Originally Posted by 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 rack, 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!

Originally Posted by 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.

Originally Posted by 333pg333

Van, what do you mean by the term 'rack' in relation to downforce?

Originally Posted by 333pg333

From what I've leaned discussing this with a number of different people is I'd agree with your point re the 'F1 teams not getting it perfect so what hope have we' type sentiment. I have had 180 degree differing views on the downforce thing. Many in here declare almost any large wing set at more than a couple of degrees A.o.A. is creating way too much drag and the car will lose way too much speed to warrant the wing/positioning. On the other hand I've had different people say that they have benefited from the addition of a large rear wing and associated frontal aero even if it's cost them some terminal speed. Mid and exit corner speed have increased dramatically which should offset the extra drag down the main straight twofold. Firstly, well faster is faster. i.e. faster through the turn = less time. Obvious of course. Secondly, the faster corner speed (particularly exit) will increase your speed down the following straight which will offset some of the lost terminal speed due to extra drag.

As for these cars not going at a sufficient speed to generate active downforce, well I'd disagree with that within reason. Some of the fastest cars in here are easily going quickly enough to generate d/force depending one what aero package they have of course. The wing I have is meant to start downforce from as low as 60mph iirc.

Originally Posted by m73m95

Of course cost, and ease of use also play a part. If that is your concern, then the big wing is the way to go.

Originally Posted by Van

And in some cases, rules... For 944 Cup/SP2, we're very limited with what we can do - especially to the underside of the car. But there are tricks: like taping up the hood and headlight seams; smaller mirrors, little "windowlets" by the mirrors; removing wiper arms; front air dam; radiator and brake duct opening size; ride height; and rake angle.

I'd love to be 0.1 second faster in every corner! I have yet to meet a race track that has more straights than corners...

Originally Posted by LS1Porch

Any articles or pointers for making an under tray for these cars? I've thought about getting under there with some sheet aluminum but i'm afraid i'd do more harm than good.

Originally Posted by LS1Porch

Any articles or pointers for making an under tray for these cars? I've thought about getting under there with some sheet aluminum but i'm afraid i'd do more harm than good.