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IO-520 Compressions

Interesting discussion. It used to be that the larger orface gage was used on engines over 1000 cu in. I guess the Continental SI says to use it for bores over 5”. I wonder what caused FAA to change AC43.13-1b?

I used LOP on the A36 with a 550 that I used to fly for work. The biggest issue I found was lag in the EGT gage. It had a JPI, and after a lot of trial and error, I found that when leaning, if you tried to lean to 25 degrees LOP, within a couple minutes you would be 75 - 100 degrees LOP and on the edge of detonation. When leaning I found that if you slowly leaned to the first indication of peak and stopped right there, in a minute or so it would be 25 degrees LOP and cylinder head temps woul cool right down, and it would run smooth as silk. Fuel flow would be in the 14.5- 15 got instead of the 17 gph rich of peak. Airspeed would be about 2 mph less.


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Oddly enough, SB03-3 makes no mention of orifice size. It references the E2M and the E2A with the .040 orifice. It makes no mention of the E2M-1000 with the .060 orifice.
Remember there are two orifices per gauge set. An internal one and a master to establish the min for a Continental. The E2-M has the Master built in.

dgapilot said:
Interesting discussion. It used to be that the larger orface gage was used on engines over 1000 cu in. I guess the Continental SI says to use it for bores over 5”. I wonder what caused FAA to change AC43.13-1b
Click to expand...
 
Steve Pierce said:
I also have a call into Continental to verify the proper gauge in their opinion.
Click to expand...

As I understand it, the FAA pub rules unless it is overriden by the Manufacturer. Since I am unaware of any guidance by TCM or Lycoming as to orifice size, it appears AC43 is your bible.
 
It is interesting because I was unaware of this until recently. The 43.13 use to list above 1000 cubic inches which the radials I use to work on fell in that category. I guess displacement doesn't matter but bore size does. Be interesting to see what Continental says.

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It would seem that TCM needs to clarify SB03-3 as to bore size.



Steve Pierce said:
It is interesting because I was unaware of this until recently. The 43.13 use to list above 1000 cubic inches which the radials I use to work on fell in that category. I guess displacement doesn't matter but bore size does. Be interesting to see what Continental says.

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Click to expand...
 
Got this from my friend at Continental this morning:

Below is a snip from the M-0 Standard Practices Manual. SB03-3 has been incorporated into this manual.


0




[FONT=&quot]Ron Humphrey
Manager Product Support
Continental Motors
888.826.5465

[/FONT]
 
For whatever reason the FAA changed the standards in the AC 43.13. Eastern Technology seems to have picked up on that and Continental did not. I would be curious if Continental did any testing comparing the two.
 
Or is it all a marketing ploy to make us think the cylinders are better than they really are? All that said, I've never seen an engine fail from low compression! Cam and lifter condition contributes to power output more than one or more cylinders with "low" compression. I've seen lots of engines that won't make static power, yet all the cylinders are in the 70s for compression.
 
I read some TCM data once where they ran a big bore Continental without any piston rings and it made rated power. It was in reference to mechanics pulling cylinders prematurely.
 
Curious about this orifice business, I googled compression testers.
Here's one from Spruce:

http://www.aircraftspruce.com/catal...Eqr6IDjkJs5P7eFliS8AEt1_j5vt_iAsaAqwaEALw_wcB

and here's a clip from the description of that tester:
"
NOTE: The ATS 2EM Differential Pressure Tester has a .040” orifice as required by Teledyne Continental SB03-3 Service Bulletin, and is the proper type of instrument to test ALL Teledyne Continental engines in accordance with the aforementioned bulletin. The ATS 2EM also complies Textron Lycoming SI-1191A Service Instruction and is appropriate for ALL Textron Lycoming engines as indicated in the Service Instruction.​
"

Here's another tester:

http://www.aircraftspruce.com/catal...5xi1QwBFEyBsSscvcoqwgfVClGPAW06QaAiqkEALw_wcB

and a clip from the description for that one:
"
Model E2A Tester, for cylinders of less than a 5.00 inch bore* with a .040 inch diameter orifice, that eliminates all guess-work by enabling you to determine the exact location and cause of your engine's efficiency loss. This tester is recommended by TCM per ​
Service Bulletin SB03-3"

and here's a link to SB03-3:

http://www.aircraftspruce.com/catalog/pdf/servicebulletin.pdf

As pointed out, SB03-3 doesn't specify a particular orifice size, but it does call out two different model testers- both of which have a .040 orifice.
 
https://www.lycoming.com/content/service-instruction-no-1191a

The orifice size of the differential compression measuring device is critical if consistent andmeaningful cylinder analysis are to be obtained; the larger the orifice the less chance of detectingpotential problems. Therefore, a specific orifice size that provides an acceptable leak rate hasbeen selected for all Textron Lycoming engines; the instructions described herein are based onthis orifice which is .040 in. dia. (No. 60 drill) x .250 in long, with entrance angle of 59/60 °.
 
I think piece should move this compression tester stuff to it's own thread and just link to it in original thread....

interesting, so by the end of this we might need 40 different testers....
 
Probably going to have to start documenting what tester / orifice was used during the checks....:crazyeyes:
 
I calledAFS-300 this morning and they are researching why they changed AC43.13-1b. It may take a while. When I hear back, I’ll let you know!


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dgapilot said:
I used LOP on the A36 with a 550 that I used to fly for work. The biggest issue I found was lag in the EGT gage. It had a JPI, and after a lot of trial and error, I found that when leaning, if you tried to lean to 25 degrees LOP, within a couple minutes you would be 75 - 100 degrees LOP and on the edge of detonation.
Click to expand...

Slightly off topic, but did that put you at the edge of detonation or at the edge of ignitable air/fuel ratio?

I don’t think going leaner than LOP brings you into a detonation margin. I think you just have a mixture that’s too lean to ignite. I think the detonation margin is the red box/red fin area.
 
CamTom12 said:
Slightly off topic, but did that put you at the edge of detonation or at the edge of ignitable air/fuel ratio?

I don’t think going leaner than LOP brings you into a detonation margin. I think you just have a mixture that’s too lean to ignite. I think the detonation margin is the red box/red fin area.
Click to expand...

Cam,

i agree with you. I ran an IO 550 in a 206, and that engine loved to be run LOP. But, as you noted, running leaner just started shutting down the engine. The “experts” claim you won’t get into detonation by running LOP unless there’s something else going on.

MTV
 
CamTom12 said:
Slightly off topic, but did that put you at the edge of detonation or at the edge of ignitable air/fuel ratio?

I don’t think going leaner than LOP brings you into a detonation margin. I think you just have a mixture that’s too lean to ignite. I think the detonation margin is the red box/red fin area.
Click to expand...

Either detonation or pre-ignition, still running but definite roughness and CHT climbing.


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dgapilot said:
Either detonation or pre-ignition, still running but definite roughness and CHT climbing.


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Click to expand...

I think you had something else going on. I’m pretty sure that’s not possible with a mixture that lean.
 
Any time that I've tried to lean beyond peak there has been a gradual loss of power with less noise and lowering temperatures, no roughness. This was with balanced nozzles. Both an IO-550 and a IO-360. Too much loss of speed for the effort.
 
Is there any chance you were using the first cylinder to peak to make your adjustments? That's what we do when running ROP, but LOP requires we adjust mixture based on the last to peak. This insures none of the others are running in the "red zone." Some engine monitors allow you to select which you want, ROP or LOP. If you normally run ROP it would sure be easy to watch the cylinder that normally peaks first during mixture adjustment. If this is the case it'd be easy to have all the other cylinders running at peak or very near. (This supposes that no air leaks etc)

I tried LOP a couple of times but didn't like giving up the speed, around 10-15 kts if memory serves.
 
Steve Pierce said:
........Using the E-2M1000 with the .060" orifice I got 78/80 without having to mess with the prop. Immediately installed the E-2A with .040" orifice and it showed 64/80 at the same prop position. .....
Click to expand...

Exactly where is this orifice that we've been discussion?
Is it internal to the gauge assembly, is it the orifice in the spark plug hole fitting, or is it the size of the master orifice used for testing the gauge?
 
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