All looks pretty negligible at first take.
in terms of aerodynamics, that is a massive change - ever seen how little an aileron deflects on an airliner to induce bank? Of course, my sketch just illustrates the principle, it's not to scale.
I get it for a plane going in excess of 100mph but at highway speeds? I will keep my mind open. What length tufts do you suggest?
not on the 77 paris GTS to the best of my knowledge. first appearance i believe was the millechodi concept 308 GTB unveiled at the 77 geneva show. your 3 guesses makes sense to me since it was on the boxer which wasnt available as a targa.
ever move the little 1 inch flapper piece that deploys in front of an open sunroof at highway speeds? it can make a significant difference. you see these airfoil on all sorts of vehicles, semi trucks, back of station wagons and rally cars were speeds are often below 100mph my hunch is it extends the airflow off the roof and delays the air from tumbling down the rear window immediately in between the flying buttresses. the question remains who knows how effectively it actually is....
Really good food for thought, that I (personally) had never considered. My passengers frequently comment on how still the air is in the compartment, considering that the top is open.
I think this is due more to the upturned lip at the top of the windshield on the GTS. It serves the same purpose as the small deflector at the front of open sunroofs.
I think the upturn at the front's main purpose is to lift the airflow over the transversal cut line between the w/s frame and the targa top. If there was the slightest misalignment (I know how highly unlikely that is on a Ferrari body), it would make a lot of noise because that area is a very high wind speed zone. The upturn seems too small to me to have any significant impact over the flow of the entire "hole". A rise in trailing edge however has a big upstream effect. Anyone wants to file off that lip and check the effect???
I would still like to fine some software and a good 308 3D CAD file to see what happens at various speeds and with different body configurations. Such as how does the euro air dam differ aerodynamicly from the US model.
The roof spoiler actually sits slightly higher up than your diagram shows, putting it into a better position to scoop air downwards: http://pictures.topspeed.com/IMG/jpg/200909/ferrari-328-gtb-21w.jpg http://pictures.topspeed.com/IMG/jpg/200909/ferrari-328-gtb-11w.jpg
Yes, quite a bit you are right. My diagram is not to scale, just to illustrate my toughest in terms of geometry. It seems to me that it would indeed deflect some air downwards towards the engine bay cover, at least in a car with a closed roof. It also looks as if it's designed not add to the frontal area (judging from the images).
Creating such a file requires a super-precise scan and several hundred hours of professional free-from CAS work. I doubt you'll get that for free unfortunately ... And any simulation of an approximative surface is irrelevant I am afraid. Why don't you contact Pininfarina and simply ask them? I am sure they know. Question is if they are willing to go and search for the information, and if they are allowed to share it - Ferrari may not give them right to do that. Or ask Ferrari directly
Like I said pages ago, I used to do this kind of stuff for a living back in the 70s and 80s. Also did experimental work. Here is a suggestion. One of you with a car w/o spoiler, tape some tell tales to the rear edge of the roof and go out and driver the car at highway speed. Have a friend video the car from the side and rear. Next, one of you with a car with spoiler go out and do the same thing. Maybe also tape some tell tales to some of the rear deck vents. This will make a fairly decent flow visualization of what is happening. Then post the videos here. A little bit of data would go a long way.
interestingly, it seems the roof spoiler was standard on the 208 turbo's and an option the 308 qv's. That may imply that the 2.0 turbo engines needed help with cooling, where as on the 3.0's it wasn't as critical. As the 328 series had the spoiler as standard, it was either a case of Ferrari feeling that the 3.2 engine also needed help with cooling or they just thought it looked good. The GTS cars create an interesting twist to all this though, as others have noted. The lip on the top rail of the windscreen pushes the air up and over the cabin area and would seem to divert the air slightly away from the spoiler, so maybe it is more cosmetic than anything else afterall. The only way it could ever be properly figured out would be to either ask the designer himself as to the thinking behind the spoiler and get him to show the evidence for requiring it (most unlikely to happen), or place full size cars in wind tunnels and do real testing of the aerodynamic differences with and without the wing, for both GTB's and GTS' models (again, most unlikely to happen, but would be interesting). As for computer simulations of aerodynamic flow over the cars, the problem is that you need an incredibly detailed computer model of the car to get any true, accurate result. It's too easy to introduce errors which could then corrupt the results.
As the 328 series had the spoiler as standard, it was either a case of Ferrari feeling that the 3.2 engine also needed help with cooling or they just thought it looked good. Phil, I don't know about your country, but it France and Germany at least, on the 328 the spoiler was not a standard, but an option: you had to pay extra to get it (I even have the prices, but I don't wan't to bore anybody with those details). As far as I remember, only the United States got the roof spoiler as a standard, not as an option?
Phill, as has been noted in this thread, you don't need a wind tunnel or computer simulations to do some basic tests and get some data.
The assumption that the spoiler helps cooling really is noting more than just that, an assumption or speculation that is the product of this thread. I could argue convincingly that it hurts cooling. But without some rudimentary data that argument would be nothing more than additional speculation. I could probably argue more intelligently on what the air flow with and without the spoiler might look like but whether it would have any effect on cooling or not, I would not care to venture. And on a GTS where the top comes off, forget about it. There is no way the flow over the car with and w/o roof panel installed is in any way going to be similar.
The little spoiler you see on the back of older station wagons and similar vehicles is to prevent exhaust from being drawn into the passenger compartment when driving with the rear window down. I used to have a full size Bronco, and with the rear window down, the exhaust was almost overwhelming unless all the windows were also down. Adding a station wagon spoiler to the back of the roof solved that problem, and also kept the rear window clean(er).... Today's vehicles have all sorts of aero "tricks" for all sorts of purposes; e.g.: flares and side skirt shapes to use aero to deflect road grime of the side pannels, little shapes and forms to prevent air column (Helmholtz) or even panel resonances, etc.
There are only aesthetic similarities. It has a very different skin. Different dims, different frontal area, huge rear lip spoiler, wing mirrors etc.
