[Andy M]

Just thought I'd repost this link here instead of just for the Canadians.

http://www.e90post.com/forums/showthread.php?t=524336

Basically, I was thinking of developing this just for my car but I had enough interest to get it to market.

F1-inspired rear diffuser with venturi tunnels designed for all E9X LCI and pre-LCI. Combinational of structural aluminum, PET, and carbon fiber. Would love to get some feedback too.

And yes, for the mods, already contacted e90post admins about getting Silver Sponsor rating once it becomes available for sale!

[JoeyBananaz18]

No to shit on this but if you need F1 amounts of downforce, you're driving the wrong car.
Your e90 would have to be a rocket and a half to get any use out of something like that.

Sorry to sound like an ass.

[Andy M]

Actually at speeds of >100 kmph, aerodynamics and ground force really make a difference. If you ever track your car, you'll appreciate it.

People will spend $400 or so for a JB4 or Cobb AP just for a slight increase in their 0 to 60 times or >$1000 for an upgraded suspension for improved cornering. Improving the underbody aerodynamics and taking advantage of underbody forces is a huge untapped area that can be improved on.

The reason I was looking for functional was because I was tired of seeing mods which were just pure cosmetic without any benefits to the performance of the car (and yes I know, this is the "cosmetic" forum...we don't really have an "aerodynamics" forum...).

Aside from the functional purpose, the majority of the PM's I've gotten though are treating this more as a cosmetic mod. So I think I've achieved what I set out to do.

And no worries about the question, I find the concept of underbody design is something lacking with car enthusiasts so it's good to bring this stuff up. The reason I started developing this in the first place was because I couldn't find anything made for the E90's already for my own car and decided to make my own.

[yakev724]

Wouldn't any underside air channels/diffusers/lips/etc. need to be rigidly connected to the frame to be able to have any significant effect on driving dynamics?

Isn't this a bit of a tall order? I mean essentially everything that's currently available just flexes a bit when air hits it, and transfers little/no force to the car's frame. How will your diffuser transfer the energy to the car itself?

I'd imagine getting low pressure under the car (at speed) would help, but again, I see the underside plastic flexing and not much else going on...

[Andy M]

It's rigidly connected to the car via an aluminum frame. It connects to the frame right in front of the rear wheel and to the OEM bracket behind the rear bumper which is connected to the frame. But that's not where the force is generated (not just down force point loads).

An ideal diffuser design is to encourage air flow as well as to provide a more gradual flow separation (which causes turbulence). And with any flow regime, disturbances anywhere along the flow path will alter the entire flow path. On our E9X's, it's at the rear axle. That's why the diffuser creates a more gradual change from the center of the vehicle (which already has a somewhat smooth underbody), over the rear axle, and to the rear bumper.

It lengthens the flow channel and provides a more gradual separation to reduce the turbulance at the back of the car so that the underbody air flow of the entire vehicle can be utilized.

[yakev724]

Originally Posted by Andy M

It's rigidly connected to the car via an aluminum frame. It connects to the frame right in front of the rear wheel and to the OEM bracket behind the rear bumper which is connected to the frame. But that's not where the force is generated (not just download point loads).

An ideal diffuser design is to encourage air flow as well as to provide a more gradual flow separation (which causes turbulence). And with any flow regime, disturbances anywhere along the flow path will alter the entire flow path. On our E9X's, it's at the rear axle. That's why the diffuser creates a more gradual change from the center of the vehicle (which already has a somewhat smooth underbody), over the rear axle, and to the rear bumper.

It lengthens the flow channel and provides a more gradual separation to reduce the turbulance at the back of the car so that the underbody air flow of the entire vehicle can be utilized.

Thanks for the reply, pretty interesting stuff! good luck