You achieved a repeatable 1.2mpg increase over a 3 mile controlled route by just filling in the gap at the top of the windshield with tape? not in disbelief but unless I missed something I just wanted to verify thats what I read. I feel like the right strip of rubber molding could be glued into that gap and lay over the windshield to provide a more permanent and aesthetically pleasing final product and it would be relatively simple. for the wind noise alone this would be something to look in to.
Just to be clear I wasn't expecting quite so definitive of a outcome from my small spate of testing. Normally if you're running tests series, you have allowances for data noise. Usually this is in the 2% to 5% range. It's also why I chose this piece of road because it shows noticeable effect when things are going even slightly wrong my cars state of tune.
As it is, we are sitting at a 4.563% differentiation in run to run data. So verging on just being data noise @ 5%. That depending on using data noise compensation @ 5%. It might even be a case of this mod being useful only at the speed I was traveling. It might make things worse at higher speed. Aerodynamics can do that.
"by just filling in the gap at the top of the windshield with tape?"
Well there was also the packing tape run from the sides of the "windshield Chrome", on my mks, to the windshield face, at about a 45° angle as well. The Chrome strip running beside the windshield on the MKS sits proud of the windshield from a quarter of an inch at the top of the windshield . To a maximum of 2 in at the base of the windshiel. Think of the sides of a pan holding water in. I think that this is big chunk of it.
Adding an incline to this 90° surface change/air fence, should likely help ease the airflow around the side and closer to the greenhouse area of the car. So it would be adhering a little better to the side glass. Not to mention possible reduction in air pressure buildup on the windshield.
I didn't test both areas individually. I do have a sneaking suspicion that that Gap at the top causes rather turbulent airflow. So possibly non-laminer flow. I'm not 100% sure if that's a detriment or not. If that Gap works the right way it reduces lift. If it works the wrong way, the airflow becomes detached.
The point is it should reduce the size of the hole the car is punching through the air. The smaller the hole the lower the drag at the rear. It's the pressure difference between the front and the rear of the car that causes drag. Just like a wing produces lift because of pressure differential between the top and the bottom of the wing.
The air curtain, if I ever get that completed. Should reduce drag by making the air stream adhere more closely to the sides of the car. Smaller hole in the Airstream for the car. Plus and a increase likelihood of the Airstream better filling in the low pressure area at the back of the car.
The tires in the air blade mod case, produce a lot of turbulent air flow that pushes the airstream away from the car side and that increases drag because of the bigger disturbance in the air. So dead air. What I'm trying to say is the energy imparted by moving through the air, should be used to help guide it as opposed to trying to coax dead air into moving into the low pressure area behind the car.
As for the wind noise it doesn't completely disappear. It does seem to be reduced to my old ears. I'd also say the noise produced is also a slightly higher frequency. At my age higher frequencies are not something I hear quite as well is when I was in my 20s and 30s. Younger ears might perceive it as more annoying or more noticeable. To me it sounded less noisy.
I would suggest thinking about your frame of reference in all of this as well. Short of hurricane winds, the air around us is motionless or should be considered relatively motionless. On the highway, air is not moving past us at 60 miles an hour. We are moving past the air at 60 miles an hour. It's our motion through the air, displacing and compressing it, out of the the way of our cars that causes problems. That movement through the air, produces the low pressure void behind us.
That is what mainly creates the drag/pressure differential. The faster we move, the larger and more energetic the air/fluid displacement becomes (x^(3)). Which is why drag load increases with speed.
