Flying Volkswagens are a bit like Texas midgets. Everything's bigger in Texas,
right? Even their midgets are six feet tall :-)

The VW Myth was spawned following WWII by those Gentleman Aviators of a
literary bent who, after winning the Battle of Britian decided to tell everyone
about it via articles in the aviation magazines. Of course, twelve issues a
year, your sea stories start getting a bit stale the n-th time they're told so
they extended their imaginary expertise to other areas, such those niffty
little flying machines coming out of Europe.

You know the ones I mean: Kubelwagen engine with a prop on one end and a Jodel
on the other.

Marvelous machine. Fly for pennies. Never a bit of trouble and the engines
were always good for at least a thousand hours.

All that from the Gentleman Aviator's single hop around the pea-patch followed
by a lengthy visit to the club house. No mention of the erks. Gentleman
Aviators do not associate with Other Ranks. Which is why they failed to
mention the annual overhaul, frequent valve jobs and dismally short service
life of those marvelous little engines. (Another round? Why not!)

Most Americans are dumber than stumps when it comes to engines and American
aviators are among the dumbest of the breed with the Internet providing daily
evidence of their failing. (Yes, you can check the oil. No, you can't adjust
the valves. If you want to watch, go stand over there.)

It's all about torque and waste heat but to the idiots it's all about
horsepower and top speed.

PEAK output of an engine can be... just about anything. You can see 300hp from
an aircooled "Volkswagen" engine for a few seconds (and note the quotes). But
if you're smart enough not to pee on your shoes you'll pay more attention to
the maximum SUSTAINABLE output. As with all aircooled engines the sustainable
output is a function of the engine's ability to cool itself. But don't get it
confused with the output that gives the greatest interval between overhauls.
That figure is even lower. And it doesn't matter what kind of aircooled engine
we're talking about -- Pratt-Whitney or Weedeater, the laws of thermodynamics
apply.

They say you can't cheat an honest man. The same 'they' also tells us that a
fool and his gold are soon parted. American aviators tend toward the foolish
side of the bell curve when it comes to flying Volkswagens, preyed upon by
slick hustlers chanting peak horsepower figures.

Every fly a Piet? (The two-holer, not the other one.) Didja notice the prop
is mounted to the clutch-end of the Model A's crankshaft? Now go look at the
typical flying VW, with the prop on the pulley-hub, a fragile little protrusion
barely three-quarters of an inch long, less than an inch and a half in
diameter, hollowed out with metric threads (the valley comes to a point...
makes a dandy stress-riser) and the circumference notched with a Woodruff
keyway that comes to within sixty thou of those nice, pointy threads.

Look at all the VW's you want. Note the fantastic schemes -- fantastic and
EXPENSIVE schemes -- that are used to try and put a band-aid on a case of
terminal cancer, in engineering terms.

The late Steve Wittman knew his onions when it came to engines. He put the
prop on the other end of the crankshaft and blew away the competition. (We got
on like a house afire when we discovered we both built our engines
ass-backwards :-)

Why'd they even do it to begin with? Because with a 20hp 985cc engine (ie, out
of the original Kublewagen; it didn't get the Big Engine until 1943 and if the
early ones never came back to the factory for overhaul, they never got one
installed) you could bolt the engine directly to the firewall and do away with
the engine mount. And the pulley hub was good for about 200 hours if the load
was less than 25hp... no problem when you could replace the crankshaft for $17
every winter... while the Gentleman Aviators were up at the club house getting
sloshed.

Remember N7EZ and its "68hp" VW engine? I asked Burt where he was going to
find such a thing. From my competitor, of course :-)

Truth is, from 1300 on up, all Type I's use the same heads -- same amount of
fin area. And most of the after-market 'racing' heads have even LESS. (Go
measure it; work it out for yourself. Increase the thickness of the casting
REDUCES the available fin area.) Hottest part of a VW engine is around the
exhaust ports. VW engineers did a superb job of controlling the air PRESSURE
within the plenum to force the maximum amount of air down thru the finned areas
adjacent to exhaust stacks.

Aluminum is a 'white-short' metal. All metals are mallable. Heat most metals,
they go through a plastic stage before they melt. But heat aluminum or
magnesium, before it melts it will go through a fragmiable stage during which
any stress will cause it to fracture. ( Foundrymen call that 'white shortness'
and treat their aluminum castings with care as they cool.)

The fact aluminim is fragmiable at elevated temperatures is why we pay so much
attention to CHT on our aircraft engines. And VW's. And Porsches. And
anything else with AIR-COOLED aluminum heads. (Liquid cooled engines are
another planet. Don't even think of trying to transfer your zillion years of
Ford V8 experience to a VW unless you've got a death wish or get off on looking
foolish.) 450 degrees on the Fahrenheit scale is the lower edge of the plastic
range for aluminum. Being slightly denser, forgings can go a little higher but
castings -- such as the VW head -- may be at risk at even LOWER temps -- it all
depends on the alloy and where you monitor the temperature. The hottest part
of the head is the area around the exhaust stack (which is where VW measures
CHT on their fuel injected engines). The classic ring-type thermocouple under
a spark plug can read just about anything, depending on how much air you blow
on it.

As every parent knows, where you stick the thermometer has a lot to do with the
reading. One of the best jokes in aviaition is all the guys flying around with
their oil temp sensor screwed into the wall of the CRANKCASE. As you can
guess, they never have problems with high oil temps :-) (Volkswagen inserts
the OT sensor in the flow of oil entering the oil pump. Readings at that point
typically run about 100 degrees higher than at the dip stick and as much as 150
more than the sump plate or crankcase.)

Keeping the oil cool in your flying VW is a no-brainer. Just treat it like an
aircraft engine. The cooling arrangement used in CAR engines is of the by-pass
type, meaning things have to get pretty hot before any cooling takes place.
With airplanes you pre-configure the cooling system prior to take-off, in
anticipation of maximum need. Once you get up to altitude you get things back
into the green then close the shutters enough to keep it there. Alas, trying
to use the car cooling system in a VW powered airplane is almost universal and
like putting the prop on the pulley hub, equally dumb.

Big-Bore Storker! Wow! Over 150hp @ 5000 rpm for an all-up weight of less
than 200 pounds.

And as useless as tits on a boar, with regard to airplanes.

Because it uses the same heads, that's why. Same fin area. Same maximum
cooling co-efficient. Same maximum SUSTAINABLE OUTPUT... which is about 45hp,
depending on the weather.

Sure, more cubes will get you out of the weeds faster. But you'd damn well be
flying the gauges AND have designed your cooling system accordingly. Because
no matter what the displacement or peak output, your life literally depends on
keeping the CHT within bounds.

So it runs your dune buggy all day at 4000 rpm. What's your manifold pressure?
How often do you do the valves. The same rpm does NOT mean the same power
output, no matter what they taught you in Auto Shop. The closest match between
a VW engine in a vehicle and one in a plane is to load your VW bus with about
two tons of cargo then go climb the steepest hill you can manage. Forever.

Time has taught me it's pretty much a waste of time to try and explain flying
Volkswagens. People want to be deluded and their wants are catered to by a
host of marvelously successful hucksters. Those who discover they've been lied
to -- and survive -- tend to be a tad shy. No one likes to look foolish;
obviously the fault must lay with the engine rather than in themselves.

VW is a car engine. You can convert it to a reliable, durable aircraft engine,
typically better in output and durability than say an A40-4. But the odd thing
is that so few people do. Instead, they turn it into a dune buggy engine and
screw a fan on the pulley hub. Go figger.

-R.S.Hoover