Are you guys still arguing over this?
Are you guys still arguing over this?
I learned a few important things from our experienced experimenters, such as I don't need or want a thermostat in an airplane.
So next question:
Do valves actually burn in a watercooled engine? Seems like the engine would blow steam and the owner would shut it off first. But I only work on aircooled engines, so what do I know.
I have to quit this. It's the reason for my periodic absences. Much too easily irritated into trying to correct something that really isn't important. Sorry about my attitude, folks.
If the ability of the heat transferring aluminum fins was unlimited, radiators would only need 1 fin.Obviously that isn't the case. Given the propensity of automotive manufacturers to reduce parts count to save money, it seems logical that if increasing the speed of the circulatory water would on its own effectively lower water temps, they would do away with larger more expensive radiators, cooling fans and shrouding. They could place radiators somewhere other than the front of the vehicle and create more aerodynamic designs. If an engine is running hot, just pump the water faster.
The reason they don't just do that is because the radiator has a limit to its thermal efficiency. While increasing coolant speed CAN/WILL have an effect on that thermal efficiency up to a point, the radiator would eventually reach a point where the area it has available to dissipate the heat has reached its maximum. A radiator does not have an infinite ability to transfer heat. I think that really is the issue. Its not that more coolant is not capable of carrying away more heat, but that the medium (radiator) does not have sufficient transfer area to utilize the benefit of the additional flow. I think thats a pretty easy concept, and I don't think it breaks any laws of physics. Anyway, that's my respectful opinion of why increased flow doesn't always have to generate more cooling. Look at Subaru engines and their history with overheating and blowing head gaskets. The factory didn't just take the simple step to just leave the thermostat out, or
to increase flow and keep temps lower. I believe they took steps to alleviate a bad design feature caused by a hot spot and a poor head gasket. You have to look realistically at solutions to problems inheirent in differing designs and take the appropriate action to solve the problem. Will removing a thermostat always cause overheating...No.
Will moving the coolant faster always solve a problem. I don't think it will.
Thinking about it from an airplane point of view, we have all read about the trial and error problems encountered by builders using radiators. They try one or two or even three radiators with placements from above to below the engine, in front, in back, everywhere. This demonstrates that depending on placement, area, air flow, and even coolant flow and air entrapment, that they have difficulty cooling. If speeding up the coolant flow was the simple answer, thats what they would be doing. Simply change the pulley sizes and your problem would go away. So, again, with all due respect I continue to believe that the ability of the radiator to dissipate heat is not infinite, is actually complying with the laws of physics, and can reach a point where additional flow does
not provide any additional benefit.
Its not about the ability of additional coolant flow being ABLE to give up more heat, but about the chosen device having sufficient means to take advantage of the additional capacity.
PS: Great article in Kitplanes
Last edited by Winginit; January 6th, 2017 at 12:23 PM.
Everything I post is just my misguided personal opinion !
Look for Torque and you will find HP !
(I'd also like to highlight the statement that auto manufacturers put in fans to increase the flow rate of air through the radiator... a good real life example of increased flow rate yielding increased cooling capacity.)
If your goal with any thread is to "set people straight", "show them what I know", "see who knows their stuff", or otherwise deliberately provoke controversy and argument, then you're here at HBA for the wrong reasons. I know arguing on the Internet has become the grand sport of the 21st century, but if that's what you really want to do, please take it to Facebook or some other place.
To keep these threads to a minimum, the best thing everyone can do when they see one is ... nothing. Don't reply, don't tell them how they're wrong, just ignore the whole thing. Don't feed the troll. Don't be this guy:
This thread really has nothing to do with homebuilt airplanes, despite the fact that (most) homebuilt airplanes have engines. As such, it's off-topic for this forum, has been achieving nothing but endless argument and, therefore...
Moderator Note: Thread closed.
Last edited by Topaz; January 6th, 2017 at 01:14 PM.
"If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau
Design Project: Conceptual Design of an "Inexpensive" Single-Seat Motorglider
Discussion Thread for the Project: Discussion: Conceptual Design of an "Inexpensive" Single-Seat Motorglider
Ok.. I'm thinking the confusion is a mix up between different things..
The whole 'valve will burn up' thing is not from removing the thermostat, but from losing coolant system pressure. The job of the pressure in the system is two fold: to increase the boiling point of the water and to raising the cavitation point.
The first is what Tony is talking about. The heat around the exhaust valves is so high that without the added pressure to raise the boiling point, the water will flash to steam, prevent the flow of water (and thus cooling) and will burn up the valves in short order.
Having increased pressure also increases the cavitation margin for the pump impellers. Without it, your pump will cavitate, slowing or even stopping coolant flow. Even at low levels of cavitation, air is introduced to the system which obviously doesn't cool very well and if that air finds its way to the heads, you once again have the exhaust valve cooling problem. The net effect is a poorly cooling engine that will end up burning itself up.
The 'tiny hole in the thermostat' is *not* 'to release steam', but to purge air from the engine, and around the thermostat, while filling the cooling system. As said, air is bad, and you need to remove as much as possible. Its important to note that now-a-days this hole is not always there. In fact, most engines in use today do not have them as they implore a different method of purging, such as cracking open a 1/8" plug or cap high up on the engine, because the thermostat location is no longer the highest point in the system as it was on the older engines. In the ones that do, the reason you place the hole 'up' instead of 'down' is that, obviously, air rises and if the hole is down you will not remove all of it, and this air, even if its a little, will displace the water around the thermostat and not allow it to function properly, causing it to open late and open less when it does, which, of course, leads right back to the engine over heating. Also, ever notice that the hole has a 'stopper' in it? Thats there because when the engine is first started, there is no pressure in the system so the hole is open, allowing any air around the thermostat to purge. Once any air is removed and the coolant begins to flow, the stopper is pushed against the hole, sealing it, stopping any flow through it, allowing the thermostat to work properly.
Ok, all that said, the reason some of you notice that removing the thermostat altogether, with no other changes, causes overheating is not because 'faster water removes less heat', but because of less pressure in the system. This is caused by a system that was poorly designed in the first place. Adding a thermostat or 'restrictor plate' decreases flow in the system, yes, but its not the slower flow that improves the cooling, its the added pressure behind the thermostat/restriction. If your system can handle the pressure, the same thing can achieved by upping the pressure in the system over all. This is usually done by going to a higher rated radiator/coolant reservoir cap.
I wasnt Valor vicTorian in any class, but I did sleep in a Holiday Express last night
Express 2000FT (hopeful - Again)