SVX spoiler = downforce?!

[Chiketkd]

Well, as I mentioned in my drifting thread, central VA ended up getting about 7.5" of snow yesterday. I cleaned most of the snow off of my car this morning before leaving for work, but when I pulled out I still had a good 1-2" of powdery snow on my roof...

When my car had exceeded 50mph on the highway, I happened to take a quick look in my rear view mirror and saw that the snow was blowing off of my roof onto the center of my rear spoiler. I decided to accelerate up to 75+mph to see if this flow pattern continued and sure enough it did. It felt almost like watching my 'spoilered' SVX in a wind tunnel...

I've been unable to find any marketing/technical literature about the effectiveness of the SVX spoiler (JDM or USDM versions) and the only wind tunnel pics I've ever seen were the ones posted in the Road & Track review of the car:

Courtesy of Earthworm's site - www.svx-iw.com/:


Anyone know the effectiveness of the SVX spoiler? From the way the snow was hitting my spoiler, it would seem that it's situated in an effective location to provide some useful downforce at possibly 100+mph???



-Chike

[n00b on demand]

Wow man you create the most colorful threads ....bringin back history with it too

[Chiketkd]

...I've been able to find discussing this topic.

http://www.subaru-svx.net/forum/show...threadid=11968

Didn't seem to arrive at a solid conclusion, however, I found Mychailo's comment interesting about needing to apply approx 25lbs of force inorder to compress the trunk lid half of the way towards the body when closed...

-Chike

[Chiketkd]

Originally posted by soobiesvx93
Wow man you create the most colorful threads ....bringin back history with it too

Thanks Tom!

-Chike

P.S. In a recent Motortrend article (03/05 issue), they pitted the three awd Mitsu Evo versions against each other - standard, RS and MR. The raised cf spoiler/wing found on two of the models (MR & standard), resulted in faster slalom times and a more planted rear end in quick esses. The wingless RS model's tail on the other hand wagged it's way around the road/slalom course and caused the car to run measurably slower times... I guess it does show that *some* factory spoilers do work.

Also, my younger brother who is studying for his PhD in aeronautical engineering (at the University of Md at College Park) mentioned that a car's spoiler doesn't necessarily need to have a sharp AOA to be effective. As long as the top and under sides of the spoiler are different lengths, the spoiler could also produce downforce in the opposite way that an airplane wing produces lift...

[mbtoloczko]

Originally posted by Chiketkd
...I've been able to find discussing this topic.

http://www.subaru-svx.net/forum/show...threadid=11968

Didn't seem to arrive at a solid conclusion, however, I found Mychailo's comment interesting about needing to apply approx 25lbs of force inorder to compress the trunk lid half of the way towards the body when closed...

-Chike

Ah hah. You already found that old thread. :-) Chike, what do you think about getting together with Tom (or Bill if he ever finishes messing with his car) and do a little side-by-side observation. Maybe grab a short video if you've got a camera that can take short movies. I might try to do the same here this weekend.

[Chiketkd]

Originally posted by mbtoloczko
Ah hah. You already found that old thread. :-) Chike, what do you think about getting together with Tom (or Bill if he ever finishes messing with his car) and do a little side-by-side observation. Maybe grab a short video if you've got a camera that can take short movies. I might try to do the same here this weekend.

Sounds like a great idea Mychailo! :-)

Actually, AmazonParrot in my town owns a 'spoilerless' ebony '92 LS-L like SVXRide. He also has a video camera and can take pics of our cars as we drive along the highway.

A trick the Motortrend guys used was to stick thin 'streamers' along the back edge of the roof (each about 4-5ft in length) and watch the way they flowed when the different Evo versions were at speed. I may also try this little trick...

Should provide some neat pics - and give us some interesting comparisons of the airflow on a 'be-spoilered' vs 'spoilerless' SVX.

-Chike

[Sidewinder]

Originally posted by Chiketkd

Also, my younger brother who is studying for his PhD in aeronautical engineering (at the University of Md at College Park) mentioned that a car's spoiler doesn't necessarily need to have a sharp AOA to be effective. As long as the top and under sides of the spoiler are different lengths, the spoiler could also produce downforce in the opposite way that an airplane wing produces lift...

Well, there's our answer. Anyone have a spoiler they're willing to saw in half to look at the profile?

Otherwise someone with a spoiler (not attached to the car) can take some measurements and we could get a rough estimate of the dimensions (top and bottom). Really, this could be a fluid dynamics problem. I might be able to find my old fluids notes and number crunch.

I would imagine the spoiler provides some downforce. After all, these engineers spent a lot (read: a lot, a lot, a lot) of time designing the car and each detail served a purpose. I doubt these guys decided, on a whim, to throw a spoiler on without actually designing it for function and aestethics.

[SilverSpear]

This was the ad over here in 1992......

[Chiketkd]

Originally posted by sidewinder
Well, there's our answer. Anyone have a spoiler they're willing to saw in half to look at the profile?

Otherwise someone with a spoiler (not attached to the car) can take some measurements and we could get a rough estimate of the dimensions (top and bottom). Really, this could be a fluid dynamics problem. I might be able to find my old fluids notes and number crunch.

I would imagine the spoiler provides some downforce. After all, these engineers spent a lot (read: a lot, a lot, a lot) of time designing the car and each detail served a purpose. I doubt these guys decided, on a whim, to throw a spoiler on without actually designing it for function and aestethics.

Good points.

I think accurate measurements can be taken with the spoiler still on the car using a tape measure.

This is a good article describing lift in detail:

http://www.aa.washington.edu/faculty/eberhardt/lift.htm

Therefore, for our spoilers to act in the opposite way that an airplane's wing does, the under-side of our spoilers will need to be longer in length than the top side (which should be relatively flat).

-Chike

[GreenMarine]

I do remember a discussion about this. From what I recall, there was information found that showed that the SVX produced downforce at the rear wing... Hopefully when I get to NC State and am in the Engineering program, we eill beable to use the wind tunnel and figure this problem out... We'll see though... I would donate my car as a test dummy though

[RSVX]

I read somewhere, I forget where though, that our spoiler/wing is not just cosmetic... come to think of it I think it was in the brochure... I could be wrong tho... where in the hell did I see that... the Road and Track Guide maybe???

[GreenMarine]

I have that guide... let me check on it for a sec

[Earthworm]

Everyone has the guide because it's online

When I was at the Reno 2004 meet, I remember hearing this from Mitch: Apparently, Chris (one of the moderators here) found that above 100mph the spoiler gives about 130 - 150 pounds of downforce. He also said that Chris found this out via some track tests.

With all the racing Chris does, I don't find it hard to believe what Mitch said.

Who knows if it's true, but anyone else care to comment?

[svxsubaru1]

I think most Subaru wings do produce down force, even the small one on the WRX has data to show that it produces a fair amount of down force at speed, but it also created front lift.