LOP - the old way

David-aviator · #1 08-09-2009, 08:50 PM

I was cruising along at 4500' today, set MP to 22" and pulled the mixture until the engine ran rough and eased it forward until it became smooth.

Several minutes later after things stabilized, I scrolled through the EIS 4000 pages until the one with the "L" in the lower right corner showed up, it is the page that captures peak egt and then shows a minus number as egt falls off going LOP. These are the numbers it showed -

#1 -33
#2 -44
#3 -51
#4 -52

The old procedure does work down low. Up high it may not, I have not tried it.

sprucemoose · #2 08-09-2009, 09:00 PM

David,

While it may have worked, the numbers indicated that you are running ROP, not LOP. What was your MP, RPM, fuel flow and OAT at this setting?

Jim P · #3 08-09-2009, 10:19 PM

You might want to take a look, but on the GRT H1 EFIS, being fed from the EIS, it will display (-) numbers both ROP and LOP. Thus, when going LOP, you need to go slow and watch where it peaks. I'm not sure what it displays on the EIS itself though. When running LOP, you probably want to watch the % power as well, especially down low.

Ironflight · #4 08-10-2009, 05:49 AM

Quote:

Originally Posted by Jim P

You might want to take a look, but on the GRT H1 EFIS, being fed from the EIS, it will display (-) numbers both ROP and LOP. Thus, when going LOP, you need to go slow and watch where it peaks. I'm not sure what it displays on the EIS itself though. When running LOP, you probably want to watch the % power as well, especially down low.

Evem simpler than that, you just look at the graph of the EGT's on the GRT EFIS, and you can see exactly if they rose to peak, then dropped. I never use the bar graphs or digital numbers anymore - the time-graph shows all four temps and their relationship very intuitively.

Paul

Tom Martin · #5 08-10-2009, 06:20 AM

I carry a Lycoming Power chart with me. The best power setting at 23 squared for my engine is exactly where the engine monitor shows peak to be on almost all the cylinders. It is amazingly close; as a rule of thumb one gallon per hour less then the peak setting is very close to where I want to be for LOP. This makes setting very fast and easy. Check the chart, for settings under 65% power, remove one gallon per hour and there you are, LOP.
Each engine will be different but I it interesting that these fifty year old power charts exactly match what my monitor says is happening. I find the power charts to be a valuable tool.

David-aviator · #6 08-10-2009, 06:35 AM

You-all are correct, it could have been ROP. But I don't think so, mixture was moved slowly from rough to smooth engine . One way to check that is to watch the page to see what's going on EGT wise. More eye ball time inside.

Percent of power was low as fuel flow was 8 gph. I don't remember rpm with fixed pitch but MP was set to 22". OAT has been hot around here lately.

breister · #7 08-10-2009, 07:33 AM

Nah, it couldn't have been ROP. If it had, the EFIS wouldn't have know where peak was, so couldn't have shown the (-) sign.

Dynon works the same way - no indication of relation to peak until it actually peaks.

dmaib · #8 08-10-2009, 08:44 AM

The "old way" should actually work pretty well IF your injector nozzles are matched. I think that is pretty much what the Walter Atkinson/John Deakins "big pull" method is. The issue with the "old way" back when many of us learned it, was that we were either operating engines with carburetors, or we had no idea if our injectors were matched. Plus, we did not have CHT/EGT indicators for each cylinder. So, we just did not have the information to know whether we were running any, or all of the cylinders in John Deakins' "red box".

$.02 worth.

sprucemoose · #9 08-10-2009, 09:07 AM

Quote:

Originally Posted by breister

Nah, it couldn't have been ROP. If it had, the EFIS wouldn't have know where peak was, so couldn't have shown the (-) sign.

Sure it could. The EFIS doesn't know whether the peak temp occurred because the cylinder actually reached peak, or because the pilot stopped leaning and began enriching the mixture (as in this case.)

Put another way- if you are in a LOP condition, then enriching the mixture slightly will cause EGT to increase. In this case, when he pushed the red knob in, EGT went down, indicating that he was already on the rich side of (true) peak.

JonJay · #10 08-10-2009, 09:13 AM

....assuming you have relatively balanced fuel flows at peaks, usually meaning you are injected. Roughness can be hard to detect but it is usually preceeded by a loss of power, at least on my IO360.
I have several cross checks; LOP/ROP computer w/bar graph, % Power, and Lycomings charts. I have found that if I lean to "roughness" then enrichen 1/4-1/2 turn, I am 50 deg. LOP. Magic.