JVB

My Feedback: (2)

What is the typical temp range for two-stroke engine heads. Thanks.

Cyclic Hardover

My Feedback: (3)

This has come up many times which is why I feel those temp guages are useless unless you own a gasser. There are no published specs for temps on a 2 stroke. Also many factors can determine why it is whatever temp it is like running rich or lean, altitude and weather. Sometimes I see a guy pointing that temp guage at his engine. That is a guy I stay away from since he has no idea what the reading he is suppose to have because there is none.

Generally when the engine gets to hot, its already in the air and if it hasn't quit or lost power yet, its about too.

DarZeelon

JVB,


I can add that it also depends on where you intend to take the reading...

At the head fins, with an infra-red sensor, you may see temperatures of 200-240 degree Fahrenheit, sometimes less, while at the base of the fins, or with a thermo-couple, you will typically see 325-375 degrees.

So, there is no single number, above which you can truly say it is too hot.


In general, if the engine too hot, you will know this...

William Robison

My Feedback: (3)

[b]JVB:

Using a thermocouple in contact with the cylinder head, up to 250F is safe with synthetic oils, using castor oil 325F, even 350F can be survived. Do remember, the internal temperature will always be higher than that read on the outside. And there are many other ways to detect overheating.

When you use an infra-red thermometer you are reading an average that the sensing unit sees, since the outer tips of the cooling fins will be cooled by the air stream to a greater extent than the base of the fins, the non-contact thermometer will always read a number lower than the thermocouple in direct contact at the base of the fins. The amount of the variation depends on too many things to say one temperature is OK and the next bad. The height of the fins, just the thickness of the fins will make a difference. Even in engines otherwise the same (Saito) an AAC cylinder and an ABC cylinder will give different IR temperatures while the contact thermometer reads the same.

This is not to say the IR thermometer is useless, it's great for comparison. Testing different props for example; you will see immediately when the temperature starts to spike as you run a too much prop and approach an overload on the engine. The place where your "Temp gun" really shines is balancing a multi-cylinder engine, getting all cylinders running at the same load. On "Serious" racing cars I installed on board data recorders, including the exhaust gas temperature of each cylinder. Valuable for racing, needless for normal driving or flying.

Conclusion: Unless you're running multi cylinder engines the infrared thermometer should be at or near the bottom of your list of things to buy.

Bill.

ajcoholic

My Feedback: (10)

Im my Fly RC reviews, I use a direct contact thermocouple (with the RCATS data unit) tomeasure both the engine head temperature, and exhaust temperature at the stinger.

In my experience testing almost 16 engines so far, I would say that the majority of glow engines running 5% to 15% nitro fuel, on a synth/castor blend fuel run somewhere between 250 and 325 degrees F with a lot of them liking to run just around the 300 F mark. I know Dave Gierke likes to see the temps a little higher, around the 335F mark and in some of his reviews will modify the engine (wrap with foil or change the plug, etc) to see the temps get to at least this mark. I basically test "as is" and record them. Of course these temps are measured at full throttle with the engine broken in and set at just under peak, on an "average" day (not in the middle of winter, nor on a 95 F day).

With a GOOD brand of infrared meter, you can certainly get very close. My Greelee meter often reads within 20 F of the thermocouple (on the low side). But you have to hold themeter almost touching the glow plug. You can't point it from a foot away and expect to get a good reading on such a small object, due to the way these things operate.

Hope thats of some help/interest.

Andrew

William Robison

My Feedback: (3)

[b]All:

Apologies - made a slight error in my last saying AAC and AAC would give different readings, it should have been AAC and ABC. I've corrected the post.

Andrew:

My IR thermometer is a Raytek, my contact unit is from B&K. Not familiar with your Greelee brand.

Bill.

w8ye

My Feedback: (16)

Greenlee is probably the most promenent tool marketing company for the electrical construction/repair trades industry.

ajcoholic

My Feedback: (10)

Bill, the GReenlee brand is a big electrical outfit here in Canada, perhaps a repackaged something else? ALl I know is it wasnt cheap and it is pretty darn accurate.

I also forgot to mention, you need to watch the engine's temps come up slowly... it sometimes takes 2 to 3, even more minutes of full thrlttle running on the bench before the head temps stabilise. A 10 second run will not give an accurate temp. I basically run the engine and watch the computer display untill the temperature stops rising.

Which could also explain why some folks take off, fly a few minutes then their engines quit (lean) and they dont catch on, because they say "it was running fine when I took off"... but it may take a few minutes of flying to get to the over-temp condition.

Now that I am testing engines (in flight) with the RCATS full telemetry system, and can watch the temps vary throughout the flight, it is very interesting to see what the engines peak at in flight, during certain manuvers, etc. Ain't technology great?!

AJC

dammitman

My Feedback: (15)

i have a relativly inexpensive IR temp reader and i have used it to see how my engines temps run,,,,,,,,its very easy to see whats right and whats not,,,especially when using modified exhaust systems. a valuable tool for one who knows how to interpret the readings.

JVB

My Feedback: (2)

Thanks for all the replies.

Cyclic Hardover

My Feedback: (3)

Sorry to beg to differ here but you do not know whats right and whats not since there are not specs. "Whats not" could be just fine for all we know. If you had a good flight and took a reading afterwards and you claim "its too hot." Well if it was a good flight, then it obviously was not hot enough.

Sorry but any claims to say these temp guages are an asset, to me are like having false hopes and relying on them could do more harm to the engine than good. Like teaching a kid to ride a bike with a pair of cracked training wheels. The you scratch your head after one of them breaks, he falls and you honestly don't know why?

Sorry but watching a guy take a reading with one of these does prove something to me and knowledge is not on the list.

Hobbsy

My Feedback: (102)

I can throw something into the mix here that AJ probably already knows and that is the crankcase on a Glow Engine runs much cooler than the cylinder area but on a model Diesel engine the crankcase runs at the same or nearly the same temp as the cylinder and head. I can only assume this is because the methanol does a much better job of removing heat as it evaporates in the crankcase. The volume of ether in the Diesel fuel is much less than the volume of methanol in glow so is not as effective at removing heat. That's my theory anyway.

rjbarthel

My Feedback: (2)

Thats right there isnt a set temp spec. But I do have a IR temp gun and I use it to make compairisons to changes . I always take the temps in the same place. Glowplug base and from about 3 inches away . I know the numbers I see are of no use but to myself . Just like JVB started this post looking for info. I sure would hate to think that the only info he got was from guys saying checking temps is B*ll S**t . Air cooled engine for the most part will always very in temps and are very much effected from ambiant air temp. I personaly Love info and I check compression of all my engines from new to used and temps and so on and I have the ifo recorded in my shopbook . I know this info serves only me but then I also use after run oil LOL.

ajcoholic

My Feedback: (10)

ACtually,
Fellows like Dave G and C Lee have done enough exhaustive testing to let us know where our model engines should be running, temperature wise. And to suggest someone is "knowledgeless" sinply due to the fact they may like to learn more about their engines by measuring relative temperatures is down right insulting.

A simple test like this : on the test stand (or in an uncowled airframe) a particular engine runs with a CHT reading of 280F. Now the engine is put into a cowled in plane, the modeler doesnt know if there will be adequate cooling, so a ground run up is performed and a CHT temp reading is taken as before. The engine now reads 305F, but he/she knows that up to 350 is safe and the plane will be OK. If an abnormally high reading was taken, the modeler can rectify thge situation (cut larger exit holes, baffle, etc) and fix the problem before they commit to flying, and a possible overheat and deadstick.

Is that not worth anything? It is to me, and many others in this hobby, and thats just one example.

AJC

Turk1

Gentlemen, any kind of data is never more than enough or unnecessary especially such a technical area..So Im appreciated all to contribute such a thread to add info.Pls. go on contributing with everykind of data here,I believe someone will take it useful maybe vital.

Flypaper 2

AJ:
To figure out how much cooler an engine runs after unloading in the air, with your onboard telemetry, what would it show for an engine that would run at say 300 degrees on the ground? Or would it change much at all? I know there are a lot of variables but what would one expect to see.

ajcoholic

My Feedback: (10)

In my experience so far (limited, since I just have three engines tested so far with the on board telemetry) the temps cool off a little - about 20 or so degrees F - in the air. The last engine, the SAito 2.20 running an 18x8 prop for example ran about 25 F cooler in the air.

However this was in all three cases on my test plane which leaves the engine uncowled so the engine is getting very good cooling from the airflow of the prop and from flying through the air. It makes sense since the plane travelling at 70 MPH shoudl get plenty of cool air over the cylinder compared to just what the prop throws sitting on the ground.

As I use the RCATS system more and on a more varied selection of both gasoline and glow engines, it will be interesting to see the various readings.

AJC

Cyclic Hardover

My Feedback: (3)

You know, the only effective way I could see associating Head temperature is to have some sort of remote sending unit from the head to a device that would warn you when its to hot (for whatever max temp it may be.)

I just don't see how you can effectively know when the engine is to hot. What are you going to do, run it on the ground until its to hot, then shut it down to cool off, then fly it. How can you know when its to hot unless its already in the air? I know what its like to have an engine overheat since I have done it several times and every engine reacted the same which was a loss of power and either deadsticked in or the throttle was wide open and i came in at an idle.

It doesn't matter who has come up with numbers, your not going to know if your their yet until its too late.

William Robison

My Feedback: (3)

[b]Just for the Halibut, and to kill a few minutes, I got the B&K and the Raytek out for a comparison.

Bang on the same reading here, but remeber everything is at ambient to no difference would be expected.

Top left is the B&K thermocouple, the sensing part is the litle ball on the end - it's about 0.020" in diameter. Top right is the Saito with the sensor trapped under the glow plug (sorry for the glare). Bottom is the B&K LCD on the left, Rayrek on the right.

Bill.

Mluvara

My Feedback: (10)

Thought I'd interject a couple of quick notes for different temperature measurements.

The infared measurements will give you a general temperature reading from the cylinder. If you have a thermocouple mounted on the ring underneath a spark or glow plug, the thermocouple will give you a higher indicated temperature. With the thermocouple ring, you are reading the temperature right at the flame. Most likely the infared will give you a reading at the outer portion of the cooling fins.

For example, CHT at the cylinder head fins (via infared) might show 250 deg F. Measured at the glow plug, you will see temperatures like 350 deg F.

The bottom line is that if you are making measurements, they should be performed via the same method to give any reasonable answers. In many cases, you are looking for the delta (change) over different runs and using that as your health check, per se. As long as you do it the same each time, you will get the answers that you need.

Michael

William Robison

My Feedback: (3)

[b]Michael:

What's this "thermocouple ring... reading the temperature... at the flame." you mention? I thought the RCATS system used a thermocouple ring, but I also thought it was held under the plug in place of the normal gasket. Do you have some method of placing the ring on the inner end of the plug?

Bill.

Mluvara

My Feedback: (10)

I oversimplified things when I said ring and flame. The ring goes underneath the plug in place or below your glow plug washer. I refer to "flame" because the plug is typically subjected to the hottest temperatures and doesn't have the same temperature coefficients as aluminum.

Some choose to measure CHT with a ring under the plug, others with a thermocouple between the fins. My point is that wherever you measure it on the engine, it will be different, but as long as it is measured the same every time, you will more than likely see the changes in temperatures that will give hot/cold indications.

Michael

PlaneKrazee

My Feedback: (14)

From these posts it's tough to know what is an average good head temp for glow, gas, or four stroke. Anyone have an opinion? It does make sense a direct read temp gauge would be higher depending on where it's mounted.

Jezmo

SkyPilot, take a look at post 4 and 5 above. They are VERY GOOD information as to my own personal experience with temps. I use a themocouple type meter made by Fluke on the bench and a Venom temp recorder on the plane or in some cases my Eagle Tree flight data recorder. My observations match Bill's, Andrew's, Dave G.'s, and Clarence Lee's very closely. I am one of those nuts that can never have "too much" data to crunch to try and improve performance. (Dang speed freaks why can't they just fly slow like the rest of the folks) LOL, have a good one.

Sorry, I forgot to add that my gassers tend to run just a touch hotter, about 15 or 20 degrees, but that is not hard and fast. Some of my gassers stay under 300 to 310 and a couple are up around 330 or 340. It does vary some based on ambient temps outside and I use it as a baseline to see where I am at relative to the last time I checked a particular setup. It's just another tool in the arsenal of trying to get that last nth degree of power out of her.

Also, some temps I've looked at on my engines

OS 40FSR = 330 to 340
SuperTigre G40 = 290 to 300
SuperTigre G51 on Gas = 300 to 320
Saito 91 on Gas = 320 to 330

PlaneKrazee

My Feedback: (14)

I have a Fluke 52 and my buddy borrows a thermal imager from work. How do you hold the thermocouple probe to the engine without putting it under the plug gasket?

I forgot to ask about four strokes and exhaust temps. My Enya 155's have the hottest exhaust temps I have ever seen. That's with them adjusted 100 rpm down running a Cline regulator. Those Enyas even after four gallons showed no ring or cylinder wear at all. All the machine marks in the ring was still there. I've never seen anything like it.