STI style roof spoiler?

[Daeldalus]

I was wondering if a sti styled roof spoiler would cause the boundary layer off the roof to trip down towards the decklid enough to make a noticeable difference in drag coefficient?

How about lowering it enough to make a rear downforce spoiler more effective?

It might look funky but TT guys would do anything that makes them faster.


not really looking to do this.... just wanting to know if it could work in theory

[Jand3rson]

On a car already shaped like a brick, probably not.

[Daeldalus]

well quite often the huge low pressure air mass drug along behind a car has more effect on drag than many seem to realize.

the bump on the rear part of the roof of the M3 is for this purpose as is the higher decklid and those two things help a M3 have a drag coefficient of .33 over the .39 of non-M E30's
also the actual STI's spoiler was designed for this exact purpose.

but the E30 is a brick on wheels....... but maybe you could use it to put air onto a spoiler that you don't want 12' above the roofline of the car......

[MPLFoster]

i've been wondering about this too...but i've been thinking about using the 'fin' style diffusers like on the mitsu evo.

although i think it would be very difficult to quantify anything without wind tunnel testing. Anyone have access to one of those?

[kamotors]

someone do it, e9 scl's and what not did it.

fiat 131 abarth had it and its much boxier than an E30

[kamotors]

E30 m3 also had the little roof strip which helped tumble the air.

[E30_Pare]

interdesting. always wondered about that different roof, and assumed the coffin trunk was aesthetics.

[MPLFoster]

really? i figured most people knew that goofy deck-lid was a factory aero mod..cuz it ain't pretty.

[E30_Pare]

so is this aero also? lol

[MPLFoster]

touché

[JinormusJ]

Lol

That's why the m3 c-pillars are so much wider: the rear angle of the rear window is much less steep than on a non-m e30. That factor, the air tumble strip, and high rear decklid helps tunnel air into the tall rear wing for downforce.

M-Sport department was on point in 88

[Daeldalus]

That one on the fiat doesn't actually look too bad.
though i was thinking more along the lines of one sticking
off the backside of the rear glass like the sti but now i wonder
which of the two styles would be more effective. though you would
have to custom make one like the fiat and you could just buy a sti one




so an aero roof spoiler plus a custom rear diffuser would equal drag coefficients that don't suck?
maybe add to that a nice front tray and splitter

[Jaxx_]

If you're worried about drag, you need to start by covering the under body and adding VGs to the roof. If you want down force, that is another story. You can't really have both.

Additionally, the rear spoiler or wing has to be extremely high to be effective--generally above the roof line is a good starting point.

I attached my spoiler that I used for autocross. It's ugly but it matches regulations. 10" tall and only starting to be effective at the top of 2nd gear(61mph). It was barely noticeable, even in the wet.

[Jand3rson]

someone do it, e9 scl's and what not did it.

fiat 131 abarth had it and its much boxier than an E30

I love that car.

[robgoesvroom]

If we are on the same page, I believe they are called "vortex generators".