HDX Lean Assist Question

[baldcaldwell]

Is Lean Assist only for LOP operations?

I'm still breaking in my engine and want to fly best ROP for now. Can the Lean Assist function help find ROP without wandering into the dreaded red box area (potential detonation)?

 

[Carl_Froehlich]

I assume are running a normally aspirated engine.

The SkyView provides a nice tool to set EGTs where ever you want them. Lean Assist is a tool to find Peak EGT then add fuel back to go ROP, or continue leaning to operate at you desired LOP point. But, I assume your real question is “how do I use these tool to run at ROP best power?

You can find ROP best power in your engine spec sheet. From that you can gather EGT data to figure out how many degrees ROP you want to be.

I suggest for your objective of engine break in a more practical approach might serve:
- First few flights, keep full rich and power above 70% other than landing and doing the much needed first stall to find out at what airspeed the plane stops . Look at your data on CHTs and EGTs. Anything unusual? CHTs will be high for the first few flights, driving the full rich requirement. EGTs should be around 1250 for full power take off. If you have any CHT or EGT outliers track them down before proceeding.
- After a few hours on the engine go up to ~6500’, leaning as your go to keep EGTs at about what you had on takeoff. Set power at some reasonable level (say 24” and 2400 RPM) and do your first lean to peak EGTs. This is a very important data run as it will tell you how far your injectors are out of balance. Get a nice GAMI data run, then do more flights as you swap out injectors (if needed) to get that balance. AirFlow Performanice sells replacement injector nozzles for ~$28 each in 0.0005” increments. On my IO-540 I had to replace four of the six. On the current IO-360 two. Don at AirFlow Performance will assist you in deciding what size you need, if any.

At this point the engine is fine to run LOP - and it will thank your for doing so. CHTs will be lower, fuel burn is lower, and plugs will not get as fouled.

Carl

 

[baldcaldwell]

Thanks for the input and suggestions, Carl. Very helpful.

Something I am looking for on the HDX is an indication of peak EGT so I can adjust 10%+ of that for ROP. I think JPI and other engine monitors have an indication of peak EGT. I select the "Lean" button and not sure what I am seeing. I've read pages 6-4 & 6-5 of the HDX Pilots User Guide which isn't very clear (for me).

 

[Carl_Froehlich]

Keep in mind when your see ROP, PEAK or LOP on the EMS display, this is only a model of your engine. It may or may not accurately reflect what is going on. For example when I‘m just on the lean side of peak using the leaning tool, the EMS still says I’m ROP.

So as I suggested, use the leaning tool to be ROP, PEAK or LOP. Find PEAK then add fuel to ~100 degrees ROP (as indicted by EGTs at -100 on the leaning tool), PEAK (as indicated by 0 on the leaning tool, or 20-30 degrees LOP (as indicated by -20 on the leaning tool).

As you can see from the screen shot, the EMS model says I’m ROP at 58% power but the leaning tool (truth) has me LOP.

BTW - on the leaning tool you see where it says ”LEAN 0.0GPH”. This means there was a 0.0 GPH fuel flow difference between first cylinder to peak and last cylinder to peak (exactly what you want). This is not as accurate as doing a GAMI spread run looking at the downloaded EMS file after your flight, but it is in the ball park.

Carl

 

[baldcaldwell]

Thank you so much again. I probably need someone to walk me through what I am seeing... I think the instruction manual assumes we know a little more than we do.

On page 6-5, when it says, "the cylinder numbers on the left side of the EGT bars are replaced by a number indicating the cylinder peak sequence, followed by the difference in its peak temperature"

I see a dash between the two numbers. Is this a negative value assigned to the difference in peak temperature?

On your example, I see #3 has a difference in peak of -11, and everything is greater than that. Does that mean you are negative 11 degrees from peak? If I go ROP, wouldn't those numbers be positive?

BTW... I will be going to see Don at AFP when I get back from Oshkosh as I have his FI system and will have hime tune it. I'm just trying to establish a good ROP setting for my 10 hour round trip flight until then.

Thanks,

 

[Carl_Froehlich]

Look at my screen shot:
- Cylinder #2 shows 1-33. This means it was the first cylinder to peak and is showing 33 degrees LOP. If would have the same indication if at it 33 degrees ROP.
- Cylinder 4 shows 4-18. So it was the last to peak and is currently 18 degrees LOP.

NOTE, once all cylinders have peaked, the degrees LOP or LOP may change as you change engine settings, but will still show the orginal order of cylider peaking until you turn off the leaning function. Useful when doing a series of GAMI spread data taking. Here down loading the Skyview files is wonderful way to determine GAMI speed and what nozzles to replace and at what replacement size. Here Don at AFP is a big help.

Also note the absolute EGT reading means little other than "you have a dead cylinder" or "you have a major problem, like detonation ". One exception, look at EGTs at full power take off ( low altitude airfield). During the climb you can use this as a leaning target to keep engine power up. Temper this with keeping CHTs where you want them.

For you upcoming trip, 100 degrees ROP is a safe target. If you have completed your 40 hour Phase One however your engine break in is essentially done. LOP ops should be fine unless your GAMI spread is really off.

Carl

 

[baldcaldwell]

Thanks again!

 

[Raymo]

Also keep in mind that the use of the lean function should not be used when you want to determine your GAMI spread with tools like Savvy provides.

 

[Carl_Froehlich]

I suggest careful review of the SkyView EMS logs after a GAMI run is as good as whatever you are getting from Savvy. Considering the pilot can see multiple sets of GAMI data runs using the EMS download I offer he will have opportunity to do comparative data analysis. Very helpful when doing a series of injector nozzle swapouts as you get immediate data on the effect of each change. Tuning injector nozzles is not “one and done”.

Carl

 

[kellym]

I suggest careful review of the SkyView EMS logs after a GAMI run is as good as whatever you are getting from Savvy. Considering the pilot can see multiple sets of GAMI data runs using the EMS download I offer he will have opportunity to do comparative data analysis. Very helpful when doing a series of injector nozzle swapouts as you get immediate data on the effect of each change. Tuning injector nozzles is not “one and done”.

Carl

Instead of playing around with several injector swaps, I ran perhaps 6 Gami tests as well as Don's suggested lean test. I then looked at the data for quite awhile and determined my #3&4 were both running cool and rich of the rest. So I just ordered two restrictors .0005 less than stock and installed them. That got me very much inside the desired Gami spread. I don't know if it made a difference, but I had all cylinders flow balanced as the engine was built. To ease the testing, I just climbed to 8000 DA, then with full throttle I pulled back to about 14 gph and began the sweep down to about 10.5. One can also just set the engine at 75% power, either via the Dynon readout or Lycoming's table at about 6500 DA then pull mixture back to 13gph. You will be LOP. If it runs smooth, you are pretty good, if not then proceed with GAMI test.