rs10

I've just posted a thread with a very similar title in the performance modifications forum, here:
https://rennlist.com/forums/performan...l#post13898932

(I wasn't sure where to post this, but then I realized that this will equally interest/disinterest owners of virtually any other 2 door Porsche, and maybe even some 4 door Porsche owners as well. And it seemed silly to have one discussion in the 996 forum, another in the 996 Turbo forum, etc.

On the other hand, the performance mod forum doesn't get a lot of traffic. Solution? Threads like this in a few forums to let anyone interested know to go to the performance mod forum.

Hope this is helpful!)

jeanmarcboilard

The link isn't working for me but I'm interested in this topic since I have an Aerokit rear wing with a non-functional GT2 front bumper. I've wondered about the different downforce and lift created by this combination, among others.

gophaster

Here is an interesting article on this topic. Seems like the methods could be feasible. Measuring drag via airflow meter voltage, never thought of that. Dont think the differences between say an aerokit tail vs standard tt tail would be big enough to measure using these methods especially since it would be really hard to get the same exact conditions between runs but its still a good read.

http://www.autospeed.com/cms/article...-Lift&A=112736

rs10

I found that while googling before starting the thread and it contributed to my thinking on the topic, though I don't think I'd pursue other methods they mention. At leasst the trunk/spring test strikes me as very hard to do well. You'd probably need the same person sitting in youor back seat before each and every mod, and it wouldn't help at all with the front ... .

gophaster

Im not sure if anything that could be had off the shelf could help. I found this suspension travel sensor...again not sure if the differences being measured could be useful for this. Perhaps for downforce over the same track/distance with back to back testing?

http://m.advantagemotorsports.com/site/Sensors.htm

Suspension Travel Sensor This device allows for the suspension travel to be monitored by the data acquisition system. The sensor outputs a voltage based on suspension position which is then analyzed using our data acquisition software. Constructed of high quality components the sensor features spherical rod ends at each end for mounting, and have an anodized metal body. Cost varies with travel range required. Typical cost $250 each.

TT Surgeon

Oem aerokit increases downforce by 20% over stock according to suncoast Porsche.

Berra

So my car would have that much more downforce compared to a regular 996 Turbo? Hmm...

Carlo_Carrera

The big question with that though is the 20% increase evenly dispersed over the entire car front to rear? And at what speeds?

z06801

As mentioned a potentiometer could be set up to calculate spring travel which could be turned into a measurement of down force at each axle, you could could get a good picture of how evenly the down force is applied.

gophaster

Yup, also is it increasing drag? Some of the crazier mile run 6t's I've seen even remove the standard factory wing, im assuming to reduce drag.

Berra

More downforce will always increase drag.

TT Surgeon

The OEM aero wing is designed to have minimal increased drag, unlike the gt2 wing which has a lot more drag given its greater lateral demension vs the aero, which is the same as the stock wing. A lot of the aftermarket gt2 wings also tend to have a different angle of attack vs the OEM version, can't be good.

rs10

The standard car has 6.7 kg of downforce at the rear, and 6 kg of lift at the front, both at 200 kmph (124 mph). So yes, it's an interesting question. Does it mean that you get 7.2 kg at the rear, and no change at the front? Perhaps, TT Surgeon, if this is what Suncoast told you, you might want to ask a follow up question.

As for changes with speed though, lift and downforce generally increase or decrease with the square of speed. There are exceptions, and with 911s it often happens that downsforce at the rear combined with enough lift at the front can cause the front to rise, messing up the aero, and causing a significant increase in front lift. This happens on the 996 GT3RS. Probably not with the TT though. The RS has 25 kg of downforce at 200, and a lighter front end. Also, drag against the wing would do more to lift the front even if it were no larger than the TT's, because it's higher.

rs10

If I understand correctly, that depends how you mean it. Things that reduce lift can also reduce drag. This may be seen as increasing downforce, if the car already has, for instance, a big wing and splitter and ends up with more downforce. On the other hand, if by creating downforce one strictly means harnessing the airflow near one part of the car to press or such that part down, then yes, you need to create drag to do it. Well, that's what I've learned from reading a lot of threads and a lot of googling recently, but it's from multiple sources, so I'm fairly convinced that's correct.

rs10

So about $1000 for all four corners. That's about what I expected. I also expect the rest of the hardware to cost about $5k, which is a lot more than I'm aiming to spend, though maybe advantage will have some surprises. There's also installation cost, not to mention the need to find someone who can do it. (It may be easy, but it isn't something the average Porsche specialist will have done before.)

My preferred method would be to use the height sensors which the car already has. Someone posted in a 991 thread that they are working on a datalogger that would do just that. Hopefully it will also work with 996s, and won't be sold at 991 prices ... .

There's also a bit more detail in the thread in the performance mods forum mentioned in the original post.