The Factory Five crew traveled to Charlotte, NC to visit A2 Wind Tunnel LLC and to test the new 818R and the 818S with optional aerodynamic parts to be sold as options to the kit. As a result of the testing, the front splitter, rear diffuser, and side skirts were qualified and released to production. The rear spoiler is being modified slightly. Here’s the report from Chief R&D Engineer Jim Schenck.
“Recently we brought both the 818S and 818R to the A2 wind tunnel in Mooresville North Carolina to get both a baseline of the standard body shape and to test the effectiveness of the additional aero parts and see if any changes were needed before they are made available. Also the data from the parts and combinations helps in tuning the race cars not just for total downforce but for front to rear balance to a help tune the car and optimize it for different race tracks and the street car to maintain a safe balance.
The first car we tested was the 818S and all of the more street specific parts designed for that car. Our baseline test was run just as the car comes with no add-ons and at street ride height, in this test we made a very small amount of lift front and rear, 28lbs in front and 18lbs in the rear at 100mph, which compares very favorably to almost all but the most exotic sports cars. The news from here only got better as almost every addition we tested showed a large gain in downforce, with the only exception being the side skirt panels which added a small amount of lift but did give a slight decrease in drag. Our best combination in terms of both downforce and balance was with the car at zero rake (street ride height of 4.5 inches) with the street front splitter, the rear diffuser, a modified rear spoiler, no side skirts, and the gap between the nose and splitter blocked off. The only part we will need to modify is the rear lip spoiler which needs to be slightly larger to balance out the effects of the front splitter. We did this with a section of an old splitter for testing purposes. Also the results show that using the splitter only with no rear add-ons would result in a very tail happy car at speed and is something we do not recommend. Overall the car showed good balance with close to neutral lift in its base configuration and even better balance and significant downforce when optimized with the optional aero parts.
Next up was the 818R with its lower ride height and much more aggressive splitter and rear wing. The baseline on the R showed that the ride height and lack of windshield combined to make the car almost dead neutral lift wise using just the standard body panels with no Aero additions. (1 lb front lift and 11 lbs rear lift at 100mph) After that we tested the set-up that was run and dialed in during the previous on track sessions to get numbers on what a comfortable aero balance was at the track. This combination included the old splitter, the side skirts, and the rear wing at zero degrees, and produced just under 200lbs of total downforce at 100mph giving us our baseline to improve upon. Switching out to the new splitter added 30 plus lbs of downforce to the front end and another 20lbs by taping off the opening between the body and splitter. With all this added front downforce we then adjusted the wing angle and added the diffuser to balance out the car. In the end our best numbers came with the extra radiator ducts taped off, the new splitter with the air gap taped off, 5 degrees of wing angle, the rear diffuser in place, no side skirts, and a level ride height of 3-3/8 inch. The max downforce produced was 120 lbs front and 164 lbs rear at 100mph, this increases to 271lbs front and 369 lbs rear downforce at 150mph. The only concern with this set-up was cooling with the extra air inlets taped off, however we were able to test this configuration two days later in 97 degree weather at the track and the engine temperature was not affected.
Our conclusions from the testing were that the rear spoiler needed to be extended for the street car, the race splitter is to aggressive for street use without a rear wing, and the car has a nice useable balance without any aero add-ons for someone who would prefer the clean look or not have the budget for the extra pieces.”