986 aero & cooling mods

[The Radium King]

well, I went to school for such engineering, but even an application of "where does the air go?" works here. quickly, where does the air go from the side radiators? down. where does the air go from the centre radiator? down. we are taking a whole mess of air hitting the front of our car at, say, 100 mph, and deflecting it downwards. think harrier jet. what effect does this have on the driving experience? understeer. from a litigation point of view (ie, after their experience with the 930 and having to remove it from the us market) would Porsche rather have understeer or oversteer? honestly, you want as little air under your car as possible - this is why cars have front spoilers and side skirts. rear diffusers are there to turn what little air does get under the car into downforce.

now then, what does Porsche to with the gt3, gt3rs, gt2? side radiators vent into the wheel wells or out the side of the bumper cover. centre radiator vents upwards. why on these porsches and not all porsches? one is an entry level street car for the unwashed masses, the other is a dedicated track weapon.

I think the fro's comment about the airflow path on his centre radiator is regarding the path the air follows from the outflow of the radiator to the top vent. the gt3rs and gt2 use a duct that requires a bunch of other changes to make it work (spacing out the front bumper, revised side rad ducts to accommodate the fact that the centre rad is moved forward, etc.); without this the flow is a bit more convoluted. however, this would only affect cooling and not aero; less flow through the centre rad is better than a lot of downward flow through the centre rad.

[j.fro]

I'm not an aeronautical engineer, but I was hoping to hear from some. (Thanks, TRK!) My purpose with this thread was to generate some discussion, share what I've done, and see what others are doing. Although I keep insurance, tags, and state inspection on my 986, it's not exactly a street car. It's built to compete in SCCA F Prepared and PCA Improved autocross classes. Winning and losing often comes down to hundredths of a second, so I'm game to try things out to see what works. In a way, it's my hobbyist racer test lab, so if someone can make suggestions, improvements, or point out fatal flaws, I want to know about it.

By the way, I have moved the center radiator out towards the front of the car, and I added ducting to channel air through it and upwards. I don't have data on the aero, but when the car gets moving, the temps drop fast. On hots days at autocross, that's important.

[KRAM36]

Originally Posted by j.fro

I'm not an aeronautical engineer, but I was hoping to hear from some. (Thanks, TRK!) My purpose with this thread was to generate some discussion, share what I've done, and see what others are doing. Although I keep insurance, tags, and state inspection on my 986, it's not exactly a street car. It's built to compete in SCCA F Prepared and PCA Improved autocross classes. Winning and losing often comes down to hundredths of a second, so I'm game to try things out to see what works. In a way, it's my hobbyist racer test lab, so if someone can make suggestions, improvements, or point out fatal flaws, I want to know about it.

By the way, I have moved the center radiator out towards the front of the car, and I added ducting to channel air through it and upwards. I don't have data on the aero, but when the car gets moving, the temps drop fast. On hots days at autocross, that's important.

You are hitting it hard! That sounds sweet. When I finally pick out a front bumper for my car, I'm going to look at doing this. I like the sound of a cooler running car and ducting the air. Very nice!