Air cooling question.

Hello, How about some hypothetical thinking . It seems to me that the VW
would cool a lot better , or easier, if the cold air entered the bottom .
Using scoops. and gravity. On redesigned cylinder tins. Went up through
the fins. Through the fan or not. And out the vents or through the decklid
if it had a bunch of cooling slots in it . Forward movement would drive
the cooling air through the engine bay. My background is aircraft
engines. Some big honkers too. 2000 cubic inch air-cooled babies. Hot
air naturally wants to rise. It would circulate cooling air upward.
Driving would be easy enough. The fan would be needed for parked and
running. Or traffic. Think gravity furnace.

The downside I can see. As with aircraft engines. Is . There's going to be a
lot of dirty air flowing through the engine bay. Road dust and crap. And of
course the fan needs redesigned to run backwards probably. Or maybe a
different setup mounted on the deck lid. Blowing out. I didn't think that
far.

Don't get me wrong. I'm no engineer. if you want to argue, Well, you are
right then. And the VW is proven. My point being the tin seals are critical.
Why. Because hot air doesn't want to go down. It has to be forced down.
You don't put your furnace in your attic for a good reason. I can see when
the car is moving getting airflow under the car pulling heat out. But
still. Apparently its not enough.

The upside. I'm betting the additional heat on top helps the engine run
better when its cold. It might heat the carb faster. I'm betting the tin
seals wont matter as much. I'm betting the engine cools a lot better. I'm
betting the interior wont get any more heat though. Unless you shoot some
straight up through the deck behind the rear seat.

I've had this discussion numerous times over the years with various vw/
356/911 friends, but it usually ends up staying on the drawing board
even though if someone had a ratty car with which to experiment, these
assumptions could be proven either way.
What we wanted to try was this: Remove the fan, replacing it with an
electric unit hooked to a temp switch - in theory, this would kick on
at low speeds/idle and go off once the car was moving. This would
allow experimenting with scoops on the bottom of the motor, hopefully
designed to avoid the exhaust pipes. Anyway, it could be a fun
driveway project to try. Upside is: Possible cooler running & net HP
increase without the mechanical fan.
Downside is: Fried motor from failed experiment (LOL)

Unless you want to make a *lot* more than stock horsepower the VW engine
is not terribly thermally limited, at least not the later models with
the doghouse oil coolers.

Also, don't forget that every Joule of heat energy you are removing from
the engine through waste heat extraction is just that - *wasted energy*.
Heat removed via the heat extraction system (which on the ACVW engine
is a combination of air and oil cooling) is energy that is *not*
transmitted through the pistons, rods, crankshaft etc. ultimately out to
the wheels.

If this were a more perfect world we'd have high temperature, high
strength, non-brittle, easily formed materials to make our engines out
of and we'd have -no waste heat extraction- whatsoever. People have
tried to do this. Back in the late 70's / early 80's they were looking
at making engines out of ceramic materials (at least the engine blocks
and pistons). They had some success in that they were able to
demonstrate engines who's normal operating temperatures were north of
450 degrees F. But, ultimately they couldn't solve the brittle fracture
problem with the ceramics and finding a lubricant that would work at
these temperatures proved problematic (I actually think they could solve
that problem now). Back in the day they were working on this technology
they were going for high efficiency/high gas mileage, but any efficiency
improvement can be spun into higher horsepower as well.

Unfortunately, this is not a perfect world and we have to make do with
the materials at hand.

I say all this to make this point. When you design an engine the goal
for heat extraction is to remove *just enough* heat such that the engine
will give a reasonable service life and will require only an acceptable
amount of maintenance. If you are pulling heat out of the engine beyond
this level you are throwing away either fuel efficiency or horsepower or
both. I see lots of guys that get really focused heat extraction and
fancy radiators, oil coolers, air ducting, etc. when in fact they are
pulling more heat than necessary out of the engine already.

That said, if you're really going to build a large displacement engine
with some sort of forced air induction you are going to have to devote
some effort at improving heat extraction. The trick is knowing when
enough is enough.

"John Stafford" > wrote in message
m...
> In article >,
> "DogDiesel" > wrote:
>
>> Hello, How about some hypothetical thinking . It seems to me that the
>> VW
>> would cool a lot better , or easier, if the cold air entered the bottom .
>> Using scoops. and gravity.
>
> You don't know squat about the ACVW and already you are ready to
> disregard decades of German engineering expertise. Go ahead. Reinvent
> the system. Don't bother to do any research. Blow stuff up. Be happy.
>
>> On redesigned cylinder tins. Went up through
>> the fins. Through the fan or not. And out the vents or through the
>> decklid
>> if it had a bunch of cooling slots in it . Forward movement would drive
>> the cooling air through the engine bay.
>
> Stupid, stupid, stupid. The car isn't always moving, you know.

That what a fan is for.
>
>> My background is aircraft
>> engines. Some big honkers too. 2000 cubic inch air-cooled babies.
>> Hot
>> air naturally wants to rise.
>
> First, you also have a big honkin propellor pouring air across those
> cylinders. They are not cooled only by forward motion through the air.
>
> Second, one of the great issues is radiated heat which you cannot blow
> away any more than you can blow aside a flashlight beam.
>
>> The upside. I'm betting the additional heat on top helps the engine run
>> better when its cold. It might heat the carb faster.
>
> We did run ACVWs without a fan or any tin. We put them in 60's BMW
> motorcycle frames. They didn't work very hard, and did not last very
> long.
>
>> I'm betting the tin
>> seals wont matter as much. I'm betting the engine cools a lot better.
>> I'm
>> betting the interior wont get any more heat though. Unless you shoot some
>> straight up through the deck behind the rear seat.
>
> The interior gets its heat from chambers that surround the rear exhaust
> pipes.

"DogDiesel" > wrote in message
...
> Hello, How about some hypothetical thinking . It seems to me that the
> VW would cool a lot better , or easier, if the cold air entered the bottom
> . Using scoops. and gravity. On redesigned cylinder tins. Went up
> through the fins. Through the fan or not. And out the vents or through
> the decklid if it had a bunch of cooling slots in it . Forward movement
> would drive the cooling air through the engine bay. My background is
> aircraft engines. Some big honkers too. 2000 cubic inch air-cooled babies.
> Hot air naturally wants to rise. It would circulate cooling air upward.
> Driving would be easy enough. The fan would be needed for parked and
> running. Or traffic. Think gravity furnace.
>
> The downside I can see. As with aircraft engines. Is . There's going to be
> a lot of dirty air flowing through the engine bay. Road dust and crap.
> And of course the fan needs redesigned to run backwards probably. Or maybe
> a different setup mounted on the deck lid. Blowing out. I didn't think
> that far.
>
> Don't get me wrong. I'm no engineer. if you want to argue, Well, you are
> right then. And the VW is proven. My point being the tin seals are
> critical. Why. Because hot air doesn't want to go down. It has to be
> forced down. You don't put your furnace in your attic for a good reason. I
> can see when the car is moving getting airflow under the car pulling heat
> out. But still. Apparently its not enough.
>
> The upside. I'm betting the additional heat on top helps the engine run
> better when its cold. It might heat the carb faster. I'm betting the tin
> seals wont matter as much. I'm betting the engine cools a lot better. I'm
> betting the interior wont get any more heat though. Unless you shoot some
> straight up through the deck behind the rear seat.
>

furnaces are routinely installed in attics around here... that said, I run a
full cooling system, including thermostat and control vanes... this
regulates the operating temperature... we don't always need *all* the
cooling available to us to keep the engine in the temperature range it was
designed to run in... that said, how can cooling be "better"? cooler does
not equal better running/etc... it's really easy to overcool a vw engine
without doing all the stuff you describe... now ifyou are just wanting to do
something different, for the hell of it.... go for it, but if you are
looking for making the engine run *cooler* than the designed operating
temperature, you are not doing yourself, or engine, any favors...

"DogDiesel" > wrote:
> Hello, How about some hypothetical thinking . It seems to me that
> the VW
> would cool a lot better , or easier, if the cold air entered the
> bottom .
> Using scoops. and gravity. On redesigned cylinder tins. Went up
> through
> the fins. Through the fan or not. And out the vents or through the
> decklid
> if it had a bunch of cooling slots in it . Forward movement would
> drive
> the cooling air through the engine bay.
I seem to recall a discussion on the amount of air the VW fan produces
(http://www.offroadvw.net/tech/wes/fan.html), it is a significant CFM
value (more than 1000cfm @4000 engine rpm). So much so that no electric
fan comes close (most electric fans are in the 200-400cfm range). This
is why race motors that use electric blowers are only good for the
track.

You are suggesting that air "scooped" from under the car will replace
this volume of air?

I'd think you'd still need an engine driven fan to provide air flow at
idle and low vehicle speeds. Only at cruise would the scoop be
functional enough (maybe). So you would need a way to switch between air
sources.