Leaning

[N8RV]

I have used the %LOP/PK/ROP function on my D-120 regularly, in conjunction with monitoring the EGTs. However, in re-reading the manual, I just noticed that that function is based on 8.5:1 compression engines only.

I have 9.2:1 pistons in my IO-360. What is the effect of this compression on the %ROP/PK/LOP readout, all other things being equal?

 

[dynonsupport]

Sounds like you have an older manual. We revisited this a few years ago and realized that the compression ratio doesn't matter. Modern software and manuals don't mention compression ratio.

For % power, you need make no changes.

For LOP/ROP/PK, you always need to adjust your "horsepower" number to make it match reality- that is to make it read peak when you see the EGT's actually peak. This should be near your rated HP, but is rarely dead on, due to lots of issues such as compression ratio.

If you think it says peak when the EGTs also are showing a peak, you are good to go.

 

[N8RV]

Thanks for the clarification. I got the info from the electronic user's manual that I downloaded yesterday from the Dynon website. If there's a more recent version, maybe it should replace the one online.

I'm just now beginning to explore the "leaning learning curve". With my last plane, I had a single EGT/CHT probe. My leaning process was to pull back the mixture till it ran rough, then push it back in. Everything ran fine and I had no clue what my fuel flow was!

 

[dynonsupport]

If you have the version off the web, it's the latest version. It shouldn't mention compression ratio. We'll check it and update it for the next revision.

 

[N8RV]

This is from the paragraph of the version I downloaded:

"... On some engines, when given the proper set of inputs, the EMS can also calculate percent power and lean-of-peak or rich-of-peak operation in real time. To do this, the EMS needs access to OAT, MAP, RPM, Altitude (from EFIS or GPS) and fuel flow, and needs to be monitoring an 8.5:1 compression ratio engine. This information is based on Lycoming and Continental power charts, is updated in real time, and is displayed near the manifold pressure gauge..."

Revision F, May 2009, page 6-2

Not trying to be a jerk, just trying to help. I don't think there's a smiley for that.