Aerodynamic Aids - What a drag, What’s your drag? Options

[chris914]

Have you made changes to your 914 body or are you thinking of it?

Here are a number of computer models comparing different body modifications to the 914 and the effects that they have on the cars aerodynamic drag.

http://www.cassidy-online.com/porsche914/aerodynamic_aids

[grantsfo]

I love amatuer aerodynamic discussions.

Anyone care to publish actual measured downforce and drag created by those huge double wing Mod cars at 40, 50 and 60 MPH from a wind tunnel? Look at surface area of those wings - I havent seen a heavy production AX car that has a wing that comes close to that surface area. Then remember wieght of a Mod car. 100 lbs of downforce on a sub 1000 lb Mod is huge differnce. What are you guys making at 50 MPH with those wimpy wings on your 1400 to 3500 lb cars? So rather than attributing wings to performance to National class drivers choice why not offer some emprical measure data? Becuase somone uses a wing doesnt mean its effective. They may have a belief that wing is effective on their bigger car.

Downforce created by wimpy little wings and spoilers I see on most production cars that AX in my opinion dont offer much at speeds below 60 MPH. And where is the front wing on 914's? Why bias an already rear heavy car with even more downforce at the back end? Youre only lightenting the front end if you dont have effective areodynamics up front. Like a 914 needs a lighter front end at speed? That blue mod car has its big wing in the right place.

I dont think either side of this postion have offered much to support their use or non use of wings for AX. I just havent seen anyone offer data other than the "fast guys" use em.

This post has been edited by grantsfo: Nov 3 2007, 11:18 PM

[jhadler]

I love amatuer aerodynamic discussions.

Anyone care to publish actual measured downforce and drag created by those huge double wing Mod cars at 40, 50 and 60 MPH from a wind tunnel? Look at surface area of those wings - I havent seen a heavy production AX car that has a wing that comes close to that surface area.

Because they're not allowed to use them. RTFR.

As for actual numbers? I can't tell you first hand, but I can tell you that some of the SM and SM2 people I know have measured 75-150 lbs of downforce. That may not sound like a lot, but it's enough to warrant changing of the spring rates, and noticeably effect the handling of the car...

Then remember wieght of a Mod car. 100 lbs of downforce on a sub 1000 lb Mod is huge differnce.

Yeah, and remember that the A-Mod cars are pulling 3+ lateral G's at an autox on a good surface. The doors slammers are no where near that.

What are you guys making at 50 MPH with those wimpy wings on your 1400 to 3500 lb cars? So rather than attributing wings to performance to National class drivers choice why not offer some emprical measure data? Becuase somone uses a wing doesnt mean its effective. They may have a belief that wing is effective on their bigger car.

Downforce created by wimpy little wings and spoilers I see on most production cars that AX in my opinion dont offer much at speeds below 60 MPH. And where is the front wing on 914's? Why bias an already rear heavy car with even more downforce at the back end? Youre only lightenting the front end if you dont have effective areodynamics up front. Like a 914 needs a lighter front end at speed? That blue mod car has its big wing in the right place.

I dont think either side of this postion have offered much to support their use or non use of wings for AX. I just havent seen anyone offer data other than the "fast guys" use em.

Geez Grant...

Simple. The cars that are really taking advantage of these wings (and not all of them are actually utilizing these wings to their full advantage) are already on the ragged edge of neutral handling. The intent of the wing is to have a car that rotates super well at lower speeds (slaloms), and isn't excessively loose at higher speeds (sweepers and fast transitions). A little extra "dynamic" weight in the back can help get that little bit extra. Otherwise, you either have a car that is planted in the fast stuff, and pushes in the slow stuff, or a car that carves the slow stuff and is a handfull in the faster stuff.

Grant, talk to the big dogs who are doing this. You live in the Bay Area, you run with SCCA from time to time. Go up and talk to Andy or Vic some time about the wings, you might find that these people really do some considerable research and testing on these cars.

-Josh2