Flat Bonneville-type spoiler

[AeroModder]

The results would appear to be no change, or too small to notice in tank averages.

Update: The spoiler is off, and replaced with trip wires to give the air a clean edge to separate from. Soon I'll be attaching the side supports I had for the kammback to give a vertical surface off the cabin to reduce vortex generation.

The spoiler appeared to produce some downforce. The bottom of the center support was actually bent inwards.

I took a look at the end of the roof and it's slope, and the glass is somewhat inset. The angle before the separation hits the trunk about an inch or two before the edge of the trunk.

[nitro-nige]

My understanding of these spoilers at Bonneville was for center or pressure.
I thought they were used to move the CoP back, ideally behind the CoG for high speed stability.
Of course they still might help for ecomodding.

[alohaspirit]

thats disappointing


now i want to do some more research into flat spoilers

[AeroModder]

My first tank without it came to around 25 MPG, so it may have some effect after all. The temparatures cooled and more rain came around after I installed it, so it might have evened out the drop in FE.
I had to fill with E10, though, because the price of unblended premium is 50 cents a gallon more than E10 regular, and it's no longer cost-effective going with the premium.

I might revisit this mod later on.

[Kyleyadon]

what about doing something to keep the airflow from detaching from the car body and then trying to reattach to the vertical sides of the spoiler. Which in theory would create turbulence between the corners of the car and the sides of the spoiler, which would probably decrease your fe gains.

[AeroModder]

I could keep my side extensions on, which hold's the body's boattail angle out further. I took those off when I put the spoiler on.

[Cd]

Did you tuft it ? I was looking at a Fusion the other day thinking of this post.
I'm pretty sure you would get better results if you knew what the airflow was doing back there.
The angle of your back window is really steep.
My guess is still that you are not getting the airflow to connect.

[AeroModder]

Never got a dry day and time to tuft test, unfortunately. But I'm quite certain it's attaching. I tuft-tested the rear a long time ago, before any modding, and found that the airflow did reattach about halfway down the trunk.

I'll see if I can get a good day after I put it back on.

[Sulfuric]

Aaaaaaah I really want to know if this would help.

My back window angle is rather steep, so I'm hoping a flat spoiler on the back would help the flow reattach. My only concern is that my brake lights may be obstructed from anyone with a vehicle raised higher than mine (nearly everyone)

[wyatt]

Observations from wind tunnel test pictures would indicate that with a boat tail, one can go to ~15deg, with a virtual boat tail off the back of an average sedan, ~10deg is more of the max. The 10deg number would assume there is nothing turning the air at the beginning. This would explain why small cutouts for windows, lights, etc. have less of an impact when integrated correctly on a steeper angle. I attached a picture of a sedan in a wind tunnel, and it looks like the air wants to exit at ~10deg. A re-build at 10deg may show real gains.