The Washington times., 1917-09-08
MOTOR CHANGES
INCREASE POWER
OF NEW NATIONAL


In 1918, the National twelve has un.
dergons but little alteration in de,
sign. About 900 Of this type are in
use at the present time. Now a new
model is announced, having all the
principal features OF the original
twelve, but with a number OF small
alterations in the engine that give
greatly increased power and, paIticu-
larly, an even more noticeable high
gear ability at low car speeds.
Taking the alterations briefly, they
comprise an increase of bore from
"a inches to "a inches. the stroke
remaining a. inches as before: a new
Intake system with a "hot spot" n
counter-weighted -crankshaft with
larger bearings, and a detachable cyl
tnder head. The Oiiing system is also
Improved, and there are some other
detail changes that will be mentioned
in due course.
Not the least important OF the
changes is the use OF the detachable
head, because the even size of com
hustion chamber which makes this
possible is OF conspicuous advantage
In obtaining perfectly regular run
ming at idling speeds, where varia-
tons in the force OF each explosion
are most easily observed. This
change in head design has not affect
ed the layout OF the engine in any
way. The valves are still arranged L
FASHION and on the outside OF the V,
leaving the alley clear for the accom-
mediation OF the starting motor, the
Sarbureter, and the ignition unit.
There are gear drives for the two
camshafts, and a silent chain for the
Ignition unit. The latter is new to
the National, being now a double
header Delco OUTFIT: II Is mounted at
the front end OF the cylinder alley,
and the shaft which operates it car
ries the fan pulley, this bringing the
belt high up, where It is well pro-
teeted from dirt and oil. and there
fore likely to have a maximum dura-
bility.
The new intake system, designed 70
allow the engine to handle heavy
grades OF gasolene with satisfaction,
divides into two parts, or rather three.
The manifold which connects the two
blocks of cylinders is water jacllcted,
forming the water outlet from the
cylinders. Its temperature is a fairly
constant quantity. Us the thermostat
In located in the pipe leading UP to
the radiator. Next come the two
eored passages within the cylinders,
these consisting OF a cross passage
leading from the inside TO the outside
OF each block and longitudinal pas
sage from end to end OF each block.
Throughout the crankshaft there is
an oil passage from end to end, and
oil is fed to each Of the three main
bearings. Should the feed to either
two of these cease by any improbable
accident, the remaining one is thus
able to supply all the bearings, while
with all three feeds in normal condi-
tion a more than ample supply is in
sured to every part. 4
In laying out the new motor a good
many experiments were made With
valve timing and a very modrate
setting finally adopted. The exhaust
opens at 43is degrees before bottom
center and closes at just under 3 de-
grees past top center. while the intake |
opens 8 degrees past top and closes - |
degrees past bottom center. The lift |
is rapid, being from a mushroom tap
pet, and the power peak is around |
:, 900 revolutions per minute. with a |
maximum torque at 500 revolutions |
per minute At 500 the horsepower is /
81 and the torque 215 pound feet: IA
horsepower is obtained at 400 revolu-
tions per minute, and the curve runs /
smoothely to the maximum OF 81 !,
horsepower at around 1900 reyolu-
tions per minute. at which point the
torqe is stiil as high as T6-pound feet.
This means that the car has a wide
speed range with especially favorable
power to weight conditions from
around 10 to 30 miles per hour,
where the acceleratiye abilities are
most noticeable. A maximum speed
IS not yet settled definitely. but IT
s nearer TO 90 than to co miles per
lour with a full size touring body
md may perhaps prove to be higher
han 40. The standard gear ratio on
iigh is 4 7-12 to I.
The chassis in which the new engine
{ fitted is identical with that of the
lrevious model OF Highway Twelve,
he outstanding features, perhaps.
einE the long and nat cantileverl
prinEs which National has now been
sing for nearly four years There
re three principal body styles sew
n n-passenEer touring car. a four-pas-
enger sport type phaeton, and a four
sssenGer roadster with clover leaf ,
eating. The latter is proving a popu- ;
n model and will constitute about
vo-fifths CT the 1917 output The four
assenEer sport phaeJon. which was ,
1own at the winter exhibitions. has a ,