Dynon Skyview percentage power and lean mode.

Can someone please advise...

We have a Dynon Skyview D1000 in a new RV-9 and have installed the latest firmware 11.1

In, Set up; we have selected Lycoming 160HP, but when you start leaning the ROP-PK-LOP indication indicates LOP when still WAAAY ROP. An avionics boffin has advised that Dynon only 'looks' at Lycoming graphs loaded into the firmware and DOES NOT look at EGT and FF to determine the peak EGT!

This is the dumbest idea I have ever heard! Could this possibly be true?

The 'fix' we have been advised to do is reduce the HP to expected cruise power and then the indication will be correct at this power.

Any Boffins on this forum from Dynon?

This might help you:
http://preflight.dynonavionics.com/2014/02/did-you-know-percent-power-dynon-way.html

Somehow the Dynon does take your EGT determine the peak.
It is written on the left side of the bar (if you have selected the "LEAN" function under the EMS page)when each cylinder reaches the Peak and to do it properly it needs to be looking at the EGTs. In your case, do you have all the cylinder peaking at the same time according to your Skyview ? It is possible but pretty rare. I guess you would rather have on the left hand side of the bars saying (if you are LOP for example):
#1 LOP-1F
#2 LOP-7F
#3 LOP-3F
#4 LOP-20F
It means that the Skyview has to take the EGTs into consideration to determine that because it is how far you are from the Peak on each different cylinder.
In any case according to my knowledge, the Skyview has nothing to do with your engine selection (in your case 160hp) to calculate engine percentage power. The 160hp you enter is only to be able to display the actual HP you are making (but calculated as (%power)x(160hp)).

I am not working with Dynon but this is my guess according to the experience I have with the Skyview.

Thanks Bastien, the problem is the %power and the LOP-PK-ROP indication, not the Lean Mode.

Selecting 'Lean' then leaning till LOP, gives all the correct data.

The problem is when leaning at altitude WITHOUT lean mode; the %power indicates LOP a long way (over 200 F) before the peak EGT is reached.

If you don't lean past peak, the engine won't know where you are. It assumes ROP, but it doesn't know. I have seen some egt's that fluctuate so much, for whatever reason, that it is going to see a peak even when way ROP. %power, I'm pretty sure, is based on MAP and RPM combined, and maybe taking into account fuel flow, but it is mainly MAP and ROM. 100% would be 29-30" and redline rpm.

Ensure your fuel flow K-factor is adjusted. I believe it is a significant factor in the percent HP and lop determination.

Dynon's site has a whole page on this topic.

Similar issue

I upgrade from a D180 to Skyview and just returned from a 2+ hour cross country. I was at 8.5-9.5k ft depending on direction of flight. I already performed a LOP study with the D180 and with WOT at those altitudes the ROP-PK-LOP worked great tracking EGT. But after this past flight with the Skyview the ROP-PK-LOP indication was not accurate. It indicated ROP when in fact it was LOP. The fuel flow was very accurate when using the D180 I never had to changed the original k-factor in the initial D180 setup, but I am not sure it is as accurate with the Skyview yet.

Anyone else experience this when upgrading?

215 hrs on D180, 30 hrs on Skyview.

As someone who TEACHES about engine management and LOP and ROP operations??I would say TURN OFF the LOP-PK-ROP function. The % power is OK but the other is a waste of screen space in my opinion. I am not sure if you can actually turn it off and still have the % power. I can honestly say I never notice it there, thats how much I care about it. A carby-fixed pitch set up will confuse the heck out of it anyway if you have that setup.

The lean find modes are next on that hit list. They are great for demonstrating a concept, and for getting a GAMI spread check done the first time, but even that is best done with the data file set at 1 second and done slowly. That is the only time it really helps.

the rest of the time use the known richest cylinder and do a Big Mixture Pull, and when things cool off if you really want to be fussy use that richest cylinder to find peak and back it off to the appropriate amount.

Of course if you want a ROP setting do the same thing in the inverse sense, know which is the leanest and pull to peak or beyond, find peak and then move the appropriate amount ROP.

The ROP and LOP indicators under the % power number seem to be incorrect to me sometimes. I do not bother with it though.

I do use the lean mode. I run ROP. I test the lean mode occasionally by leaning the way you learned in your trainer ( lean to roughness and about two turns back in rich) while not looking at the D120.

When I lean until roughness, and a couple turns in with the mixture knob in the rich direction it puts me right at the numbers that the D120 tells me when I lean it out and then go ROP just using the D120 screen.

David,
On SkyView, The LOP/ROP status can be turned off while leaving the % power up.

As much as I respect your knowledge about engines and running LOP, I do believe the state is a useful tool. When tuned properly, it is accurate, and can give you an immediate sense if the big pull got you where you need to go, or if you forget to change the mixture as you climb or descend or change your MAP.

It's also a really useful tool when first learning about your engine and getting the feel for when you are LOP at different power settings before you just know that X GPH at these settings is where you like to be.

After 200 hours when you know the engine and the numbers by heart, I agree it's not as useful, but it's still a good cross-check, and it was a great educational tool in getting to the 200 hour point. I've flown with 10,000 hour pilots that don't understand pumping losses and were amazed to see the plane speed up at 26" MAP vs 24" MAP with the same fuel flow, so anything we as an industry can do to help people learn is a good thing.

I'd hope the first thing on your hit list would be the poor implementations of % power that are out there. Many of them do not follow the OEM data curves at all, and can be off 10% when ROP and are totally worthless when LOP. At least Dynon's is accurate and unique in being able to be correct when LOP. Given that most people follow the rule of thumb of "no LOP below XX% power", accurate % power is a key to getting more people to do LOP operations easily, and Dynon is a leader in this area.

Now all of that said:

1) Fuel flow is used, so you need to make that accurate first.
2) EGT's are not used in the automatic LOP/ROP calculation so they are irrelevant. This doesn't mean we're stupid, it means we're smart
3) Once FF matches fill ups from gas pumps very closely, then you need to manually lean VERY SLOWLY in the manual lean mode, and check if the automatic mode matches. If it does not, adjust your HP number as needed.

Over on the Dynon forum this question was posed as well, and the OP mentioned he only has 5 hours on the system. I don't know if his engine is also 5 hours old or not, but most engine manufacturers suggest you run 75%+ power and ROP for a while during engine break in, so just a suggestion that you might not want to play with LOP ops when you first fly the plane.

--Ian Jordan
Dynon Avionics

Dynon support
Which way do you adjust your hp when they don't match?
Mine still shows the ROP indication when the manual mode using EGTs shows lean of peak
I also have 9 to 1 compression Pistons.

Page 7-59 of the install manual:

"If you are getting an auto Lean-of-Peak indication that is coming on too early, before the engine actually peaks while leaning, lower this number. It is not meant to be a measure of actual horsepower produced, as engines that are more efficient will act as if they are lower horsepower in the calculation. This will be particularly true if you are running a higher compression ratio than the stock charts are based upon."

In my case, the indication still shows "ROP", when the manual leaning method shows LOP so I guess I should increase the HP.