Greg Kwiatkowski provided a December 9, 1968 internal Chrysler report of the 1969 Dodge Charger 500, one of two 1969 Charger variants created for racing and produced for retail buyers to meet NASCAR and USAC rules. The Charger 500 was a fine short-track car, while on superspeedways, where top speeds were much higher and stability was more important, the winged Dodge Charger Daytona was the ideal. Both were far more aerodynamic than the stock cars, which required a great deal of work with the windshield and back glass mounting and the grille—using exposed headlights on the 500 and hiding them under an aero nose on the Daytona.
We have rewritten the report in places to help it flow more logically and to make it easier for non-engineers. The purple ink in the image below is likely due to it being mimeographed.
Sections taken directly from Wallace’s memo are in quotes.
In September 1968, Buddy Baker made numerous test laps in a prototype Dodge Charger 500 at the Daytona International Speedway. In late November, Baker and a new prototype Dodge Charger 500 made numerous tests on the same track. G.M. Wallace summarized that the second car, as tested, should be a “competitive race car with a good chance of being successful. Performance is superior to the 1968 Fords and Mercurys in both speed and handling.”
Baker reached a peak speed of 192.27 mph, finding the car to “have excellent handling and to be very controllable. This is 6.1 mph faster than the run during the September test at Daytona with car 046, the 1968 Charger converted to a 1969 Charger 500. The major factors involved in this increase in speed are different tires, greater engine power, underbody to body angle, bracing bars in the engine bay, heavy flywheel, wider rims, lower airflow to the radiator, and weather differences. Axle ratio, exhaust pipe ends, spoiler length, and other factors were also tested. Preliminary results indicate that in the 190 mph range it takes 17.5 horsepower to increase the lap speed one mph.”
Both cars had 1969 Charger 500 body shells with carefully reshaped rear windows. Car 046 had the floor pan parallel to the body as in the Charger R/T, while the new car had the floor pan at a 1.5° angle to reduce wind drag. “The engine in the new car is mounted lower in the car since it is to be run with a dry sump system. For this test a normal wet sump oil pan was used, with the bottom of the pan being below the legal minimum clearance.”
Both cars were run with the same car sill height. “Both cars ran single carburetor ram manifolds, although the new car had the new design air cleaner and a different advance curve in the distributor. The engine from the new car has not been checked on the dynamometer as yet, but it is estimated to be about 10 horsepower better than the engine that was in car 046.
“The September test was run with Firestone tires of the same type as used in the July 4th race. This test was run with Goodyear tires that they say are the same as their July 4th tire, although the tires had no compound identification on them.”
Another difference between the September and November cars was the addition of bracing bars which bolted across the rear corners of the engine bay.
“For a baseline condition, both cars had the grille completely blocked with tape, with air for the radiator coming in through the hole under the bumper. On car 046 the air for the oil cooler came in through this same opening, while on the new car the oil cooler air comes in through the left inboard headlight opening.
“Car 046 ran with a 2.94 axle ratio, while the new car had a 3.07 axle ratio in baseline conditions. There were also differences in weather conditions between the two tests.
“We developed a correction factor for weather differences, so to remove this variable, all of the speeds and speed differences will be given corrected to 29.92” Hg [inches of mercury] dry air and 60°F unless otherwise stated, the air pressure and temperature seen during the first week of practice in February 1968. The corrected best speed obtained on car 046 in September was 189.02 mph (186.18 mph observed). The baseline speed for the new car is 191.34 mph for an average of several runs (188.8 to 189.7 mph observed speeds). This gives an advantage of 2.32 mph for the new car over car 046. An approximate breakdown of this difference, accounting for 2.32 mph, is:”
| Goodyear tires vs Firestones* | + .94 mph |
| Engine with 10 HP more | + .55 |
| Engine compartment braces | + .31 |
| 3.07 axle ratio in place of 2.94 | - .21 |
| Floor pan angle and other changes | + .73 |
* The Goodyear tires added 0.94 mph to each lap over the Firestones. Moving the Goodyears from the usual 8.5” rims to 9” rims (by width) added 0.51 mph with the first set of laps and 0.20 mph with the second set.
“With the exception of the underbody angle each of these differences was evaluated in a separate test. The differences shown above can not be considered as exact, but the general levels are believed to be valid.” The most successful changes were:
| Baseline speed | 191.34 mph |
| Reducing airflow through under-bumper opening | + 1.80 mph |
| Heavy flywheel | + 0.76 |
| 9” wide rims | + 0.20 |
Changes that did not help were uncovering the grille, which dropped 2.6 mph; a long front spoiler with four inches of ground clearance, losing nearly 1 mph; and cutting the exhaust pipe ends off square, dropping 0.6 mph.
“One major factor that does not show up directly in the speed numbers is the handling of the car. Buddy Baker found car 046 difficult to control and very susceptible to winds. With the new car he found the car very easy to drive at all speeds including the maximum, even with considerable wind. He thought that he could race the car at 192 mph, the only limitation would be the tires. The tires used were good for only 2 or 3 laps at these speeds before they would get too hot and start to lose their grip.
“This very good handling is a very great difference from the Fords, which both from appearance and drivers’ comments were very difficult to control at qualifying speeds. The handling of the new car was so good that when the speed was slowed down to 187 mph, Buddy complained that it was boring to drive.”
The only factor tested that had a direct effect of the handling was the removal of the bracing bars in the engine compartment. This was done as a blindfold comparison with the bars in, out and back in again without the driver knowing what changes were made. ... the driver noticed a definite difference in the handling of the car, with a noticeable deterioration with the bars removed. The speed loss was .38 mph and .24 mph for the two tests.
Other factors may affect the handling of the new car compared to car 046. One factor is the underbody angle, which may have an effect on the aerodynamic stability of the car. Another factor may be the new steering gear mount, which is much more rigid than the previous design. There are many other differences between the 1968 and 1969 race cars that may have an influence on the improved handling of the 1969 design.
“The basic aerodynamics of the Charger 500 continue to be very good. The air inlet area through the grille and under the bumper is the area where the most can be done to reduce the drag of the stock body. The speed is increased by 2.60 mph by completely blocking the main grille, another 1.80 mph can be added by blocking most of the under bumper opening and leaving a slot of 30” x 1” just above the spoiler. The oil cooler inlet was also restricted in this final condition. This results in high but not excessive oil and water temperatures, but with the lower opening open and the grille blocked the temperatures are low.
“Blocking the grille and reducing the opening below the bumper reduces the drag by around 14%, equivalent to about 77 HP. While the rules prohibit such blocking, similar results should be obtainable by using a fine mesh screen. An indication of the very low drag of the Charger 500 package is that during the horsepower per mile per hour testing, the car would still lap at an observed 181.5 mph with a small carburetor that reduced the engine power to about 440 hp, less than the later track racing wedge engines.
“A longer front spoiler was tested to see if it would improve handling or increase speed. This spoiler was 4” from the ground rather than the 6.5” of the normal spoiler. This long spoiler reduced the lap speed by .96 mph, and did not seem to have any important effect on handling. The suspension travel measurements indicate some reduction in front lift, but this did not show up as an important change in handling.
“Uncovering the front grille seemed to increase the front lift to some extent, based on driver comments.”
“A heavy drag racing flywheel resulted in a speed difference of .76 mph. The heavy flywheel had an inertia of .1824 slug feet squared and weighed 38 pounds, compared to the standard flywheel, which weighs 19 pounds and has an inertia of .0937 slug feet squared. There is no immediate indication of why the flywheel does improve lap time, although this has long been considered a speed secret at Daytona. ... preliminary study does not show any change in engine acceleration between the two flywheels. This will be investigated further and reported on later, but the test results do indicate a definite advantage for the higher inertia flywheel.”
The car was built with a 2.94 axle ratio; switching to a 3.07 ratio dropped 0.21 mph in lap speed, which was small enough that they didn’t change back. Changing the ratio increased engine speed by around 300 rpm and reduced average engine power output across the entire speed range; the reasons for this were not clear, and were awawiting tests with the engine as it was installed in the car (all horsepower ratings seem to be “gross” or brake horsepower, without accessories). “The rpm spread from minimum to maximum averaged about 550 rpm, which is about the same as in the September test, even though the lap speeds were higher.”
“The ends of the exhaust pipes on the new car were cut parallel to the centerline 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 .61 mph. Since such a small change in pipe length would be unlikely to represent a change of 10 HP due to exhaust tuning, this must be caused by the air flow and pressure conditions at the ends of the pipes.”
“There has always been a question as to how many horsepower it takes to increase the lap speed one mph at Daytona. For this test the Engine Laboratory prepared three smaller carburetors to reduce the engine power by up to 24%. The three carburetors 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.”
Non-car factors which affected the lap speed included temperature, humidity, barometric pressure, winds, and track temperature. Wallace had already created correction factors for barometer, temperature, and humidity for drag racing, but “For track racing the effects of weather are more complex, and it has been more difficult to develop a successful correction factor. Such a factor has now been developed, and it appears to do a good job of correcting the observed lap speed for temperature and humidity.”
It turned out that barometric pressure was not especially important, since it increased both engine power and wind drag, cancelling itself out. His correction factor included pressure but it was normally not a real player.
The following chart shows sample corrected and uncorrected speeds for three runs with the car itself having exactly the same equipment in each case:
| Run | Date | Time | Observed Speed | Corrected Speed | Temp. | Humidity | Correction Factor |
|---|---|---|---|---|---|---|---|
| 6 | 11-26 | 4:30 PM | 189.13 | 190.10 | 66° | 63% | 1.0050 |
| 8 | 11-27 | 11:45 AM | 188.44 | 190.32 | 75° | 57% | 1.0100 |
| 10 | 11-27 | 12:45 PM | 188.09 | 190.18 | 78° | 52% | 1.0111 |
This shows that the formula worked remarkably well, taking around 1 mph in track speed variation and minimizing it to just 0.22 mph. He did qualify this by noting that the carburetor was not properly set up and there were some unsealed air leaks, so the car was capable of higher speeds. The correction factor was tested during the actual qualifying races, by multiplying observed speeds by the calculated, weather-based correction factors. During the various tests at Daytona, they saw that the correction factors would influence track speeds by around 2.2 mph.
“Al Unser’s qualifying speed of 183.53 mph in car 046 is corrected to 184.34 mph. For the first day of qualifying for the July race the correction factor was 1.0168, so that Charlie Glotzbach’s pole winning 185.16 mph is corrected to 188.27 mph, an increase of 3.11 mph. Lee Roy Yarbrough’s fastest qualifying time of 187.05 mph is corrected to 190.19 mph. During the various tests run at Daytona during the past year we have seen correction factors between 1.0067 and 1.0183, a difference of 1.2% or about 2.2 mph.
— G.M. Wallace
He wrote,
I was at Chrysler Engineering from March, 1953 to October, 1971. I spent the first two years as a student engineer in the Chrysler Institute of Engineering Graduate school. From 1955 until 1968 I was in the Performance Lab, where we analyzed performance of future models and concepts.
We did what today would be called Performance Simulation. We calculated acceleration and fuel economy originally using Frieden desktop calculators and later using early mainframe computers. (It took two to three hours to calculate the acceleration data on one vehicle combination.) Using this data we helped make decisions on such mundane things as axle ratios for next years models to analysis of new type of automatic transmissions. But with this job I interacted with almost all parts of Engineering except Styling, and had a pretty good idea of what was going on most of the time.
I was a race enthusiast from the beginning and was always able to find time to do performance estimates on various people's race car programs. So when there were real Chrysler race programs, I was involved in estimating performance. By 1967 I was spending half my time on race projects, mainly NASCAR, so in 1969 I was officially transferred to work full time in the race group. I was very involved in the Daytona Superbird programs, the race cars, not the street cars. I was responsible for the chassis and drivetrain development of the 1969 STP-Plymouth Indy Car program.
Bill Shope later added, “ I can vouch for George's willingness to help in such endeavors as he helped me to make valid performance predictions for the car. Calculated results were essentially identical to the car’s actual runs on its first appearance at the NHRA Nationals in Detroit. George also developed the empirical relationship between quarter mile speed, vehicle weight, and horsepower which was universally used by the Ramchargers to both predict performance and to evaluate the competition. In preparation for the 1960 NASCAR compact car race on the road circuit at Daytona, George calculated the average speed for the winning car. I can't remember how many tenths of a mph off he was, but I distinctly remember the amazement that a calculated value could be so close to the actual!”
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