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Discussion in 'Technical Q&A' started by benjie, Dec 1, 2003.
Too fast, too furious, too expensive, too stupid, tomorrow.
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Yeah sure .. ! Who do you drive with in Sunday Morning ? I used to go a lot to those morning drives but not for the last 2 years as I have trouble waking up
So I assume you drive a 550 ?
Mines are the Brembo 8pot with 360mm disc
Sorry, but what I said is correct, what I did not say left room for people to misinterpret what I implied.
I was not trying to imply that the GT does not A) use, nor B) posess copious quantities of downforce obtained from underbody surfaces.
I was indicating that the wing and the undebody were taken as a single system and co-optimized.
Throwing a wing on a 360 does not use this co-optimization, and will result in less tham optimal downforce and or understeer.
Note to the casual observer: the air channl runs the entire underbody surface of the road car and is fead air from the center of the nose. The splitter on the GT blocks a lot of air from entering teh underbody area, so the GT uses some air from the front, and more aire from the sides. The underbody pannels need to be different to allow the side ways air to flow laminarly to the diffuser to gain maximum downforce. The road cars, underbody front section does not have a 'good' shape for this airflow.
As well it should. But here I think Ferrari could habe made a cap/washer that would habe sealed the plugs where the screws hold the underbody pannel on.
And if you look at "Race car aerodynamics; the science of speed" Joseph Katz on page 208 figure 6-41 shows the influence on the rearward position of the wing and how it interacts with the underbody tunnels.
[QHOTE]The flared side skirts of the stradale and GTC cars, help create more pressure differential from over to under the car, by improving the floors efficiency.
It is advantagous to get downforce from the floor, as it has a low drag penalty compared to a wing.
The wing is a good thing for all 360's, as they all tend to be taily at high speed and when braking heavily, especially as the suspension gives significant rear toe out on droop, and the wing helps keep the back level. The wing is used in conjunction with the adjustable front splitter to achieve a balance. The GT even has a removable front panel in the front bumper, so an engineer can chose to alter the air flow to the floor to achieve the drivers requests.[/QHOTE]
Sounds like the long a-arm geometry of the F355 would have been superior here over the short arm 360 approach.
So do I.
One more thing:
Perhaps the FIA or ACO have rules about the wing extending beyond the rear bumper. (Based on the ricers around here) road cars have no such limitation! By placing the rear wing such that the lowest pressure point (1/3rd back from the front of the aerofoil) directly above the rear bumper, that low pressure region can extend down the back of the car and accelerate air in the ventruies, magnifying the underbody aerodynamics.
But a caution:
Race cars with heavy aerodynamic loads, and expecially when they obtain this downforce from the underbody, are extremely sensitive to the pitch of the car. See page 192 and 193 in "Race Car Aerodynamics; designing for speed" Joseph Katz (again).
So I go back to my original position: if you like a wing, and don't want to return the suspension to utilize its downforce fully and safely--its rice--but go ahead--its your car. If you want the wing to alter the performance envelope of you car, then go ahead--also--but arm yourself with the best availabile litterature, and get the job done right.
For the money you are better off having a spoiler and airdam engineering together by a company such as Pennon Composites. They do great work and will actually help your car.
Not getting into a slanging match, but you said.....
"Aerodynamic note: The 360 GT is not allowed to utilize underbody aerodynamics and therefore HAS to use above body aero to be competitive."
The fact that the 360 GT has a blanked off front bumper, means the floors are used MORE, as a greater vacuum is created. This leads to pitch sensitivity problems, but are manageable.
That's why I said you were incorrect, and it leaves no room for misinterpretation. I actually didn't even comment on your other theory about wing placement, which is fine, by the way!
The toe change on 355 rear is equally as bad as a 360, but the roll centre on the 360 is slightly better.
If a wing is needed for the 360 is still inconclusive for me I have driven my CH now with Hoosier slicks in anger and the car is a dream I have not had the data logger on so I can not support my claims with data but the car is super fast - I will go to Portland next and hope to have the DAS system working by then
I experience the nervousness in the back during hard braking into Turn 2, i.e. from 140mph down to 60+mph scary - surprisingly it was not such an issue with the Stradale I checked the rear toe-in for both cars CH 2.2mm vs. CS 3.0mm Phil is spot on with his advice and that is what I will do next (besides softer springs)
PA is a very technical track with turn 1 taken at around 150mph being the highest speed turn; just as disclaimer but I still have hard time to see what band aid the wing is and what it should solve besides the one problem above
If you have a 360CH your data is being constantly recorded whether or not you use the pit lane transmitter.
It's just kept in huge files bookended with ignition cycles. It can be extrapolated and read quite easily (kind of!), But it's memory is limited. Basically, they usually hold about 1 hour of running data, but this includes warm up time etc, so if you've done something you're interested in in the last hour of driving, get the data out now.
You can just remove the large DAS box behind the passenger seat area and take it to a race team and they can plug it into one of their cars and remove it all if that helps, they don't need the whole car.
The wing helps a surprising amount under braking, even at quite low road speeds. Rear toe needs to be high as mentioned...about 6-8mm total is fine, more if needed.