912 Tuning question

[thermalator]

Does anyone have a link to documentation describing the tuning methods AND the philosophy behind it ? I have looked at the standard maintenance docs etc but nothing on tuning

In particular I want to figure out whether(how) the needles are profiled for richer at WOT etc. (like Jabi)

FYI

I run mine with a VP prop, So I like to use the following cruise settings

sLow cruise 19in, 3800rpm (this can result in vibration at low altitudes, so always fiddle till happy)
High cruise 21in, 4300rm

Sometimes I run WOT at an altitude that results in 19in, however I seem to get soot all over the bottom

Edit WOT=Wide Open Throttle

[Mogas]

First of all, wots WOT?
When you state manifold pressure of 19", 3800 RPM, what altitude or more specifically what density altitude are you talking about?
Rotax recommends cruise RPM of at least 4600, those engines don't like to labour at low RPMs.
What are your fuel burns like and what airframe?
Interesting discussion
Mogas

[thermalator]

WOT=wide open throttle

Airframe is a Lambada motorglider
Low cruse is 90kt, hi cruise is 100kt (not a quickie) & approx 15lt/h. I have no flow meter

I just want to understand what the design tuning is & how much richer it runs @ WOT, if at all

WOT is in theory the most efficient throttle setting but not if carb is non linear, as the Jabi's seems to be

Also how accurate is the altitude compensation ? anyone seen a graph of such - I like to fly high

[Mogas]

Ah ok, sorry, only info I can find is fuel flow vs manifold pressure at sea level in the operators manual which I suppose you have seen.

[Rudix]

The 912 also uses Bing carbs like the Jabiru and YES, it does run substantially richer at WOT, if you have EGT meters you will see that they drop at WOT.

[Morph]

I'm afraid we are all at a bit of a disadvantage here because we use rpm and fuel flow as opposed to manifold pressure. None of our planes have instruments that read manifold pressure