The Real Scoop on the Scoops?
Greg Kwiatkowski's Discovery
Regular visitors to the Aero Warriors site are familiar with Greg Kwiatkowski, as he has contributed a great deal of interesting and unusual material to the site. Greg's prototype Daytona wing and his recent find and purchase of the real #88 racing Daytona have been recounted here, and several documents and photos that Greg has collected over the years are also on display.
Because of Greg's enthusiasm for Chrysler products (as well as the fact that he works for them), Greg has had the opportunity to meet and speak with many of the people involved in the development of the Dodge Daytona and Plymouth SuperBird. And one of these encounters some time ago lead to a very interesting find about the cars' fender scoops!
To help with readability, the scoops paperwork Greg found in Larry Rathgeb's files has been recreated here. Notice the data shaded in purple - the scoops (exhausters) are credited with a 3% reduction in drag! A photo of the actual document is available.
In 1986, Greg was offered the opportunity to look through some old Chrysler paperwork belonging to Larry Rathgeb. Those familiar with the winged cars will remember that Larry was in charge of engineering for Chrysler's stock car racing program during the time that development work was being done on the cars. Greg made copies of much of Larry's rare documentation, including one piece of paper which is particularly significant to this discussion. The document has been recreated at left, and although it carries no date or identifying signature, it was found among documents that Larry told Greg he had authored during the Charger Daytona development. Look closely at the area shaded in purple.
The document seen here is pretty self explanatory. A Charger 500 (presumably a race prepared car) was used as a baseline for aerodynamic testing, with changes to the Charger 500 evaluated in relation to the drag produced when it was in the Charger 500 configuration. So, in the case of the first change to the car's configuration, the Charger 500 front end was apparently replaced with a long nose that included an optimum front spoiler set-up (whatever that was). The accompanying entry from the "Effect" column shows that this nose combination exhibited 9.5% less aerodynamic drag than the standard race Charger 500 front end. Several tests were obviously conducted, with the one most germane to this discussion shaded in purple. This particular entry concerns itself with the scoops (or "exhausters" as they are referred to here) and the aerodynamic advantage they afforded. As recorded in the "Effect" column, a 3% reduction in drag was noted when the exhausters were added to the baseline Charger 500 set-up! And of course this directly contradicts what Chrysler has been claiming about the scoops (exhausters) for the past 30 years.
Because there were no pictures or drawings included with the Rathgeb paperwork, some may question whether the exhausters mentioned were in any way similar to what actually ended up on the Daytonas and SuperBirds. And if they weren't, then perhaps "apples and oranges" are being compared here. If that really is the case then, this document still provides very important information. It discloses that Chrysler had some device, called an exhauster, that when mounted above the front tires reduced drag by 3%. And wouldn't it then be logical to conclude that Chrysler, knowing this, would not end up mounting something on the cars' front fenders that returned any less than this 3% drag reduction? So whether the exhausters mentioned in Larry's paperwork are similar to or very different from what eventually showed up on the cars, it seems reasonable to conclude that the exhausters actually found on the race cars yielded no less than a 3% drag reduction.
And yes, there is an assumption being made that the document presented here is genuine. It seems extremely unlikely that this document would have been created by Larry Rathgeb, Greg or anybody else in order to rewrite history on the scoops. For the purposes of this discussion, the document is accepted as genuine.
How The Exhausters May Have Reduced Drag
Generally speaking, reducing air flow under racing vehicles will improve their performance. In the case of the winged cars, air flow under the vehicles caused drag because air collided with the aerodynamically "unclean" undersides. One result of this disruptive air flow under the cars was probably some degree of upward force being applied to the vehicles' bodies because of "trapped" air. Front spoilers, found on many racing automobiles including the Daytona and SuperBird, were designed to prevent or "spoil" much of the air flow underneath the cars. Yet another method to reduce air flow under stock car racers was to lower them, and that is where this particular explanation is rooted. The exhausters (or more correctly the holes in the fenders beneath them) provided a pathway for air to escape from under the cars, where it would otherwise be trapped as the autos moved at high speeds. With air trapped under the vehicles, their bodies would ride higher than with the exhausters, resting on this cushion of trapped air. And because the bodies were setting higher on this cushion of air, even more air could flow underneath them. Providing an escape path for this trapped air allowed the bodies to set lower than they otherwise would, and thus less drag was produced because of the reduced air flow under the cars.
And why were the exhauster scoops mounted over the fender holes? A vacuum would be created directly behind the trailing edge of the scoops as the air rushed by. This small vacuum may in fact have aided in air extraction from underneath the cars. Without the scoops, any vacuum effect over the tops of the fenders would probably have been much less pronounced, if not totally non-existent. This same principle is used in NASCAR's Winston Cup series today, as the exhaust headers are cut in such a way as to be flush with the rocker panels of the cars. The air rushing by helps "pull" the exhaust out of the headers.
Also note the name exhauster. Webster's Dictionary defines exhaust (including the noun form exhauster) as "to let out or draw off...to draw out the contents of...a conduit through which vaporous gases are emitted...an apparatus for drawing out noxious air or waste gases by means of a partial vacuum..." The name exhauster seems to support the contention that the scoop devices were in place to release something from somewhere, like air from underneath the front of the winged cars perhaps?
An additional benefit of the exhausters, and one unrelated to drag, is a reduction in ride height which in turn lowers the winged cars' center of gravity. And generally speaking, the lower the cars' center of gravity the better, especially as it relates to their ability to handle turns. Lessening air flow under the vehicles also allows greater control over the attitude or "rake" of the cars, as the bodies in some cases would probably have a tendency to be levered up by air flow while moving forward. By lessening total air flow under the cars, a more consistent rake angle could be maintained, which was especially critical for the winged cars.
As alluded to by Chrysler aerodynamicist Gary Romberg in two of the quotes above, the exhausters were the subject of speculation among Chrysler's racing competitors. To the extent that the exhausters distracted the competition and "psyched them out", they were also arguably of some benefit.
And it should be stated clearly somewhere in this article that the exhausters may well have provided tire clearance, although calling that their only function (or even their primary function) is what Greg's paperwork has called into question. It would certainly be ironic if the needed tire clearance was necessary only because of the reduction in ride height due to the functioning of the exhausters.
What is Chrysler's reaction to Greg's discovery? He hasn't approached Chrysler engineers (past or present) en masse with the paperwork, although the few he has asked about it have had no response. If and when the opportunity presents itself, Greg will contact other engineers that worked on the cars to see what reaction they might have. If appropriate to do so, their responses will be reported here.
Greg Kwiatkowski's discovery of the air exhauster test results certainly provides ammunition for those that feel there is more to know about the "why's" of the fender scoops than Chrysler's tire clearance explanation. Whether the drag reduction benefit the exhausters offered has been a jealously guarded Chrysler secret for 30 years or just a small bit of data lost in the hectic environment of the cars' development and manufacture remains unclear. Hopefully someone from Chrysler will now step forward and help put Greg Kwiatkowski's discovery in perspective. But until then, the exhausters continue to be a bit of a mystery.
The author attended the 1999 Mopar Nationals in Columbus, Ohio and not surprisingly several of Chrysler's new and exotic offerings were on display, including several Dodge Vipers. The photos at left document an especially interesting aspect of both the street Viper (top) and its racing counterpart. Notice the louvered openings on the front fenders above the tires. They obviously aren't for tire clearance, as the closely spaced transverse louvers would impact the tires just as a solid fender would. Why these fender openings appear on some of Chrysler's contemporary high performance vehicles is certainly worth pondering. Perhaps the Internet District Court's indictment that introduced this article is closer to the truth than most realize!