so ive been up in the air about making a rear diffuser for the cobalts.
ive been doing tons of research and everyone comes up with the same few guidlines. i am looking to increase the gas milage of the car and also promote better handling and safer high speeds.

the guys over on the fuelsavers website have been making them for alot of the cars and seem to gain what they need from it, but all of them keep argueing about the angle of approach and if it should have a seperation angle on the blades, and how many blades is too many.
generally they are saying 25 degrees is way too much from front to back, and 7-12 degrees on the seperation of the blades from front to back seems to be the sweet spot but the number of blades seems to be low, like 2-4

the people trying to race on the other hand say 25 degrees from front to back is good, with the blades being straight and many more blades is the way to go. but they also got into it going back and forth about how low it needs to be and what not...

now the subaru guys think height has nothing to do with it, because subaru put a god awful one on there cars and they have about 9in of ground clearance.

so my question is. knowing that we have a huge area of low pressure buildup under the cobalts behinf the rear axle and in front of the trunk... i want to make a diffuser for that section. but does anyone know how many degrees the angle is from the bottom of the rear axle to the bottom of the body kit section in the back of the car?
does anyone have any suggestions, or things that i might not have considered? do you think i should leave some space for air to travel up the top of the diffuser and go out of the vents on the rear section of the body kit, or close that off?

ill be using diff methods to see what kinds of gains can be had and if the unit actually works, but im sure if nothing else it will look cool when its done

thanks for the input

 

id also like to do the vortex generator setup as well to try and make the most out of the diffuser, and ill be testing them with and without the highrise spoiler on the car, using a tuft string test

 

you think too much lol and youd never get to drive at the speeds where those things help so just stop now

 

rtblue on ontario cobalt clubs made one for his car in alloy its really nice looking

 

im in for pics/info somethin like this might help at ze track no?

 

i get your train of thought but the fuel saver guys that make them notice a difference at low speeds so ther eis something to it

 

wish there would be dope rear diffusers for balts

 

in for results and pics

 

In for pics, i thinnk 4 blads would be good not sure on the degrees tho

 

I wouldnt daily drive with one. Being less than an inch off the ground it would get ripped off on anything. I would make a detachable one for racing but they arent legal in my class with the scca.