Best, DennisT