I havn't forgotten. My contact is still working on it as I gave him quite a long list of questions. I received an email a few days ago saying he was still on the case but needed to check info with other depts (some on holiday). As soon as he has all the replies, and I get them, I will post for all to see.

 

I raced a STOCK CGT rolling 50mph/80kph beat it until 125mph/200kph then it passed me...Here is my vid accelelartion

http://www.youtube.com/watch?v=FU7Eb5S75qo

I know it is not accurate but my 100-300 AROUND 26sec

1 Bar and pump gas

 

maybe the test car ran a slightly bigger diameter. i haved seen test cars that looked like 18" but fat tires.

 

The 997 GT2 press kit lists 0-300 km/h in 33.0 sec. I wonder if that's accurate? If so, that's pretty close to what you guys are seeing with the CGT. That's interesting with 605 vs. 530 hp.

 

Hi Bill,

The question of the rather modest CGT acceleration at high speeds is very puzzling, especially since the car is a beast at lower speeds. After doing some research I think the answer is quite obvious to me now..

The CGT is one of the cars to have the highest downforce in any "mass" street car produced, except the Koenissegg and another one I believe.

Basically it puts around 200 lbs of downforce at 124mph and a whopping 640 lbs at top speed. In comparison the 997turbo puts 35lbs at 124 mph and the 997GT2 puts down 64 lbs at 124 mph.

I don't have the data but I would think that the GT2 would see around 3-400 lbs less downforce than the CGT at top speed.

All that incremental weight coming from increased downforce, factored into the CGT's power to weight ratio would put it in GT2 territory, and then one needs to add the worse CdxA of the CGT over and above the downforce handicap (or advantage depending how one looks at it).. Does it make sense?

 

Very interesting point of view, the effects of downforce. This downforce would presumably increase cornering ability. How do you then explain the Nordschleife times between the CGT and GT2 being so close, for cars so far apart in power? And, how can you get perfect aerodynamics (to generate the downforce in the first place) in a cabrio? in other words, following this theory, cornering performance should degrade massively once you remove the roof panels.

 

Avoyvoda,

Long time no seen!

Certainly the main objective of this massive downforce on the CGT is to improve handling characteristics and mainly make it a safer car. With increased downforce many other things get into play and must be balanced, suspension, tires, brakes (changing weight bias with speed due to Fr/Rr weight ratios) etc..

I cannot comment on the 'ring times posted by Walter R., he is a factory driver after all, however there is so much more coming into play such as suspension and chassis dynamics etc.. Neither power, nor downforce alone will mean much in determine who should do better I think.

The CGT 's impressive downforce does not come only from its upper body, but rather from the work down under the chassis, which has reduced considerably lift, therefore at high speeds, the downforce created on the upper side of the car is not fighting the lift created from air passing under the car, with an overall big improvement on downforce. This was used in earlier F1 cars through the use of some ducts streaming air upwards from under the body length, until those ducts were banned by the FIA because once they hit curbs etc, those ducts broke, and the F1 cars became very unstable.

This has the advantage of increasing impressively the downforce without impacting drag in a great way, like what a big sloped wing would have. This is probably the most difficult part of balancing downforce and drag on your car I think, but looking closely under the body for improvements would certainly be a big plus. I don't think roof panels help downforce in any way??

 

Jean, I was thinking the same exact thing. Motor Trend Magazine (October 2004) performed high-speed coast-down tests in two directions to measure drag at 200 mph. Here's what they found:

Enzo: 837 lbs
Ford GT: 874 lbs
CGT: 889 lbs

BTW, why is the new GT2 nearly as fast as the CGT around the ring? The answer, I believe, is based on several factors:

1. Less drag in the GT2 (but possibly less high-speed stability than the CGT).
2. More and flatter torque in the GT2.
3. The CGT's long wheelbase may be better suited to long high-speed sweepers than for tighter lower-speed turns. That's kind of what the CGT chassis was designed for originally.
4. The GT2 has very predictable and controllable oversteer. I don't think the CGT can be as easily controlled at the limits.
5. Better tires on the GT2?

It would be interesting to compare these CGT specs against the new GT2:

Wheelbase: 107.5"
Track, f/r: 63.5"/62.5"
Length: 181.6"
Width: 75.6"
Height: 45.9"
Ground Clearance: 3.4"
Weight dist, f/r: 41%/59%

 

I'll take a Ford Gt please!!

 

With a 5" ground clearance, you make a good point. You'll just need the room to open the doors; and be sure you're OK with the engine note and build quality.

But that's another thread.

 

Good points Bill.

The Nurburgring is such a diverse track that it would be almost impossible to make a wild guess. Overall gearing is one to also take into consideration, chassis stifness is another for which I don't have any data, etc..

 

trim out the car for high speed - disconnect the rear spoiler, and see what difference that makes.

A good friend, whose family has been racing Porsches in all their varieties since the earliest days, and who has driven virtually every model ever produced and owns some of the more outrageous cars that he drives really hard on the street, remains surprisingly level headed about the C-GT. Yes he loves it, and has driven the **** off it on track and street, but he can't see that its worth so much more than a Gallardo, which is interesting, given his heritage.

I wonder if history will show the Enzo and the C-GT to be over-hyped - at Fiorano the 430 Scud laps faster than the Enzo, the GT2 snaps at the C-GT at the Nürburgring.

I don't 'know', but I think that 'top side' downforce (the result of wings) has a greater effect on speed and acceleration than 'Mr Suckee' (underbody configuration). A high downforce wing configuration increases resistance. Perhaps some NHRA asfficionado would care to comment on wings on dragsters.

R+C

 

Time for a change of meds.

Gary

 

For increased downforce using add-ons, you typically have to increase the angle of attack or the size of the aerofoil, both of which are very detrimental to drag. Whereas reducing the lift from underneath impacts downforce much more than drag.

A magazine test of a 993GT2 with, and without, the rear wing resulted in a 1 second+ difference (close to 250 feet distance) in acceleration up to 270 kph (<170mph). Keeping in mind that most of this difference comes at speeds above 125 mph or so, the impact is quite substantial. Their estimated downforce created by that wing at max. angle was about 400lbs (included banana extension).

In case the Nordschleife is not probably the best indication of how capable a car is, here are the fastest Hockenheim lap times as tested by Sport Auto. This track is recognized to be one of the most difficult for any race team as a result of its very difficult balance between downforce and speed.

 

It seems that the sub 28s 0-300kph as Porsche claim is indeed possible. This guy has been saying he can get there for a while and has now proved it.

Now got to figure out how his car accelerates much faster than the others which have been tested

http://www.rennteam.com/showflat.php...fpart=all&vc=1