Page 4 - Combined_59_OCR

Results of Second Test of 1969 Dodge Charger 500 at Daytona International Speedway

T i res

To
Firestones used in the previous test9 set of the Firestones wa obtained and run©
The Firestones proved to be <>94 mph s Lower than the Goodyear o

A comparison was also made between the Goodyear tires mounted on the 8©5H rims
that have been standard until now,- and the same type Goodyears mounted on ffiferims
This comparison was run twice, and showed ©51 mph the first time and ©20 mph the
second time©

Flywheel

A heavy drag racing flywheel was installed on the engine in place of the stan
dard flywheel, and resulted in a speed increase of ©76 mph© The heavy flywhee1
had an inertia of ©1824 slug fto^ and weighed 38 Ilk, compared to the standard fly*
wheel which"weighs 19 lbs© and has an inertia of ©6937 slug fto^o There is jio Im­
mediate indication of why the flywheel does improve lap timeg ai though this has
long been considered a speed secret at Daytona© Engine speed was recorded during
these runs as witft all of the runs made, but preliminary study does not show any
change in engine acceleration between the two flywheels© This will be investi-
gated further and reported on later, but the test results do indicate a definite
advantage the higher inettxa flywheel©

Axle Rat

The car was originally built with a 2 O94 axle ratio& but this was changed
& o 07 ratio after the first few runs.> This resulted in a loss of o21 mph in
speed© Since the difference wa : ■ so small the ratio was not changed back© The axle
ratio n nang 0 resulted in an increase of about 300 rpm across the bo ard9 and
appearantly .reduced the average engine power output over the speed range0 This
can not be answered completely until a power curve is available on the engine as
it was installed in the ctir©

The rpm spread from rain imum to maximum averaged about 550 rpm, which is about
the ame as in the September test j, even though the lap speeds were higher o

Exhaust Pipes

The ends of the exhaust pipes on the new car were cut parallel to the center-
line of the. car© For one test short extensions were welded onto the pipes to
give ends that were perpendicular to the pipes© This change reduced the lap speed
by 061 mph© Since such a small change in pipe length would be unlikely to repre­
sent a change of 10 HP due to exhaust tuneing9 this must be caused by the air flow
and pressure conditions at the ends of the pipesc I

Ho r se power / MFI1

There has always been a question as to how many horsepower it takes to in­
crease pie lap speed one mph at Daytona© For this test the Engine Laboratory pre­
pared three smaller carburetors to reduce the engine power by up to 24%© The three
carbureters were run along with the standard carburetor and give a good picture of
the power - lap speed relationship,, These four carburetors will be compared on the
engine from the car on the dynamometer to give accurate values© Until this data is
available we have only the approximate power levels© Based on these approximations
the car requires 17©5 HP per mph in the 190 mph range© When the correct engine
data is available a more detailed analysis will be made©