Ford Sierra XR4i Bi-Wing Spoiler?
 

Hey all, do any of you have info/explanations of the aerodynamics behind the Bi-wing spoiler on the Ford Sierra/Probe III concept. I’ve read that it reduces drag, but I’ve also heard that it’s a measure for creating downforce. I’ve not found a concrete answer yet.

Just off-hand, looking at the angle of the back glass, the spoiler more than likely does reduce drag primarily by reducing lift. I've never seen an analysis of it on that car specifically however.

Here is a site-wide Google search for bi-wing. https://ecomodder.com/forum/google_s...5679j6676099j7

It's not helpful to me because I have Prefs set to max number of posts per page instead of 20, and Google's search is page oriented.

Maybe you'll find something there. F1 front wings have gone away beyond bi-planar.

It reduces pressure under the wing, so causing better flow attachment and allowing the rear spoiler to work better.

Not the vehicle you requested, but adjacent?

Porsche 911 Ducktail - Study/Alternate
https://ecomodder.com/forum/showthre...e-36229-3.html

https://www.topgearbox.com/cars/ente...t-rs-cosworth/
http://forums.pelicanparts.com/uploa...1616437886.jpg

I don't remember if the "25 lbs of down-force" comment was from a video or post in that thread.

I do recall finding the Escort RS Cosworth when doing a search on the XR4i, so there may be common material in videos and articles floating around the Internet.

Bet it's turbulent as sin back there.

Cosworth
 

I think I posted on this car a decade or so ago. I suspect it's in my lectures.
From memory, it was a homologation special for rally racing. The rear addition provided downforce at the expense of lower top speed. 20- to-30 counts extra drag. Two-to-three miles per hour slower.
I'll try and find it.

Interesting that this come up, I’ve considered a version of this for drag reduction on my Ion. Everything angled to reduce drag though

explanations
 

Lutz J. Janssen & Friedl W. W'u'lfing were the co-inventers.
If you can find a copy of United States Patent No 4,533,168, it has their full explanation.
I got mine off micro-film at the Dallas Public Library. It could be available online.

Thanks all. I’m still in search of a boat tail alternative, then. Still very interesting, and visually surreal.