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CHT questions again

JDA_BTR

Well Known Member
So 50 hours into flights now. Cyl 3 and 4 seem good at 330 while 1 will run at 355 and 2 at 385. I have cylinder 2 baffling as clean and sealed as I know how to do and had it looked over by an rv10 builder.

I got the advice here to just wait it gets better. But at 50 hours it seems it should be better already.

The area I’m not real sure about is where the uppper canopy seals around the air inlets. Also not sure about the foam at the prop governor but it seems good with a dimple on half the width from the big nut on top of the governor.

I suppose I will leave the top on and remove the bottom cowling and investigate.
 
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Did you keep the dams in front of cylinders 1 and 2? I removed the one on the left and cut the right one down by 50%. Evened out the temps out nicely.

Also be sure to check magneto timing.
 
The dams don?t seem to matter. I did cut back the max advance of the pmag but the timing is right.
 
Just to be sure, what are the conditions when you hit those temps. I'm assuming your concerned because these are cruise temps. If so, what RPM, fuel flow, MAP, density altitude and OAT values correspond to these numbers?

The 385 is concerning to me if this is what you're getting in normal cruise. I will see 385 only after a long climb at Vy and it will drop sharply when in normal cruise.
 
Well it is summer in south Louisiana so it is 95 degrees out. But I can climb to 7500 with a DA of 9000 and set up 22/2400 approx. Oil temp will be 195 and slowly fall. I keep my climb speed around 120 kts and this keeps temps under 400 on cyl 2. I lean for max economy with EGT peak and all EGT peak within 0.2 gph of each other so I think the fuel injection is good. Cruise is 172 kts and cyl 2 drops to about 380 with OAT around 58 degrees F. Cyl 3 and 4 around 325 and cyl 1 around 350.
 
I would swap sensors with another cylinder and see if the reading is consistent with another sensor before I did anything else. Or you can do the boiling water check and make sure it reads 212 in a pot of boiling water. If those checks give consistent results, I would start looking at other possible reasons. 385 in cruise is high based on other 14s but it's also within Lycoming's "acceptable" range.
 
It is not the sensor checked that a while back. I think it is probably how the seals fit at the inlet. I suspect that air is going out the front corners of the inlet and that might change the diff press around cyl 1 and 2 reducing their air flow. 3 and 4 are great with the ram pressure in the back of the baffling driving the air down.
 
I believe your temps are not bad as they are but I understand your desire to improve and make them better. They seem a bit hotter than most 14s.

One area I would suggest to check is the bottom part of the baffle where it wraps around the cylinder and see if air can scape the baffles on the sides and not reach all the way to the bottom part.
 
Take the cowl off and post photos...inside of upper cowl, baffle seals, lower cylinder wraps at cyl 2
 
Ok will do on the pics. I did go after the sides of the lower cylinder baffle and sealed along those edges. Didn?t seem to make a change.

When I put the top cowl on I don?t feel like the inlet is well sealed. I feel like the seals at the forward end of the intake ramp will flex out letting air out up there. Not sure it matters. I?d love some pics of other?s intake areas to see how your seals lie there. It is super tough to make pics of that in closed assembly.
 
I am getting close to an oil change and will take some pix next time my cowl is off, but take a look at the inside of your upper cowl and see the markings of the baffles seals. It usually leaves some marks and one can tell the area that has a good seal and area that is not touching or making good seal.
 
I feel good contact of the upper seals on the upper cowl reaching into the intakes. And when my top was off I do have telltales from the baffling.
 
Data point FWIW

Doc, following this closely because my CHT?s trend similar to yours. I?m on the road so I don?t have my exact numbers handy. My #2 runs hotter but I don?t think I?ve seen over 385-390 in a high power climb. Cruise numbers are fine (below 360] but still warmer on the forward jugs. I have not modified or removed the dams on #1 or 2 yet but did check for leaks on the inter-cylinder baffles. My upper cowl seems to seal but I will check around the inlets when I get back home.

If I can ever get finished with phase 1 maybe I can fly over and we can compare notes.
 
Here are some images. First is the left intake, then the right intake, then the number 2 baffle from the bottom. Its amazing how rough things look with the flash when without a flash they look pretty decent!

First we have the inboard and outboard left intake. The top of the left outboard (right side of the pic) it seems air can flow out to the corner nothing really keeps the top baffle from springing that way.
leftintakeinboard.jpg

leftintakeoutboard.jpg

leftintakeprop.jpg



The right side
rightintakeinboard.jpg

rightintakeoutboard.jpg

rightintakeup.jpg


And finally the baffling at the bottom of number two cylinder. The pics make the sealant there look really goopy; in reality there isn't that much there.
num2baffle2.jpg

number2outboardbaffle.jpg
 
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I am also due for an oil change, first one after 50 hours. So with temps what they are, is it time to switch to the ashless dispersant oil? My oil consumption is very low so I think the answer is yes. I don't read anywhere that temps would prolong the use of straight mineral oil.
 
Did you put a spacer between the baffle and the forward face of the #2 cylinder?

This has been discussed a few times on the forum. It ca effect the number three cylinder as well. There have been many clever solutions
 
Did you put a spacer between the baffle and the forward face of the #2 cylinder?

This has been discussed a few times on the forum. It ca effect the number three cylinder as well. There have been many clever solutions

Tom,
The RV14 baffling kit is prepped and comes with those spacers and air channels.

JDA,
On your first photo with regards to the governor, my baffle was doing the same thing and getting pushed to the opposite direction. I put a dab of RTV on the governor body to help retaining the baffling to the correct orientation and has been working well. I highly doubt that this effect any or much losing air but it helps it in the correct orientation.
Lastly, have you installed the foam spacer on the top part of your governor. If not, you could lose much air thru the gap that was cut in the upper ramp for the governor. That needs to be sealed well.
 
First we have the inboard and outboard left intake. The top of the left outboard (right side of the pic) it seems air can flow out to the corner nothing really keeps the top baffle from springing that way.

leftintakeprop.jpg

All seals should be arranged so plenum pressure forces them tighter, not blow open.

If the foam (or other sealing method) doesn't close off flow through the governor opening, it is a huge leak path, and could easily result in poor pressure over your hot #2.
 
I think the foam is good the gap you see is into the dead space under the inlet ramp and doesn’t go anywhere.

Good point on the baffling needs to come in and not squash out. There isn’t anything to make that happen on the forward end of the ramps. Unless I get the rubber situated to the very inside of the inlet but that doesn’t look right with the way the upper cowl joggles to the lower.

I’m wondering if some properly applied flox would be worthwhile. Or maybe make an inlet strip of rubber for the upper cowl like the lower has.

Dan maybe I should fly over Saturday and get some help or advice if you are willing.
 
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Question: at the inboard side of the inlets is the rubber from the ramp put inboard of the lower cowl rubber? Or outboard sticking into the inlet. I’ve always had it inboard seems to lie better that way. ?
 
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So I investigated the top cowling carefully. At the outboard sides of the ramps the ramps didn't quite seal to the top and there were about 3 inches of slightly open space there (1/8-1/4 gap). On the right I don't think it mattered much. On the left it would mean that air going up the governor hole could go across and down the gap next to the #2 cylinder.

So I floxed the gaps. I played with the lower baffles some. I sealed the sides of the baffles better. I made sure as much of the inlets as possible were sealed with gasket material even though it made the seals a little weird looking the way they laid down.

The OAT at 3500 ft this evening was 72 degrees (S. Louisiana...). The max temp I got on the climb was 389 (on number 2), and cruising around 25MAP, 2400RPM and fully leaned #2 temp got up to 382. It would have been more before my changes. #1 is next in the 355 range and #3/4 very cool 310/315.

So I made things better OVERALL, but haven't made #2 cooler compared to the others. On the other hand it isn't crowding 400 when I lean it hard either....

So maybe it is time again to just sit back and see what the temps do over the next 40 hours. I'm at 60 now.
 
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Where is the oil cooler air vented from?

On my James Plenum 6 with an outlet to the oil cooler behind the left rear cylinder, that cylinder runs 25-30 degrees hotter than others. I have an oil cooler door that I can use to close flow to the cooler. When that door is closed, the back left cylinder temp goes down about 20 degrees

The cooler vent “robs” enough air from that cylinder to make a difference.
 
regarding the governor seal. I am not sure what you meant by floxing the gap? Making gap smaller will help but air will still take the easiest way out of the plenum.
To seal this area I made a small plenum for the governor. Take a soup can that is larger than the governor and lay two or three layers of glass around it. When set, pop it off the can and then glass this piece into the governor cut out. This will ensure a complete seal in this area.
I had forgotten that the 14 baffles had incorporated the improved cooling on the forward part of number 2 and the aft of number 3. Take a look at this area again and see if you, by chance, plugged the gap with sealant? This gap is on the forward out board part of the cylinder and lets the air go down and cool the hot forward top of the cylinder.

Not all engines are the same and not all cylinders are the same. It is possible that you have a hotter number 2 cylinder. Take a flashlight and look down the cooling fins from the top and make sure that there is nothing blocking airflow. A few years ago, quality control had gone for a **** and I found a bunch of casting sand and slag in the fins of a brand new cylinder. A little competition from ECI and Superior greatly improved Lycoming quality.
 
So I investigated the top cowling carefully. At the outboard sides of the ramps the ramps didn't quite seal to the top and there were about 3 inches of slightly open space there (1/8-1/4 gap). On the right I don't think it mattered much. On the left it would mean that air going up the governor hole could go across and down the gap next to the #2 cylinder.

So I floxed the gaps. I played with the lower baffles some. I sealed the sides of the baffles better. I made sure as much of the inlets as possible were sealed with gasket material even though it made the seals a little weird looking the way they laid down.


So maybe it is time again to just sit back and see what the temps do over the next 40 hours. I'm at 60 now.

Tweaking baffles are often incremental and we all take those as they are gained so great job there.

One other area that is worth checking? the foam/dam that we create and install under the left upper ramp inlet need to seal well. This is the foam that goes right above the governor which you just worked on. If that is not sealing, you could have air scape on the opposite side that you just fixed.
 
Tom I will look and see. I didn?t put sealant on the front of number 2 because the piece has to come off for the filter. I?m not sure exactly where this designer gap is supposed to be in relation to old baffles.

The oil cooler is no factor it is low right behind number 3 which is very happy.
 
The cowling and inlets are much better then RVs in the past. That does not mean that there are not some improvements possible.
Note the following picture

http://halie.com/o5v.jpg

Ideally the inlets should run parallel to the direction of flight or slightly diverge. You can see in the picture that the top of the plenum is correct but the outboard edges actually converge. This causes both turbulence and a decrease in the size of the inlet. I cut the offending corner off and then clamped the proposed rubber baffle in place. After waxing a new edge was formed that solved the problem of turbulence and at the same time making a perfect seal with the baffle material.

Here is the modified lower corner. After it is done you can do the upper inlet corners to make a perfect inlet. It really is about an hour a day for two or three days to get it done.

http://halie.com/o5W.jpg

Here is the final inlet picture

Note I have also cleaned up the inboard corners as well, this provides both a better seal and at the same time a better flow of air.


http://halie.com/o51.jpg
 
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A little thread drift...sorry

Tom, yours is one of the first RV-14?s flying. How many hours and any unexpected surprises?
 
The RV14 is a wonderful airplane and is a great cross country machine. I had to chose between the RV14 and the Rocket and I decided to stay with my rocket. The RV14 sold with about 60 hours on it and the new owner has been flying for quite a will now and is very happy with the plane.
I would certainly recommend the RV14 to new builders. Van's has done a great job with this aircraft.
 
AHA! In my zeal to follow instructions and the posts here I sealed the gap between the zero-fin area of the forward #2 cylinder and the baffle forward of it where the ramp is aft of the air filter. So no air could flow to the forward bottom of the outboard half of the #2 cylinder.

Dug out the sealant there, which was very secure. Buffed back the edge of the filter-retaining aluminum part to keep the gap when installed. Had a 3/16 or so gap now. Checked on the #1 side no such feature on that one; cylinder looked good.

So in climb, 92 OAT, cylinders 1/2 same at 365, 3/4 same at 335. 3500 feet level out, running hard, OAT 75, temps drop then lean to peak and temps 1/2 362, 3/4 330. So a significant difference front pair compared to aft pair, but the #2 problem is solved; it is just like #1 now.

I have a feeling that significantly cutting down the bracket in front of 1 and 2 will let more air go there. Not sure what the guidance here will be on that.

But the light bulb went off on the "check the gap forward outboard #2" and reading the old posts about how the #2 problem was solved in other birds.
 
Congrats on finding the problem. You will feel much better about working your airplane now. Those differences between the front and back are not great. If it bothers you you could gradually close the back lower cylinder baffles until things even out. A bead or two of caulking may be all you need on the aft cylinders.
 
I think I'm going to think about it and live with it for a while. 365 running super hard in the hottest weather is perfectly fine. I'm not sure what I would do on the aft cylinders to push air forward that wouldn't just raise the temps on the aft cylinders?
 
Any updates?

I have 100 hrs on my -14 and even though the engine is running great I still get a warm #2 cylinder. My rear cylinders are always great with #1 being 20 deg warmer and the #2 is 15-20 degrees warmer than #1. Besides trimming down the dams in front, anymore ideas to balance these temps out?
 
None. I've decided it is the way it is and I'm unable to change it! Mine is just like yours. But well within satisfactory operating limits in every regime. Climbs just fine with no high temps on a 100+ Louisiana afternoon. Does get to about 395 if I'm really aggressive.
 
I have 100 hrs on my -14 and even though the engine is running great I still get a warm #2 cylinder. My rear cylinders are always great with #1 being 20 deg warmer and the #2 is 15-20 degrees warmer than #1. Besides trimming down the dams in front, anymore ideas to balance these temps out?

Changing those dams made a very significant difference on mine. I ended up completely removing the one on the left and cutting the right one down by about 50%. I was very compulsive about sealing all the gaps in the baffle material and I also re-shaped the baffle material that attaches to the cowling inlets to more completely seal at the inboard/outboard edges. On the left side, I made the entire piece longer to get a little better overlap just in front of the air filter - made it easier to get that properly in place when removing and re-installing cowling.
 
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Turner that is all excellent work. I did a lot the same. I modified my dams a lot, and pretty much perfected the baffle seals at the inlets. I still have #2 20 deg hotter than 1, and 1 is 10 degrees hotter than 3/4.

I think that a method to balance the flow and have less go to 3/4 and forcing more down up front is what is needed; I decided to not do that work. But the best idea I had on that is some sort of tab that could be screwed in between 2 and 4 to keep more air forward. It probably isn't the best idea there is.

Another idea I had was to put a bump/ridge/profile on the upper cowling lower surface that did the same thing, so when the cowling was placed it would make more air stay forward for #2. Not sure how that would look in practice.

I like having a dam in front at least some because I don't want insects at high velocity crammed into the small spaces there between the baffle and the cylinder. With a dam they get smeared on the dam and not the lower cooling path. Awful lot of them here.
 
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