Webb

Webb

Well Known Member
Sponsor
Under warrantee, I sent my MT prop back to a factory service center since it was “burping” grease from around the blade seals. Not really bad but enough to put a mist on the windscreen.

While it was off and since my condition inspection is coming due next month, I decided to clean and rotate the plugs, get the engine (IO360 8.5:1) boroscoped, and check the compression.

I have been running both ROP and LOP depending on the altitude. I won’t run LOP unless I’m at least 9,000 feet or more. I also use 2,200 rpm for my cruise speed. Typical TAS ROP (9.5 gal/hr) at 9,500 feet is 163 knots and LOP (7.2 gal/hr) is 158 knots.

At 194 hours, scope was normal wear and everything looked good. Mechanic was impressed at how clean the engine compartment was.

When I stopped by and saw the mechanics note, the compressions listed were 73/73/72/71. At first I thought they were low, but noticed something about an orifice in earlier post (size matters) and if memory is correct, it was 0.049 (something Gil was talking about). I was pleased that they were so close together.

Not having any previous compressions to compare it against since this is the first condition inspection, I’m wondering if the compressions are good, average, or poor?
 
Last edited:
Webb said:
<SNIP>
At 194 hours, scope was normal wear and everything looked good. Mechanic was impressed at how clean the engine compartment was.

When I stopped by and saw the mechanics note, the compressions listed were 73/73/72/71. At first I thought they were low, but noticed something about an orifice in earlier post (size matters) and if memory is correct, it was 0.049 (something Gil was talking about). I was pleased that they were so close together.

Not having any previous compressions to compare it against since this is the first condition inspection, I?m wondering if the compressions are good, average, or poor?
Click to expand...

I'll take a stab at it and add my 2cents.

The Borroscope will give you much more info than the blow bys.

The blow bys are just an early/easy indicator that something is amiss.
Your blow bys so close together mean you have good even 'wear'.
Not all of us has boroscope kit, since it is a bit expensive.

What is important now is to take it back to the same person next time, he uses the exact same method, and exact same equipment, for you to get a trend. Jumping around using different people, different methods and different equipment will just confuse you and your readings.

For comparison for what ever it is worth. I bought the Aircraft Spruce Blow By Tester, WITHOUT the ORRIFICE adjuster. I will use the same one throughout my airplanes life.

My first blow by test after 1 year of operation of a brand new Factory standard XP-IO-360 on 170H hobbs / 140H Tacho time (Dynon normalises Tacho time to 2500RPM, hence it is less than 170H). My airplane/airfield is situated at 5500 ASL so most of my flying is 7,000 ft+, most of the time LOP and on Mogas.

I went flying to heat the motor, then back to hangar to take the blow by readings asap: 79,78,76,78 over 80 PSI.

My my #1 always coldest and #3 always ran hottest so it kinda makes sense 79 vs 76. My #2 and #4 run about equal temps and both are 78.

The TRICK is that I have a 1 year reference point now. I made some baffle adjustments to raise #1 temps and lower #3 temps.

Next year I will use the same kit and method and compare to this years figures, if they jump out significantly, then first thing to do is go fly and gun the engine hard for 2 hours and repeat the test. If it is still out, then it is time to visit someone with a boroscope to check.

I hope that helps.

Rudi
 
Last edited:
Numbers at 96 hours

I tested mine at 96 hours borrowed equipment and they were 78,79,79,80. I was mainly checking the engine for problems after the pmag timing failure.

Hans
 
This is the post....

Webb said:
...
When I stopped by and saw the mechanics note, the compressions listed were 73/73/72/71. At first I thought they were low, but noticed something about an orifice in earlier post (size matters) and if memory is correct, it was 0.049 (something Gil was talking about). I was pleased that they were so close together.
....
Click to expand...

...you remembered....

http://www.vansairforce.com/community/showthread.php?t=40643&highlight=orifice+0.040+compression

It is a 0.040 orifice for our Lycomings per their Service Instruction
 
Hey Gil.....I called Eagle Engines and talked to Lou about the numbers. He was very please with the closeness. He told me to keep doing what I've been doing.
 
Test new engine?

I really like the idea of using the same method and equipment every time.
Does someone have a recommendation for a reasonably priced tester ?

Also, would it make sense to test a new engine prior to it's first operation as a baseline reference point? Mine will be ready to run early 2010. (XIO360 - stock from Van's)

Thanks

Steve (RV-8 fastback builder and former Supercub owner)
 
The E2A model...

...is the one with the Lycoming recommended 0.040 orifice --

http://www.chiefaircraft.com/airsec/Aircraft/Tools/CompressionTester.html

axlr8r said:
I really like the idea of using the same method and equipment every time.
Does someone have a recommendation for a reasonably priced tester ?

Also, would it make sense to test a new engine prior to it's first operation as a baseline reference point? Mine will be ready to run early 2010. (XIO360 - stock from Van's)

Thanks

Steve (RV-8 fastback builder and former Supercub owner)
Click to expand...
 
axlr8r said:
I really like the idea of using the same method and equipment every time.
Does someone have a recommendation for a reasonably priced tester ?

Also, would it make sense to test a new engine prior to it's first operation as a baseline reference point? Mine will be ready to run early 2010. (XIO360 - stock from Van's)

Thanks

Steve (RV-8 fastback builder and former Supercub owner)
Click to expand...

Ditto, get the 0.4 orifice one from Chief or Spruce

I bought the standard EA2 one
http://www.aircraftspruce.com/catalog/topages/presstester.php
Standard Tester 12-01012 $69.75

If I did it again, I would rather buy the one with E2-M Master orifice adjuster Tester for $90+, gives you more options if needed.

Regards
Rudi
 
More update and a question

While the plane is down, on Saturday I was going through the firewall forward knocking out items on the condition inspection. One guys from TCM was there and I had a chance to talk to him about the compressions. Turns out my compressions were right in line with a new engine he just tested. My guess is his gauges read a bit lower than some other places.

Every thing that he saw on the boroscope looked good except there was one thing that puzzled him. On top of the valves he said there were tiny reflective areas that look like little itty bitty stars. He had never seen anything like that. He wasn't concerned, just had never seen it before. It wasn't anywhere else in the jug, just on top of the valves.

Any ideal of what would reflect like that? (Maybe my engine is making diamonds from carbon - lol).
 
You must log in or register to reply here.