Extending the Decklid (Toyota Echo)

[MTrenk]

"Bigger" and "smaller" wakes don't really matter, it's the measured turbulence, which... you have to measure through trial and error or CFD. Smaller wakes can create more turbulence than big wakes depending on the resulting flow of the air, but you can't really argue over because there isn't any evidence lol

As far as the Fusion goes, I see that the back end of the spoiler certainly matches up with the face of the trunk, but to my eye, it sure seems like the beginning of the spoiler is raised a bit (maybe less than an inch), and I only say this because if they did raise it an inch at the beginning, they did it for a reason. But it is no matter anymore.

[CigaR007]

Does the tuft-testing reveal any hope for an extended decklid ? Should it be flat or raised at a certain angle as some have suggested ?

For some reason, I want to try and mimic the Renault Logan eco2, with perhaps a slightly extended version of that spoiler. The combination of VGs and that decklid seems like a good idea on a 3-box car. My Echo has a somewhat similar design all-around and it could benefit from it. The detached airflow in the middle of the rear glass needs to re-attach more smoothly for an extended decklid to be efficient. Am I wrong ?

[MTrenk]

No you aren't wrong, but the tail will completely change how the air moves past the rear window. Air moves in relation to pressure, so making the spoiler could in fact change the angle the air comes down off the back of the rear window. Never really know until you run tests.

[Sven7]

Originally Posted by ChazInMT

I was thinking that it would be a pain to walk around, sticking out so far would require stronger engineering due to the leverage moment that is there. Invariably, the more it sticks out, the more it invites some miscreant to push or pull on it which would cause sudden and catastrophic damage.

So build it well and attach razor blades to the trailing edge. Done and done.

[MetroMPG]

Another option to consider: Holden raised the entire decklid surface of this limited production 3-box car to reduce both drag & lift (and add some ugly):



Holden Commodore VL SS - sourceAutospeed.

[ChazInMT]

Mauricio, don't fall into the trap of thinking "attached" flow is the goal, VG's and little spoilers may help "attach" flow, but if they create lift (=drag) or vortices (=drag) then it means nothing. You want to build something that sticks with the template to get a good benefit. IMO nothing you put on that trunk lid is going to gain you much. Part of the reason is the Back of Roof to Top of Rear Glass region (TORGR) on your car has a very good radius for drag reduction already. I wish I could find the paper where I saw the details on that, but it turns out if you have a healthy radius there, it is a pretty good drag reduction shape. The Renault has a fairly awful TORGR radius, and I'd bet real money that whether that spoiler thing on the trunk was there or not, the difference would be almost undetectable. The Holden is a box of kleenex compared to your apple shaped car. I know you maybe think a Kamm is ass ugly, but (butt?) I think it is the only thing you can do which will actually gain you a significant difference in aero drag reduction.

[CigaR007]

Thanks for the input but a Kamm tail or boat tail is not going to happen on this car. I believe I will have to test a few configurations and proceed with an optimization. This will not be an easy task but I am willing to experiment and learn something new.

[Frank Lee]

...I want to try and mimic the Renault Logan eco2...

Looking at those pics wondering if the vgs and rear extension actually work? Cuz it's all soooo much steeper than template...

[MetroMPG]

Frank: that's the point of VG's! To energize the boundary layer so it can follow a "non-template" path without separating.

The question is how do you know that the net energy cost of adding VG's is less than the benefit of getting that airflow to the spoiler for clean separation.

[Frank Lee]

that's the point of VG's!

I know! But that car is really steep.