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Permalink Reply by Don Burkholder on February 9, 2021 at 9:18am

What temperatures are you seeing now? What is your current climb out RPM? Cruise RPM? As you know, engine load will determine what is best for efficiency and safe engine operation. Copied below is....

                Tuning the Bing Carburetor on Jabiru Aircraft Engines

1. Make sure the propeller will allow proper rpm. We check this by observing rpm as we
are rolling down the runway at take off power. We do not do static run ups as the
information we need can more easily be obtained while the aircraft is on the go and we
don’t have to worry about overheating and other tie down issues. The minimum target
in this phase is 2650 rpm with 2750 desirable.
2. Then we observe rpm in a normal climb out at or around Vy. The minimum target here
is 2750 rpm with 2900 rpm as the desired result.
3. During the climb out phase at full throttle we observe EGT’s. The target for the center
of the range is 1225. We might expect to see one cylinder near 1150 and another near
or even above 1300 but the center of the range would still be 1225.
4. After reaching a safe cruise altitude we set rpm at cruise power at 2850 rpm (the range
can be 2750 – 2950 but we find that on Jabiru aircraft with 3300 engines that 2850 is

about right). We again observe EGT’s after temps stabilize in cruise. For 2200 engines
the rpms should be 100 rpm higher than mentioned here.
5. We then reduce throttle as we observe EGT’s to find the peak EGT rpm. Usually EGT’s
should increase as throttle is reduced and at a certain throttle setting will begin to
decrease. We expect peak EGT’s to occur at 2600 – 2700 rpm.
6. One final observation involves comparing EGT’s at cruise power from the left side of the
engine to those from the right side ‐ cylinders 2, 4 & 6 VS cylinders 1, 3 & 5 on the
right.

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Permalink Reply by Ralph Sanson on March 7, 2021 at 2:16pm

you should ask over at 

https://jabcamit.groups.io/g/main/messages

where some members are doing this regularly.

The actual EGT is unimportant it is the drop in EGT from the peak that is found while adjusting the mixture leaning which is the reference level for making the final mixture setting, usually its set between 25 deg.F to 75 deg.F of the reference and if you have individual cylinder monitoring the first to reach 75 deg. lean of peak or the last to pass the setting for desired rich of peak should be the mixture setting for that cruise condition. My KS Avionics "mixture miser II" gauge has these calibration marks on the scale, they provide good instructions how to use it

http://www.ksavionics.com/

Ralph

I dont think anyone uses a HacMan for ROP as the standard Bing carb setup does this anyway.

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