How to decide whether to remove rear spoiler to decrease drag, improve mileage

[k.civic.f4i]

looks like purely downforce to me

[Speed_Bump]

Hi all, I'm trying to decide if my spoiler is doing anything at all to help my mileage.

carphotos.cardomain .com/ride_images/4/400/2161/38498580001_large.jpg
(copy and paste without the space to view link)

This is similar to what my car looks like. The spoiler has a slight upward lip if you look close, but I am unable to determine whether it was designed with FE in mind or teenagers in mind, haha!
Any thoughtful help is appreciated!

[winkosmosis]

Originally Posted by Speed_Bump

Hi all, I'm trying to decide if my spoiler is doing anything at all to help my mileage.

carphotos.cardomain .com/ride_images/4/400/2161/38498580001_large.jpg
(copy and paste without the space to view link)

This is similar to what my car looks like. The spoiler has a slight upward lip if you look close, but I am unable to determine whether it was designed with FE in mind or teenagers in mind, haha!
Any thoughtful help is appreciated!

That looks like it helps.

[daedalus921]

Speed_Bump:

The Capri's rear end is made such that air has a hard time separating from the vehicle without creating a lot of turbulance. My opinion is that your spoiler is probably helping air separate more cleanly.

Another thing that I might recommend looking into is whether or not your bumper is acting like a scoop, trapping air under the car. If you can find a way to help air get out from under the car better, it would speed up the air flow under the car as well as help fill in the low pressure area directly behind the car.

[Speed_Bump]

Thanks Daedalus and Winkos, I think that I will just leave that part of my car alone.

I need a replacement front fascia as the lower part of my air dam has been broken. Maybe while replacing the fascia I can add a partial grill block and underbelly pan. These are projects for different threads though.

[capnbass91]

Ok, so from what I got from all this is this:
A spoiler that points up in the back increases drag, therefore decreasing the aerodynamicness of the car, but keeps it on the ground better which is only good at reeeally high speeds.
A spoiler that is flat or slightly pointed down is good, helping the air flow over the car and decreases drag.

My car's trunk curves down a lot at the end, so as long as its not over like what 12/13 degrees it helps, right?

[BamZipPow]

Make 4 more posts then...

[capnbass91]

I got a spoiler that curves a bit at the top for really cheap, ill just sell that and get one that's flat.

[Piwoslaw]

I've noticed a lot of Toyota Yarises (Yarii? Yarum? Yarisitachi? "Yaris Yaris"? It's like Indonesian; you double up the noun to pluralize it.) with a spoiler on the rear hatch. Not the typical way-up-there-and-ravage-the-airflow spoiler, but more like a roof extension:

They give the rear a small Kamm effect:

I've seen so many of them in Europe that I'm starting to think they are OEM, yet not all Yarises (Yarii? etc....) have them.

[euromodder]

Originally Posted by Piwoslaw

I've seen so many of them in Europe that I'm starting to think they are OEM, yet not all Yarises (Yarii? etc....) have them.

IIRC, they were a Toyota option.
Rear spoilers weren't standard on most Yaris.