Engine temp.
 

Can anyone explain tthis to me:

A car engine is run at an optimum temp of 250-280F why?

An airplane engine is left to dry in the wind with no regards to the temp.

A boat pours cold water through the engine, and dont reach much more than lurke warm.

How come they dont have to operate in the same temperature range?

Why is it so important that a car is run at the correct temp, but the other two types of engines are "overcooled"?

RE: Engine temp.
 

Actually there`s no such thing as optimum temp for car engines either;) It is just a very common myth amongst car-newbees who think they have to constantly check the temp with a tempgun:) Tune all engines for performance and don`t give a damn about what the tempgun says.
I have had car engines that had to run very hot and lean to run great and others that runs great at much cooler temps. A long time ago I threw my cheap innaccurate tempgun as hard as I could into the ground and have never missed it one bit[sm=idea.gif] When the engine runs great the temp is fine. The engine will tell you if it is to lean or too rich, just whatch it and listen to it. The same goes for all kinds of engines, car, heli, plane, boat.....

RE: Engine temp.
 

Actually, they do. The internal temp is the thing that counts. You have to interpolate when measuring outside temps.

Not really "overcooled." The engineers who decide on the size and shape of the cooling fins are taking the heat transfer rates from inside parts to the outside fins into consideration. In fact, on airplanes, we sometime have to put baffles inside the cowls in order to direct enough cooling air past the cylinder fins. Look at some heli engines. They have large "heat-sink" heads to make up for lower rates of air flow over the fins.

CR

RE: Engine temp.
 

An engine that's tuned correctly and used for it's intended purpose (car, plane, heli, boat) will reach whatever temp it gets to. The thing with car engine temps is that most who use cars have never had any other experience with tuning an engine so can't tell by ear when it's tuned correctly. A plane engine is dead easy to tune by ear because there's always a high and almost constant load with ground running but this can't be done with a car so it's trial and error. When you know what to listen for with a car then you'll never need a temp gun.

RE: Engine temp.
 

I'd like to believe that model engines have this much engineering effort put into them, but I doubt it. Most if it is based on past experience or emprical testing. Air cooling is a tricky thing. Glow engines are not too critical of cooling while gasoline is more critical. Even though the a model airplane engine is out in the breeze the airflow around the cylinder isn't particularly effective. A proper cowling and ducting would have much less drag and only a very small cooling airflow would cool it just as well.


Automotive engines have a set operating point due to the water cooling system and crankcase oil. Running too hot will boil the coolant, running too cool is not efficient, and causes wear among other things. Two stroke air cooled engines just need overheating prevention.

RE: Engine temp.
 

Engineering begins with the concept, carried through to initial production. Empirical testing begins after the prototype is assembled. I wonder how you'd fare in a conversation with, say, the engineers at Saito. The original Saitos were pioneers in engine metallurgy & production.

CR

RE: Engine temp.
 

I think they would enjoy a conversation with me, as would I, thank you.

RE: Engine temp.
 

It should be noted that some of the best engines were produced by machinist's not engineers. Fox, Veco, and the K&B lines all had engines which were originally designed by machinists not engineers. Although I suppose engineers have helped improve designs, I don't think it normally is a lot of fancy engineer design going into most engines. Engineers are probably spending more time figuring our how to produce them cheaper and improving manufacturing techniques than the actual design.

RE: Engine temp.
 

I'd love to be there when you tell them there's little engineering in designing a model engine. :)

CR

RE: Engine temp.
 

Model glow engines are not rocket science. We have copious amounts of oil available, virtually unlimited cooling, a fuel which tolerate a wide air fuel ratio, and an ignition system that is not critical. On top of that, if the price is low enough, most customers consider them disposable. In the next couple weeks I'll be designing and building my own design from scratch.

RE: Engine temp.
 

I find it more easy to tune a car engine than an airplane engine (perhaps because I started with cars)... and tune them without a temp gun.
Sadly, nearly every new car drivers rely on the DAMN temp gun (and often sets the engines too lean), and don't learn to listen to the engine.

In the nearby car club, the top driver’s mechanic (father) spends A LOT of his time to adjust the engine, because he only adjusts the engine by the bloody temp.

He don’t realize that the temp of the engine is changing because of the surrounding temp, humidity, the amount of fuel in the tank, way of driving etc. etc.. And he doesn’t understand that the idle mixture is mainly controlled by the high needle screw: Ones the high needle and the low needle screws are properly set, the only thing to adjust is the high speed needle.

RE: Engine temp.
 

I'll bet your idea of designing and building a model engine is to assemble a bunch of off-the-shelf components into a package and then hang your Logo on it. There's a lot of that going around. Well, I have news for you: engineers designed those components from scratch. And you can still go wrong if you don't use components from suppliers who applied top notch engineering, including the metallurgy, to them. ;)

CR

RE: Engine temp.
 

Come now Charley, you're making many assumptions for not knowing me. I have a lathe and a mill and know how to use them. I might take offense to your assumptions about my abilities, but I won't. I could list my accomplishments or post a list of books in my library, but I won't. Today is a happy day for me. Otherwise, I'd give you an earful, or rather screenful. I'm quite surprised how you are offended that I don't think somebody else made as much effort to produce something as you think they did. Unless you were one of those engineers at Saito. For some reason you think designing an engine is an impossible task left to only those so holy as to have been doing it for 40 to 50 years. What will we all do when those engineers are gone? Surely nobody will be able to design model engines then.

This is my last post in this thread.

RE: Engine temp.
 

Duke Fox was not only a machinist. He had lots of other expertise. I met Duke and chewed the rag with him at the Nats several times. Fox Manufacturing is not just a machine shop. It's also a foundry & did lots of government work. Duke made runs of engines when the manufacturing equipment wasn't tied up on other contracts. Also, Duke didn't operate in a vacuum.

As to K&B/Veco, I don't know what Clarence Lee's educational background is. I guess you could ask him. I did know the late Bill Wizniewski of K&B. He was an educated man AFAIK.

But the whole act of building an engine rests on the work of engineers and physicists who developed the metallurgy and designed the components and production machinery to make the components. Sure there's empirical expertise, but not without the engineering base.

CR

RE: Engine temp.
 

I kinda noticed the cooling fins on the back side of cylinder on some big Supertiger engines that had a lot more area... than the front fins. A cooling thing I bet! Capt,n

RE: Engine temp.
 

Charlie not trying to start an argument but l do take exception to the remarks to Greg
I have personal knowledge of his skills and ability and the engine to back it up a diesel conversion of a 4 strk ASP 52 a very nice adjustable compression chamber that screws in the glow plug hole and the bar is even locked with allen screw not just a press fit . It had to decked the push rods worked on valves set for new clearances the throw adjusted so they do not strike the piston carb worked on and some other things I am sure he did too, I am not a machinist but the end result is a sweet running engine that puts the 4 strk Enya diesel
in the dark ages

I doubt he will just throw some off the shelf pieces together martin

RE: Engine temp.
 

I don't think you know what an engineer does. Most do not design mechanical components. That is left to designers and draftsmen for the most part. They only need to look up fits from published books and their experience. Most of the engineers are experimenting with new materials, testing new ideas, researching new methods, or figuring out a faster or cheaper way of manufacturing. Some would not even know how to design an engine. I don't think there is much of this going on in model engine's except maybe at the largest manufactures such as OS and Saito.

RE: Engine temp.
 

I doubt there is a single physicist designing model engines. They are too busy figuring out how to make fusion reactors, or how quarks work. I even doubt any model engines have any body working directly with metallurgy. Instead their metals suppliers will let them know of new materials that will make their engines better. You don't know that an engineer doesn't do the same job they did 40 or even 20 years ago. It has become very high tech research stuff. Some are the underlings to physicists, the designers of the fusion reactors and atom smashers they demand. Not many designing model engines, except maybe as a hobby.

RE: Engine temp.
 

When he was designing engines under his name, which was the basis of the Veco and many K&B designs, he was a machinist. I don't know if he received a degree or not. Duke Fox was a technician and a bit of a self taught engineer. But today an engineer would not even learn anything about a machine shop, except that an industrial engineer would time and study the manufacturing methods, and devise faster better methods. Well at least sometimes they are faster and better.

RE: Engine temp.
 

It's obvious you missed my point in the above excerpted quote. You should reread it for better comprehension. Hint: Didn't say physicists were designing model engines.

CR

RE: Engine temp.
 

I would think most engineers used by eng. co.s are moonlighting or on retainer or family member. OS, Lee,Fox and all the others no matter the background, wanted to make small engines and that is where they put their talents, and except for maybe Jett or Laser engines, everything is copies of 20+year old designs; nothing new under the sun. Most new modelers are not interested in the mechanics of something which is why they can have such a hard time; a big boost for electric, and only in the last decade has the hobby become a consumer hobby.

Most machinists are very good self taught engineers as they are the first to know if the design is stretching too far the materials used; they are the first line of defense to tell the engineers if there might be a problem. The only ones who make things happen, though no matter the background, are the curious.

RE: Engine temp.
 

I think it's stretching things a bit by invoking physicists unless it's meant that without a physicist we wouldn't have the transistor that made modern computers possible which in turn made CNC machinery possible. But a good machinist with the proper equipment can make an engine at least as good as a CNC machine. Just not as fast. But that good machinist relies on someone with a modicum of engineering to design the engine. A lot of trial and error has led to the slow development of modern engines as we know them and in some cases this development has been an off shoot of racing, the same as happens with cars. A perfect example is ABC technology which came about because of a problem with cast iron pistons in 2.5cc (.15 for the Yanks :)) in control line speed. Say "thank you Super Tigre" :).

As for engine temps and cooling, which is what this topic is supposed to be about, there's so much variation with the amount of cooling designed into different engines it's near impossible to say what's enough. Probably the worst cooled engine (going by fin area) is the Fox 35 (yes, I know it's designed to run in a 4 stroke most of the time) while among the best would have to be Super Tigre. Come to think of it the Dooling 29 is probably even worse than the Fox with a couple of fins around the cylinder and none at all on the head. And no one can say that was a badly designed engine!

But no engineer would design cooling fins as we have on our engines. The best cooling fins should be triangular in shape to give the greatest mass and easiest heat path closest to the liner then taper down as more heat gets extracted over them. The machinists said too hard/costly so we have straight machined fins. They work well enough.

RE: Engine temp.
 

I know what you were trying to say, and you are wrong, physicists don't design model engines, nor the tools, nor the metallurgy. Not even a lot of engineers are doing that nowadays.

RE: Engine temp.
 

You are a trip! Instead of rationalizing what you think I was "trying to say," you should try to comprehend what I actually wrote. Maybe if you reread all of my posts you'd get a clearer idea. Nowhere did I write that physicists designed model engines. The idea was that they did research OVER the YEARS that lead to the metals, etc, that engineers could apply to designing small engine components. I don't think I can be clearer than that.

Just as an aside there are plenty of physicists who aren't on the leading edge of research, folks with a BS who took their undergraduate degree into the real world to make a living. They aren't all brilliant PH.Ds. I've known a few.

Now, I'm done. This thread has drifted far enough.

CR

RE: Engine temp.
 

Carley, Sport_Pilot are correct, it is not difficult for a homemachinist to make his own model engine. The model engine are not a complicated engine to design and make. I know what i am talking because i has builded own model engines.

The basic knowledge are timing, compression ratio depent on which fuel are selected, stroke/connecting rod ratio, stroke/bore ratio and what the engine are designed to use either it is a sport engine or racing engine. Take a trying and failing and modificate the engine parts before the engine are a perfect engine.