Bill Verburg

To tell you the truth, tire air pressures seems to have a bigger effect, I've only been to LRP this year and its a slower speed track compared the WGI. I've been trying to get a better handle on the NT01 pressures compared to MPSC. Everyone else is on Hoosiers so not much feedback from the rest of the guys

nine9six

Bill,
How long does it generally take to flip your car from track to street, and street to track?

Bill Verburg

As long as it takes to change tires and peel off the #s

Cupcar

I am surprised the 993 RSR and 993 RS/CS have the same aero lift data given their difference in ride heights as well as added wheel arch flares.

Usually lift data is very ride height sensitive.

Bill Verburg

I'me sure it is,

Not having separate Cl for RS/CS and RSR, I used the came Cl for both hence the same lift.

I used factory data for all the coefficients except the RSR lift C's

Bill Verburg

here's a refined version of the aero chart, still not perfect but shows relative values

k722070

I had the chance to follow comparable cars last summer(not 911's), only difference being they had wings and splitters(and slicks, but I'm leaving that out). they were able to pull away a few tenths in medium and high speed corners which was interesting and made me think about getting proper aero on my car.
I've read some lift numbers for 911's but not 993's with no spoiler, only bill's numbers of about 77lbs of lift with stock setup. my car should be close to that since the front ride height is 130mm. maybe only 62lbs of lift since I have a turbo front bumper. but I have no idea how much lift with spoiler down.
as a test for our final track weekend I left the retractable spoiler down for a session to get a sense of the time and handling difference.

the time difference was substantial, an amazing 5.78 seconds best lap to best lap. final top speed on the two main straights wasn't much difference, 3 to 4 mph.
the big difference is the speed on short straights after a high speed corner. for example a corner named witchcraft top speed at the previous straight is exactly the same but at the apex with no spoiler I'm going 6.6mph slower(73.4 vs 80), and 7.5mph slower at the end of the following short straight. that sector, apex to end of short straight my non spoiler car loses .5 seconds.
the max LatAcc with no spoiler is 1.33, spoiler up is 1.46

spoiler down the car didn't feel unstable, only slightly less planted when trying to get on the throttle out of a turn. I can't remember noticing a difference on the long front straight.
overall my lap times in the no spoiler session were 4-5 seconds slower than normal. I don't know much about aero besides the basics but this seemed like an interesting test so I thought I'd post it.

pp000830

Where did you get it?

Bill Verburg

The thing I notice w/ the Cup/CS aero over the older Rs aero is how much earlier I can get back on the gas and depending on the following straight length I can also get into another gear and often carry the corner in a higher gear, a lot depend on the speed that can be carried into the corner. It's an awesome feeling in the really fast stuff.

race911

Pretty amazing. I take my cue from the record holding cars out here that I know (STU S2000 and GTS3 E36 M3), and it seems they've carved about 1-1.5 sec/lap off at Thunderhill once they got sophisticated.

Personally, using Thunderhill T1 it's amusing to find my min apex speed in the oh-so aero tuned Spec Miata is 2MPH faster than the faux RS (and that's only 3MPH quicker than that first gen DL1 showed in my 100% stock bodied '73S back in the stone age of DA).

race911

Speaking of aero, one of our own Down Under with a sorta stock 944 Turbo: https://rennlist.com/forums/racing-and-drivers-education-forum/839955-going-136mph-min-through-a-90o-turn.html

Martin S.

my $0.02. Bill writes, "First observation is that the interior rear view mirror is almost useless." That is so true with the 993 RS CS tail. That can be remedied by moving the adjustable wing and installing uprights and toping it off with a 60" Crawford wing, with a 1" gurney lip and end caps.

When I put on my Crawford wing last December, that was the first thing I noticed, I could see out the rear view mirror...I also noticed the car was at least 2 seconds a lap quicker on the high HP, high speed tracks.

Ernie J

Hi All, just like to tell you that Mantissport working with the University of Ontario, Canada.Will in the new year be able to test race cars in their full scale windtunnel. downforce,drag, pitch and roll and yaw. Also 4 post shaker available.

k722070

as an update, I put on the front taco holders and what mashaw calls the 3.8 993 tailbase.
this won't be apples to apples lap times because my suspension has changed and this was the first timed session of the year for me so I'm pretty rusty on the track.
but it is the same car/engine, tires, pads and driver, conditions were similar.
and it is unlikely I will drive this track configuration again this season.

so, data for the same corner, witchcraft, at the apex then end of short straight
no spoiler 73.4mph 82.3mph
spoiler 80mph 89.8mph
aero 88.9mph 93.5mph

top speed at the end of the painfully long front straight and max LatAcc were the same for spoiler vs aero, as was lowest speed in slow corners.
the big difference is being able to carry more speed through 65+ corners.
once I settle on an alignment, sway bars, wing angle and get used to driving on the track again it looks like the car will be quite a bit faster.

Ed Hughes

Nice improvement!