[VAC] Re: Fw: Towing With A Manual 5Speed Transmission

["Carol and Oliver Filippi" <ofilippi@xxxxxxxxxxxxx>]

Some comments on modern high speed engines.

High RPM is what destroys engines.  [Actually it is the piston speed
(starting and stopping or the reversing of the reciprocating mass)]

Modern vehicles typically use higher speed (more revolutions per minute)
engines than in the past, to generate power.  This allows the automaker to
install a lighter powerplant which means better fuel economy.  This works
well in an automobile which is under relatively light load most of the time
[compared to a truck or a tow vehicle climbing a hill].
Racing engines are typically high RPM designs (once again to get maximum
power with a minimum of weight).  However, racing engines are carefully
designed to REDUCE PISTON SPEED - typically by shortening the stroke (the
distance the piston travels each engine revolution).  This is done by
increasing the number of cylinders (which is why Ferraris have 12 cylinders)
and increasing the bore (cylinder diameter) to get the necessary cylinder
volume with a shorter stroke.

Racing engines also have very light pistons (aluminum, and now even plastic)
and connecting rods to reduce the reciprocating mass.  The speed of the
piston is what loads the crankshaft etc. and in turn the bearings.  Turbine
engines and turbochargers [have no reciprocating parts] spin at very high
speeds and do not suffer bearing failure unless there is poor lubrication.
Doug Roe, a former Chevrolet engineer, and now an automotive consultant
taught me this years ago.  That is why a turbocharged diesel engine has such
a long life and is used in bulldozers and earthmovers where a little extra
weight would not be a major problem.  The turbocharger allows the engine to
develop more power (and torque) at lower RPM, hence the increased longevity
(it also cools the exhaust gases which extends the life of the exhaust
valves).

High RPM gasoline engines tend to have low torque (torque is what you need
to accelerate the load (trailer) and therefore have to be geared down via
the rear axle and transmission to gain torque at the expense of RPM.

PS  I wish General Motors would put their new Duramax diesel engine in a
Tahoe/Yukon.  That would be the perfect tow vehicle.  Full size pickup heavy
duty frame, short wheelbase for easy maneuvering,  lots of torque for towing
and super fuel economy (better than 20 mpg towing or not).  In addition, the
engine is not noisy (new fuel injection system) and very fast, even with a
heavy load [can out accelerate the big 400 + cubic inch gas engine].

The engine is so powerful they had to install a super heavy duty multispeed
(8 if I remember correctly) Allison automic transmission transmission on
this puppy.

Oliver Filippi