SkyView D1000 percentage power and leaning

[Chalkboy]

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!

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.

Your advice please. Thx.

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[mmarien]

There is some discussion on %power and LOP here:

dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1409279759

 

[dynonsupport]

When you say WAAAY ROP, how many GPH early is it reading LOP, and at about what power setting? Also, how slowly are you leaning?

Your avionics guy is half right. We don't pay attention to EGT since it doesn't mean anything, however, we do look at fuel flow. Peak EGT is the indication that you are near the LOP/ROP point, but there are other ways to determine that, so we don't need EGT. Our system can determine LOP/ROP without requiring you to actually peak the engine- you can literally turn on SkyView in flight and it will know if you are LOP or ROP, which you can't do with EGT's.

It is correct that you should adjust your HP number to make it read PK at the same time the EGT's peak when you manually lean. This is all covered in the install manual. Different engines behave slightly differently, so you do need to adjust. Also, any errors in fuel flow will change this as well, so make sure your fuel flow is accurate first.

 

[Chalkboy]

Thanks for the info. We have only done 5 hours so far and the K factor for the 'red cube' is still 68000 and has not been refined as we are refueling from drums.

We will return to the manual and RTFB. 

 

[DBRV10]

I just posted this on the VAF site, it applies equally to this thread.

Cheers!

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.
__________________
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David Brown
Advanced Pilot Seminars-Australia

 

[mmarien]

As someone who TEACHES about engine management and LOP and ROP operations

No mention of an oxygen sensor? Is there any discussion of that where you teach? and what are the thoughts there?

 

[DBRV10]

O2 sensors or Lamda probes are fine but…..EGT probes do the job just fine.

The O2 sensors do not play well or very long on avgas though.

Some people look for a hard and complicated way to do something very simple. The problem then is they are not technically up to understanding the more complicated way of doing it.

So the EGT method is by far the best solution for the most number of pilots, and even then only a very small few actually understand it very well. The rest look for a cookbook approach to things.

 

[mmarien]

The O2 sensors do not play well or very long on avgas though.

If you look at the screen shots on this forum, a few show a burnt EGT probe or two. Dynon has commented that they were looking for another source for EGT probes. On the other hand I put a couple hundred hours on my o2 sensor since I installed it and it seems to continue to work just fine. It's also relatively cheap at $70 compared to $35 x 4 for EGT probes although I spent more like $100 per cylinder for high temperature EGT probes last time.

If you are suggesting that the lead in 100LL is a factor in the life of an o2 sensor you may also want to look at Lie #6 about lead scavenging in 100LL. Theoretically I shouldn't have a problem with lead buildup on my o2 sensor or my plugs if I follow that advise.

Some people look for a hard and complicated way to do something very simple.

What could be simpler than directly measuring the oxygen content to determine mixture? Peak EGT only tells you one mixture setting (stoichiometric) which isn't very useful according to a trusted voice in aircraft maintenance. EGT is extremely useful for troubleshooting engine problems, but as a leaning reference it leaves quite a bit to be desired in my opinion. On the other hand, o2 sensors can help you determine a whole range of power settings from maximum power to best economy as shown in this graph. It's not a guess at 50 degrees higher or lower. An o2 sensor directly reads the mixture.

Not that I endorse any one product but here is a good place to start looking at getting more out of your engine. You might want to compare the cost of that to a full set of EGT probes and weight the benefits of both before you dismiss the concept.

 

[DBRV10]

The couple of hundred hours on your O2 sensor, was this using Avgas or UL mogas?

If you have an O2 sensor that does not mind the use of leaded fuels please let me know, I know a few folk who will be keen to see it.

Peak EGT only tells you one mixture setting (stoichiometric) which isn't very useful according to a trusted voice in aircraft maintenance.

It is true peak EGT is only representing one mixture, but from that point knowing a few facts you can easily find the optimal setting where BSFC is at its best.

And what you really want to know is where the BSFC is at its best. And that varies depending on the variable of power being produced (MP/RPM) and the fixed losses in the engine.

Take note of the brown clouded curves, typical of a mid range power and a higher range power. With lower powers the peak in 1/BSFC is closer to 10-20dF LOP.

Sure you can do things with a O2 sensor, but then you will have to come up with a BSFC table to work on. Or silly pick a number

As for trusted sources in aircraft maintenance, perhaps they need to spend a few hours at the Carl Goulet Memorial Engine Test Facility, and see what EGT and TIT can be used for, with great accuracy, measuring everything you could possibly want to know.

 

[mmarien]

I'm not really interested in analyzing my engine to death or I would follow up on your advise. I'm happy I found an easy and inexpensive way to measure mixture and thought check what the experts are saying about it. I see there is still a little skepticism.

Impressive graphs though. Cyl#6 looks a little hot. Can you explain why it's hotter than Cyl#4 when they have the same fuel burn?

 

[DBRV10]

From 12 years ago? No, probably just cooling airflow on that dyno run, who knows what nasty things were being down to it.

 

[mmarien]

So we agree - no useful information in those graphs.

 

[DBRV10]

Ahhhhh I would not be so sure. What do I agree about that has no useful information in which graphs? There is a heap pf really good data that comes off them if you know how to use them.

I really do not get your point. :

 

[mmarien]

You supplied a pile of graphs to prove your point. I asked a question about the graphs that you couldn't/didn't answer so I have to assume that if you don't know what the graphs mean then they don't add a lot of useful information to the discussion.

I'm done here. I've already stepped over the line between discussion and abuse and I apologize for that.

 

[DBRV10]

Perhaps you were being out of line, but let me try to explain.

I asked a question about the graphs that you couldn't/didn't answer so I have to assume that if you don't know what the graphs mean then they don't add a lot of useful information to the discussion.

I did answer as best as i thought was necessary, but let me have another go. The engine dyno graphs were not to show anything in particular, they could have been fictitious (they are not) but more so to show what kind of data you can get from a properly instrumented real time dyno. In the world of General aviation there are not too many (read 1) of these and this one is slightly better than than the FAA's own test facility.

The answer to the CHT on that snap shot for the CHT being so high, well it could have been just as I said, cooling airflow on the stand. It could also have been post some detonation testing and that cylinder was the one that had been detonating. And that is quite possible.

Back to O2 sensors, where are you sourcing reliable with avgas probes and how much are they?

 

[mmarien]

If you go back to my post #7 in this thread and follow the external links you will find that I use a Bosch o2 sensor. I don't have the new LSU 4.9. You can also learn that there is a lead scavenging component to 100LL. Documented here: Lie #6

On the other hand, CHTs below about 300°F create another problem: lead fouling. Our engines operate on avgas that contains large amounts of tetraethyl lead (TEL). Even so-called "100LL" contains enough TEL to keep the EPA awake at night. The purpose of TEL is to enhance the octane (detonation resistance) of the fuel. Unfortunately, it also can cause lead deposits in the engine, particularly on spark plug electrodes and in piston ring grooves.

To prevent such lead fouling, avgas contains a "lead scavenging agent" called ethylene dibromide, whose job it is to dissolve excess lead and let it pass harmlessly out the exhaust pipe. However, ethylene dibromide doesn't do its scavenging job unless combustion temperatures are fairly high. That's why lead fouling problems tend to emerge when CHTs are below about 300°F.

So if you keep your cylinder temperatures toasty warm your plugs and your o2 sensor should last a long time.