Trouble Keeping O-470R CHT's <400

Hunter

Hunter

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Hunter
I have a factory reman O-470R with 85 hrs in a C182J with all new baffling. I am a little concerned with the CHT's I am getting on #2 and #1. Those cylinders run 45-50 hotter than the other 4. I try to keep them below 400, but I am finding it very hard to do. I climb full rich at no more than 400ft/min or they get over 400. When I lean during cruise (cowl flaps closed), its hard to lean below 14.5-15gph.
I have attempted to attach pictures,
cruise at 4500, IMG_1384 (1).JPG at 6500IMG_1391 (1).JPG (both leaned to @85 ROP)
Thanks for any help y'all can provide
 
Check the baffeling. It doesn't take much of a gap to disrupt the cooling. I've been all over that with my first engine.
 
before successfully blaming the product or install, you'll likely have to rule out the usuals - timing, fuel flow, baffling leaks (are all the rubber baffle seals bent the right way?) etc
 
Stewartb said:
Add cowl louvers. Or leave the cowl flaps partially open.
Click to expand...

louvers and the lip are great, but even without that those CHTs are out of whack, think he's got other issues.
 
As usual, James discredits somebody's post and offers nothing.
 
What's your takeoff fuel flow? The common cause of high CHTs is lack of fuel. If you get hot at takeoff/climb out it's hard to get things leveled out.

Ream the jet. You can enrich by using carb heat to validate the need for more fuel.
 
Stewartb said:
As usual, James discredits somebody's post and offers nothing.
Click to expand...

Sounds like someone needs a hug...and a education.

Can't help ya with the hug, but let me educate you.

The louvers are a great mod (as is the lip), I got the louvers on my wagon as I'm sure you do too.

Thing if this dude is hitting the temps he's hitting he's got other worries, perhaps the louvers would mask the issue, but the issue would still be there.

Perhaps it's timing, baffles, fuel issues, etc, but even without louvers he shouldn't be hitting those CHTs, sure add the louvers, but first find the root of the issue.
 
I'd bet a new reman is timed correctly and baffles are good. Sometimes they run hot because the factory can't get the carb right. I've had that happen myself on a reman 470. TCM had a local shop ream the jet. Lean carb setup is very common on remans. But the OP pictures aren't scary hot at all.
 
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I don't know why you assume the baffles are good. It doesn't take much of a bend on a piece of baffling to screw it up. I found a 3/4" piece completely missing up where the #1 (Lycoming) cylinder tucks up in the nose bowl. It's enough to screw up the flow to that cyl.
 
Because most mechanics are careful with baffles when installing new remans. At least the mechanics I know are. If there's a baffle problem it's more likely an owner doesn't install the top cowl properly and the seals tilt outward rather than inward. That allows top cowl pressure to blow the seals out instead of forcing air down through the cylinders.

One other thought. Typically #3 or 4 are the hottest cylinders. When #1 or 2 are hot I'd look hard to rule out an induction leak at the Y pipe. Induction rubbers always get inspected and tightened when my cowl comes off.

The redline is what, 460*? Occasional 400* CHTs aren't a problem. Most airplanes see a 15-20* decrease so if cruise temps go from 400 to 380 that's a win. Like I said, two easy tests will tell the OP a lot. Run with partial cowl flaps open to simulate the affect of louvers or run with carb heat on to simulate enriched mixture. Both will probably help. Lots of guys use partial carb heat with 470s to level the temps. Another thing guys in cool climates do is insulate the balance tube. Without that 5 and 6 run rich and cool. In that case 1 and 2 being hotter isn't unusual.
 
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The fact that cylinders 1 and 2 are both showing hot I think is a clue. I would for sure be checking the baffling and don't forget the inter cylinder baffles. Something is messing up the airflow around the back of the engine. The first 100 hours or so are critical to the life of the engine and is the time of highest probability of problems occurring. Fix it now or wait and really fix it later - meaning spend more money later.
 
I've got the 182A (no cowl flaps until the B version). I've been thinking about toying with a lip but don't have a good place to start. Anybody got a reference on approximate dimensions, attach mechanism, and the like?

The cylinder temps are OK, but the oil temp is close to redline in the summer with OAT ~115dF or so.


Thanks,

Jim
 
The OP is probably just improperly reducing the throttle/MP after takeoff, instantly increasing the CHTs. According to "Deakin," the worst thing you can do to your engine.
 
What's the right way? Is there concensus? After liftoff I prefer to reduce RPM to reduce noise but stay full throttle to cruise altitude. Fuel keeps it cool.
 
Thanks for all of the info. This is my first plane, and I did all of the work/upgrades at once. My A&P/IA that did most of the work recently passed away, so I don't have him to ask.
I THINK the baffles are all good, I'm anal about having them all tucked to the inside. There are some ripples toward the rear that I don't like, but not sure what else can be done about that.
FF at T/O is 22-22.5. MAP is 27-28 WOT. At @1000ft I back RPM's to @2450 and to MAP to @25. I'll change this and keep WOT to see if it helps. What should my RPM setting be in climb after 1000ft?
 
Hunter said:
Thanks for all of the info. This is my first plane, and I did all of the work/upgrades at once. My A&P/IA that did most of the work recently passed away, so I don't have him to ask.
I THINK the baffles are all good, I'm anal about having them all tucked to the inside. There are some ripples toward the rear that I don't like, but not sure what else can be done about that.
FF at T/O is 22-22.5. MAP is 27-28 WOT. At @1000ft I back RPM's to @2450 and to MAP to @25. I'll change this and keep WOT to see if it helps. What should my RPM setting be in climb after 1000ft?
Click to expand...

What does the POH say for climb settings?
 
Straight from the POH...
Normal- 23" and 2450RPM
Maximum Performance- Full Throttle and 2600 RPM

I was thinking that 2450 RPM would give me more cooling. I'll try to make a flight today and leave it full throttle and 2600.
 

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Hunter said:
Straight from the POH...
Normal- 23" and 2450RPM
Maximum Performance- Full Throttle and 2600 RPM

I was thinking that 2450 RPM would give me more cooling. I'll try to make a flight today and leave it full throttle and 2600.
Click to expand...

The reason to back off to 2450 RPM is for noise. 2400 RPM would be good, like max for the slightly more modern O-470-U. The reason for full throttle is for utilizing the "economizer" valve for cooling.
 
Haven't had a chance to go up yet, but took some pictures of the baffling.

What can be done about the ripples? Are they the possible culprit? IMG_0104.JPG
 

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It looks like your back baffle rub strips are freely open to the back side of the engine rather that being pressurized to seal against the cowl halves. Those black seal things should be facing forward so they self energize and seal against the cowl with ram air pressure.

And what is that white stuff that seems to be in the cylinder head fins? It looks like a fuzz of some sort. Have you been around cottonwood tree fuzz or something? The space between the head fins has to be clean - all the way through to the bottom side of the engine. Maybe you can blow it out with compressed air - but that may just force the fuzz whatever it is?) to pile up on the bottom side of the engine.

Think of the air pressure across the engine to be crudely the same as maybe 1 foot of water. The air has to be forced through the fins, and not allowed to bypass the fin system as the baffle system distorts under pressure.
 
The rubber seals ARE facing forward, I don't know how to make them "seat" against the cowling any better. I'm open to suggestions.
It does look like fuzz in the pictures, but its just paint flecks.
 
Most rear baffles use segmented silicone seals. Trying to make that radius in one piece causes puckers. Whether that's the source of your problem or not, you can do better.
 
Update: I called Airforms (who made this set of baffling) and they told me to make slits in the rubber so that they would seat better against the top cowl. I did that, and took a test flight. Definitely made a difference!!
I think after a few flights the heat will help to seat the rubber a little better. I'm trying to upload my process to YouTube :confused:
 
I'm still having trouble with my temps, and called Continental's mechanic for some help. He's telling me to take some RTV, and seal up between the cylinders and the baffle forms. I'm hesitant. Anyone done this before?
 
Hunter said:
I'm still having trouble with my temps, and called Continental's mechanic for some help. He's telling me to take some RTV, and seal up between the cylinders and the baffle forms. I'm hesitant. Anyone done this before?
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Ugh. RTV makes a mess and if it gets into the wrong places it makes things worse.

The O-470 has some small baffle parts behind the oil cooler. One runs along the top aft side of the cooler, and a small one fills the gap between the inboard end of the cooler and the crankase at the back of the cooler. Seen some of this stuff missing sometimes. There's a hard-to-seal gap right under the crankshaft behind the spinner, too.

The cooling system relies on pressure differential between the top of the engine and the bottom. Lots of things can decrease that differential...leaking baffle seals, seals bent the wonog way, holes in the lower cowl that shouldn't be there, and so on. Any air getting past the engine without going through the fins or oil cooler is not only wasted, it's wrecking the pressure differential.
 
IMG_1914.JPG IMG_1910.JPG I went ahead with the RTV, got the thing as air tight as it's gonna get. The gap behind the spinner puzzles me though. How in the world can you seal that up?
 
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