Aero Test Results (Splitter, Spoiler)

Test Results

I got a lot of funny looks that day. 

I tested the splitter and spoiler at speeds up to 80mph. The alumalite is known to hold up to 160mph if braced correctly. I am confident that it will hold up to my car's current maximum speed. I noticed my car was a bit lower in the front without the spoiler installed, and there was definitely much more front end grip at speed.

Splitter extends 7" from the R-package lip. Splitter is 4 inches off the ground. Measured about 6" away from the centerline of the splitter at 1.5" behind the leading edge. 

Spoiler is 7 inches tall at its longest (vertical) point, and smaller around the center due to the curvature of the trunklid.  I measured 3 inches away from the hinge edge right in the middle.  The other note was taped up to the center of the rooftop.

Test Tools

I used Grant's differential manometer. This type of manometer simply measures pressure differentials from two different spots. The two nodes were mounted on opposite sides of the splitter, right at the same spot. It is a very useful tool; if you want to do some aero mods I recommend that you get it. Not that expensive. One thing to note is that this is probably best used to compare one readout to another. The results are only going to be good for a ballpark figure. 

Results and Test Method

I took 25 samples, ditched the readings from when there were other cars around me, and ditched outliers (there weren't much), and averaged out the results. Temperatures were around 58-61 degrees.

Splitter: It created about 0.165 psi at 70mph, and about 0.222 psi at 80mph. 

Spoiler:  About 0.120 psi at 70mph, 0.145 psi at 80mph

Analysis

Grant's 5-6" splitter on his SRT-8 made about 0.177 psi at 80mph. His splitter sits 1 inch higher than mine. Splitter height seems to have a very drastic effect on net lift generated. 

A very approximate figure, using the entire area of the splitter is 73lbs of negative lift (downforce) at 70mph, and about 93lbs of negative lift at 80mph. The lift generated around the sides are significantly lower than the lift generated in the center, so the figure might be a little bit optimistic. Next time I will measure at more points. I think in reality, I think it will be close to 50lbs of negative lift. That is about 2% increase in traction, overall, ignoring the dynamics of my car, at 70 miles per hour.

The splitter actually curves in, so the effective area of the splitter will be greater than the spoiler, at least in theory.  The ends of the splitter are not sealed to the trunklid, the trunklid is curved, and lastly the splitter is only 48" wide.  I actually have no idea what kind of downforce levels to expect here.  To further complicate things, the airflow at the rooftop might not have been a good representation of the ambient pressure.  I'm just going to call it 55% of the splitter and throw out 30lbs of negative lift at 70mph on the splitter. 

Significant, but my cornering speeds at my home track is about 35-55mph, so I will have to see how much it will help with my laptimes. There is a real chance that it might not at all, because of the drag penalties of the spoiler I will be running.