Airdam and splitter

For most of the test we used a 4″ splitter on the airdam. I wanted to see what removing the splitter extension would do. We expected a loss in downforce, but I wasn’t  sure if drag would go up or down. You see it both ways online, with CFD data showing that a splitter reduces drag, and the occasional internet expert claiming that drag goes up. 

SplittersFront ClRear ClTotal ClCdL/D %HP @ 100mph
VGs, splitter, wing-0.20-0.61-0.820.521.5757.58
VGs, no splitter, wing0.18-0.64-0.470.530.8858.75

Score one for the CFD team, the splitter reduced drag slightly. When I removed it, the drag went up from .52. To .53. More importantly, we lost a lot of front-end downforce. Our raw data showed a loss of 69 lbs on the back straight, which calculated to a .38 delta in front coefficient of lift. Let’s see what that’s like in OptimumLap. 

SplittersWatkins GlenWaterford Hills2010 SCCA Nationals
VGs, splitter, wing2:24.321:20.421:03.54
VGs, no splitter, wing2:25.651:21.121:03.89

Obviously, if you’re running just an airdam, and the rules allow it, add the splitter. It’s significant.