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Captain Avgas

Well Known Member
I recently had an exchange of emails with GRT about adding special functions to assist with Lean of Peak operations (see following). Perhaps those who have operated LOP with the GRT EIS/EFIS can comment as to whether there could in fact be improvements made to the current system to facilitate more convenient/safer monitoring.

To GRT 23/5/06

Hi Todd, you are probably aware that in the last couple of years there has been a dramatic and resurgent interest in Lean of Peak operations for piston engines. This has probably been sparked to a large degree by engine management research performed by Gami Injectors and by the information desseminated by Advanced Pilot Seminars.

If you would care to go to the following Vans Airforce Forum site (Traditional Aircraft Engines Forum) you can see quite clearly the huge interest in LOP operations by RV builders and flyers.

In this Forum there are currently 4 threads running similtaneously that singularly relate directly to LOP operations. They are 1. Effective Timing. 2. Lean of Peak. 3. Detonation and Pre Ignition. 4.LOP in carburetted Engines.

Although they have been running for less than a week they have cumulatively attracted 4538 viewers and 287 posts. That sort of interest in a VansAirforce topic is virtually unprecedented. You can view the forum here.

For many builders the decision in future about whether to instal a sophisticated EMS may depend on their intentions to run LOP operations....and their choice of a brand of EMS may depend on the features in that EMS that facilitate LOP operations.

It is noted that your current EIS 4000 EMS does not appear to have any special pages or functions that would enhance the convenience or safety of LOP operations. May I respectfully ask whether it is GRT's intentions to expand their software at some time in the not to distant future to facilitate LOP ops.

From GRT 25/5/06

I haven't attempted to follow or read all of the discussion about lean of peak, and rich of peak engine operation, and how to do it with the GRT EFIS or EIS, but I understand from Todd and yourself that there has been all sorts of discussion on this matter.

I think there may be some confusion about how this is done with the GRT EFIS or EIS, as it is very simple.

The procedure for leaning to rich or lean of peak is:

1. Select the lean function on the GRT EFIS or EIS. (EFIS- Use the softkeys to select "LEAN" from the engine monitor page. EIS - Select "Reset" from the "Save Lean Point Page" which is accessed by pressing the center and left buttons together.)

2. Lean the engine slowly until a cylinder peaks. The first cylinder to peak will be identied by both systems. Both systems show the number of degrees from peak for each cylinder that has peaked. This value is displayed as a negative value, showing how far that cylinder is from peak, such as -50 deg F.

3a. (LEAN OF PEAK) You are now at, or just lean of peak. If you want to operate on the lean side of peak, keep leaning until the first cylinder to peak is the number of degrees desired lean of peak (such as -50)

3b. (RICH OF PEAK) You are not at, or just lean of peak. If you want to operate on the rich side of peak, enrichen the engine until the first cylinder to peak is the number of degrees desired rich of peak. (such as -50)

Notice that the only difference in the two techiques is which way you move the mixture control after reaching peak. It really is that simple. I get the impression some people are trying to come up with all sorts of odd logic to somehow display if you are rich or lean of peak. Maybe this can be done, but why, and how reliable is the logic? Its so simple to lean to either side of peak, the display shows you exactly how many degrees you are from peak. Its just a matter of moving the mixture control in the desired direction after reaching peak. Feel free to post this so others can comment.
CONTINUED
 
Continuation

To GRT 1/6/06

Dear Greg, thank you very much for your response. I appreciate your effort.

The trend to LOP operations is rapidly gathering momentum in the Experimental field as more builders/pilots become aware of the advantages such as cleaner, cooler running and fuel savings. No doubt this trend will intensify as Avgas prices continue to rise. Interest is also growing in LOP ops as more builders move to more sophisticated engine monitors which are capable of monitoring the CHTs and EGTs for all cylinders.

It is generally agreed that LOP ops are not safe without monitoring all cylinders as the protocol for LOP ops are more critical than for ROP ops.

I understand what you are saying about using the GRT EFIS for LOP ops and I personally know of a number of pilots who use your system for exactly that purpose. However it seems to me that with just a few minor software modifications your system might allow for LOP ops to be undertaken with greater safety and less pilot workload.

For instance (and please correct me if I am wrong....I don't have one of your systems to check) your system indicates the first cylinder to peak. For ROP ops this is appropriate. But for LOP ops you really want to know when the last cylinder peaks. This then becomes the critical value because this is the cylinder most likely to slide back into the undesirable Peak EGT zone.

In addition the individual EGT screen bars could change colour when pilot programmed EGT limits are reached. This would warn the pilot when any cylinder EGT falls outside of a desirable preset LOP range.

When I have your response on this interesting issue I will post all of our communications on a couple of the more salient RV email forums so that others might be better informed.

From GRT 2/6/06

When leaning, it is easy to watch to observe which cylinder is the last one to peak, although the EIS does not record this as it does the first EGT to peak. This is accomplished by watching the individual EGTs on the leaning page, and observing the last one to change to a negative value.

I think your concern about falling back into the peak EGT range is well addressed by the EIS in two ways.

1. The simplest way to tell that a EGT has returned to near peak, is to observe the digital leaning page. When the EGT returns to within 10 deg F of peak, the actual EGT is shown instead of the negative value showing how far from peak you are. This 10 deg F range is also programmable. This does require monitoring the leaning page however.

2. You can set alarms for the maximum increase and decrease in EGT after you start tracking them. This would generate an alarm when an EGT goes back up by more than the amount you set, and would perfectly address your concern.

Our EFIS has the same capability as described above also.

I wasn't aware there was any danger in operating at peak EGT as long as you stay at 75% power or less. I have to wonder how practical it is to worry that much about the EGTs, and how far from peak. For instance, turbulence will cause the load on the engine to vary, which causes the EGTs to vary. Typically this is less than 10-20 deg F, but this could be enough to generate some nusiance alarms.


If it really is a bad idea to operate near peak EGT, that would seem to suggest that maybe its not worth trying to operate lean of peak, as the risk might not be worth the benefit.

END OF EMAILS
 
Why not use an O2 sensor?

I admit this is only an idea, but why couldn't one rig up an automotive oxygen sensor to the exhaust port on the cylinder that usually peaks first? You might even be able to program the GRT EIS to accept it as an AUX input. Wouldn't that show which side - Rich or Lean - you are on?

Personally, I think Greg is right, that it's not worth the trouble if you just watch the graph on the EFIS display of EIS data. I hope to test this concept in a couple of months on my so far unused Superior IO-360 Plus! Translation - I don't, yet, know what I'm talking about, just asking the question.

h
 
Bob,

Interesting discussion! Was that Greg that answered you back from GRT? Since you asked for experience, here is what I've learned form the first 170 hours with my carb'ed TMX360 and GRT EFIS - it really is as simple as your email exchange indicates. Now let me first to say that I am pretty old-fashioned in my engine management techniques - I generally don't lean above 75% power, or if I'm above that percent power, until I'm above 5000'. Old learning dies hard... Once I have met those conditions, I used to just lean by ear until I got roughness, and enriched two clicks (this was on my old Yankee with an O-320).

When I finished breaking in this new engine, and started leaning, I did it very carefully, essentially using the exact technique Greg describes. It is incredibly easy, since the first cylinder to peak gets a box around it. I staretd out peaking, and then enrighening to 50 ROP. On later flights, I found that the engine didn't start getting rough until the first cylinder was close to 50 LOP. Interesting. Very easy to monitor.

With a little more experience, I found that for any given altitude, I could pretty much lean by pulling the lever to the same spot on the console - very repeatable fuel flows and EGT's. I have started doing that as my first cut, and then tweak form there. To be honest, I am still experimenting with where I like to run - LOP or ROP - but right now I am in a phase where I am leaning to the minimum fuel flow for a percent power as shown in the Lycoming tables - this turns out to be darn near spot on the old "lean to rough, and then enrichen". The differnce between that and the 50 LOP is usualy a couple tenths of a gph, and the Fuel Flows are almost exactly what Walter's equations (from one of the other threads) show for a given power setting.

My personal feeling is that if I had to hawk the EGT's and tweak the mixture frequently in order to run LOP, I'd be spending to much time running the engine, and not enough time flying the airplane! ;) (That is an exageration folks, but the intensity of some of these discussions make it seem like that is how seriously folks are doing this!)

Anyway...that's my experience, and I'm not claming it is right or wrong for anyone - and I'm still learning and experiemtning anyway. Short of having a FADEC system that automatically adusted the mixture for you, I am not sure how much more helpful the EFIS can be - it's pretty intuitive.

But that is what is cool about the experiemtnal world - experiemnts! :D

Paul
 
hevansrv7a said:
I admit this is only an idea, but why couldn't one rig up an automotive oxygen sensor to the exhaust port on the cylinder that usually peaks first? You might even be able to program the GRT EIS to accept it as an AUX input. Wouldn't that show which side - Rich or Lean - you are on?
Click to expand...
Unfortunately, O2 sensors and leaded fuel don't play well together...
 
First and last

Ironflight said:
Bob,
Interesting discussion! Was that Greg that answered you back from GRT?
Paul
Click to expand...

Paul, yes all GRT correspondence came from Greg Toman. I believe that knowing which cylinder peaks first (as per GRT EFIS) is suitable for ROP operations but not so handy for LOP operations when you really want to know the last cylinder to peak.

I do note that all of the high end engine management systems, including those produced by JP Instruments (EDM 930) and Electronics International MVP-50), provide information on the first and last cylinders to peak.
 
Quite true

Bob Barrow said:
Paul, yes all GRT correspondence came from Greg Toman. I believe that knowing which cylinder peaks first (as per GRT EFIS) is suitable for ROP operations but not so handy for LOP operations when you really want to know the last cylinder to peak.

I do note that all of the high end engine management systems, including those produced by JP Instruments (EDM 930) and Electronics International MVP-50), provide information on the first and last cylinders to peak.
Click to expand...

You are quite true with your comment. If you want to see the best software that supports LOP, look at how the JPI monitor work. EI is a close second. That later has a free manual on how to do it, which should give you the "procedure", it would simply need to be implemented in the GRT software. They way they do it now, could be used, but it's very prone to error and guess.

Here is the link to the free EI manual...

http://www.buy-ei.com/The_Pilots_Manual_by_EI.htm
 
Bob Barrow said:
Paul, yes all GRT correspondence came from Greg Toman. I believe that knowing which cylinder peaks first (as per GRT EFIS) is suitable for ROP operations but not so handy for LOP operations when you really want to know the last cylinder to peak.

I do note that all of the high end engine management systems, including those produced by JP Instruments (EDM 930) and Electronics International MVP-50), provide information on the first and last cylinders to peak.
Click to expand...

I understand what you're gettig at Bob - you'd like the system to automatically tag the last cylinder to peak. the bottom line with the GRT EFIS EGT display is that you're looking at all four cylinders, and you see a "delta from peak" number appear for each jug on top of the bar graph. It is trivial to see which ones have peaked, and which are left to peak. You don't even have to see the peak happen - you just see the one with the smallest number from peak.

I may just be describing poorly, so if you get a chance to see one in action, you'll have to decide for yourelf. But you might be surprised!

I think another interesting question that never gets asked is "how accurate and repeatable are all these EGT sensors anway? What are their hysteresis characteristics? Are we really measuring with a yardstick what we want to cut with a scalpel?" In my business, we are constantly aware that the numbers we look at have to be understood for their limitations - more good engineers have been fooled by lots of numbers after the decimal place that aren't real anyways.

Paul
 
Leaded Fuel - oops/Get the EFIS

I should have remembered about the lead. Thanks.

The GRT EFIS, Engine page, has a time-series graph of all cylinders. The answer (to first...last, not necessarily ROP/LOP) is to get the modern package, not just the EIS. How does that compare to the others for overall price and features?
h
 
Am I missing something here?

:confused:
When I run LOP using my GRT I watch the first cylinder to peak and then continue leaning until that cylinder is running about 10 LOP. The other cylinders at that time may be at peak or still ROP. If I were to continue leaning until the richest cylinder was running LOP then my engine would be stumbling badly.

You can see the earlier post of my engine operation while running LOP: Cyl 4 is 8 LOP, 3 is Peak, 2 is 12 ROP and 1 is Peak.

Thoughts?

http://www.vansairforce.com/community/showthread.php?t=7826&page=3&pp=10
 
R.P.Ping said:
:confused:
When I run LOP using my GRT I watch the first cylinder to peak and then continue leaning until that cylinder is running about 10 LOP. The other cylinders at that time may be at peak or still ROP. If I were to continue leaning until the richest cylinder was running LOP then my engine would be stumbling badly.

You can see the earlier post of my engine operation while running LOP: Cyl 4 is 8 LOP, 3 is Peak, 2 is 12 ROP and 1 is Peak.

Thoughts?
Click to expand...
Balance your injectors to achieve zero GAMI spread. It's easy. Give Don Rivera at Airflow Performance a call. http://www.airflowperformance.com
 
I'm with Roger. LOP with a GRT EIS 4000 is no big deal. Look at the digital EGT page and continue to lean until all values are -ve. As Roger says, at that point a carb'ed engine is unlikely to be running smoothly. I don't see any need for an EIS 4000 s/w change, I think all the functions are there. Anything else would probably just complicate the moding.

Pete
RV-6A, O-320 with a carb & EIS-4000
 
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