High chts low oil temp

Started flying my newly refinished experimental cub. I decided to have cylinders
rehoned and new rings due to a little bit of rust on the walls. Engine came out of a certified cub with 56 hours since lycon overhaul with port and polish. Removing cylinders to check cam and followers found heavily domed pistons. Called lycon with part number and determined 10:1s with deck height shaved for another half point boost. Running one pmag set 2 ATDC and jumper in. Rear mounted seven row airflow designs cooler which is supposed to run 5-15 degrees cooler than standard seven row.

Its been cold here in Alaska and during break in with cruise prop nice low CHTs 330ish running hard and high airspeed. They actually come up when backing off to more normal cruise power settings, must be where pmag starts advancing. Averaged 12.5 gals
/hr during initial break in flights. Climbs can send hot cylinder over 400 if not careful. Switching pmag off definitely drops cht. Cruising 75% power on subsequent flights hottest cylinder can be up to 370 Which comes up at lower power settings where other one drops. Inverse at higher settings hot cylinder drops(#4) and #3 comes up. Generally around 20-30 degree difference. Oil temps only getting 120ish. Pressure barely drops if at all. Suspected gauge but felt sump and cooler at shutdown and it’s barely warm to the touch. Infrared thermometer showing it a bit over 100. Started taping off cooler and now have fully blocked. Getting 130 ish now and cooler and sump feel warm at least on shutdown. Sump measuring 130ish with thermometer. Interestingly didn’t change CHT on #4. Current thought is the Selkirk cowling. It is open around air filter and carb to lower engine with a big exit right there that has a lip for lowering pressure. Also big cheeks at 3.5 inch gap. Thinking there must be tons of cold air blasting the sump and carb. Lots of surface area cooling the oil.

Next step is to verify sender accuracy with boiling water at first oil change. I’ll also probably retard pmag a little more and/or try disconnecting manifold pressure tube. If CHTs continue to be high might have to look at carb work to get more flow.

Anyone experience anything like this? Anyone have experience with Selkirk cowl?

Flying.eth said:

Cruising 75% power on subsequent flights hottest cylinder can be up to 370 Which comes up at lower power settings where other one drops. Inverse at higher settings hot cylinder drops(#4) and #3 comes up. Generally around 20-30 degree difference.

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This is due to the position of the carburetor butterfly valve. When the valve is partially open the fuel/air mixture doesn't flow evenly to all four cylinders. When the butterfly is full open there is a more even fuel/air distribution. Your indication is a hot cylinder trading places with a cooler cylinder. This is Normal.

That makes sense. It does have the center mount sump which should help even them out I would think. Now if I could just get cht/oil temps figured and earthx/pad mounted alternator to work properly I’ll be set.

Recoil temp, Have you confirmed the vernatherm is functioning correctly?

Flying.eth said:

That makes sense. It does have the center mount sump which should help even them out I would think. Now if I could just get cht/oil temps figured and earthx/pad mounted alternator to work properly I’ll be set.

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Which alternator and what's the issue?

Web

Block the impact side of the cooler, not the back side. And for a high compression engine? Smile that you aren’t fighting high temps. Lots of guys would like some of your problem.

PS- I’m not buying the airflow over the sump comment. If your cowl allows intake air into the bottom cowl your cylinder temps would be hot. Hot hot.

stewartb said:

Block the impact side of the cooler, not the back side. And for a high compression engine? Smile that you aren’t fighting high temps. Lots of guys would like some of your problem.

PS- I’m not buying the airflow over the sump comment. If your cowl allows intake air into the bottom cowl your cylinder temps would be hot. Hot hot.

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Got a smith cub with lycon 10 to 1 and Selkirk carbon cowlings since 2011 . It runs lasik electronic ignition it ran hot .put vans pressure baffles on and made rubber seals around carb and AirBox so no cold air goes around. Just like a stock 180 hp cub I have .big improvement. Real good fuel burn 51/2 to 6 gal running 44 boer . 90 mph on 35

I haven’t checked the vernatherm yet. I’ll try tape on pressure side of cooler.

It’s an SD8 pad mounted. If I turn battery off volts jump around 9-16 volts. It is charging but barely. Earthx seems to drop voltage quickly too. I have very low electrical load. No battery solenoid, no lights other than led landing light with pulse. No avionics other than four point engine gauge.

Gntw sounds pretty much exactly what I’ve got going do you have pictures of the seals you made? I have a vans baffle kit as well.

Flying.eth said:

I haven’t checked the vernatherm yet. I’ll try tape on pressure side of cooler.

It’s an SD8 pad mounted. If I turn battery off volts jump around 9-16 volts. It is charging but barely. Earthx seems to drop voltage quickly too. I have very low electrical load. No battery solenoid, no lights other than led landing light with pulse. No avionics other than four point engine gauge.

Gntw sounds pretty much exactly what I’ve got going do you have pictures of the seals you made? I have a vans baffle kit as well.

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Have to go get pictures don’t know how to post pictures, can text or email u

9072400224

Flying.eth said:

It’s an SD8 pad mounted. If I turn battery off volts jump around 9-16 volts. It is charging but barely. Earthx seems to drop voltage quickly too. I have very low electrical load. No battery solenoid, no lights other than led landing light with pulse. No avionics other than four point engine gauge.

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You are turning the battery off during flight? If so, don't. Any time the alternator is working, the battery should be on line. Check the voltage at the battery, with a digital meter, with the engine turning at ~1200 rpm or more. It should be 14.2 volts (ideal). When you turn on all other loads, it should not drop more than a few tenths of a volt. Let us know what you find.

Web

Reads 12.8 volts at 1200-1500 rpm. Battery reads 12.7. It does keep it charged flying, barely. If I turn on my led pulse lights it will start dragging it down. Earthx seems to draw down easier than before. Testing systems before ever flying it wouldn’t drop.

Tried tape on pressure side of cooler. Got oil temp up to 150, but significantly warmer ambient temps. Struggled to keep CHTs from climbing too much.

You're going to have to troubleshoot the system as you are not getting the proper voltage to the battery for recharge.

Pull out the diagram for the SD-8 system. Note the voltage on both sides of the output breaker, at the NO contact at the relay, and at the red lead on the voltage regulator. See if one of these test points reads the 14.2 volts that it should. If not, set your voltmeter to AC and measure the voltage across the two blue leads at the voltage regulator. This voltage should be considerably higher than 14 volts and the voltage should vary with engine rpm.

If you have low AC voltage, the alternator is bad. If you have good AC voltage but bad DC volts, most likely the reg is bad. Of course that is assuming good connections and good grounds.

Web

12.7 volts on everything downstream of regulator (battery voltage at that point). AC upstream showing 16-17 volts at 1500 rpm. Regulator issue I’m guessing? What about the crowbar, could it be the issue? The earth x doesn’t seem to hold a charge very well either. They’re going to look at it and test it for me. It’s new like the rest of the system. Put the odyssey in its place in the meantime.

12.7 volts is NOT enough to recharge your battery. That's why the battery shows low power, it was never recharged fully. The crowbar circuit will force the 2 amp control breaker to open. If this occurs the warning light will be illuminated. The crowbar also resets by turning power off and back on. I'm guessing that there is a problem with your alternator. Remember that this alternator can be used in a 14 or 28 volt system. The only change is the regulator. This means that you should be seeing 28 volts or more at the AC lines.

Web

Any word on this? Inquiring minds want to know.

Web

Been busy flying for work to pay for flying for fun.

Charged up an odyssey to try in place of the earthx. Going to pull the cowling and check all grounds and connections.

As far as engine temps going to install an oil cooler shutter for oil temp. For cylinders going to retard timing a little more, try and do what I can to improve baffling including sealing off around the air filter. I think I also need my carb jet drilled up a size or two. Might try the latest and greatest nozzle Cubcrafters uses.

Switching batteries isn't going to help. As per post #12 you're getting 12.7 volts at the battery. Put as many batteries in as you like and 12.7 volts will still be to low to recharge them. These are permanent magnet alternators that require no battery power to energize. Look at the diagram for this system. There's good info there.

Web

Some updates on the temps and charging.

Installed an oil cooler shutter and sealed some leaks in the baffling. Can keep cylinders under 400 in climb now, still using a cruise climb. Number 3 is now slightly warmer. Oil temp is running 180-190 with shutter fully closed. Still think it’s a bit lean based on some more testing. Waiting on the improved pepper box nozzle from cub crafters and ream it out one size larger than current nozzle to help with climb temps and try and even out chts/egts. Between that and a few more baffling improvements should be running cool in the climb.

As far as charging after talking to B&C I decided to pull the regulator and send it in as it’s still under warranty. They tell me they have an improved regulator that I’ll likely install in place of the original. Removing it one of the wires to the alternator did pull out of the butt splice. Appears like was making good contact, but could be part of the issue.

Flying.eth said:

. . . butt splice . . .

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Web

The Pepper box nozzle may run quite a bit leaner. Be prepared to drill it out a few times to get the mixture right. Did you polish or reshape the Venturi/carburetor throat any?

I haven’t gotten around to pulling the carb yet. If the jet on the pepper box nozzle is drilled larger than my current nozzle it shouldn’t be any leaner right? The carb was done at lycon along with the engine. I didn’t notice any polishing when I installed it, but probably didn’t look that close. I’ve heard from some folks that a hotrodded lycon engine/carb combo tends to be on the lean side.

A pepper box jet will most likely run leaner. So do a baseline test with what you have level flight 500 ft AGL 2400 RPM. What is the egt rise before first cylinder hits max get? It should around 150 degrees. If you have that the paperboy can level the cylinders a bit but may require a bit of work to get back to that acceptable level. I think I remember a guy that pulled his carb over 15 times just to get it drilled right!!! Very happy with the results but just throwing a drilled pepper box in is pure luck if it works! The few I have seen run very lean!!!
DENNY

Thanks for the heads up Denny. This is nozzle 47-862 cubcrafters is using in the 340. According to Marvel Shrebler it flows the same amount as 47-773 which is the stock nozzle in my -32 carb. Going to open it up a bit more than the nozzle that’s in there. Might take a few attempts but hopefully should lower and even up the temps a bit.

Check your PM and give me a call when you get a chance
DENNY

Re drilling main fuel distribution nozzle: you can go as much as 3 drill # sizes up. I don’t recall drill size #’s but believe .114 or #32 is original size of pepper box.
three sizes up did the trick for me under roughly the same circumstances you describe.
I would go up incrementally though.
FYI - Any larger than 3 # drill sizes will exceed the inlet valve orifice size of -32 carb resulting in exhausting fuel in the float bowl faster than can be replaced.

!! Prior to doing anything, confirm where you are with Denny’s recommended leaning procedure and keep careful records as you go.

Currently get 100 ROP per the test numbers. Like to get at least 150, maybe even a bit more. I can always lean in cruise.

Dug up my old notes:
here’s what I was seeing 10 hours out of the crate from Lycon.
# 3 cyl:
which is interesting because I compared it to the dyno print out data sheet that came with the engine. Not sure what planet they tested the engine on, but nothing like my numbers.

edit: these numbers were collected after first fuel nozzle modification.

Sounds similar but even leaner than mine. You said it was a lycon build as well, any carb work done? -32 carb?

Yes, Lycon 160 build with all their whistles and bells. -32 carb.
looking back at data:
.094 nozzle drilled to .101 recommended. (Pepper box)
should be flowing around 16.5 gph wot level flight near sea level.