[A/S] Engines in smaller tow vehicles

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

Modern engine design for passenger vehicles (not work trucks) tends to be
optimized for adequate performance and fuel economy, NOT towing performance.
Consequently, these passenger car engines are typically smaller
displacement, higher RPM engines (which develop their power at higher
revolutions per minute). For heavy duty use, such as towing, one needs
TORQUE (or twisting power) preferably at LOW RPM. This (for the most part)
requires a larger displacement engine (like the engines of old in American
cars) which are now only typically installed in heavier duty trucks. Thus
the modern passenger car power plant is the exact opposite of the "ideal"
design for good performance with a heavy load - i.e. your trailer.

The only magic the automaker can use to make a high rpm engine more suitable
for towing is to add variable valve timing, turbo or super charging, a lower
(higher numerical) rear axle ratio, and more gear ratios in the
transmission. {Mercedes, for example is offering a SEVEN speed transmission
these days - vs.. the typical three or four speed variety.)

Note that the life of a piston engine (all other things being equal) is
mostly dependent on keeping the RPMs down.  Engines that require higher RPMs
to produce the necessary power are being stressed a lot more in a towing
application, and likely will have a shorter life (or be more prone to
failure - or be closer to the hairy edge of a potential failure). The higher
the RPM, the more mass that is flying back and forth at higher speeds. [For
the purists, reciprocating mass in a high RPM engine can be reduced by
shortening the piston stroke, which usually means more cylinders [the reason
some Ferrari engines are 12 cylinder designs is to reduce piston speed](and
more parts, which increases the cost and complexity of the engine).  No
wonder your little V-6 is not the optimal power plant of choice for towing!

Diesel engines tend to develop their torque at lower RPM, and thus an
adequate size diesel engine is better suited to towing than a comparable
displacement gasoline engine.  [A case in point: the diesel powered
Volkswagen Toureg with the diesel engine is a faster accelerating vehicle
than its twin, the Porsche Cayenne with a large twin turbo gasoline engine!]
Turbo chargers on diesel engines actually lengthen the life of the engine,
since still more torque and power is developed at lower RPM which, in turn,
adds to engine life.

Although the newer, larger Japanese pickups now have larger engines than
they used to, the engineering design trade off is still in the direction of
higher RPM, lower displacement engines, and all that comes with it.

So you see why the list members who trailer the most with minimal problems
use heavier duty pickups with either large gasoline or diesel engines.

Oliver Filippi