333pg333

+1 Andrew, get onto Autospeed. Clever guy runs that site.

NZ951

Will do, I remember looking up articles on there when doing the intake.

rlm328

The sensors are linear and measure travel. On a high speed straight you should be able to tell if the rear is being loaded for a wing and for a splitter you should be able to tell what he front end is doing. Put the sensors on before any mods to get a base line, and then as you add the mods you can tell if it is helping or hindering with grip levels or whether you need to change spring rates, etc.

NZ951

My thoughts around grip levels and braking etc was to use ABS sensors hooked up to a Motec Dash...

Where do you get these suspension travel sensors from?

rlm328

They are just slide sensors. They attach to the body and to a traveling part of the suspension.

Here is motec's sensor. Bottom of the page.

Http://www.motec/sensor/position

Here is an example

74goldtarga

I think anything we might do is guesswork, however, looking at factory race cars will give you a starting point. Is your priority aero for downforce (I'm assuming so). In that case you want to run the car as low as possible, seal the front and sides (splitter / side skirts) and run a diffuser to channel the low pressure zone from behind the car underneath the car. Then if you can add a wing that sees clean air and some dive planes (not sure what angle to put these at) you've got a pretty good start - actually measuring the effectiveness of these additions would be pretty difficult and comparing between different designs would be at least as tough - but I think there are gains to be had by starting with basic principles.

audisport

Yup, autospeed...

You can start here on part 3 of this series and click back to part 1. Also use the search on "aero" in this DIY area and find quite a bit more...
http://autospeed.com/cms/title_Under...2/article.html

333pg333

Here's a couple better pics to illustrate Bob's point.

audisport

Auto Meter also makes a data logger system that is probably not that expensive with suspension travel sensors ect...

kghaas

I have a real life example on DIY Aero. I own an Lotus Seven S4 which I eventually will modify to go on the track. I have asked some of the experienced Seven drivers if fitting wings has any effect. The common answere is that it has an effect about 1-2 seconds per lap on a 1.5 miles circut. This is with a propper set up racecar whit an expert driver.

Her is one example:

This car does a 1.5mile circut 1-2 sec faster with front and rear wing. Grip is way better in high speed corners. The drag effect is not feelt on the straights. On some tracks the wings have less to none effect.

The driver is an expert driver, and winner of the Swedish racing series Modsport.
It shows that you can add wings and get an effect.

For those interested, here is an in car video from one of the races:
http://www.youtube.com/watch/?v=zv-mCxx1V90&hd=1

rlm328

I don't think anyone is not saying aero is beneficial. What most of us are struggling with is how best to quantify the results for any given modification. Most of the larger outfits use wind tunnels which I would say is out of most of our capabilities. The other is work as a group and figure out what works best for a given platform. Most of us are data hogs who want to look at some time of data stream to determine what we did is working or was a glorious mistake.

Duke

Creating downforce is easy. But balancing drag vs downforce is the tricky part!

333pg333

McDonalds Drivethrough....create downforce now!

Van

There was a thread in the NA forum a few months ago where a SP2 racer took his car to a wind tunnel for a few hours of testing. He was pretty limited to playing with tire pressures to raise and lower the car - but discovered that rake, as well as ground clearance, plays a big role in downforce (or minimizing the upforce).

However, looking at his data and my average cornering speed, we're talking about a very limited contribution to grip... I think there is more to be gained by reducing drag - like covering panel gaps, removing mirrors, covering side windows, etc. - and getting a little higher top speed on the straights.

To change subjects slightly, shock potentiometers can tell you a lot! I put them on my car at the end of the season and I'm still trying to figure out the data. It's interesting to note that, even with a full cage, my car exhibits 2 degrees of body twist while cornering (left or right) - imagine how much it would twist without a cage!

m73m95

I argue that the underside of the 944 rubber spoiler creates more downforce than the lip at the top (I think the taller Le Mans spoiler got it wrong). The rubber spoiler extends the low pressure area created behind the car, effectively pulling the spoiler (and car) down. If you want to make more downforce with it, make it longer, not taller. This will also create more drag, as you're increasing the low pressure area behind the car, but I bet the difference between the drag of that vs the drag of a huge, hatch mounted spoiler, would be less.

I view the 968 spoiler as more of a diffuser. It smooths the air flow, for less drag. Its purpose is not for downforce, though I'm sure it does create some.

This^^

F1 designers spend hundreds of hours in the wind tunnel, and change their designs nearly every race. Even the best engineers, with the best computers, in the world cannot create a "perfect" design. They still use glo-vis paint to test their parts. As said above, you can do the same with some yarn and someone with a camera in another car. That is how the Shelby Daytona's body was tweeked..and it won a few races.

With boundary layers, high and low pressures, drag, lift and downforce all needing to be accounted for, its extremely difficult to get right by "guessing". The 944 is pretty aerodynamic, even by today's standards. The most gains (IMHO) are made from under the car, and around the wheel wells (high pressure areas). Also, venting the air trapped under the hood should give a good gain. Added wings and downforce should be used to balance the car, more than sticking it to the road. Even the high powered cars just aren't doing the speed needed to maximize benefits of a ton of downforce...not to take the hit of the added drag anyway.