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What's your CHT's run at?? Should I be worried??

scottperry

Registered User
Hood River, Oregon
Heading for Alaska in 10 days and my CHT's have been running high. They've always been high compared to what most people tell me. It's an O-320 160 horse. Yesterday I took her up to 6000 feet. Outside air temp was 57. At 2400 RPM my hottest CHT was at 406 and my oil temp was at 215. From what I understand, Max CHT on the gage says 450, but Lycoming says it's 500, with a max oil temp of 245. I recently reworked the baffling and tried extending the lip on the bottom of the cowl, to no avail. I also tried putting some baffling on the front of the cylinders (about half way up) and it did cool the back ones down about 15 degrees to 385 and warmed the front ones up to the same. Mechanic says we can move the oil cooler to inside the cowl and block off the old hole to the tune of $2000 including the STC. What do you guys think??
 
I have a 160 HP O-320 and an EI UBG16 gauge. My CHT's run mid to high 300's. I've seen temps slightly over 400º in a climb. I only burn 100LL - car gas may run hotter.

Oil temp rarely goes over 190º in any condition. The cooler is a Niagra Cub Cooler - works really well and is mounted in the orginal position.
 
My O-320B2B 160hp with Borer prop runs CHTs in the low 300's in 65% (2350) and mid 300s at 75% (2450) on a high 50F/low 60F day, and has never seen 400 even in 80F day in climb. Oil temps 170-180, never seen 200. Cooler mounted on rear baffle, Charlie Center bottom cowl lip as part of his STC. PA-12 though, so your mileage may vary.
 
I closely monitor my O-320 160HP 150 TSMOH on my Pacer with temps similar as the others have mentioned.
Recently flew over to Idaho from Seattle area in Late June at 2350-2400RPM with a 74-57" prop. CHT never went over 375 in climb at 2550 with OAT of 65. Oil temp always holds at 180. Oil cooler is standard out in front with oil thermo valve on engine.

Appears you have a hot running engine if both oil and CHT are high. Suggest you look into baffling. Are you sure the Baffling and cowl seals stay in place in flight with 70MPH air pushing on.
Oil starts to breakdown at 240, so better fix this before you go.
I use auto fuel also and have found 100LL will bring EGT down about 50 Deg, but has little effect on the CHT.

So you are the guy that is causing this global warming issue. Eh?[/u]
 
I run a 160 with 82-41 prop, I always set cruise power at 2500. On a normal day in the low 60's my cht will run around 340-360, and my oil temp will run about 185-195. Egts about 1330-1350. I have a rear mounted Niagra cooler, with the Charlie Center extended lip, all new baffling, and am running the E.I. gauge. When you are climbing are you running full throttle? Also, what kind of oil are you running. In my experience, I have found that the Phillips xc 20-50 will run about 10-15 degrees cooler than straight 100 aeroshell. Ron
 
Scott

What is your cruise speed when you experience these temps?

I don't believe moving your oil cooler to the back will help cool down oil temps it would more then likely increase temp slightly and increase the cylinder temp slightly. Your robbing ram air from the baffles and sending it through your cooler. Just my thought.

I would agree installing one of the new niagra coolers would help but it would be most affective mounted in the original position. IMHO

Cub_Driver
 
Bayonet or spark plug probes and what CHT gauge are you using? Spark plug probes generally read 50 degrees high and some gauges (Westach) use a differential method between a set of connections in the cockpit vs. the probe.
 
Taking her to Cubcrafters this morning to have Stan take a look. I'm not sure what type of temperature probes I've got. I'll give a full report on what we decide, but I'm definately leaning toward a Niagara oil cooler to get the oil temps down and having the baffling reworked to get the CHT's down. Thank you for all the advise and suggestions gentleman!
 
Niagra Cub Cooler, definitely! Leave it in front... CHT's, well, Piper neglected a few features that are common with other aircraft. Even Piper aircraft...
Ramps in front of the cylinders, 20 deg F.
Closing off the big hole down the front of the engine, 27 deg F. Don't forget a cooling air source for your generator/alternator...
Extended lip on bottom of cowl, 10 deg F.
I got 40 more degrees by locating a binding rocker arm in my number 4, 20 deg F,
and a deflection vane on top of the number 4, 20 deg F. Went from CHT=OAT + 390 to CHT= OAT + 305
so, now I'm not replacing cylinders like they were going out of style.... :-?
 
Wow! Fobjob, that's the kind of temperature decrease I'm looking for. I'll make those suggestions to Stan at Cubcrafters and see what we can do. Should be done by late next week. I'll give a full report. Thanks for your info!
 
cht-egts

My pacer with a 0320 here in the heat will run 325-350 cht, oil temp might get to 200. It has the cooler in the back, made very little dif, but I moved it for the skytech starter install. I run auto fuel in everything including my skybolt with 0540. Saves me a bunch on maint, fuel, etc. I also use Phillipps 20-50, with 30 hr oil changes. Right now today our density altitude is 7900ft
 
Bear in mind that closing the hole in the front of the motor takes a lot of sheet metal work..and don't forget the air scoop and scat hose for cooling the generator/alternator...the ramps in front raise the front cyl CHT, so a half dozen 1/4 inch holes in them negated that problem. I plugged the holes in front of the #2 later, when the deflection vane over #4 pushed down so much air between the cylinders that it lowered #2's CHT by 20F as well as #4's....The object was to get everybody's CHT down, but even, also. I don't want to get into all the things I tried that DIDN'T work, like enlarging the cheeks on the cowl sides.... :roll:
 
I have a 160 hp, 0-320 with a Borer 82/44 prop and Niagara cooler on the left rear baffle, Also a Leading Edge exhaust which, according to Lycon data, results in 173 hp. I kind-of-sort-of closed up the old cooler hole in front by fabricating a fresh air vent to plug in there. I still have the starter hole because I like to inspect the teeth on the little B&C starter. I have never installed the little hinged plate around the carburetor that makes removing the lower cowl a pain -- Cubcrafters left the area around the Carburetor open -- good enough for me. I have tight baffle seals -- good enough to distort the top cowl, http://www.supercub.org/phpbb2/viewtopic.php?t=18686&view=previous

I don't believe in the theory of "pressure cowls" for old rag wing Pipers -- seems to me that if you blast enough air top and bottom, it all works out. I have tested this theory several ways. Air in to the top should be forced through the cylinders but OK to mix it then with more air coming in around the bottom cowl. Cowl outlet cheeks probably are not large enough at 2.3 to 2.5 inches max. -- but this would ruin the paint job to fix. I have no extended lip on the bottom cowl -- this might help to depressurize the top and eliminate the top cowl's slight bulging. I think my cowl is outlet limited.

I use Exxon Elite 20W-50 with Camguard. Timing is set to specs. I have an EI temp gauge to watch all four EGT and CHT. The CHT probes screw into the cylinders. I don't lean very agressively. When the hottest (#3) gets near 1300F I'm happy -- that is with the mixture about one inch out. I know I can raise the oil temp at least 10F by getting more agressive leaning, so why do it? Engines are expensive!

At 2400 rpm, 2000 ft asl, 1000 ft agl, 80F ambient ( last Wednesday) my oil temps leveled out at 190F. It take 30 to 40 minutes to get to a stabilized temp. EGTs were in the 1200 to 1280F range. CHT were in the 305 to 340F range. I probably was burning 8.5 gph maybe a little higher. I could lean down below this but .... why?
Darrel
 
You ought to get one of these:
http://cgi.ebay.com/magnehelic-gage...tem&pt=LH_DefaultDomain_0&hash=item27b37b4ecd
The suction side pressure relative to cabin(or static) ought to be about zero, but when I started, it was about plus 2.9 inches of water....plugging the leak from the high side to the low side increased the suction and (synergistically),
helped everything else I had done....that's why it's the most effective thing to do.....but, it's also the hardest.... :(
---------------------------------------------------------------------------

Lycoming specs their motors at 4 inches of water differential pressure....
 
Naah Darrel, you don't want it. Why? Cuz I put a HUGE $3 bid on it! Dunno though, if it has two ports - - -
 
fobjob said:
You ought to get one of these:
http://cgi.ebay.com/magnehelic-gage...tem&pt=LH_DefaultDomain_0&hash=item27b37b4ecd
The suction side pressure relative to cabin(or static) ought to be about zero, but when I started, it was about plus 2.9 inches of water....plugging the leak from the high side to the low side increased the suction and (synergistically),
helped everything else I had done....that's why it's the most effective thing to do.....but, it's also the hardest.... :(
---------------------------------------------------------------------------

Lycoming specs their motors at 4 inches of water differential pressure....

You could also use an old airspeed indicator to determine pressure differential. Place a line from the pitot connection on the gage to the pressure side (top) of the engine and a line from the static connection to a point under the engine. The higher the airspeed number, the higher the differential. This would help while making the changes to your baffles. 4" of water is about 85mph+/-.
 
Well, I guess I would learn something by more testing. But just on a gross overall basis, I have opened up the lower nose, closed the lower nose and got little or no reaction from any of the temps. I think that because my baffle seals are very tight and that the upper chamber obviously is well pressurized, the more or less flow that comes through to the bottom of the cylinders just doesn't matter ... all that upper chamber flow must be overpowering the pressure below as it looks for a path out. And keep in mind that I'm not trying to solve a problem since I think my temps are normal.
Darrel
 
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