Quote:
Originally Posted by AeroModder
Measuring the angle with GIMP, it's about a 16 degree angle from the roof to the tip of the spoiler. With no spoiler, it's roughly 19 degrees to the trunk edge. The window is about 35 degrees.
To mount a kammback at a 13 degree average, I'd have to extend the spoiler another 3 inches.
I've driven 130 miles so far on this tank and I'm about a gallon or so above half, so we'll see what the tank average looks like around the 7th. |
CAR and DRIVER's experiments revealed that for drag reduction,a spoiler should never angle up beyond 30-degrees or there will be a concomitant growth in drag.
The spoiler is creating a locked vortex over the backlight/boot area with the free stream above,skipping over the vortex and re-attaching on the spoiler.
The low pressure above the backlight/boot is 'contained' by the spoiler. The impacting flow on top of the spoiler,as well as the lower pressure of the walled-off wake behind it provide the downforce.
I think the Kamm extension was allowing what Hucho refers to as 'overshoot' and this prevented any chance of re-attachment onto the trunklid,leading to the drag increase.
The Mercedes EVO 190 suffers the same situation,but their rear high mounted spoiler does allow for re-attachment on the wing,although not on the boot.