"Morgans" wrote in message
...

"Peter Dohm" wrote

2) The automotive engine stress tests could very well be exactly what
the
name implies--Stress Tests. In other words, they may well be very
carefully
designed tests to predict certian common warranty problems on new engine
models--as used in automobiles where they commonly operate between idle
and
20% power, with occasional bursts of full power and occasional demands
for
maximum power from cold engines.

I remember it more as a worst case abuse test. LOTS of WOT running, some
of
it for longer periods of time than certifications tests.

The test does include long periods of WOT, in addition to a lot more types
of extremely severe service. My point about the idle to 20% power is that
most of the engines sold will be used in automobiles with mostly very
lightly loaded operation, interspersed with bursts of acceleration onto
highways and occasional panic acceleration with cold engines. As I
understand it, the real purpose of the tests is to accelerate the possible
failures of a few critical parts, such as vibration dampers and head
gaskets, in an effort to predict and control the long term costs associated
with warranties--and especially extended warranties and service contracts
which can frequently by 7 years and 100,000 miles.

Based on that possibility, it would be
very usefull to know the engine coolant outlet *and* inlet temperatures
and
flow rate as well as the oil outlet *and* inlet temperatures and flow
rate
during the sustained high power run. (Remember that they have chillers
on
line which probably have far more capability than the engines under
test.)
There are a few other things I would like to know, specifically for any
engine which I might consider for conversion, such as any additional
steady
speeds which might have been tested; but those temperatures and flow
rates
would tell whether the engine showed any promise when using any
plausible
cooling system in an aircraft.

Good point about flow rates and temperature.

From the guys that have used Ford and Chevy V-6's, they have not had a
problem with cooling if the system is well designed to create a good
positive air pressure. Shoot, instead of real radiators, most use two GM
air conditioner condenser radiators. It seems like cooling must not be
too
hard, with those two little radiators.

The only problem stated is that they can not sit for too long, without
overheating.

It's good to hear that the cooling works reasonably well at normal power
levels--at least for the V6 engines. There are basically two cooling
problems to overcome at idle: First, there is the usual problem of
downdraft cooling in which the air must be pushed downward even though
convection wants to move it the other way--and a lot of air cooled engines
have the same problem when the installation is entirely designed around high
speed and low drag and the cooling inlets are simply too small to get the
job done at idle. The second problem is peculiar to liquid cooled engines
in which most of the coolant in the radiators is positioned lower than most
of the coolant in the engine--the water pump needs to turn fast enough to
move the coolant in a direction opposite from its natural convection. The
result is that a lot of V6 and V8 engine installations with offest reduction
drives (usually belt or chain) probably suffer from a "double wammy" in
terms of cooling difficulty at idle. OTOH, some of the inverted
installations, such as Steve Wittman's conversion for the Tailwind, which
had updraft cooling and the radiator mounted above the inverted crankcase,
should be immune from those problems--although I neglected to ask Steve
Wittman that question and have not had an opportunity to ask anyone else
with real world experience.
(He was in attedance and had the V8 Tailwind on display at SnF a number of
years ago.)

I always wondered why they don't put little fans on the radiators, as is
standard for auto applications. I know, a little more weight, but if it
got
me though long taxi situations at fly-ins, and big airports, that would be
weight I would be willing to carry.

I don't know the real reason, but fans would definitely restrict the airflow
at speed. That could be a greater penalty than the modest weight.

Peter