GAMI Lean Test Question...

[Rob Caldwell]

I have 55 hours on my new Lycoming IO-540 (experimental Bearhawk 4 Place). I am also a customer with Savvy Aviation and use their SavvyQA service to review my engine data from the Dynon Skyview HDX.

The Savvy Tech sent me instructions to perform the GAMI Lean Test & Inflight Mag Lean Check (see attached).

My question is... Mike Bush talks a great deal about staying out of peak mixture to avoid detonation. He even refers to going LOP as the "Big Pull" to avoid staying in peak mixture too long. Get out of that portion of the mixture curve as fast as possible. However, the instructions for the GAMI Lean Test indicate going from ROP to LOP very slowly, between 3 to 4 minutes. And repeat this step at least 3 times.

Trying to understand this conflicting information.

Any thoughts?

 

[tsts4]

Rob, the lean test should be done at altitude, say 7000-9000 feet at cruise power/prop settings which should yield 65% or less power. At those power settings the red box goes away and no mixture setting will hurt the engine.

 

[Rob Caldwell]

Well there you go... Makes total sense! Thanks so much!