thevirginian

Although my cowl of my WH Sukhoi is nicely baffled, I recently measured the cylinder temps of my Brison 6.4 after a flight. 250°F on the rear jug, 245°F on the front jug. The DA100 in my buddy's Extra measured "only" 170°F. He said I am way too hot. Now, what is hot and what is "just right". I believe this topic may have been discussed before.

bubbagates

My Feedback: (32)

I'd call that a bit too hot though BME will tell you that's pretty normal on the 115 Extreme.

Are the baffles going right up to the cylinders about the center of the cylinders and is the exhaust exit big enough and are you maybe a bit too lean of the oil mix

JoeAirPort

My Feedback: (41)

Maybe it's just a little too lean.

thevirginian

Baffle goes right up close to the fins of both jugs. I run a mixture of 40:1 Belray MC-1. All my louvres are cut open in addition to a big opening on the bottom of the cowl. I don't think I am running lean. What if my ignition advance is not set right? I have a mechanical ignition advance on this motor. At WOT it should be around 28-30° TDC. If it's less than that could that overheat the motor? I may have to check this.

JoeAirPort

My Feedback: (41)

Just a theory but I wonder if yours runs cooler than the DA while it's flying because of the baffling....but when you land yours seems hotter because the baffling now keeps the engine hot with no air moving through it. So the DA with no baffling appears cooler on the ground. I know it's weak but I thought I'd throw it out there. I'd be concerned too with that big of a difference. Get some Eagle Tree telemetry and get numbers in the air.

altavillan

My Feedback: (1)

As Joe is saying there's too many variables. Only inflight monitoring will really tell whats happening.
Without inflight monitoring here is what to look for and how to come up with some conclusions.
Take off fly fast and hard and land as quick as possible and check temps imediately. Check again in about a minute and see if the temp rises as the piston heat goes out to the cylinder. A long idle to where you are standing will heat the engine up.
Fly again but this time do a cooling lap before landing and retest for heat.
Now watch your pard set up for a landing. Does he come in long and slow to cool the engine?
Next pull the plugs. Dry brown and crusty will indicate close to max safe temps. Dry blackish brown and slightly wet will indicate a bit too cool and rich.
White clean and slightly blued electrodes means start shopping for another motor.

Rotax engines red line around 400 and I figure our small engines are safe to about the same. They measure at the plug.

Tired Old Man

My Feedback: (1)

250f is not too hot.

The problem is measuring after a flight, where the plane has been flown back in a descent and low power setting, cools the engine very quickly. By the time you get to measure the temp it's a lot lower than it had been in flight. You can start sticking rings at 180c, or 356f. You won't harm a cylinder, case or piston at that point but carbon generation that sticks rings is quick from that point on. Better bearings handle that much heat and a little more but cheaper ones can loosen the bearing seals and start leaking.

thevirginian

The question arises how accurate and reliable is a handheld Infra Red Thermometer. But if I measure my motor and then my buddy's with the same instrument under the same circumstances I will get a fairly reliable comparison. It tells me he's running a lot cooler. And that's what concerns me.

Tired Old Man

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You can run an engine too cold. Wet carbon forms quickly and power generation is reduced due to unburned fuel exiting the engine. You're building a fire so don't expect to to have a refridgerator. I would hope to see somewhere around 248 to 266f, or 120 to 130c if it was mine. Peaks of 300 to 320 for hovering and long uplines would not be out of line.

Tired Old Man

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The demi gods of the universe won't let me edit.

I forgot to add that 250 post landing may be indicating that you are running pretty hot in flight. Post landing temps with a heat gun are not very useful. You know what the other guy has on the ground and you know what you have but you don't have a clue to what's happening where it matters; in flight.

thevirginian

I remember I used to have around 170°F myself, but that was last year late fall where the temps were in the sixties, if that high. When I measured last Sunday it was in the low nineties. But like I said I need to check if my ignition advance is where it supposed to be: 28-30° before TDC at WOT.

altavillan

My Feedback: (1)

Lots of little things will kick up the temp and seam sudden.
Such as,
The asphault runway was hot. A tail wind while taxiing prevents cooling flow. Your gas's octane could have been cooked off or it was a bad batch at the pump or old fuel. You might have been pushing it a bit hard before landing. And as you mentioned it was much hotter out.
That doesn't take into account yer buds plane seamed cool. And since the brison isn't a real power house it should be a cool runner. So checking the timing and evan backing it off during the summer isn't a bad idea at all. And opening the high speed needle will lessen the heat also.
Still 250* and a nice brown plug kinda says everything is good to go. Thats about normal for one of my engines.

Gatorb8

get one of those digital temp guages/thermocouples that measures max temp during flight, that will be more accurate. too many variables with a post flight infrared gun....don't trust them
Gb8

Tired Old Man

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Rewgarding the Brison not being a powerhouse. I found why mine was not foing well last Sunday. When the crank was redone and after putting the heads back on I never
checked the timing. We were flying that thing with the timing set at close to 50 degrees after TDC. It would have run better backwards... Let's see how she does this weekend

thevirginian

After checking I found the timing at WOT to be approx. 20° before TDC. I don't think that would cause the motor to run hotter, would you think so? Hey Pat, how big is your cowl opening on your Suki? Do you mind snapping a pix of your cowl for me? As I mentioned before I opened all louvres in addition to a cut-out on the bottom.

thevirginian

Oh, I forgot to mention one little change . I switched from an Evolution 26x10 to a Vess 27B. Could that put too much load on the engine?

altavillan

My Feedback: (1)

Vess props aren't famous for loading an engine but going 1 size bigger should cause the engine to run a bit hotter. A larger prop normaly will make you have to open the needles a tad so if you didn't adjust them it might have been a bit lean.

Tired Old Man

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Sorry, but I don't have a big Sukhoi around anymore to take pictures of...[&o] A couple degrees of timing won't have much of an impact on the temp. I'm inclined to go with Altavillan with differences in approach, taxi, and throttle work on the ground making the differences between your buddies plane and yours on the ground temps. I commente on the timing on my Brison to let Altavillan have an idea why mine ws runnng so poorly when we aere out last weekend.

Tower has a temp gizmo for about $25.00 that will record the high temp attained in flight so you can check it when you get back on the ground. Too many things effect the results obtained from a heat gun to place much stock in one. The worst being that at best you can only obtain a temp while standing next to a plane well after all the real work of flying was done.

noahb

My Feedback: (67)

I use the venom temp monitor on my DA-100. I actually have two, one for each cylinder. They are about $18 off ebay maybe cheaper. I lengthen the wires on mine and ran the temp displays inside the fuse for easy access. I then route the thermocouple to the highest fin closest to the spark plug (on mine, its on the back side of the head) then I snug it tight against the cylinder. It records max/min temps and current. Works great as I can see what type of temp I hit after I hover, then do a long upline.

Hope this helps.

noahb

My Feedback: (67)

another thing that helped my temps alot was to make a low pressure lip on the cooling exit on my cowling. My temps dropped like 40 deg. when I did this mod. Could not believe that I was getting that much high pressure build up right there. I have mine baffled which helped, but man did the low pressure lip help out a bunch.

Tired Old Man and RTK have been alot of help to me. Listen to Tired Old Man, very intelligent when it comes to engines.

RTK

My Feedback: (1)

As mentioned, many variables come into play. If you are concerned, by a on-board temp gauge as described. Most people don't have a clue as to what temps their engines hit in the air, 300*'s is no big deal in certain maneuvers.
Baffling and good air extraction can cut temps up to 100*'s, I have proven it to myself on more than one experiment on more than one plane.
By the way, I believe Rotax's red line somewhere around 450*'s

Tired Old Man

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Temperature redlining is something I've been in disagreement with some engineers over for a couple of years. Without the whole song and dance, you really never want to achieve redline or even close to it. To make it there means an engine tear down and rebuild or worse, a replacement. You should never have an engine running so hot, so loaded, or so undersized that it burns itself up trying to get the job done.

thevirginian

Thank you guys. You've been a great help. I'll try the trick with the low pressure lip like noah mentioned. That makes sense to me and is easy to do.

Tired Old Man

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An item we touched opun in another thread is the possibility of hot air stagnating inside the cowl. The Sukhoi has a very deep cowl and it's quite possible that hot air is reaching the back of the cowl and getting trapped there due to a lack of circulation. Even with all the open louvers it's possible for air to become trapped behind an engine if it wasn't forced to follow a given path. That would cause an engine running at a reasonable temp to become hot from surrounding trapped heat, and for the hot air behind the engine to prevent enough cooler air input. A form of heat soak perhaps.

Along with a low pressure generating cowl lip aft of the engine, consider building an air dam and deflector out of light materials immediately behind the engine. Close off the top of the cowl behind and above the engine with a half bulkhead mounted on the top of the engine box. It would need to block air movement from the deepest part of the cowl and also to act as a ramp directing the air out of the cowl. 1/32" ply would work pretty well, as would things like coroplast

JoeAirPort

My Feedback: (41)

That a little like what I touched on earlier. The baffling's great while you're moving but while taxiing, and parked in the pitts, the air gets trapped. If you have the bottom of the cowling cut out for pitts mufflers, you'd think that while you're parked, the air would get sucked in through that opening and rise out the front of the cowling....albeit a little slower with the baffling.