Macca

Did some data digging today on Track day 20 September. John. I think Im reading this right. I checked the full lap from end of Session 5 lap 2 and beginning of lap 3 and full lap times out at rolling average time. Rolling lap best 2/3 = 1.13.18.

Theoretical is optomistic (1.12.18). It started at 1.09s! I cut out all the out lier just using the 12 quickest laps (all within 0.9s of each other) to try and bring this into reality (i.e. consistency) . They were the last three sessions of the day as the first was wet, second was drying then 3rd was cancelled due to hail. Session 4 started at 2pm and track was starting to dry out. Session 6 was only damp in three places, only an really an issue exit T10.

Am I reading this correctly John?

Its really interesting what the AIM traces can tell you. Ill youtube the full lap.

Macca

Its mad aye. There are a few of them including over at 180kmph at the Ring over on the 991 GT3 board. Scary stuff.

John. Wait and see how you feel after Hermans rebirth. Also for the final bill. If you can bring yourself to use the car after all this effort you may well find a cheap stock 964 is a bit of a disappointment!

Macca

Also on that subject. Ashley from NZ Classic Car mag is after a good 993 C2 6spd (under 100K NZD) if anyone has a lead. PM me and Ill pass it on....

John McM

I believe the fastest running lap time is reasonably accurate but the best possible run has never been borne out in the real world.

Macca

The "theoretical best lap"? I agree. Hence I used only the 12 fastest laps from the last three sessions (approx 7 full laps a session excludes L1 & Last lap). S 50% of the laps from the last three sessions with a max delta 0.866s (i.e. consistent). I figured this was as accurate a sample as I could create. 1.12.18 dosnt sound unrealistic for the car (although I believe it is for this driver!). The human analysis I had done using a sub set of this data showed maximum likely best of 1.12.8...

Im learning new functionality with this thing. If will show slip angle of wheels etc. Very useful but takes mucho time to analyse where you went wrong using timed video footage.

The rolling lap seems sound. In my actual best lap (session 4) I was slightly slower in all sectors. The track was getting drier each session but obviously in 5 I couldnt stitch it all together (fastest was 1/10th off overall fastest).

The car is 100% factory settings for these laps. Geo is stock from the factory. Ive been trying to figure out if I should be making any changes for my next outing. Even though the laps are consistent there still appears t be time on the table from mistakes so I dont think playing around with sway bars or geo is a good idea yet until the times improve. The car is handling very neutral (touch understeer on entry T2/5) balance on exit oversteer on radius sweeper T10 and over the hill. I dont want to bugger around with the settings and loose my base....

John McM

Sorted out the logistics for the rear shocks today. John is removing them from the body tomorrow and couriering them to Autolign for their refurb. It was touch and go whether they would be ready pre Christmas but with the commitment to get the shocks to them now they said that they will start no later than 9/12. There are five sets ahead of them in the queue. I don't pretend to understand the refurb process but was a bit surprised to hear that they would replace the shafts as a starter. If the end result is as new then I'm happy. I expect a bill of ~ $700 for that. You could argue that new shocks would have been easier, but I like the fact that I've kept the RUF fit out intact. Plus I really like how it handles with that set up.

I expect the body and gearbox to arrive at the same time as the shocks so I'm preparing for a very busy period up to Christmas. The anticipation of driving a near new condition 25 year old 964 is palpable. Brand new paint with all of those little details popping etc. However I'd still like to do a stripped 964 for the track and reuse some of the items I already have.

Macca

$700 sounds very reasonable John. A new set of shocks would have been minimum 5K landed?

John McM

The fronts were $1,300 so it's $2,000 minimum so far to have 1990 technology.

Pel

The GT3 rs is owned by a Takapuna businessman, he may have a few interesting Porsches incl a 993 Turbo S.

Macca

I spent a day on data analysis. Reviewing also footage of Nigel Cs fastest lap a few weeks back.

The AIM with ECU feed is very useful but it takes alot of time to learn what you are looking at and what has significance.

I learnt alot of things. Much of it you all knew already. The two turns that make the biggest difference to a lap time at HD are T10 & T1. Ill post a incar shortly of a single full 1.13.18 lap in the GT3. The lap was taken from turn in T9 to turn in T9 within a single lap but not at the traditional start line. The difference between this lap (where I nailed T1 and got the best traction I could given the damp exit of T10) is 0.65s better than any other lap (almost all other laps I would not optimise one or the other and occasionally both!). Getting them both right saved 0.65s on the best lap and getting them both wrong lost 0.35s over the best lap (so a delta of almost 1.0s!).

The big surprise came in the fact that all things being equal (i.e. traffic, surface condition, tyre pressures) there is more time in getting these two corners spot on than the mistakes you will make in all the other corners combined!

My best time video shows almost identical lines to Nigels best lap. Where I can say he is optimal is also in his braking. Surprisingly it is not as much later than others (infact when following Paul it appeared Buba was braking earlier), rather the way he modulates his brake pressure. Hard on, taper off (trail). Interestingly when looking at my fastest lap the brake pressures were 15% lower at maximum threshold but 20-25% longer in duration.

So the simple out take from all of this is to get the best lap times find your fastest line in T9/10 and practice it. The fastest line will be the one that works best fr your car and driving style.

T1 looks to be all about position on track before entry, braking timing, force and modulation, turn in point and smoothness and accuracy of turn in and exit. getting the first 4 right allows you to get WOT earlier and make up good time on exit. Again this will different with car, but T1 rewards being a little brave to find out what line works for you.

For the infield the braking pints, gear selection and turn in are the areas to focus on.

I learnt alot from this exercise t the point where I can now visualize what my quickest lap feels like to drive in my head. There are definitely a few areas Ive found I could improve. Up over the hill Im using 2nd for almost all of my laps but 3rd works better and for 6 & 7 speed cars suggest using 3rd through T2 and over the hill to save time depending n your ratios. Over the hill needs more brave pills (yet to swallow). B51 is really interesting as I have data to suggest with the GT3 an earlier turn in with a flatter line works better than the line with the older 993 chassis.

I hope some of this is useful to those going to HD next month. Have screeds of data Im working through but most of it quite specific to my car and driving. However there is definitely some information in there to help all drivers...

Macca

Here's the video without sound (not sure what happened). Ill post the video with sound later.

Here is the trace (T9/10 of lap 2 session 5 is faster as you can see then T1 onwards of lap 3 is quicker). P.B lap was actually in session 4 which was damper so go figure...

Macca

here it is with sound (but the picture is not as clear or smooth). Unfortunately the noise under brakes is the warped front rotors making vibration via cage where mic is mounted.

racoguy

Here's the latest from the paint department, the panels are ready for top coat and the car is getting the last couple of bare metal spots attended to before that is also ready for a new coat of Grand Prix white.
Looking great so far, should come out nice and straight, ready for John to put in the garage and never drive it again he jokes of course!

Removing the rear shocks today and installing my spare set so that we can get a jump start on getting those rebuilt before the Christmad rush.

996tnz

Macca, your AIM analysis looks 100% credible, and you seem to have done as I do ie discard all first and last laps, plus any others featuring in the 'best lap/best rolling lap/best theoretical that have implausible splits (ie more than about 5% or so faster than the next fastest time for that split).

Fast car and nice driving.

FWIW (unless it is a known failing specific to 991 GT3s) your rotors are much more likely to have had some excessive localised pad transfer from having had hot brakes clamped while stationary than being warped. They'd probably clean up OK if scoured?

Agree too about T1 and 10 being key to a good lap at HD. T10 I'm getting increasingly happy with, while T1 is at the top of my own homework pile.

I think that John's right about it being pretty much imposiible to actually hit your theoretical best lap (without significant car or driver development) but it does give some indication of what the car could meet or exceed with a pro in the seat perhaps.

@Pel - seems a pretty fair price you're suggesting for the 996T, though I don't watch the market so would favour others' opinions.

RS ZWEI

Looks like Andrew Whittaker has a 991 GT3 Cup Car: