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engine head temp
Does anyone know of a "rule of thumb" to be used for an engine head temp? How much difference is there between 2- stroke and 4- stroke? :eek:
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RE: engine head temp
Actually, this is something that we just don't worry about in airplanes. Because of the propeller blowing air across the engine overheating usually isn't a problem on an airplane.
Ken |
RE: engine head temp
ORIGINAL: hurk1 Does anyone know of a "rule of thumb" to be used for an engine head temp? How much difference is there between 2- stroke and 4- stroke? :eek: Temperature measurement when used with caution could be a good tuning tool but most tend to reject the possibilities and very little data exists. Bill |
RE: engine head temp
There's no set figure for head temps because it can vary wildly from engine to engine. The only way you can do it for a particular engine is to use a known good fuel, start it and tune it by ear or with a tacho then check it's temp for that particular day's temperature. If it's a hot day it'll run hotter and if it's a cold day it'll run cooler. Basically, if you can tune by ear then there's no need to use a temp gun (or a tacho).
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RE: engine head temp
Recently I replaced a stuck ring in an old engine. Although the engine runs good and the high needle is set at 700 rpm off peak the engine often smells hot. Measuring the head or cylinder base temperature against another similar size engine might provide another small piece of data to judge the tuning.
The engine is being run in reverse pusher configuration and a temperature comparison running in reverse tractor configuration might also yield interesting information. I need another test instrument. Bill |
RE: engine head temp
ORIGINAL: BillS .....friends shoots the temperature at the base of the cylinder and uses 220 F to 250 F as a guide while the engine is running. Temperature measurement when used with caution could be a good tuning tool but most tend to reject the possibilities and very little data exists. Bill I'd agree with Bill. In my readings, a properly set engine runs from about 220-250F so I tend to keep it in that range. This does not mean that a perfectly running engine at 260F is a indication of problems though..... and all reading were taken on the bench at about 1/2 (+/-) throttle. I try to keep in mind that the hotter the engine, the more the parts swell. I've measured both extremes. At 320F the engine was obviously running lean, and I've measured a 180F on my Evo .61NT..... and everything seemed fine, I think it coughed a little in the air though. I think head temp almost falls under the "Too Much Information" catagory. The temp is relatively useless unless we are talking about extremes. Besides, in the air you can't measure it unless you have a data logger. |
RE: engine head temp
I have read several engine reviews where the head goes to 320o+ and feeling good according with the reviewer. I like to read the Andrew Coholic reviews from FlyRc because of the tools he uses to measure the heating of the head and the exhaust, I believe that they are very accurate regardless of the performance of the engine. As a magazine review, every engine test is a top one, and a must to have, but you have to read between lines to really know how the engines will behive.
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RE: engine head temp
Hi BILLS
I'm not familiar with the description you use "The engine is being run in reverse pusher configuration". Is this the same as my Canard? I describe my Canard as using a pusher mounted engine and a pusher prop. The direction of rotation of my engine is standard, not reversed. Is your engine running in reverse direction? On my Canard, the engine will overheat while trying to tune it. I always must replace the prop with a "standard" identical prop to tune it and then put on the pusher prop to fly it. Have you been doing that? |
RE: engine head temp
ORIGINAL: Villa Hi BILLS I'm not familiar with the description you use "The engine is being run in reverse pusher configuration". Is this the same as my Canard? I describe my Canard as using a pusher mounted engine and a pusher prop. The direction of rotation of my engine is standard, not reversed. Is your engine running in reverse direction? On my Canard, the engine will overheat while trying to tune it. I always must replace the prop with a "standard" identical prop to tune it and then put on the pusher prop to fly it. Have you been doing that? Bill |
RE: engine head temp
Hi Bills
Just a fine point. I did not mention turning the prop around, at least I don't things so. If you turn a prop around, the direction of air flow is still the same as it was before. However, the amount of air that is moved is noticeably less. In many cases the plane is not capable of taking off. My Canard uses a Pusher prop with a standard rotation engine. To prevent overheating shortly after initial engine starting, I try to get into the air withing 30 seconds of star- up. If I need to tune the engine, I replace the Pusher prop with a Standar prop, more correcty called a Tractor prop, of the same type, diameter, and pitch, in order that the engine does not overheat. I have never used a reverse rotating engine like you are using, so I may get tthe following wrong: On your reverse direction running engine, running in Pusher configuration, I believe you must use a Standard Prop, more correctly called a Tractor prop, but mounted backward. If all of this is correct, then I believe that in order to prevent overheating while tuning the engine you need to use a Pusher prop as I have described, but also mounted backward. Once tuned, you need to switch props. All of this may be difficult to follow. It is very difficult for me to write down. If I have gotten this wrong, please someone correct me. As someone once put it, it's all in the details. |
RE: engine head temp
If your engine overheats it will happen in the air. All the times I have had it happen, It has been with different engines and came directly from setting a bit to lean. About 2 minutes into flight, I would lose pwere slowly to apoint I am full throttle on the tx and going nowhere and land with the engine running at idle speed and stick still full forward.
I've had it happen enough times to clue into it before anythng really bad happens. |
RE: engine head temp
ORIGINAL: Villa Hi Bills Just a fine point. I did not mention turning the prop around, at east I don't things so. If you turn a prop around, the direction of air flow is still the same as it was before. However, the amount of air that is moved is noticeably less. In many cases the plane is not capable of taking off. My Canard uses a Pusher prop with a standard rotation engine. To prevent overheating shortly after initial engine starting, I try to get into the air withing 30 seconds of star- up. If I need to tune the engine, I replace the Pusher prop with a Standar prop, more correcty called a Tractor prop, of the same type, diameter, and pitch, in order that the engine does not overheat. I have never used a reverse rotating engine like you are using, so I may get tthe following wrong: On your reverse direction running engine, running in Pusher configuration, I believe you must use a Standard Prop, more correctly called a Tractor prop, but mounted backward. If all of this is correct, then I believe that in order to prevent overheating while tuning the engine you need to use a Pusher prop as I have described, but also mounted backward. Once tuned, you need to switch props. All of this may be difficult to follow. It is very difficult for me to write down. If I have gotten this wrong, please someone correct me. As someone once put it, it's all in the details. Bill |
RE: engine head temp
I'm with cyclic, A plane running lean or a new engine will run hotter and often fall off after full throttle. Meaning the rpm will climb up then fall off a TAD indicating rapid temp increase from being new(tight) or lean and things tightening up. I have seen many new ringed engines do this when you(and me) get in a rush to get her all broke in and lean it out a little too early. I was always told if you can smell "Hot" it's too hot. Like shutting down and hearing fuel sizzle in the carb throat.[X(] probably an indication your running too hot.
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RE: engine head temp
Hi Cyclic Hardover and chris6414
What kind of pusher planes do you two fly? Engines? I have used a Magnum 28 engine, an OS 46FX engine, and an OS46AX engine, all in pusher configuration, and they all have overheated on the bench when using the pusher prop and allowed to run for a while. |
RE: engine head temp
I got an opportunity for some flight time today and found ground tuning to be much different than conditions in the air. Generally my ground tuning left the engine too lean in the air and two early landings were necessary. My approach is evolving to about 800 rpm rich on the ground. Then fly and watch for slight sag on extended up line or sag on a long high-speed run. If either sag occurs throttle back, land and richen a couple of clicks.
Bill |
RE: engine head temp
This question has been asked several times, and usually ends up with the same answer. Most people don't seem to think that head temp is very important, till it happens to them.
If you scan the car forums you will find a lot more information and fixes for it. I recently had this problem. I had the engine adjusted a little rich at full throttle, but would flameout within a minute or two after takeoff. I checked the head temp with a laser temp gun at the glow plug on the ground. It was readint about 350F. I had to richen the low side needle to get it down to 300F. The engine seems to like that better. |
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