Tuning OS91 SZ-H (p/p'd) High end.

[Aviation addict]

Guys,

I'm in the process of running in and tuning an OS91SZ-H (with pump) and wanted to know how you guys tune yours.

I've only ever had an OS50 Hyper before now and so am not used to 90 size performance therefore am struggling to know if I'm way rich - or getting close.

I'm using Magnum 20% which is a particularly smokey fuel so going on the smoke output isn't really practical.

So far I have set the 'Idle' then as per other postings concerning the SZ engine have closed off the 'Medium' speed needle completely. Right now my High needle is at 2 turns open, but I understand that I should be able to get it down below 1 1/2 turns [obviously I appreciate that everyone's engine/pipe/climatic conditions are different].

I don't need to tune the engine for max performance with the flying I'm currently doing, but equally I don't want it coughing to death on excess fuel.

What parameters and flight test do you guys use to tune your High end?

[WayneBrown]

governor OFF, Do a full power, full pitch climb out. If its rich, it will bog and sound lazy... Lean it until it accelerates fast enough to scare you, but does not have that rattling lean sound. Call it done and fly it.

[Aviation addict]

Thanks Wayne. I'll try do that today weather permitting. If you'd said do an inverted funnel I'd have stuggled - but a full pitch climb out is something I can do. Cheers.