Hot C85-12 Engine

[sburke]

During Cruise at 2300 rpm I typically see a 140 degree oil temperature over ambient (ie. at 80 deg F I see 80 + 140 = 220 deg F which is right at the limit according to the Continental engine manual. I am seeking comments from folks that have carried out provisions of the "Helps and Hints No. 26" on Engine Cooling. My cowl bug eye's look like they are the size described in the H & H writeup. My next step is to pull the rear baffle in so they hug the cylinders. I am a little confused about how the air outlet at the firewall tunnel is enlarged, anyone have a photo?

[Paul Agaliotis]

Sam,
Generally these little engines run pretty cool. If you see 140F that's pretty cool for 80 deg. day. The temp bulb indicates oil temp as it exits the engine. Here in CA you might need to open the cowl, but I've never needed to.
Paul

[sburke]

Sam,
Generally these little engines run pretty cool. If you see 140F that's pretty cool for 80 deg. day. The temp bulb indicates oil temp as it exits the engine. Here in CA you might need to open the cowl, but I've never needed to.
Paul

Paul,

My engine was at 220 deg F with an outside temperature of 80 deg F so I was at the limit according to the Continental Manual. How can I get it lower?

[Nathan K. Hammond]

Sam, I ran into the same problem of over heating when I installed the Super-85. After doing all the little tricks; tighten baffles, open eyelets, and blast tubes, I ended up cutting the firewall. It was fairly straight forward using the supplied drawings and basic hand tools. The first cut is a little nerve racking...

I'll snap some pics of my firewall tomorrow and post them for you.

But first, I'd pull the temp probe and boil it in water. It's easy to check and make sure the gauge isn't fibbing before cutting metal. Use a soup can and propane torch, no need to pull the whole gauge out.

nkh

[N86250]

I am a little confused about how the air outlet at the firewall tunnel is enlarged, anyone have a photo?[/quote]

If your aircraft was manufactured as a 7BCM, this was already done. jrh

[MikeB]

This is the lower baffle modification on my L16/0200. Mine had been cut out for the baffle but apparently never installed. I just bent mine from some stock material but the part number is 4-732. I suspect Wag Aero might have some in their Safe Air parts. Note: most of these I've seen are 'tucked in' under the bottom cowl lower opening but I opted to leave mine on the outside as the inside ones tend to collect oil inside the boot cowl and leaving it on the outside tends to blow any oil residue away (in my opinion). I think the idea behind the modification is to open the area for a little more air flow (and probably smoother). I typically see around 165-170 degree oil temperature on a normal (80 degree) day with about 350 cylinder head temperatures on both rear cylinders. For colder temperatures I made a partial cover for the outlet to keep the oil temperature up. Works great and keeps my feet wam .

Guess I don't understand the 140 + 80=220 oil temperature. The oil temperature reading is taken at the screen housing so it's reading actual oil temperature on your gauge. If you're reading 140 degrees that's what your actual oil temperature is regardless of the ambient. I understand that ambient will affect oil temperature (in other words if it's hotter outside the oil temperature will rise ...most likely) but what you're seeing on the gauge is still the actual oil temperature reading. At least that's the way I see it and I've worked on all kinds of equipment (engines, transmissions and rear axles) with oil temperature gauges.

I do agree that you don't want to see more than 225 degrees on your oil temp gauge. Ideally you'd like to see somewhere in the 180-190 range in my opinion. My little A65 Champ would have a hard time getting to 140 during the winter months unless I covered the lower outlet.

Mike

Hope this helps!

Mike

[sburke]

Mike,

During cruise flight (ie. 2300rpm) my oil temperature gauge reads 220 deg F with the outside air temperatue at 80 deg F, this represents a 140 deg rise above the ambient temperature. Your temperature rise above ambient is only 80 degrees, that's great. I plan on checking the calibration of my oil temperature gauge.

I have attached a photo of my firewall, can anyone tell if I have the modification discussed in Hints and Helps 26? My aircraft was manufactured as an L16A, not sure what that means with regards to this firewall modification. From looking at this photo I see a rounded feature at the base of the firewall.

[MikeB]

Ok! Now I see your reasoning and yep! You already have the firewall modification and I see it's 'tucked in' as most of them are. Tightening up the baffles are a good first step. I'm assuming the hole between the right and left baffle seal on the rear is covered some way or you'd lose a lot of cooling air through there. I was concerned when I installed the 0200 engine that I'd have overheat problems (considering the higher fuel burn) but hasn't materialized. I actually have more trouble keeping the temperature up but I spent a lot of time building the baffles and baffle seals. Although I can't say one way or the other I've heard that even extra room around the exhaust pipe exits through the lower cowl can cause a loss of cooling air. I guess you have to think of the space under the cowling as a 'pressure chamber' and force as much air as possible around the engine crankcase and cylinders so any loss or restriction of air would cause a temperature rise. Although I don't see it on the photo I assume you have the 'pan' from the oval hole in the nose bowl to under the engine block.
I've seen where some have added a 'blast tube' from the rear baffle to shoot on the oil screen housing area but I'm unsure if that actually helps cool or just makes the temp gauge read lower and make one feel better (or if you have an external oil filter a blast tube on that may help, too)
Mike

[Nathan K. Hammond]

Looks like you already have the firewall mod. I'd put a blast tube on the temp probe HOUSING or the oil filter if you have one.

For those still wondering, here's the firewall mod...








nkh

[jepropst]

Sam, as a data point, I flew my Champ with a C 85-12 with the O-200 upgrade the other day. Ambient was 66 degrees, cruise at 2400 rpm, oil temp gauge registered about 170 degrees. I also have a thermocouple in the front left oil galley that registered 191 degrees. Do you have any photos of your baffling? As Nathan mentioned, there should be a baffle on the bottom of the engine that does not appear to be there. My firewall baffle is similar to other photos posted. I use to have the air blast tube on the oil screen housing but an infra red thermometer indicated that it did not actually reduce the oil temp, but did reduce the gauge temp. An infra red thermometer aimed at the oil filter will give you a good indication of whether or not your oil gauge is in the ball park.

[sburke]

John and Mike,

Attached are some photos of my engine baffle setup, what I plan of doing is to attempt to pull in the baffle against the rear cylinders with a wire.

[MikeB]

Sam,
What I see looks good other than when you put the cowling on make sure there are no 'open holes' in the rubber seal where the air can leak through. I'd take a good flashlight and check the baffle seals after the cowl is installed. I see you do have the pan under the engine block. Just go through the pressure cowl and look for leaks and places to tighten the baffles. I'm assuming you have the cylinder baffles on the bottom of the cylinders (usually held up with a spring or wire hooks).

I suppose the next step (if none of this works) would be to install an oil filter and put a blast tube on it. They also make some kind of a cooling skirt (for lack of a better term) that slips over the oil filter and is supposed to reduce the oil temp.

And be sure to check the gauge.

Now for my dumb question: how did the battery wind up on the firewall? It's supposed to be behind the rear seat (technically ).

Mike

[joea]

Sam,

Get some silicone in a tube and close up the gaps! Look at the bottom photo and you will see gaps between the valve cover and the metal surrounding the cover. Close these up and force the air to go between the cylinders and really cool something.

Also have you calibrated your temp gauge? Am wondering if you are really running this hot.

Lastly did you ever fix your oil pressure issue?

Joe A

[sburke]

Joe,

As you will recall during cruse flight with an oil temperature of 210 deg F I experienced an oil pressure drop to 21 psi at 2300 rpm on my overhauled C85 engine. I have given all of these details to my engine re-builder. He had suggested that I add two thick washers under the spring of the oil over pressure regulator but I did not do that. I had read over a number of Continental engine related blogs on the subject of washers under the spring to bring oil pressure up and I was convinced that it would only make a difference to the high pressure limit not the cruise pressure.
My engine re builder and his AP/IA came to my hanger recently and checked the calibration of the oil pressure gauge which was good. He then proceeded to remove the oil pressure regulator and placed two washers under the short spring. I did not say any thing but was convinced that it would have no effect on cruise oil pressure. The plan was to remove the engine and take it back to the shop if this step did not help the situation. To my supprise, upon power up the idle pressure came up to 39 psi at 139 deg F oil temperature at 750 rpm. I then proceeded to take my Champ up to 3000 ft and circle until the oil temperature came up. After about 15 minutes I had an oil temperature of 208 deg F at 2200 rpm with a steady oil pressure of 31 psi. At this point I am happy with the performance of my rebuilt engine.

I have attached a photo of the crank case cooling shroud, someone has asked about it.

[Nathan K. Hammond]

I don't see any inner-cylinder baffles. Have they been removed in this photo?

nkh