EGT Mystery Resolved - EI SR-8A a Fine Tool

[Darrel Starr]

We have an Electronics International SR-8A analyser in our Super Cub. It scans all four EGTs and CHTs. Over the last season, I would watch it scan periodically and got used to the temps I saw and the relationship of one cylinder to another. For instance, #4 is always the hottest CHT and #3 is the hottest EGT. That is #3 WAS the hottest EGT until a few months ago. As the ambient temps got cooler, #2 EGT slowly passed up #3 until more recently #2 has been running 20F higher than #3 instead of 20F cooler. Now none are running particularly hot but still ... Why?
After noticing this, Bob Eckstein performed the annual inspection and compression was up so we ruled out a leaking valve. We switched #2 and #3 probes but that did not reestablish the "normal" EGT relationship between #2 and #3.
My nose cowl still has the original starter hole but with the small B&C starter so it allows quite a bit of air into the lower cowl and there are large air gaps also in the nose around an air box I made that replaces the original oil cooler. So I have been suspicious that the #2 intake tube has been getting a direct shot of cold air (whereas all other cylinders have an exhaust pipe in front of the intake pipe warming the air surrounding the intake pipe). If the intake pipe is too cold, fuel in the air-fuel mixture may not stay vaporized and might liquify out, leaning the mixture when it gets to the cylinder.
I disassembled the #2 intake track and noticed that the inside of the oil sump-to-cylinder tube was coated with a thick layer of fuel dye. That might be normal but I think that is circumstantial evidence that fuel has been condensing in the tube. I installed a new hose section connecting the oil sump to the intake tube and a new gasket at the cylinder but actually the intake seemed to have been sealed properly as originally assembled by Larry Cassem (as one would expect knowing how careful Larry is). I did find that the primer line fittings at the #1 and #2 orifices were only finger tight, that is the only thing I saw that might have allowed some outside air to enter the air-fuel mixture and lead to a leaner than normal mixture.
Also, along the way we installed a cover over the oil cooler because oil temperature was running only in the 160F neighborhood.
Today, Minnesota warmed up to 35F so we took a ride. For the first half hour as oil temp stayed below 160F, the #2 EGT was still running 20F hotter than #3, in the 1260F to 1280F area. BUT then as the oil temp climbed above 180 and stabilized at 185F, the relationship changed. At that point #3 EGT returned to being 20F above #2 as it "should" be. That happened I think because the oil heated the mixture enough so the fuel would stay vaporized in the cold intake tube. So now I am confident that the reason for the apparent leaning of #2 in cooler weather has been the cold #2 intake tube and that I need to protect it from a blast of cold air coming in the lower part of the nose bowl.
Now I know that none of this was serious enough to damage the cylinder and that I never would have known this variation even existed if I had not been watching the SR-8A but still it is gratifying to be able to see an anomoly and to be able to follow a trouble shooting procedure using this fine analysis tool.
Darrel

 

[kevin]

Hi Darrel,
I am glad that this worked out for you. We have become so used to modern technology that I often wonder how we ever got by without it all of these years. I would like to install an engine analyzer in mine when I am ready.

 

[Darrel Starr]

Flew N18SY today with ambient at 30F and oil temp slowly coming up to 172F after 30 minutes and with the #2 intake tube covered with an insulating blanket of Koolmat. With this insulation over the #2 intake tube, the #2 EGT ran 20F cooler than #3 just as it "should" even at the cooler oil temps as the engine was warming up on climb out. So, I believe that this confirms that the #2 intake was running too cool and allowing some of the fuel (a small quantity) to condense out before reaching the cylinder before it was insulated. I'll leave it that way for the winter.
Darrel

 

[skywagon8a]

This is interesting Darrel. It makes me wonder what would happen if all four intakes were insulated year around? Would there be improved atomization in all four cylinders providing greater efficiency? Perhaps slightly better fuel consumption? Would the difference be enough to measure?

 

[Darrel Starr]

Good question, I was wondering that also ... maybe someone with some insight can chime in. I could see wrapping intake tubes in insulating tape then dipping that in something like a silicone liquid to bind it all together or possibly just have insulating sleeves made for the intakes. What makes #2 the target though is that it is the ONLY intake tube that does not have an exhaust pipe running just in front of it so it is the only intake pipe exposed naked to the cold air coming in the nose.
Darrel

 

[cubdriver2]

Technology is a great thing, some times all that info just tightens up your sphincter muscle, most times I'm content just knowing that there's still noise coming from up front :lol:

Glenn

 

[Mathew Sharp]

Matt

 

[Darrel Starr]

I liked your response Mathew.
Darrel

 

[garyh]

QUESTION? Is #2 the left rear cyl. and #3 the right front(by prop) as it is on my c90?
gary

 

[Dave Calkins]

GaryH, hope this helps you. Lycoming #2 is the front left.

Lycoming front right is #1. Aft right is #3

Continental front right is #3. AFt right is #1

 

[Darrel Starr]

Since I brought this topic up, a couple of IA friends (Bob Eckstein and Larry Cassem) have told me that they have seen winterization kits for 4 cylinder and 0-300 6 cylinder Continentals that have included a snap on "diaper" cover for th oil tank and snap on sleeves to cover the intake tubes ... does any of this ring a bell with you guys? Apparently these were common on early 0-300 powered 172s if that helps to jog the memory.
Darrel

 

[Roger Peterson]

On my 0-200. #3 EGT is always 200 deg hotter than the others. Right front with no exhaust in front. My CHT is always 80 deg hotter. I just insulated it and waiting for the wind to die down so I can go ck it out. Been working on the problem for 5 years and I bet this fixes it.
Will post as soon as I ck it out.

 

[cubdriver2]

Since I brought this topic up, a couple of IA friends (Bob Eckstein and Larry Cassem) have told me that they have seen winterization kits for 4 cylinder and 0-300 6 cylinder Continentals that have included a snap on "diaper" cover for th oil tank and snap on sleeves to cover the intake tubes ... does any of this ring a bell with you guys? Apparently these were common on early 0-300 powered 172s if that helps to jog the memory.
Darrel

I have one that I've used on my C90 and I don't think it does anything more then keep the oil warmer when your parked or keep the oil colder when your trying to preheat

Glenn

 

[Darrel Starr]

cubdriver2 -- if possible, please post one or more pictures of this kit.
Thanks, Darrel

 

[cubdriver2]

cubdriver2 -- if possible, please post one or more pictures of this kit.
Thanks, Darrel

Darrel I don't have any pix, but imagine that your wife, girlfriend, or significant other knitted you a pouch to keep your ballsack warm with some flaps and snaps to keep it pulled up and help it stay in position, it's like that but hopefully bigger :lol: It's like a daiper, then there are the sleves that go on the intake tubes, they are little blankets with snaps along the long sides that go around the intake tubes and snap together to make little insulated cylinders around the tubes. sorry that's the best I can do.

Glenn

I just realized your a 0320 so your sump is different the a C90

 

[superchamp]

EGT

While we are on EI and EGT subject - I have an EI UB-8A analyzer on my Pponk 0470-50. Last fall on occasion I would get a high limit differential warning on my #1 cylinder EGT, indicated by one bar and the numbers 1999. This means that that cylinder EGT is higher than any other by a preset amount. I didn't set the limits on my unit since it came with the plane, but it looks to be 200 degrees. The light would come on occasionally in cruise, but now always. This winter when I run it just to circulate the oil (not flying it, on straight floats), almost immediately the #1 EGT will give me a red light and the high limit differential. If I manually toggle across the cylinders and come back to #1, for a few seconds it will read anywhere between 1300 and 1600, and it will change temp up and down in this range rapidly and after 5 or 10 seconds it will go to the bar 1999 and stay there. My question, do I have a bad probe? or is this erratic temp reading a sign of a valve/cylinder going south? This is a 70 hour SNEW ECI Nickel Titan cylinder.

 

[Darrel Starr]

I had a similar situation, one of the EGTs went bananas -- found that the thin covering on the probe wire was bare and apparently was grounding out intermittently. That is my guess in your case also. These wires are just barely covered with a VERY thin insulating layer. I like the system but these dainty wires are a major headache. EI needs to take action.
Darrel

 

[mvivion]

Superchamp,

Your problem may be associated with the O-470's propensity to run really rough in cold temperatures IF the front induction crossover tube is not insulated. The standard fix for that is to tie wrap some foam pipe insulation around the forward induction cross over tube.

I've never run an O-470 with a graphic engine monitor without one of these, but if it doesn't have insulation on the forward cross over tube, it won't run for crap.

And, while we're on the subject, if you are not flying that engine, you should NOT be starting it and running it on teh ground. You are NOT doing your engine any good, and in fact, according to several recommendations from the engine manufacturers, they say to either pickle it or DO NOT run it on the ground, since you'll never get it up to operating temperature, and therefore never get rid of the moisture that accumulates from heating, starting, and running on the ground. You need to get the engine to AT LEAST 180 degree oil temp for a half hour or so. That's next to impossible to do on the ground, and the temperatures aren't likely to be even unless you're in flight.

Don't run these things on the ground to "protect" them in winter storage.

Don't believe me?? Give Continental a call. Loren Lemen will answer that one.

MTV

 

[superchamp]

EGT

At the annual this spring hopefully the cylinder will check out OK and we'll find a bad wire to the proble. Actually, I am running the motor hard enough to get the oil up to 183-185 degrees and letting it run there for 10-15 minutes, after preheating the night before. Start up to shut down time is a good 30 minutes. Monitoring CHT EGT and oil temp the whole time, and cycle the prop a number of times. I would have preferred to pickle it, but I was too busying hunting last November to deal with it. Now its sitting in a snow bank in my front yard and I have had no desire to tear into it for complete pickle job in the bitter cold. I discussed running it twice a month with my mechanic and he said as long as I preheat, then run it hard enough to get the oil over 180 for a period of time without overheating the cylinders, its not much different than taking a couple short flights a month. I'll bet the majority of the planes in this cold climate aren't pickled and don't get run twice a month, not that it makes it right, but it is reality. The best part of way I'm doing it is I get to smell the 100LL burn, here the motor run, and listen the XM radio while I fiddle with the engine monitor and dream of flying over Canada in a few months.

 

[StewartB]

Wow. You really think repetitive ground runs of 30 minutes are helping your engine? I'm on MTV's side. I wouldn't do it!

By the way, nickel cylinders won't rust.

Stewart

 

[superchamp]

EGT

Well could be my mechanic is wrong on this, but if you bring your oil to operating temp and keep it there to burn off moisture, and your EGT and CHT's are in normal operating range - thanks to our cold air up here - how does the motor know its on the ground and not in the air? All the operating parameters are virtually the same as if I were flying- I'm seeing the same temps & pressures as I would cruising around on a October day. Not being smart, just looking for enlightenment. My other option is to do nothing and just let it sit. I missed my opportunity to pickle it last November and then it got cold, bitter cold, and from the pickle procedure I have done in the past you need to remove plugs, which means remove the cowl, all of which I'm not going to do in mid- winter in northern MN outside standing on a ladder in a snow bank with the wind blowing. If you think just letting it sit for 4 months without being run is better for it, I'm all ears. Does running it once/twice a month qualify as repetitive? As far as rust, what about the cam or crank? And not all the cylinders are nickel. Probably will end up that way one at a time, from what I here about the big continentals.

 

[StewartB]

The difference? High power settings and 150mph ram air to pressurize the cowl. That's what my airplane was designed for.

FWIW, I change my oil to Phillips or Aeroshell anti-rust with some Camguard added and park the plane. I don't do the desiccant plugs or tape the exhaust pipe shut or spray the cylinders with oil. Clean anti-rust oil and park it in the cold, where water is solid and rust is really slow to form. And my cylinders are steel. 15 years and no storage problems yet.

The hardest thing on an engine is starting and stopping. The weak spot on a big bore TCM is the cylinders. My engine is better off sleeping in the cold than being heated, started, and cooled off again for nothing. At least that's my attitude.

Stewart

 

[superchamp]

Thanks for the advice stewart, although changing oil on mine involves a cowl removal for all practical purposes, and I'm just not up for that at minus 20F. Next fall I'll try to do a change in late October to a rust preventative oil. Some say the hardest thing for a motor is not to be run at all. I know that to be a fact with two strokes such as chain saws and boat motors, I'll throw in my plow truck and skidsteer on that theory also. Running them few times in the off season sure seems to help it start when its needed come winter. I agree with very little rust forming in the cold dry northern climates. I am hitting 2000 rpm for a while in this warmup. Why would pressurizing the cowl matter? Not enough air in the fuel mixture?

 

[StewartB]

Not advice, just opinions. I was always taught to minimize ground operations.
Over the years that's become engrained until I believe it as fact. It may or may not be correct, but that explains my perspective. At any rate I enjoy the discussion.

A pressurized cowl ensures adequate air flow over all air cooled surfaces. Cylinder cooling is very important with big bore TCM engines. It's especially difficult with Pponks.

Stewart

 

[skywagon8a]

The CHT gage only measures the temperature at the cylinder head. There is no way to know what is happening to the cylinder barrels. Unless it is flying, you will not get the cooling air completely doing it's job. Does metal rust when it is stored in a block of ice? I don't know, perhaps someone here does?

 

[superchamp]

EGT

skywagon may be on to something, it would be a lot easier and quicker to pickle an engine in a block of ice up here, just put the hose in the top of the cowl and fill'er up.

 

[mvivion]

Superchamp,

I've discussed this topic with several engine overhaulers, as well as TCM technical reps, and they ALL say DO NOT run an engine on the ground periodically in lieu of proper pickling.

As Stewart says, I really don't think you necessarily have to do the full pickling process, the most important part of the process is to go to a preservative oil.

Here is Lycoming's guidance on ground running an engine:

"Some operators are running the engines on the ground in an attempt to prevent rust between infrequent flights. This may harm rather than help the engine if the oil temperature is not brought up to approximately 165˚ F, because water and acids from combustion will accumulate in the engine oil. The one best way to get oil temperature to 165˚ F is to fly the aircraft. During flight, the oil normally gets hot enough to vaporize the water and most acids and eliminate them from the oil. If the engine is merely ground run, the water accumulated in the oil will gradually turn to acid, which is also undesirable. Prolonged ground running in an attempt to bring oil temperature up is not recommended because of inadequate cooling that may result in hot spots in the cylinders, baked and deteriorated ignition harness and brittle oil seals which cause oil leaks. Pulling on engine through by hand if it has not been run for a week or more is NOT recommended, and can result in increased wear. Refer to Lycoming Service Letter L180.
If the engine is flown so infrequently that it does not accumulate the operating hours recommended for an oil change (25 hours for a pressure-screen system and 50 hours for a full-flow filter system), then the oil should be changed at four-month intervals to eliminate water and acids."

While this is Lycoming speaking, the principles are the same.

But, it is YOUR engine, so....enjoy! :roll:

MTV

 

[superchamp]

EGT

I believe you Mike and Stewart, and won't run again. However, say you are into the winter (like me) and pickling or oil change is no longer an option(like me). Are you better off just to leave it sit for the winter, or run it? Which is the lesser of two evils? I just spoke with a mechanic friend who used to take care of a number of DeHaviland and Cessna products in NW Ontario. He said they never pickled them. They sat outside all winter without running. He also said in all those engines that he pulled apart, not one ever showed signs of rust. He claimed that all those engine parts were well coated with oil, even when they would pull apart an engine in February that hadn't been run since September. This was his real world experience, he recommends in my case just don't run it anymore. Back to the original EGT question, his opinion is its a bad probe, a sticky cylinder or valve guide problem probably wouldn't give these erratic EGT readings. He also felt it would run rough if I had valve problems developing. We'll find out in April.

 

[mvivion]

SC,

I guess I don't understand why pickling isn't an option now. I've changed oil outdoors in some pretty cold weather, and it sure isn't fun, but....I'd buy some pickling oil and/or change the oil and add CamGuard, and button it back up.

I know people also who've parked engines all winter and maybe never had a problem. Understand that the "problem" may not show itself for a long time, though.

I also know people who've had problems, probably associated with poorly stored engines.

I'd warm it up enough to get the oil to flow, dump the oil, and pickle it. I probably wouldn't bother with the cylinders at this point, though.

MTV

 

[superchamp]

eGT

If I can reach underneath through the cowl flap and get to the oil drain, I may try it. Last time I helped my mechanic we pulled the whole cowl cause we just couldn't seem to reach in there and get something under it so oil didn't run all over creation, plus we were changing the filter. Pulling the cowl with a 3 blade prop by yourself is impossible. Getting it over the exhaust when its jammed up against a blade in the front makes for lots of bad words and scratched paint. It took 3 of us to get in back on last time. The obvious answer is to change the oil in Oct before you park for the winter when its warmer and you have a helping hand. But I had too many ducks and deer to kill then to worry about it.