New Swift aero mods - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

lunarhighway · 03-23-2009, 04:27 AM

Quote:

But there is a genuine spoiler mounted at the middle of the back, is it helping or is just for look?

i don'tt htink it's for looks, i've seen something similar on another small car that was designed as a pure economy maschine

the citroen, AX

it has plastic panels in non load bearing areas, weighted below 700 kg, had a 0.31 Cd and could achieve over 80 mpg.

the spoiler was molded as part of the plastic trunklid, and although i don't know exactly what it's supposed to do i guess it might help to prevent some nasty vortex from forming.

ptr · 03-23-2009, 01:27 PM

From what i see in this video starting at min 1:30, it seems that a spoiler placed there will reduce turbulence, but by how much i don't know. After i will instal it i will tell if there is any change in FC. For the moment i'm trying to make a rear undertray because it is cheaper..

http://www.youtube.com/watch?v=8-O_F7ZrX2A

NeilBlanchard · 03-23-2009, 02:02 PM

Hi,

There is no way a spoiler in the middle of the hatch, below the window has any real function.

lunarhighway · 03-23-2009, 04:57 PM

Quote:

There is no way a spoiler in the middle of the hatch, below the window has any real function.

why not?
i don't claim to have the answer to what if does, but here's another example.

the angle of the hatch is more close to what one would consider aerodynamic, but it still is far to steep to have any attached flow.

yet i think the sides are more important in this.... the airflow coming of the sides of a vehicles acts in complex ways with the airflow of the top. the sides of the swift in the original post seem rounded so they don't promote separation... the spoiler might interact in a positive way with this flow.

NeilBlanchard · 03-23-2009, 10:59 PM

Hi,

Yeah, I think that some people thought that a spoiler might help (and probably doesn't hurt, either) -- but the only thing it can do is provide a visual effect.

MetroMPG · 03-23-2009, 11:24 PM

ptr: the roof mounted wing in that video is sure to increase drag: it increases frontal area, and is designed to produce downforce. The wake is going to be larger.

As for the mid position wing, the only way one can have any meaningful effect is if the hatch angle is shallow enough that the wing can interact with flow coming off the roof (which is the case for the Pinto - not attached, but also not in "dead water"). It will have little to no effect if it is sitting in the dead water zone, like this Mk 1 Golf/Rabbit:

EDIT: and based on the steepness of the AX rear glass, my guess is the bump on the AX hatchback is cosmetic.

Christ · 03-23-2009, 11:30 PM

My comment at the beginning of this still goes unanswered, that it must have some interaction with flow when you consider the tapered/rounded sides of the car, and the obvious wrap-around effect that the flow would have there, coupled with the wrap of the spoiler around and over the tail light section, obviously protruding into the area above the sides of the rear wheel housings.

I can't say authoritatively whether it will adversely affect flow or positively affect it, but I'm sure it's not benign.

MetroMPG · 03-23-2009, 11:46 PM

I'd wager it's close to benign.

The flow on the side of the car is more than likely predominantly horizontal. The spoiler's orientation is horizontal. For the small amount of spoiler surface that might be exposed to flow wrapping around the side/rear transition before going turbulent, I just don't see it doing anything significant.

I also don't think the pic shows the spoiler extending to the "side" of the car. I think it's 100% behind the belt line of the greenhouse.

Christ · 03-23-2009, 11:57 PM

After further review, you may be correct... it seems that I saw something that wansn't there in the pictures of the Swift... It is in fact 100% behind the car, does not extend past the inner box walls, and probably doesn't do too much to manipulate flow, if anything.

Even given a very extreme angle, it would most likely modulate flow very little, if at all.

*Sinister voice* "Until we meet again, MetroMan!"

ptr · 03-24-2009, 02:37 AM

I understand, i won't buy that spoiler and that way i will save some money for the aero mirrors.
I will do by myself the rear undertray, and hope for a improvement like what i've read here and on the honda fit forum aero improvement - rear undertray testing - Honda FIT Forums
For the front undertray i can buy something which is better than nothing: