New Swift aero mods
 

Hello,
I have a Suzuki Swift with a 0.32 drag coeficient and i want to do some aero mods. I've lowered it by about 1inch. But from what i've read here the major problem is the back of the car. The problem is that all of the rear spoilers mounted at the edge of the roof are pointed upwords, so will increase drag. But there is a genuine spoiler mounted at the middle of the back, is it helping or is just for look?
I live in Romania, Europe, and here the fuel is pretty expensive.... around 1.1$ per litre.

The middle spoiler is in a dead zone so it won't have any effect.

What you can do is use some kind of plastic material (don't know what is available in Romania), to cover the openings for the fog lights

Thanks. Then for the begining i will smooth the fog lights and block the upper grille..

I'd bet a dollar that middle spoiler is doing something... watch the rear 1/4 panels... the tops sweep right into it, and chances are, the flow hasn't detached at that point, so it's making contact w/ the duckbill.

How much or little effect it has is hard to determine, but I can almost guarantee that it's catching flow off the rear 1/4's.

Those are nice looking cars btw. Nice clean styling. It's like a more modern looking Mini

Here is a full view of the back of the car. When it's raining the back window is getting full of dirty water (from the road) very fast while i'm moving. I think that the spoiler is changing something with the flow who comes from the car and stayed attached to the back.

Ah, sweet, you've got one of the pretty Swifts! How do you like it thus far? Also, welcome to ecomodder!

Well the car is very fun to drive and the 1.5 engine is very good. The average fuel economy is around 32mpg (i've converted from L/100km) calculated in 15k km. But we don't have the roads to drive very economic, 99% of the road is just 2 lane with high traffic.
Here are some pic's of before and after i've lowered the car.

I have blocked the upper grille and it seems like it is a improvement of around 2mpg, still testing.
I want to change the side mirrors because i think they are making a big drag by the noise they make at around 70mph and upper. I found 2 types of aero mirrors but i need some opinion on which is better. Here are the stock side mirrors and the aero ones:

Your guess is as good as mine as to which is actually better... though just going by what I see, and (pretend to) know, the last picture is going to be the best, it has less advertised area (frontal area).

The second picture looks nice, but I'm afraid that's all... the big hole near the door just creates a "funnel" effect, which is good for making noise right next to your ear, as the outrushing air expands back into the air stream. That hole will probably penalize you if anything, so I'd stay away from mirrors (or anything) that create another point for flow to split into more than one pattern.

There's my 1/50 of a dollar... at least I think I'm right...

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
http://i77.photobucket.com/albums/j5...r_20071126.jpg

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.

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

Hi,

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.
http://i77.photobucket.com/albums/j5...-spoiler-z.jpg
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.

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.

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:

http://www.metrompg.com/posts/photos...tta-wake-z.jpg

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

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.

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.

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!"

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:

Sure, it's better than nothing, but it's not going to help as much as a full front belly pan, and those holes are going to kill some gains, especially the front one... you can probably already imagine the parachute effect that one particularly will have, since part of it is cut through an angle.

Looking at the first pic, it would be pretty simple to just get a sheet of ABS plastic and trim it to fit the mounting holes in the bottom of the bumper cover, then trim it back to fit into the cross-member and between any moving parts on either side.

If you really wanted to get fancy, you could make some spats on the front belly pan at each side that would keep the air from flowing through the suspension components that can't normally be covered, due to movement.

a thin sheet of alluminum and some braces won't cost that much... thin aluminum can be bend to straight edges over a sharp table edge fro example.... since you're not building it for offroading the aluminum can really be quite thin... if you fold up all the edges at a 90 degree angle the resulting shape is far less floppy than the original sheet, and when attached to existing or fabricated supports it will really work well.

mine cost around 12 € if i remenber correct

mine can be seen here
http://ecomodder.com/forum/showthrea...html#post35193

i've also made a small simulation of the hatch spoiler,... the result is see saw pattern of alternating vortices, the spoiler below the window seems to prevent the upwashing vortex from rolling over the window. this could prevent the deposit of dirt etc... in this case the bottom of the spoiler seems more important than the top, wich might explain the shape of the ax spoiler
http://i77.photobucket.com/albums/j5...ay/spoiler.jpg

the pink area is a residue of the big pink vortex... so likely it won't help FE, but if won't hurt it eider and it will keep the window clean

Hello ptr, and welcome on-board.

Why not trying rear wheel skirts ?

Also you didn't talked about your driving style. Since I'm doing pulse & glide (in neutral, engine on) I improved a lot: the secret is to wait, wait, wait... Of course on 2 lanes roads some people may be angry about that, but more and more people are going more slowly.

I put rear wheel skirts (coroplast and tape) at the beginning of the current tank and I can coast longer. On two low down slopes I can see the car accelerating while it was slowing down before. I can also feel the car being more nervous, and my old "fast accelerations" habits are coming back :o.

I didn't finished my current tank yet (I love my logic so much ;)) because I'm waiting to see when the idiot light (ie empty tank) will lit on, but I should beat my record :)

Denis.

If the weather is ok i will try to make at least a partial front undertray, i have something like coroplast but thicker. From the same material i intend to do the rear undertray.
My driving habits are normal, using engine brake a lot, drafting when it's possible. But these mods are not really helping in my country. The fuel is poor quality and we don't have the roads to drive steady for a long time. The best fuel consumption i got so far was last summer when i made a trip to other countryes in europe. The fuel consumption was 37mpg over 3100miles , with AC on and most of it at speeds like 80mph.

Well, today i finally mounted the front undertray. I hope to have the time this weekend to test it. It looks like this:

Hi all... this is my first post!

Anyway, you may try to put some vortex generators at the front undertray as well. AutoSpeed.com has a good article about it.