Rotary Engine wrote:

> The statement about air-cooling being inadequate above 40HP should talk
> to Teledyne about their 12 cylinder air cooled diesels used in tanks in
> the dessert. Hurant Karribian

Besides this one with no name there were the two comments from Thomas J.
and Bill Jepson that are copied here.

"Not arguing, BUT just imagine how one would get enough air around a 300hp
rotary. Even if you plaster cooling ribs all over I doubt you would be

able

to get all the heat away. It seems to me; at least with the higher power
rotaries you need the water cooling part to get the produced heat energy
away fast enough. Once away from the engine you can expand the surface in
the radiator to whatever you desire.....

Thomas J."

"Rolf,
I am not mentioning this as an argument just as information. The "certain
power" you are talking about must be pretty high. As an example I offer

the

Porsche 917-30 Can-Am variant that was dominating the unlimited Can-Am's

at

the end producing over 1000 HP from 5 liters with multiple turbochargers.
An engine that used a lot of "unobtainium" to be sure, but it was air
cooled. The point? It is what the engine is designed for, not the cooling
method that is important. Water cooled engines have proven to be more
efficient, quieter, generally more durable, and lastly more consistent
across a range of temperatures than air cooled engines. The reasons
proceeding are why water cooled engines now dominate.

Bill Jepson"


No name:
I was talking cars! The 40 hp was in reference to the VW beetle that was
later upgraded to about 60 hp or so having that four cylinder opposed air
cooled engine in the back. (They actually had to retard ignition on Number
3 cylinder only or it would overheat.)

Cars need to be quiet, as Bill said. There is  little space and cars are a
different animal than tanks. The reason for air cooled tanks is greater
simplicity and reliability. No one cares about noise or space in tanks or
even hp consumed by the large cooling fans.

Thomas,
I can see your point regarding limited fin area in a rotary. But here too,
I was talking generalities regarding reciprocating piston engines. Fair
enough, the radiator can be sized to whatever… That sure is an advantage.
Too bad no one is producing air cooled rotaries. But then for what

purpose,

air cooling would really only be suitable for aircraft use.

Bill,
You too are quite right too, just like the others. In cars, noise is of
concern as well as efficiency and consistency, especially at low speeds
which I had already said.

Being able to build high hp engines with air cooling is actually proof of
my statement that air cooling can suffice too if designed for a specific
purpose, 1000 Hp Porsche or large 12 cylinder tank engines.

This is the point, in aircraft there is always a high relative air

velocity

available which makes air cooling an option and certainly a good
alternative.

The fact that car companies spent billions and came up with water cooling
for car engines is not proof that water cooling is also best for small
aircraft.
That is really the point I was trying to make. After all, the conventional
boxers, of Lycoming and Continental are air cooled, and I suggest it is

not

the outcome of not enough R&D dollars spend.

I really wonder what Honda used in their "experimental" aircraft engines.
Anybody knows this?

Rolf Pfeiffer

The big problem with liquid cooling is instability of the cooling
system. When it reaches the boiling point of the coolant it goes
unstable. While an air cooled engine continues to increase it rate
of heat transfer as the engine warms up. Delta T in a liquid cooled
engine is limited to about 110 F. Delta T in your typical air cooled
aircraft engine can be up to 400 F.

Read my "How to Cool your Wankel" artical on the subject on the ACRE NL

web site.

http://www.rotaryeng.net

Paul Lamar

I don't know if this is true for the Rotary, but pretty much all air-cooled
piston (reciprocating...:) engines use some fuel for cooling too.
That was one of the major polemics when Porsche changed to liquid cooling.
"Not gonna be a REAL Porsche any more" "Hey, Porsche's are AIRCOOLED!!"
Supposedly Porsche had no choice because of emissions and/or fuel
consumption.
It seems like no one cares anymore today! (......about the cooling system in
the Porsche!)
However this was certainly true with the VW-Bettle - that one probably used
1/2 the fuel for cooling! 10 to 11 liters for 100 km, at 60 hp.... (that's
around 19 to 20 mpg ??)

Thomas J

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