New (to me) Supercub... Running hot? Charging issues too

Re: baffles. Here's an older thread with some info to consider. http://www.supercub.org/forum/showthread.php?53119-My-SQ2-Mods

Mount a GoPro in there and see what your baffle seals are doing in-flight. Air is supposed to go down-around-through cylinder fins. When your baffle seals aren't working, goes straight out the back...

The PC680 manual warns against going over 15.0v, most AGM's chemistry can't take it. I put a sticker on my typical 2/10/50 amp charger: no agm's!

Skywalker said:

The PC680 manual warns against going over 15.0v, most AGM's chemistry can't take it. I put a sticker on my typical 2/10/50 amp charger: no agm's!

Click to expand...

Automotive type chargers are constant voltage chargers. That means that the voltage will remain at a set point, usually 14.2 to 14.5 volts. Only the charge current is regulated. If you have worked with nicad batteries, that charger is a constant current type. The output can be set to a desired level and the voltage will rise or fall in order to keep that level of current moving.

I have a limit of five amps on most non lead/acid batteries, but that is simply due observations over the years, not any rocket science. With ANY battery of ANY type, a slower charge rate over a longer period of time is better for the health and longevity of the battery. A high charge rate (more amps) will cause the battery to heat up and can cause internal damage. Think 'one amp overnight' instead of '15 amps for an hour'.

Nothing wrong if you don't want to use that charger on your AGM batteries, but it's an unnecessary precaution. If you set it on the 2 amp setting, you'll prevent heat damage to your batteries.

Web

If you ever truly kill an Odyssey overvolt charging can tickle it back to life, but you need to sit there and monitor it. A liitle too long on high will cause it to deform the case.

If my plane saw 15v I’d be on the phone with B&C to get my voltage regulator fixed.

Lol. I once blew the rubber sealing plugs out of an old Odessy. Before that, I didn't even know those plugs were there.

Web

It's hard to tell from your posts if your regulator is outputting 15+v all the time or is it sometimes 15+ and then cuts out or appears to charge at 12v? Also do you have a B&C LR3(B or C) brand regulator?

If it's a B&C LR3 type, in addition to the trouble shooting steps in the B&C (assuming that's what you have?) installation instructions there are two other I use that seem to help.

1) Check the voltage between the ground at your battery and the ground of the regulator. This should be zero or very close. Any reading here will be amplified by the two reference diodes inside the B&C regulator and will change in a disproportional amount the output to the field windings(which elevates charging output) and the base of the crowbar latch that is designed defibrillate your expensive electronics as it pops your bus circuit breaker.

2) Check for continuity between pin 4 and 6. If it exists then your output transistor (the thing on the outside of the case) is shorted and your regulator is running wide open. I don't think this is your problem but worth checking.

If all connections are true and the trouble shooting guide steps test ok, then see if your new battery charges ok. If it still charges at an elevated voltage then there is an adjustment screw on the regulator. Per the instructions adjust it to factory setting making sure you are checking the output voltage at the battery.

Good Luck - Jerry

The 10 amp setting on my cheapo Century charger will run right over 15v on a small batt, I only use smart wall blobs on small agms.

'Cheapo charger' sounds like the operative phrase. Check the voltage on a lower setting, if available. If not, don't use it I guess.

Web

I like battery tenders. I still keep a manual charger to get some life in a lead acid battery because some "smart" chargers can't deal with a fully discharged battery. Lead acid batteries will eventually go the way of the dinosaur. IMHO.

I like the ideas. They will have to wait till next week. Flying the jet now.. not near as fun, but pays a hell of a lot better.

I'll get after it. I'll get it all figured out. It was probably just under 15.. and not consistent. At times it would show 12.1 or so. When it was showing 15.. I could trip off the field current, and it was slowly drawing down towards 12.


JP

My typical auto store 2/10/55 charger on the 2A setting takes my fully charged PC680 from 13.02 to 15.5V in 15 seconds. The label on my PC680 says 14.8 max. AGMs should be on Tenders.

Mechanic reported that he thought the #2 intake has been leaking since new. (40 hours, 8 years) I hope that was the source of some of my temp issues. As I said.. leaning it at cruise yielded no increase in RPM before it dropped off. It's fixed now. Got my 6.00s on (for the skis) and the new battery is in.

I'll get to test it on Tuesday.

He did say that the carb was a carb for a 160hp.. so he didn't think drilling the jet would be necessary. He didn't get to some of the baffle sealing I wanted to do.. but I'll do that when it's in the heated shop for ski install.

JP

If you still have problems Check the mag timing (did you figure out what mags you have) and pull the carb to look at the jet. Just because the carb fits does not mean that it has the proper jet.
DENNY

I did speak to him about timing. I didn't remember to ask him about it (I'm in Kansas, he's in Maine)

We'll see what next week brings. My plan is to fly the hell out of it, do an oil change with analysis. See where I'm at.

JP

exhaust

As an aside..

Not sure if you'd call this the seaplane lip. Unlike some others I've seen.. my exhaust comes out in this outlet, and not forward like some.

JP

JP

I you are seeing cyl temps north of 450 please don’t “fly the hell out it” until you have addressed hi temp issues.

lots if discussion on this issue in the past, quick summary:

1) check that engine is operating correctly,
no intake leaks, timing is correct etc.
check accuracy of your probes
2) baffling, often overlooked but critical.
place a light source by firewall and look thru cowl inlets, (in a dark hangar helps)
you should see NO light, little leaks add up.
I recently replaced poor fitting felt baffling with well fitting silicone material
and dropped #3 CHT 30 deg at cruise.
3) carb, mixture leaning authority - at least 150 deg EGT sea level at 2300 rpm, more if you are in really cold country.
theres no “160 hp” carb, just a 150 carb that may not be delivering enough fuel. (Hope your mechanic is not the same guy that missed the leaves between your cylinders during pre-buy )

Other things that that can help - sea plane lip, bigger cowl doors etc.. lots of work for minimal return.
hope these and previous suggestions help, good luck.

Exhaust valves not completely closing can cause high CHT & EGT temperatures.

I was under 450 on a cold day.. I guess i'm making the assumption that the lean condition was caused by the number two intake pipe being loose. I'll find out when I get home and can fly it.

New battery installed.

I think in looking at other's pictures, and using my recollection only...

My baffling was in contact with the aft lower portion of the #3 cylinder fins. It seems from others that this area should be 'stood off' and have some space between that low corner of the cylinder and the baffling.

I wasn't getting any rise out of the rpm while leaning in cruise. Until that issue is fixed, you're right.. I won't be flying it a bunch. I hope we've gotten the bulk of the issue. I do have plans to do some better air sealing when it's in the shop for ski install.

Thanks.. I'll follow up once i get to fly it.

JP

Your in good hands with those Twitchell boys. Good old fashioned Mainers, they still do business on handshakes. They will get to the bottom of it

when you get it flying let's hook up and fly. You can get mixed up with the rest of the pack that runs around here. You will never be the same

jim

Jim.

Thanks. I've been banging around here a while. Started at 3b5 over 30 years ago... when I was 14.

I went off to aviation college.. taught at twitchells when I was still in school. With graduation coming up.. Mike just told me.. You graduate this spring, right? When I said yeah.. He said.. good, you're gonna go fly for Roger Currier. That's how small town works.

I never did a pre buy. The plane was right at my home airport. I'm still a little nervous about how little it flew... but I hope we've got the major issue addressed.. and a few tweaks are still to come. We'll see. This stuff is a journey.. not a one and done. Looking forward to getting my skis in a couple weeks. I'll spend my time doing tweaks while it's in the heat.

JP

I wouldn’t expect an RPM rise from leaning in cruise. I pay little attention to RPM when leaning through idle cutoff. What’s important is leaning authority in level cruise with a warm engine. If you can’t demonstrate a 150* EGT rise between full rich and peak you’re running too lean. Especially as temps get cold and air gets dense. You need more fuel flow for cold weather ops. If you’re lean your engine will get hot on climbout and probably will never recover to normal temps during cruise. If you were lean in summer temps, be very careful in colder temps. Don’t get too caught up in talk about jet size. Your carb is simple and the main jet is the simplist part. It’s just a brass pipe. If you need more fuel? Ream it a little larger. If that isn’t enough? Ream it a little more. You’re experimental so you don’t even have to keep quiet about doing it.

An intake leak at #2 doesn’t explain high temps at #3. Fix the baffle at #3 to allow air to flow down the aft side.

None of this stuff is hard. It should be fun. Get in there and get your own hands dirty. Dial that plane in and enjoy it.

Thanks stewart. Yeah.. The leaf or two I got wasn't helping. I saw a little piece sticking out in the corner.. then found them once i got on a ladder.

Even with that.. I think the baffling around number 3 isn't 'right' for this engine in this plane. I'll try to get a good picture before I start messing with it.

The EGTs were quite high.. I'm hopeful that they ALL were because of the really bad leak at 2. I guess we'll find out. Thanks for the tip on leaning. I'm in line with your thinking. I'd rather have the fuel available.. then lean with the mixture.. than want more and not able to get it!

I'm working through an intercom issue. Since Im at work.. I'm reduced to using a few pictures I took of cockpit.. zooming in to find model numbers, then looking up manuals online. I have a few ideas for hopeful quick fixes via settings, then changes to wiring. doing all I can with internet research. Stinks to not have a heated hangar.



JP

JP11 said:

The EGTs were quite high.. I'm hopeful that they ALL were because of the really bad leak at 2.

Click to expand...

That leak at #2 only addresses #2. And you should get a rise in rpm at cruise when you lean the mixture.

Leaning in cruise gives me about 20 or so RPM increase. 160 HP, and the carb is unchanged from when it was on my 150 HP.

I got a chance to fly it yesterday. The simple stuff.

I found the baffling behind 3 still needs work. I was able to get it away from touching at the corner.
3 is still the hottest. In a climb to about 2k.. at 50kts or less, I was seeing CHT around 460. Cruising around 3 was just over 4.. Others 350.

I'm still suspect of EGTs in general. They always read 1300+ . I was able to lean at cruise and get about a 100 increase

Oil temps were stable about 120 to 140.

Voltage was consistently in the 14 to 15 range. (plan to turn down the regulator a bit)

Mechanic forgot to check the timing. That's the last suspect at the moment. I think they are slicks.

I'm going to do some baffle sealing in a couple weeks when it's inside for the ski install.

I got to test my aux tanks. Seems it moved most all the fuel (I've got 24s for main, and 10 aux each side.. not sure how many long trips I'd want to use them)


JP

I would recommend you stop doing hard climb outs. At least until you get the temp issue cleared up. Clean the cowling hinge and put aluminum duct tape over the hinge. Sounds like you are on the right track and I suspect things will get better. If your slick mags need a overhaul (new SB out) I would trash them and get a set of Bendix.
DENNY

What charging system do you have? And how are you monitoring voltage? I.e. voltmeter in panel or handheld?

Web

CHT gauge(s) and probe(s) calibrated together? Dunno whether those probes are thermocouples or thermistors, however there could potentially be a mismatch. If thermocouples, if I recall correctly I think all of the wiring connection pairs need to be at the same temperature (i.e. same location). At least I think mis-calibration should be ruled out.

Thermistors reduce their resistance when heated. That's what varies the reading on the gauge. I've never seen them on CHT's or EGT's.

Thermocouples actually produce a current flow in response to being heated. Works great and extremely accurate. Unfortunately there are two types of probes used on general aviation systems. K type and J type. Doesn't really matter what the difference is for us except when replacing probes. You need to match the wire colors of the probes removed. J type will be a red wire and a white wire and the K type will be a yellow wire and a red wire. I don't care what the parts store tells you, DO NOT wire up probes of a different color than what was installed by the manufacturer. They are not interchangeable. As a common sense item, just install probes provided by the manufacturer and you'll be safe. A quick visual will show you if someone installed a wrong probe. Just look for the odd one out of the bunch. And while you're in there check that each EGT probe is installed at the same distance from the exhaust flange. There is not exact distance called out but there will be a range of minimum to maximum. They need to be installed within this range and all at the same distance. CHT probes can be two different types. One is installed in a well in in the cylinder head and the other goes under the spark plug just like a spark plug gasket. Check and see if you have one probe that is of the opposite type than the rest. For best accuracy they should be all of the same style.

As has been mentioned, if you want to check for one odd probe, put them all in an oil bath and heat it slowly. Use an accurate thermometer to monitor the oil temp and watch the gauge. If all probes match the rise in heat, you're good. If one is off, then it's time to troubleshoot. Swap probe positions on the harness and see if the odd temp follows the probe or stays in the same position on the gauge. If you have and older system, check if the wire length is critical. With some older systems, you were not allowed to cut any wires to probes. If you cut them to length for installation, then it would disrupt the calibration of the gauge. All of the newer systems allow you to cut wires to length as long as it's not the thermocouple wires themselves.

Web