If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
This year's annual
Now I would never, ever do this myself. Nor would I ever think of doing it
to an airplane. However, I have this friend named Ernie that told me about it. You have a low compression cylinder that you believe to be stuck rings. You pull the top plug and put the cylinder on the compression stroke at TDC. You pour Marvel Oil into the cylinder until it is full right up to the plug threads. You leave it 24 hours, rocking the prop back and forth a few degrees every so often. Drain the MMO out the bottom plug, replace both plugs and go fly half an hour. According to Ernie, 99% cure rate. Jim "B A R R Y" wrote in message ... On 5 Nov 2006 06:09:49 -0800, "Jay Honeck" wrote: Was this due to lead fouling? It was due to something fouling, maybe lead, maybe coke... |
#22
|
|||
|
|||
This year's annual
B A R R Y wrote in
: In my case, the fouling was on valve seats. How would a fouled plug kill compression? G Duh good point. Not exactly sparking is it during the test? Told ya I wasn't mechanically inclined!!! Allen |
#23
|
|||
|
|||
This year's annual
B A R R Y wrote: Do you taxi full rich? We used to, which occasionally have us slightly low compression readings on one or more cylinders in the hangar. The low cylinder would move, as there was nothing really wrong. G We now lean aggressively until we get to the runup area, and have never seen the problem again. Our home field is 250 MSL. Can you (or anyone else) explain the mechanism of this? Why a full ruch taxi would affect compression? I routinely lean the mixture for idle and taxi because I've learned that at my home airport (KORL) the plugs can foul between the ram and the run up area. But I don't understand (and I'd like to be educated) how it affects compression. John Stevens PP-ASEL |
#24
|
|||
|
|||
This year's annual
|
#25
|
|||
|
|||
This year's annual
On Sat, 04 Nov 2006 23:28:52 +0000, A Lieberma wrote:
I think that the high copper count doesn't necesarily mean anything drastic... It was the "significant change" from prior analyse that is causing concern. The company faxed over the report and suggested to contact Lycoming. The A&P feels the way you do, except to keep an eye on it and get the oil analyzed again on the next change. We just had a copper issue in an engine (O-360) about 200 hours past TBO. Mattituck said "fly 15 hours and then retest". The A&P that contacted Mattituck converted this to "don't fly the airplane until the engine is overhauled". Unfortunately, at least enough of my partners took the A&P at his word regardless of the evidence I found to the contrary (none of which was conclusive, I admit). They were all concerned that the bearings were about to seize. I'm certain that, had this engine been younger, the reactions would have been more reasoned. But there's this incredibly strong belief, apparently, that at TBO an engine should be taken out and shot. Even if they do "know better" than this, the slightest problem is an excuse to pull the overhaul trigger. I'd be very interested to learn what the source of copper is in your airplane's oil. - Andrew |
#26
|
|||
|
|||
This year's annual
On Mon, 06 Nov 2006 15:59:25 +0000, B A R R Y wrote:
coke up valves I'm guessing that this doesn't refer to the Pepsi competitor. So what does "coke up" mean? - Andrew |
#27
|
|||
|
|||
This year's annual
Can you (or anyone else) explain the mechanism of this? Why a full ruch
taxi would affect compression? I routinely lean the mixture for idle and taxi because I've learned that at my home airport (KORL) the plugs can foul between the ram and the run up area. But I don't understand (and I'd like to be educated) how it affects compression. John Stevens PP-ASEL Not exactly the aircraft perspective you are looking for, BUT in recip race motors for sports cars, you do hot cuts if you want to read plugs or do compression checks. This means you rev the motor to 4 or 5 grand, stabilize it and shut off the ignition. We find differences in the numbers we get just from excess fuel in the cylinders with idle cuts. Running at idle is a rich environment and the small washdown you get can make the numbers get funny on leakdowns. Another thing to consider is that in the trucking industry, idling loads the top compression ring gap with sootlike deposits that hinder compression sealing. It is something oil companys are VERY concerned about. So you now have 2 data points from very different places that show you that idling loads up the rings and effects the compression readings. YMMV -- Have a great day Scott |
#28
|
|||
|
|||
This year's annual
It's the heavy black carbon deposits that can build up on the valves,
piston crowns, ring grooves, etc... Nasty hard **** (technical term) Jon Andrew Gideon wrote: I'm guessing that this doesn't refer to the Pepsi competitor. So what does "coke up" mean? - Andrew |
#29
|
|||
|
|||
This year's annual
"pbc76049" wrote in
: Not exactly the aircraft perspective you are looking for, BUT in recip race motors for sports cars, you do hot cuts if you want to read plugs or do compression checks. This means you rev the motor to 4 or 5 grand, stabilize it and shut off the ignition. We find differences in the numbers we get just from excess fuel in the cylinders with idle cuts. Running at idle is a rich environment and the small washdown you get can make the numbers get funny on leakdowns. Interesting you mention this, so we just may be able to get aviation perspective in the next day or two. I went to the airport this morning to see what was up with the corrosion and found out that will be fine, but the cylinder with low compressions isn't making the cut again after the leak test. So, my A&P wants me to take it in the pattern, running full throttle when I can for about 10 minutes and bring it back down for another compression test. He is of the thinking that a high RPM will show a truer reading, is my guess. If the compressions don't come up, then we will have to send it off to get it serviced. I would have flown it today, but thunderstorms and small planes don't mix too well, so I have to wait until this slow moving systme moves out. Allen |
#30
|
|||
|
|||
This year's annual
I'm convinced compression readings vary with everything including
day-of-the-week and the phase of the moon etc. My 172 M has (eventually) met compression for 31 years (I guess that would be about 120 readings) but for about 10% of the readings it required a retest 10 hours later to get a cylinder above 60, at which point it would be back up. Through the years numbers though were completely inconsistent except that the inconsistency was inconsistant too. I always used the same compression measuring rig (I called it the heart failure model) so that was not the source of the variation. John Thorpe preached that removing the upper spark plug before compression testing could drop debris on any open valve faces reducing the reading. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
This Years Annual!! Oh Boy!!! :) Simi Long! | NW_PILOT | Owning | 8 | November 9th 05 10:53 PM |
Washington DC airspace closing for good? | tony roberts | Piloting | 153 | August 11th 05 12:56 AM |
Ten Years of Flying | Jay Honeck | Piloting | 20 | February 19th 05 02:05 PM |
millionaire on the Internet... in weeks! | Malcolm Austin | Soaring | 0 | November 5th 04 11:14 PM |
Annual Coronary | Jay Honeck | Owning | 19 | May 24th 04 03:47 AM |