Chuck Jones

I have a factory aero kit on the TT....came originally with the rather wide front spoiler that lasted all of about three weeks before the speed bumps ate it.

I switched over to the FVD type of front lip sold by Sunset Porsche for around $270 rather than try to stay with the $800 OEM one.

Recently, I found that the C4S lip, which is raised in the center to give more ground clearance....will also fit the 996TT...all the slots line up perfectly and it pops right into place and requires only two phillips screws at the ends to hold it into place.

My question revolves around what the consensus of opinion would be regarding the aerodynamics of using a C4S design in lieu of the FVD design which has the same width and down pitch all the way across. The factory aero lip is a good 3/4 inch wider than the FVD type....and the C4S design eliminates the down pitch in the middle for better clearance I guess. You can't run a rear spoiler without the front due to the front going light on you at high speeds, but what's the consensus about a modified front lip like the C4S....with top speeds around 150.??

I'm not looking to break any speed records, just wondering about aerodynamics of investing in the less expensive lip since I seem to go thru about one or two a year. The C4S lip is only arout $140...

Land Jet

I don't think you will even notice the difference Chuck.

Chuck Jones

I decided to go with the FVD spoiler again rather than try the C4S one...at least for this time around. Jeff at sunset Porsche is going to take some pictures of both lips next to each other to show what the actual difference might be. In the meantime, I am going to go with the one what seems to produce the maximum downforce.

If anyone is looking for an brand new OEM aerokit front spoiler for half the usual price, give me a PM. I wont' use the factory one because the clearance is just too low for me and I go thru them too quickly. They're usually around $800 per set.

Loren

You will likely feel a little more lift at 160+ MPH

Chuck Jones

Since I've never been to 160, I guess I'll never get that lofty lifty feeling

Macster

of any bolt on/add on equipment seller must be able to show testing results. If there are no results claims are false and the add on equipment useless, or worse.

Given the speed at which you intend to use the car I'd be very leery of using any aerodynamic add-on replacing any existing aerodynamic component on your car without seeing some reliable proof the add-on has been tested and any claims are backed up by testing.

Sincerely,

Macster.

Chuck Jones

I've never seen any sort of scientific correlation between the factory aero kit and the front spoiler lip. I'm sure there must be some sort of measurement for down force, but has anyone seen any informaton or specs on this? Some downoforce must be necessary when runnint a rear wing, but what's the formula for what's accepatable or required versus the negatives of not having enough downfore???

Mikelly

Everyone who'se ever done any testing in a windtunnel raise your hands...

Chuck, I will offer this up...

I have the C4S front lip.

I have the Aerokit front lip, although destroyed by a groundhog at over 135MPH.

I have the OEM Turbo front lip.

I have the ROTEC Carbon copy of the Aerokit lip.

My car is setup at midway thru the GT2 ride height range. I could not tell ANY differences in ANY of the lips at 80MPH or lower. However, above 80MPH you can feel more grip on corner entry with the aerokit front lip, in cooperation with the GT2 rear wing as set up on my car with an aggressive street alignment of 1.5 front and 2.0 rear negative camber with zero toe.

Now, all that said, I've never damaged a lip driving into a parking lot, over a speedbump, or on any other objects (*other than the 30# rodent at the track!). You have to angle the car to clear these obstacles. You also have to pay attention and be aware that you are hanging a little low for some objects in the road.

All this said, the OEM TT and C4S units are remarkably flexible and what I would run instead of anything made of glass or carbon if you don't want to worry about "casual" contact with hard surfaces. The Turbo Lip is also very functional aerodynamically and is I think the best overall compromise for the aerokit rear wing, if you aren't going to run the matching front lip spoiler. The unit has a functioning canard design at the side, and the air ducts in the bottom were designed to work with the channels in the inner fender liner to pump cool air directly to the brakeduct scoops at the control arm/spindle. The C4S lip has these as well, but gives up a little frontal area coverage, both from the center cutout, as well as the overall height of the lip. It simply doesn't hang down nearly as low. Although I have one and have used it, I prefer it least of the OEM lip options, but it has the most clearance of the OEM designs I've seen and/ or own.

Hope this helps!

Mike

Macster

something to back up the claims. If an aerodynamic "aid" is offered but no claims are made then you are on your own whether the device will help, hurt, or have no affect.

Given I value my life and my car should I ever travel at 150mph I would want to be darn sure the car's stability not in any way compromised by the addition of some piece of cheap fiberglass. 150mph is the flight speed of some aircraft.

The ad hoc tinkering of one's car for the sake of some questionable cosmetic benefit at the risk of upsetting the car's high speed stability simply amazes me.

The front splitter/lip is intended to prevent air from going under the car. The less air under the car the less likely air pressure will build up under car. This reduction of air under the car helps engine cooling, brake cooling, and in the case of the Turbo increases the air flow through the intercoolers which helps remove heat from the incoming compressed air and thus increase engine output.

So, with an ill-conceived "aerodynamic" modification one could reduce vehicle stability at speed (and even at less than hyper-legal speeds -- in some places in USA 80mph daytime limit legal and I've driven at this speed in high winds which can see the car's actual air speed over 100mph), reduce engine cooling efficiency, and reduce engine output.

That's real smart car mod'ing, Not.

I don't have it handy but Porsche has published downforce/reduction of lift numbers and coefficient of drag numbers for its cars. Thus as these cars come from the factory, outfitted with factory standard body parts, or with Porsche tested optional parts, one has confidence the car's critical stability at speed is not compromised nor or other car systems (cooling, heating, brake cooling, and for Turbo cars intercooler performance) compromised.

But for the layman to mix/match body parts....

Sincerely,

Macster.

RSA333

Have done extensive testing, including full scale wind tunnel tests at UMD engineering, in the past to set up 993 Turbo Evo GT2 race cars (IMSA). Our experience is that one needs to get proper fore and aft spoiler balance as well as downforce for certain tracks. The Daytona high banks were a challenge - the cars felt very 'light' and hard to control at high speed if you did not get them adjusted just right. You can also get good information from Porsche Motorsports North America (PMNA).

However, unless you are tracking your car, it does not matter IMHO. It seems to be what people like to see on their cars.

Chuck Jones

Mike, Mac, and RSA: Thanks guys, that's exactly what I was looking for. I have to admit that other than the original factory aerokit lip that came with the car, most of my damage has been done by a problem I have with depth perception when parking in lots....I don't judge the distance too well and end up bumping the lip against either the concrete stop blocks or the sidewalk curb when parking straight in. I've not had a problem with angling over speed bumps and just threw that in as an excuse or example.

My biggest concern was with the fact that there are a number of aftermarket lips out there that may or may not work well with the rear GT2 aero design...and I've gone thru two sets of the.....I guess you'd call them the FVD type design lips. I don't really hit 150 and did so only once at Thunderhill, but I have hit 120 and that's what started me wondering about the aerodynamic relationship between the front lip and rear aero wing. It would appear that the relationship, although important.... isn't that critical unless you're really running at high speeds and over an aggressive course, in which case Porsche designed their factory GT2 type aero setup to work together; and tested it that way. I won't spend the money for another of the $800 version. I did find an FVD type one for $250 and it's in the garage now... so based upon the info I got from you good folks, I'll continue to run the slightly narrower "FVD" type that has the openings for the brake ducts and is made of a composite that's a lot more forgiving than the plastic factory one. It also comes in black and seems to work well as a color combo for the midnight blue. Thanks again guys.

Mike: Out of curiosity, how did you like the performance of the C4S lip as compared to the others? Was there a particular speed at which you noticed the onset of a performance issue? It's practically the same as the other version, even has the brake ducts, but that rise in the middle has eliminated some of the downturn on the lip. Do you have any idea why Porsche designed it this way? Or was it just to provide a bit of aesthetic variation. I would think that aesthetics aside.... it would have to accommodate a performance concern in terms of handling at higher speeds.

Mikelly

I noticed with the C4S lip that previous "frontal plant" wasn't there in tight decreasing radius corners. I'd develop understeer that wasn't there with either of the other lips. Nothing else was changed when I noticed this condition, so I can only contribute it to either the lip, or the lip and conditions of the road, which I didn't notice to be different from previous drives thru this route.

I never got to run the C4s On the track though.

I CAN tell you that the GT2 wing, along with the TT front lip worked well together at speeds in excess of 160MPH at VIR on many many laps...

Mike

Chuck Jones

That tells me what I want to know.....

GreggT

I changed to the C4s lip (painted-filled) in 2002 as soon as the part was avail in NA.
I would imagine that stability at speed is affected by many things in the way the car is set up.....height, rake, suspension, etc.....but in my case the car has always been incredibly stable at 160 or so (using OE rear wing).
I have just changed my rear wing to something larger, stationary, and custom.....so I'm probably pressing my luck and anxious to see how she feels next time out.

TT Surgeon

The OEM aerokit provides 20%+ more downforce at 130mph, according to porsche motorsports, The rear wing must be used in conjunction with the front lip for AD balance. I would avoid mixing AD parts. Keep in mind the c4s lip is designed for a car without a rear wing, hence it's less aggressive design.
When I had the OEM aerokit on my old c4s, you could really feel the difference at a high speed track like pocono or the glen. Like mike said, just be careful.