I guess the question is, what do you do in this scenario? Seems all noninvasive techniques are kind of exhausted.
I'd check for a sticking valve before doing anything else. Did you notice where the air was escaping from during the compression test?
I guess the question is, what do you do in this scenario? Seems all noninvasive techniques are kind of exhausted.
I'd check for a sticking valve before doing anything else. Did you notice where the air was escaping from during the compression test?
Some more happy news. A&P chopped out my front baffle air dams, worked on my baffling, adjusted my idle mixture, took off on a full power steep climb 2000fpm and highest cht was 389.
Did you do a Ring Flush? That's about as noninvasive as it gets, and a cylinder with rings that stick occasionally is a perfect candidate for the procedure.I guess the question is, what do you do in this scenario? Seems all noninvasive techniques are kind of exhausted, so do you pull the cylinder and open a new can of worms in terms of risk? I guess I could carry my extra cylinder around with me.
I agree with the note that a true "0" compression would be unusual except for a wide-open exhaust valve but, even then, might not be zero.
If your mechanic is familiar with the Rope Trick I would drop that (likely) exhaust valve out and check the valve itself (carbon fouling) and the guide (carbon fouling). Both can be cleaned up and the valve put back in.
I also might agree with the "zero cold, normal hot" might leave you in a field somewhere. That also sounds like a sticky valve that will some day stick open and stay. Ask me how I know that..... My compression was not zero until the day I brought it back after a near off-field landing and checked the compression. Stuck exhaust valve with NOISE coming out of the exhaust. This was in the Cub, not SuzieQ.
Or you can just fly and see what happens......
Did you do a Ring Flush? That's about as noninvasive as it gets, and a cylinder with rings that stick occasionally is a perfect candidate for the procedure.
Did you do a Ring Flush? That's about as noninvasive as it gets, and a cylinder with rings that stick occasionally is a perfect candidate for the procedure.
Were the front cylinders the hot ones originally? [#1 and #2] ?
I had an o-360A1A cylinder that would line up the ring end gaps in about 150 hours. It did it twice and all measurements were in book limits. Changed out cylinder and piston and it has not happened since. Could not figure out if it was the cylinder or piston because all measurements were per the manual.
cylinders do not lose compression when the ring gaps line up. Air is very clever and does not need a straight path to move effectively under pressure. If this were a real issue, manufacturers would have devised a way to keep the rings in the desired alignment many decades ago. Yes, forcing the air to turn does slow it down just a bit, but the difference is quite insignificant at 80 PSI. Even less so at the 150-200 PSI in dynamic compression. Even less so at the hundreds of PSI during combustion. OTOH, If someone filled down the rings too much, leaving an excessive gap, that can reduce static compression.
They were all hot. I actually think #3 was the hottest by a hair, but they all ran pretty close. He did the washer trick on #3 just in case. Either way, he's been sending me videos of aggressive climbs and still not getting to 400, so I am happy on that front.
You need to change A&P's. If I skimmed all the post correctly the plane has been fine, and the engine monitor says all temps are fine. Then you took it in and he said 40, then 0, then 75, but now there is an overheating problem???
0 is almost impossable. I would say either a bad gauge, or he was not checking it on the compression stroke. Now the timming is off to cause overheating and he performs surgery on previously working baffels??? - run like ****. Either he does not know what he is doing, or the timming marks on your flywheel are not indexed correctly. Either way, your A&P sucks.
So if they were all hot, that points to baffle sealing problems.
Removing the dams in front of #1 and #2 will increase airflow on those two cylinders... stealing air from the aft cylinders.
Given your location, these are aggressive climbs in what 50F air temps?
I mean, I'm happy progress is being made, and your cylinder issue seems to have been some sort of fluke, but I'm still a bit bothered by the approach. If temps are all hot, fix the leaks FIRST. Then decide about the dams.
I see lots of A&P's rip out those dams, with the logic that you don't see them on Cessna 172's and Piper Cherokees. Planes with much bigger inlets.
Yes it was cold. There are quite a few RVs I’ve seen out here with those dams removed and two people with 7s told me they got cooler CHTs once they were removed. I’ll keep an eye on differences in CHT.
Then check out this thread ... https://vansairforce.net/community/showthread.php?p=1510158&highlight=wrap#post1510158
This is a monstrous thread you linked me to. Are you focusing me on the page with the link with the intense baffle mods?
Yes. Point being Dan, who has studied the cooling air flow EXTENSIVELY has added a lot more dams to the airflow in search of good cooling + efficient use of cooling air.
I'll be interested to see if your CHT's are still balanced front to rear without the dams. I've put dams IN on two RV7's and improved the front to rear balance. Let us know how it is when you get it back.
For experiment purposes aluminum duct tape works great for creating a temporary dam if you want to try with & without.
For temporary dams just put a piece of velcro in front and you can adjust to virtually any size fast.
Art
Now the timing is off
And they did...
In the 70's, my 2 stroke Tohatsu motorcycle piston had a pin in the gland to keep the ring in one place so it would not rotate and catch on a port. The ring was designed to seal around the pin.
At a dilution of 640 to 1, is there any value remaining in the MM oil??I run 2 ounces Marvel Mystery Oil mixed in 10 gallons gas. I’ve been doing it forever...