Z4 E85 | E86 diffuser

[koolchris99]

a) i think it looks a bit rubbish, i like the full carbon OEM one..

b) if i put that on my car it would touch the ground.. i think i have 70mm clearance.

 

[exdos]

here are some pics from today, the spray on the back of the car is even with just water runs showing.

Mac27040, many thanks for taking those photos for me.

If you look carefully, you can see that you actually have vertical streaks in the water that are aligned vertically in the central area of the rear panels directly beneath the gap under the wing, which shows that the air wraps itself around the back of the car where normally it would just be in a vortex. You don't have the same streaking around the "Z4" and the lock. The streaks fan outwards as they get lower, which suggests that these streaks are made by air flowing over the top of the car, rather than air passing from the underside. This being so, the air from over the top of the car is joining the air passing under the car leaving a neater wake than would otherwise occur. Likewise, the air passing over the top of the rear wing will take a different path and create some downforce. I would say that this part isn't just cosmetic, it actually works.

 

[koolchris99]

are you really trying to say the diffuser adds to the aero???!

the spoiler maybe produces a bit of downforce,

but the 'diffuser' is 100% cosmetic. we dont have a flat floor for starters.

 

[exdos]

are you really trying to say the diffuser adds to the aero???!

Nope. All I've said is that the spoiler is working.

Having said that, there's already an undertray between the silencers in the Z4M rear bumper in the photos, which acts as a diffuser. The black plastic so-called, "diffuser" in this thread may actually do something, because it's an inverted set of vortex generators, but whether or not it would improve the function of the OEM diffuser, I'm only guessing.