Page 1 - Combined_38_OCR

INTER COMPANY CORRESPONDENCE

October 9, 196 9
TO - NAME DIVISION PLANT/OFFICE
DEPT Special
H. P. Bruns Vehicle Development Engineering Office Highland Park
,-rtOM - NAME DEPT. DIVISION PLANT/OFFICE
W. P. Wright S&M Engineering Space Huntsville

SUBJECT:
Automobile Hood Scoops and Cowl Scoop Tests

During the week of August 17, 1969, Engineering Car No. 046, a race version of
the 1968 Dodge Charger 500, was taken to Talladega International Speedway for the purpose
of collecting data for evaluation of hood and cowl scoops used for inducing carburetor inlet
air. This memo reports the results from those tests.

Two basic configurations were tested. The first configuration utilized the normal
air intake source in the car cowl area to feed the carburetor while the second configuration
used a specially designed flush hood scoop (called a N.A.C.A. inlet) to obtain carburetor
air. These two configurations are sketched in Figure 1.

Modifications to configuration 1 were made by the addition of several sized deflec­
tors mounted over the standard cowl intake as shown in Figure 2. Three pressures were
recorded in the carburetor intake area: static pressure (Ps), which was measured by
mounting a probe flush with the carburetor inlet wall; total pressure (PT), measured by
a probe facing directly into the intake air flow at the carburetor inlet and on a plane in
line with the static probe; and dynamic pressure (q), which was a physical summation of
PT and Ps (q = PT - Ps).

Total pressure (Pt) remained essentially insensitive to configuration changes,
having the following average values at noted engine RPM's.

Engine RPM PT (psig)

3700 .130
4500 .182
5200 .231
6000 .343

Table I lists the measured values of Pg and q at the various engine RPM's. Significant
fluctuations are noted in both Ps and q with no trends apparent. This phenomenon is
attributed to a variable throttle setting being required from one condition to the next to
achieve the desired nominal engine RPM value. Relocation of the static pressure mea­
suring point to the plenum area immediately preceeding the carburetor intake removed
much of the measured fluctuation of this pressure and to some degree established trends
in the data.

110-7879 REV. 1-63