Jean

James, anytime

I will just need from you some information about the car (non-standard 964T stuff) and we can run a simulation. I have old data from VMax concerning length of track, slope, etc.. if you have any VMAX data from your car before latest mods it would be even better.

Looking forward to see the end product.

TB993tt

James, many thanks for sharing your project in this thread, I have enjoyed reading it

I have no doubt that you are going to get your 700hp and it is going to be 700 ferocious hp not the chassis dyno kind which may wilt once some heat gets into the system, yours will be relentless and scary and will push your car to at least 200mph at Bruntingthorpe I have no doubt......

With this in mind is it worth going over the other considerations for the Bruntigthorpe run ? (I am sure you have many times but it would be good to chat about it on here ?)

Firstly your aerodynamics:
I posted the raw data on another thread, from Paul Frere (RIP):
Frontal area: 1.88 sqm
Cd: 0.35
CdA: 0.658
CLf: 0.00
CLr: 0.01

Porsche claimed rear lift at maximum speed as per diagram below ~5kg

And yes Jon, yours is the one with 40kg of lift at 160mph



So the basic 964 turbo whilst slightly higher Cd compared to the 993tt (0.35 vs 0.34) has virtually identical CdA (0.658 vs 0.656) this will not hinder your 700hp in its achievement of 200mph...

The 964 turbo has some good lift numbers with zero front lift according to the CLf number and only 5kg rear at ~180mph..... these are encouraging and much better than the 993tt which lifts quite a lot more at high speed.

Here is a pic of the 230mph Cartronic car and the pdf below has some more pics to consider, note these cars have the sloped screen:



http://www.cartronic-motorsport.de/e...r_revanche.pdf

So you have a good base for the high speed in terms of lift.... Ruf was quite involved in making the wide bodied 964s go very fast and he came up with a lip for the bottom of the front spoiler (I don't know if you may already have this ?) I had it on my 460hp 964 turbo see pic below:



I think this lip would be a good idea..... I would be concentrating on the chassis, condition and spec of shockers ? You want them all to be working well and for Bruntingthorpe the equivalent of a PSS9 6 setting IMO, so you can soak up the irreglarities but still be poised. I would want the car low, as low as possible then the Ruf lip can stop any air getting underneath, I would go with a slightly nose down attitude.
With your power there is going to be considerable squat, even at the very high speeds, I am not sure how one can compensate for this, maybe just harder rear suspension settings ?

Lastly brakes: This is the "problem" with Bruntingthorpe, when the vmax started most cars "only" hit 160mph and braking from that is no problem. At 200mph it is a different story. When I did 195 in the Carrera GT it felt like it "only just" had enough brakes to stop in time !. Look at the spec of Leon's RT12 - this is what you really need for stopping from 200+mph. So what about brake specs ?

What wheel/tyre combos are you going to run ? Which sizes and tyre brand ?

I am excited for you but at the same time apprehensive that "we" (yes Jon you included ) take 200mph and more importantly stopping from 200mph in a short distance maybe a little too lightly, the lemming syndrome is a powerful thing !

It would be great to hear your thoughts/strategies on the above ?

JBL930

I won't deny i'm concerned about going much above 190mph, even more so now you mention i'm getting 40kg of rear lift! What does that mean in laymans terms Toby, remembering i'm going in a straight line so no need for high lateral traction. My car is totally stock externally, with the exception of ride height, bigger wheels and Ruf 'A' piller fillers. I was thinking of removing the wipers, and obviously folding in the mirrors, but that's it. Here is some data from one of my last high speed runs, the car felt pretty good and had enough stopping distance. But i'm well aware that another 5mph up at this speed is a LOT, what would you be doing to my car if you were me?

JamesE

So, basic aero spec will be std Flatnose + no gutters and no sunroof. This includes the turbo S rear spoiler. I have the RSR front lip spoilers, which I think is basically the turbo S front spoiler(s).

Suspension was custom built by Manthey on KW Clubsports, currently badly set-up, but i'm sure RC can sort that out. I've asked for custom ARBs from RC, but not sure they will be ready in time for Vmax.

Brakes are currently 993tt, but have a set of full race spec 993 gt2 fronts with 15" discs from RC. These need to be referb'd and probably wont be ready for Vmax.

I suspect Vmax will form part of the shake down and we'll do another smaller day to go for true Vmax. I remember the early days before some of my mods and thinking I wasn't going to stop from 170mph in time. I don't really want to go through that again. That said 195-0 was no drama.

As for predicting power, i'm not sure. The engine will take a lot of boost for a 911. A lot of time has gone into the head sealing and temperature control. For me, death or glory runs hold no interest. I'm looking to show what sustainable power can be produced through quality engineering with an air-cooled engine. That said, I will run 1/4's at the Santa Pod at silly boost for bragging rights, but Vmax is all that separates us from the animals....

Jean, I don't have any AX22 logs from Vmax but do have previous top speeds.

JamesE

Oh, wheels. I have 6 sets to choose from

But basic choice will be:
Original speedlines on 285 rears, R compound.
BBS 996 5 spokes, 285 rears on MPS.
BBS Mags 265 rears on MSPC
BBS Mags Slicks
BBS Mags R888

Looking at that aero screen, ummmm......

I will be keeping stock wing-mirrors but I think PC is making a quick release mech. so I can take them off. However, I intend to leave them on as that's cheating as far as i'm concerned.

TB993tt

Jon, The 40kg of lift is a top speed for a stock 930 - you will be going ~30mph more than that ! I don't know how to calculate the increase in lift as the speed goes up but it will increase......

This bad boy did 218 mph on its Guiness record runwith 580hp - don't appear to be any special aero aids.... I guess it is check all suspension components for correct function, check geometry and ride height and check brakes....

Oh and James - another "aero" screen

TB993tt

I think what I describe as Ruf splitter" is in fact what tou say about, two lips either side ? I think you have a good combo there....
All good stuff, you will want a "road" set up for the high speed straight line stuff, no silly cambering
993tt brakes will be fine, my 993tt with completely stock brakes (RS rear calipers) inc pads stopped very well.... no issues there
smaller day

It's going to be a monster, very excited for you
I know sounds a bit barking from somone rolling on carbon fibre but I would not use the mags for these runs....I'd stick to OEM.
Trye wise apart from the latest N0/N1 Mich cups I wouldn't risk track tyres at these speeds, you want proper Porsche tested autobahn stompers from one of the "biggies" Michelin, Conti, Bridgestone, Pirreli.... ?

JBL930

I'm on Bridgestone Potenza SO1 285 rears, can't remember what the fronts are? Brakes are 993C4 fronts and the 930 fronts fitted on the rear. I will be fitting 993tt big reds all round, but trying to work out how to fit the rear calipers, not sure if this will be done before VMax, but i'm trying. It seamed to stop from mid 180's ok as it is http://s139.photobucket.com/albums/q...un183mph-1.flv But i'd feel better with more stopping power, especially with no ABS

JBL930

So other than the aero screen, no gutters, little mirrors and slightly different front spoiler... what allows this car to hit 218mph? Because in any universe that is REALLY quick!!

TB993tt

RS Tuning 580PS and a longggg autobahn !

This is the first car tested by a Magazine in the 0-300kph sprint. According to the writer they were discussing how long it would take and 40 seconds was banded about as being realistic....... it took under 30 !

JBL930

I don't doubt the speed Toby, and if it's an RS engine then it'll have all it's horses. What i mean though is aero wise, how is this stable at that speed, when it's not a million miles off stock looking. It's not even as low as mine! Maybe this 40kg of lift isn't much to worry about?

JamesE

Aerodynamics are quite complex. There are plenty of higher-order effects, so relatively small changes can make a BIG difference to top speed and stability. The aero screen has got to be worth a lot even before 2nd order stuff, wrt top speed.

TB993tt

There was a quote in the magazine about it being wide body vs the Ruf CTR of the day which is narrow body and RS (don't forget ex Ruf head engineer) saying "yes we are well aware of the extra drag of the wide body" and that was it ! they let the numbers do the talking as it spanked the Yellowbird....

I guess in terms of Cd and CdA the front bumper probably helped make it more slippy and of course the sloped screen but in terms of handling at these speeds - the guys who drove these things are just heroes, yes you're right they must have had the big lift also, probably 200kg at 218mph ? but still 1000kg keeping them on the ground, they just found the widest straightest autobahn and "stroked" it up there.....

I remember the first time I did 193 at Brunters in the 993tt and I totally **** myself, I couldn't believe how "wandery" the whole thing was over 170, really scared me....... 40 runs later and it felt "normal" - doesn't mean its not still dangerous tho'
Then you drive a Porsche with aero designed for these speeds and realise just how precarious the old set ups are......

JBL930

So you're admitting to turning into a *****.......I'd of never thunk it...

You won't be coming for a run in mine then?

TB993tt

Been there done it and survived - will leave it to you big boys

I will be watching from the other lane whilst Preuninger's latest and greatest looks after me