Aerodynamics of Jim's Ferrari P4/5

Hello,

The other day I saw a video interview in which Jim mentioned a very interesting tidbing about his car's aerodynamics. Namely, the exhaust - besides acting as a sort of active aerodynamic aid by blowing on the rear wing or what have you - is used to fill the "void" in the back of the car, a place where vortices form, create vacuum, and slow the car down, and have a positive aerodynamic effect.

Did I misunderstand this? If not, what is this termed? Can anyone supply any other information such as where this is normally used, other cars that use it, and what sorts of benefits it has?

Thanks in advance!

 

Jim was probably referring to "induced drag" as result of the vortices. The exhaust system acting to reduce downstream vortices would have the positive aedodynamic effect of reducing induced drag, one of the components of total drag of the vehicle.

 

We spent three days in the wind tunnel on the P 4/5 project. The first time was with my Enzo to establish base lines.

The second was with a wind tunnel body of P 4/5 on the Enzo chassis that we could change with foam and filing.

Our goals were to balance the down force, lower the drag and shape the openings to provide proper entrance and sufficient exit. I was surprised at how small a tune made such a large difference. We were able to reduce the inlets considerably and tune out wake vortices's with the mirrors for example.

The idea of the exhaust chimneys was to smooth out air flow disturbed by the cockpit and enable more air to flow to the wing.

We copied the design of the Ferrari 2003 F1 exhausts. The exhausts are also ceramic coated which seems to make them flow better.

All in all P 4/5 is more balanced aerodynamically than an Enzo, has less drag, and more down force.

We're going to put Dino Competizione into the wind tunnel next week and it should be interesting to see what her aero is.

We won't be foaming and filing her...

 

where do you do your tunnel testing?

 

Pininfarina's wind tunnel in Turin.
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That is just so cool!

 

I can't see what the wheels are rolling on Jimmy? Are there drums in the floor, or something? And how are they keeping it still?

 

http://arc.pininfarina.com/english/impianti_galleria.html

 

Ah ha........

Thanks for the link. That clears it up. I bet it was kinda weird the first time you saw the car just sitting there with the wheels moving. Did you ever think it was gonna rocket off the belts? Or wait a minute, it looks like that picture is of your car on the old system with the rollers, but the one in the link has it on the new one with the belts. So they used both then huh?

 

Thanks, Jim. I found the video and this is the line that had me curious: "...it [the exhaust] backfills the low pressure area made by the car..."

Any idea what the percent improvement is for a system like this as opposed to not utilizing this method?

Oh, and here's the video: http://www.garage419.com/episode/419_20080212 (kinda annoying host, but bear with it)

 

great thread.

the P 4/5 is an Automotive Icon of the modern age.

 

With Aero everything makes a difference and small differences add up.

 

Thanks all!

 

Where do you do yours, Brian? Swift in California?

 

Lordy, just about everywhere:

Lockheed in Atlanta

Langley in Virginia

ARC in Moooresville

Gurneys in CA

Lola tunnel

Williams tunnel

Swift tunnel

Shrivenham in UK

First two are full scale tunnels (fixed floor)

rest are model tunnels (40% usually) with moving floor

Never in Pinin Farina tunnel

A lot of work now is CFD

 

For Jim,

Is there any chance you would release the actual aero data from the P4/P5 project to the public? I would be very interested in knowing the actual numbers. I could trade for LMP car data, like the Audi and Bentley and Lolas.

 

I'll talk to PF.