To Huck, gabriel pagliarani:
Even if it is correct the statement that only 6.1% of heat dissipated was thru oil and not by water, there is not
a direct link between the max power and the thermodynamichal enthropic efficiency you are referring to. Enthropic efficiency of any Otto engine is very poor but it increases with height due to the fact that the "delta t°" temperature of combustion chamber minus temperature of external environment is higher at top ceiling (-60°C) than at ground (+3°C ISO)
During WW2 there were only few american engines in which oil cooling was more effective by injecting oil in the upper sky of the combustion chamber and at the basis of the piston after having reached the upper dead point. This sophisticated cooling solution was re-developed during '80s by Suzuki on GSX-R air/oil cooled bikes. I had it. Wow!
The proportion which the two systems (oil and cooling) take part in taking away the heat from the engine is not directly connected with the enthropic efficiency or with anything else. It depends on the capability of the cooling system to take it away (the balance is based on this figure), not on the amount of the heat itself. If I have a small oil cooler, the amount of dissipated heat would be small and the temperature of the engine would rise; the rest of the heat would have to be dissipated by the cooling system. Some part of the heat, indeed, doesn’t need to be taken from the engine away, it could be (and it actually is) just “transported” to a cooler part of the engine (in this case, “cooler” means less warm :o))) ) The only limiting factor in the oil cooler size is the oil temperature, or maximum operational temperature, relatively. I hope that you know that the main oil purpose is to provide lube to the engine, the cooling system is there to cool it.
The descending amount of dissipated heat by the oil is due to its descending proportion on the cooling and this variable changes its value according to recent altitude. Based on the fact that the output oil and cooling mixture temperatures are different we might expect some temperature difference between the cooler and the air. Also the proportion of heat dissipated by oil and water we can expect to vary with the altitude. Following data are for DB 605 A, but I suppose they are nearly the same.
Let’s take sea-level (15 °C) and full throttle height – 5800m (-22.7 °C). The output oil temperature is 125 °C, with tolerance of 5 °C. The maximum output temperature allowed equals at sea-level 135 °C, or 110 – 120 °C in case of
Volldruckshöhe. In case of cooling liquid, the figures are followed: the output t is virtually 100 °C and for a brief period of time (10 minutes) it is permitted to cross it up to 115 °C (h=0) and 109 °C (FTH).
Let‘s do some basic calculations. The difference between oil and extrernal environment equals 110 °C (h=0) and cca 138 °C (FTH). The same for cooling liquid: 85 °C (h=0); cca 123 °C (FTH). So the oil temperature difference (t of the oil minus t of the environment) rises +25.5% (138÷110) or, in case of cooling liquid, 43.5% (122÷85), respectively. The cooler size are constant, but the bigger cooling liquid t difference means that in high altitude the proportion will be more favourable.
Enthropic efficiency is very poor but it increases with height due to the fact that the "delta t°" temperature of combustion chamber minus temperature of external environment is higher at top ceiling (-60°C) than at ground (+3°C ISO)
I’m not sure if I understood you well, perhaps you could explain it to me... That the enthropic efficiency rises thanks to the increasing temperature difference inside engine (in the cylinders, respectively), or due to decreasing outside t? Should it mean that that the t in combustion chamber (or in cylinder) is constant? If so, why there have been introduced devices like intercoolers or heat exchangers (places where the air is being warmed by the exhaust before it goes into the engine itself; used e.g. in gas turbines )..?
If I took your statement
ad absurdum, I would say that you’ve just discovered new physical principle contradicting the keeping-energy principle :o))) The combustion chamber t (if I supposed that it doesn’t change with outside t change and set it e.g. equals 900 °C) would not rise even if the sucked air t was about 1000 °C or 1500 °C? So the CC functions like a fridge? :o))) The truth is that, “thermodynamical enthropic efficiency” as well as heat effectiveness doesn’t rise with the altitude. The conditions under which the engine works (decreasing back pressure (for better scavenging and greater volumetic efficiency), decreasing pressure under the pistons) do change, that implicates better mechanical efficiency... The problem is, that the higher altitude, the lower air pressure. That’s why the aircraft engines do have got a compressor, which, of course, does take a part of power.
But, I haven’t discussed the biggest nonsense yet. :o)) We’re not interested in figures showing t of cylinders and surroundings, but only in the figures for the cylinder t – let’s say the t of the air coming in and out of the cylinders. The reason is that the work equals difference between heat brought and dissipated, and the work area is cylinder... This can be the only fact we have to take into account concerning engine heat efficiency (but, of course, this is valid only for an ideal circulation and it is not good to make statements based on this)
There are three monumental mistakes in your judgement:
1. you assume that pilot still uses full throttle after he is hit, since you list the 6% oil cooling figure on the heat balance at full throttle setting
But you didn’t take into your account that the engine t doesn’t decrease so fast, let’s call it “heat inertia”. Even if the pilot immediately after the plane is hit had set the throttle back, the heat accumulated in the engine would have had to be dissipated... There is no evidence (and no reason, too) to assume that the oil/water proportion would change in any way according to throttle, the operational t both of them doesn’t vary substantially, so the proportion would be similar. The oil share will never be 50 %, to reach this figure the oil would have to be much warmer and its cooler (which size is unable to change) would have to be capable of dissipating this amount of heat.
2. you don't take into account the fact that the heat carried away by the cooling system is only a part of the total heat generated by the engine
Yes, but the exhaustion do not increase their proportion... Compare the block t with the exhaustion t...
Btw, should I understand your statement that you consider 50 % dissipated by oil from the total amount of heat produced, or just from waste heat (carried away through oil and water coolers)..?
3. you assume that the heat balance remains the same after the coolant starts to leak
No, I don’t forget it. But the oil t can’t rise unlimitedly – it can light up – what was the reason for setting maximum operational temperature as 135 °C? :o)) And consider the cooler, which dimension is not capable of dissipating much more heat (and increasing its size is counterproductive – you increase the air resistance)
From the figures you have in the DB603G specification you can deduct the procentage of the total heat that gets dissipated by the cooling system, and with aproximation by the exhaust, at full throttle. You can also compute the total heat produced by the engine at full throttle setting compared with the total heat produced at cruise setting, and compare how much heat is carried away by cooling system at full throttle and cruise. I'd like to see that you are able to do this basic calculations before getting further into this topic.
So why don’t you do this, if you want to convince me? :o))) Unfortunately, it is not easy, you would have to have very accurate data for DB 603...
Yes, DB605A was capable of 15 minutes of operation at low output before seizing, provided only the radiators were hit. Although I do not have a direct account for DB603, DB603 was just a scaled up DB601 and DB605 was just a slightly modified DB601 for larger displacement. The cooling scheme of Me-109 was very similar to that of Me-210/410.
Once again, can you please post here you source? Bf 109 has for each cooler (each of them under one wing half) its independent branch capable of being closed by a valve, so in case of damage there was a chance that the liquid won’t run out and to avoid seizing. If the engine in the same started to overheat, it caused increasing oil t (and decreasing viscosity), that caused higher clutch slip and the engine lose power...
However, the “Wunderwaffen envy” has no chance to get me :o)
Best regards
by gabriel pagliarani on 02 Jan 2005 18:29 
DB were upside-downed V engines. How do you remove oil from the hull of pistons after injection? 8) Another 100% non-senses from you. Sometimes try to draw on paper your thoughts before staring insane querelles. (I have not forgotten your mad statement about piston velocity: if you want I 'll explain to you why there is no link between instant power and piston velocity only by PM) The same consideration about the oil-cooled head of your 2 stroke marine engines : try to draw four extra holes for valves in your "so easy" oil-cooled head and you begin to understand (if you could) the reason why 
About the experience about engines of my own, much better my own tested ignorance ("expertize" for you, "experience" for me) than your unskilled aknowledgement. I opened and closed a lot of engines, you none. 
I also don't get why the Heinkel Uhu was used in other capacities besides a nightfighter ? Then again Im pretty lost in statistics. 
