Jean

Thanks for the correction Kevin. I think it is worth mentioning the gearshifts when comparing with magazine runs since the difference can be an incremental 1/2-1 second on a shiftless run.

Marty, A car doing a 60ft in 1.6s is at or below 3 seconds 0-60mph, that leaves him with almost 7.5-8 seconds to do a 60- 130mph with high 10s. With this sort of boost they run on a quartermile, these cars should be well deep into the low 6s.

A 300kph run might show on some of these cars what boost and heat do to performance under load of 4-5-6th gears.

TB993tt

Sportec SPR1
997 based bespoke machine from Sportec.
option 1:
T70
700hp/810NM 1345kg
100-200kph 6.3s
100-300kph 17.9s
T80
100-200kph 5.6s
100-300kph 15.9s
802hp/880NM 1360kg

I am not certain if the above acceleration numbers are manufacturers claims or verified by indy source ?
Undoubtedly very fast times but for such lightweight cars with such massive hp claims I'm not sure if one should expect more ?
The 6.3s 100-200 of the 700hp car says to me more like sub 600hp at that weight - having said that, the 996/997 tuned cars have never really seemed to perform in that measure for some reason

Jean

TB

Interesting data, thanks for posting. Yes it would be interesting to know if this was an independent test.

As far as performance, the RT12 with 650HP and RWD does the 100-200kph in 6.55s, so this car is claimed to be faster by 0.25s with the 700HP kit, are the weights different between the RT12 and tis one? I know the RT12 is quite lightened and 2WD.. ? You are faster than both in fact!

Stummel

Not to bash TB, but he did the run without a passenger.
AMS tests with full tank and passenger if this makes a difference.

For sportec I have seen some tests where they did not reach the claimed numbers in acceleration...
But without a doubt they make some special stuff.

TB993tt

Stummel, you know its not bashing, its pursuit of facts
Do you know if the Sportec test above was done by AMS ?
Even with a passenger if the claimed weight is correct the T70 would be at 1500kg, which is only ~25kg more than mine.
The RTS4 996GT2 based car at 1363kg tested by Flat 6 mag did 100-200kph in 6.2s with claimed 807hp -they didn't take it to 300kph but if the above Sportec acceleration numbers are accurate then this measurement would have been much more telling......

Stummel

I have not seen any test of the T70/80 and I doubt that they would send both cars for a magazine test.

Who knows if they already build more than one prototype car?
Have not yet heard anything of a customer car. Look at the RT12 and you can read plenty about customer cars...

Kevin

I know a fair amount about the SPR1 project.. They are working on car number 3 right now. There is some nice engineering ideas and new manufacturing techniques installed on this car.. Such as 2 injectors per cylinder with twin throttle-bodies.. One can look at the turbochargers and muffler bypasses.

TB993tt

[QUOTE=Kevin]I know a fair amount about the SPR1 project.. They are working on car number 3 right now. There is some nice engineering ideas and new manufacturing techniques installed on this car.. Such as 2 injectors per cylinder with twin throttle-bodies.. One can look at the turbochargers and muffler bypasses.
That's pretty
Kevin, can you establish if these acceleration numbers are calculated estimates or actual tested and if the latter the weight of the test cars ?

Kevin

TB, I know that the car has been on Nardo and a few other tracks. This includes Michilin tires test track. They were testing acceleration and lateral "G" for tire loads.. It seems like all the present tires manufactured in 19's and 20's aren't rated enough to handle the weight and speed..

To answer you question more directly, I will ask this weekend about the numbers and how they arrived at them.

TB993tt

A couple of new additions here:

Ruf RT12 (1500kg) 100-300kph 21.4s
9ff 997 cab (narrow body with hard top 780hp) 100-300kph 17.4s

I am becoming more interested in 200-300kph (124-186mph) times as they do not necessarily follow the 100-300s, here are some:

Ruf RT12 650hp 15s
Gemballa 750 (996tt) 12.3s
9ff 997 cab 780hp 11.5s
RS Tuning GT2 542hp 17.8s
RS Tuning 996tt 569hp 12.8s
Carrera GT 23.5s
997tt 28.4s

Obviously the one that stands out is the RS 569hp 996tt and what I do not understand and find difficult to account for is the effect of aerodynamics and their role over 200kph......

Some numbers dug out from various tests:
Stock 996tt Cd 0.295 CdA 0.58 downforce @ 200kph front -6kg rear +6kg
Stock 996GT2 Cd 0.31 CdA 0.61 downforce @ 200kph front +2.2kg rear +7.5kg
Stock 993tt Cd 0.339 downforce @200kph front not known rear -17kg

The down force which the 996GT2 creates at 200kph presumably increases as the speed increases, how much effect does this have in slowing the rate of acceleration as the speed rises compared to the lower downforce 996tt - how much contribution to the RS 569hp cars stunning 200-300kph time can be attributed to the relatively low drag body ?

In relation to the 200-300kph numbers above, the RT12 and Gemballa must be hampered to "some" extent by their special spoilers ?

These are all fascinating questions (to me ) and must be balanced against the inevitable reality that all of the above engines will heat soak away an amount of their rated hp (with the added body drag increasing that relative rate of heat soak) the aerodynamic dilemma throws another variable into the hat !

I am looking forward to adding Markski's beast to the list

markski

hopefully by next weekend or so Ill have some data....
the 1/4 mile track doesnt allow me to do a 300 KM... so its not easy to do the the run without getting in trouble...
markski

Jean

TB

Interesting data and very interesting questions. I think the two most overlooked things in comparing performance between cars are the weight and aerodynamics effect, people tend to focus more on HP and torque.

I had posted sometime back a topic that addressed exactly these questions, here is the link.
Acceleration Calculations and Aerodynamic Impact It might be too heavy to digest but I will give a practical example in numbers.

Let's take a 993TT with the 450PS kit.
Aerodynamics: 1.93 X 0.34
Acceleration from 200-300kph: 27.1 seconds
The data above is not magazine data, it is from a model that I use to simulate performance and it takes all these fatcors into consideration. Therefore, while the numbers (27.1s) might be a bit off since I used dyno sheets to extrapolate performance, the comparison between bodyworks and their impact should be quite accurate. This is assuming no head wind and the air density being reasonable for around 20 degrees C.

The formula that calculates aerodynamic drag is the following:
Wind resistence at speed:
((Vkph/3.6)^2)x Air density x Cd x Area x 1/2 Mass

So at 200kph
The negative acceleration suffered due to wind:
((200/3.6)^2) x 1.2 x 0.34 x 1.93 x 0.5 x 1650 = (-0.73) m/s.sq
At that speed, this 450PS 993TT is accelerating in 5th gear at 3.0m/s.sq (in a dragless environment), so the net resulting acceleration after the impact of drag would be: 3.0-0.73 = 2.27m/s.sq (this is what you would see on a datalogger)

At 300kph
((300/3.6)^2) x 1.2 x 0.34 x 1.93 x 0.5 x 1650 = (-1.66) m/s.sq
Acceleration in 6th at that point (zero drag): 1.99m/s.sq.
Net (datalogger ) acceleration: 1.99-1.66 = 0.33m/s.sq. approx.
About 84% of the engine power is channeled ONLY to beat drag.

Let us talk in practical terms now. Base is a 993TT 450PS with 993TT drag.
Acceleration 200-300kph:
Stock 993TT:
CDA: 0.66
Time: 27.1s.
Drag at 300kph: 1.66m/s.sq.

993TT with 996TT Body
CDA: 0.62
Time: 24.8 s.
Drag at 300kph: 1.56 m/s.sq.


993TT with 996GT2 Body
CDA: 0.67
Time: 27.9s.
Drag at 300kph: 1.68 m/s.sq.

993TT with 964 N/B (Yellowbird)
CDA: 0.57
Time: 22.5s.
Drag at 300kph: 1.45m/s.sq.

All the above numbers were obtained through data at a multitude of points involving acceleration Gs, rolling resistence, aero drag, torque etc, etc..for every 0.05 seconds, they are not an average.

I can draw a graph of time vs speed and drag showing the acceleration lines and gear shifts etc, same as what a datalogger would, for the above simulations, it will take a while, but idf someone is genuinely interested I would not mind doing it.

I hope this answers your questions

leonsamonas

tb ,,,you're full of sh**..IMHO

TB993tt

A valuable well considered contribution to the tech forum

That just jogged my memory, the 200-300kph which my car ran at vmax when it was at ~520hp it managed it in 19.2s


Jean can you crunch those numbers for what my car running 520hp should achieve with a stock 993tt body and then compare to the actual to see what additional drag I am running ?

Jean

TB
The results on my model are 19.3 seconds 200-300kph based on an estimated 1.96 x 0.35 CDA. You have GT2 flares and fatter than stock tires.
100-160kph: 3.3 seconds
100-200kph: 6.9 seconds
200-300kph: 19.3 seconds
60-130mph: 7.9 seconds

With a stock 993TT CDA of 0.66 your acceleration would have been:
100-160kph: 3.3 seconds
100-200kph: 6.8 seconds
200-300kph: 18.4 seconds
60-130mph: 7.8 seconds