Not so Smart aerodynamic fairing

[GasSavers_Antoine]

Am I the pessimist here ? While most seem to have good results in modifying the aerodynamics of their cars, my experiments show no or little improvement ! I did three modifications :

1- Grille block with a polyethylen film covering tightly the two grille openings and bumper. Only one pass B.

2- Smooth cover hubcaps made with coroplast at the rear and light cone shaped cardboard at the front. AABB.

3- Front skirt, made of a flat piece of 1/8" veneer and 4" lawn edging, from the bumper down 2" to the ground. Covering the lower grille. One passB

The experimental road is a fast downhill 1 km section coming to a flat section for a total of 2,4 km to a stop sign. There is a slight up portion 10 meters from the stop. I had to turn left at the stop sign for a few hundreds feet. You can see it on GPS map:

Starting point: N47.14277? W70.26101? Elevation: 132 meters.
Stop sign : N47.15844? W70.28457? Elevation : 42 meters.

The test were all done as follow: From a standstill at the top, engine off, accelerating downhill without power ( gravity only), and measuring the MAX speed and the distance before the car stops.

Wind : Strong side wind (90?), and then a head wind after the stop sign.

Acuracy: Rounded up to the whole number ( no decimals), which is about 1% variation on 100 km/h. Speed taken on Scangage and GPS. Distance on the GPS but rounded to 25 feet. These experiments were not intended for scientific acuracy but for gross evidence of + 1%. I didn't want to write down acurate numbers to the hundred'th (0.00) because of the wind factor which is not constant.

Results :

The pass A ( without modifications) ( 3 times) was executed at 99 kmh avg. and for all 3 ( so no noticeable standard deviation) and distance = stop sign + 300 feet. So:

0- Stock car: 99 kmh max speed and distance = stop sign + 300 feet.

1- Grille block : 101 kmh max speed and distance = stop sign + 400 feet.
2- Smooth hubcaps: 100 kmh max and distance = stop sign + 400 feet.
3- Front skirt : 97 kmh max and distance = stop sign + 0 foot.

Conclusion: The gross measure give about 1% increase for the first two tests and a decrease of 2% for the last one.
The skirt test surprised me a lot. It might be because the skirt was flat and the stock car is rounded at the front. The undercarriage is also covered with plastic except the engine compartment.

What do you think ???