Damage sensitivity(diveplane and louvre damage)

[chernaudi]

For anyone who paid attention to endurance races(especially Petit Le Mans), the fender louvres, on the Audi R8 especially, tended to become badly damaged by the end of the race due to tire pickup. This also happened with the R10, and almost all the other prototypes. I've heard that the R10's front fenders being more tightly fitted over the tires has lessend the damage done in longer races, but also contibuted to them becoming damaged in some sprint races.

What I'm trying to say is how badly does this effect the car's handling. I've heard that having holes in the top of the front fenders vents air out of the wheelwells, and on ground effect cars, it improves the functioning of the front diffuser. Appearently, the FIA and IMSA learned of this, and to counter this, the teams installed louvres in the fenders. This was done to get the bes of both worlds, more downforce from the louvres, and wheelwell ventilation. And diveplanes are also esily damaged.

In other words, how badly does this effect the car's handling? I know that this varies from car to car, but the R8 and R10 seem to go about their business with this damage as though nothing happend. Does anyone have an answer to this?

[skycafe]

I often have wondered, since it is an advantage to be missing some louvers which would allow increased airflow, if they are made extra flimsy?

robert

[tux]

i always thought the louvers were there so you couldnt see the wheel when looking down on the car

[broadrun96]

I had heard on speed that the damage usually resulted in better front downforce and removal of broken and/or loose fins in the pits would result in time/stop and go penalties. Not sure the exact specifics of how the opening of the vents would help but I'm sure allowing the air out has got to help front downforce and thus turn-in. Also no idea how the damage would be harder on the car on sprint races, except they could be running a softer tire and thus more marbles coming off. Only really noticed it alot on the Audis, but really can't remember alot of onboards from the Dyson Lolas.

[MulsanneMike]

You're talking about a 2-3% change in downforce and I suspect most drivers can certainly compensate for that. Wouldn't read anything else into it. Also consider there is a corresponding drag increase. If the cars looses them in the race it is of little consequence (as we've seen). But if you're in the wind tunnel hunting for those percentages you don't hesistate to tack them on. And note the regulation states a minimum louver area (25 sq. in.), not a maximum. So clearly they dirty up the car a bit and the aero guys would be leaning towards not using them at all if the regulation wasn't in place (especially at Le Mans). The louver minimum area came into being after the CLR flips as a way to shift downforce forward (coupled with the reduced rear wing endplate area regulation).

[chernaudi]

As I mentioned, this doesn't seem to matter at higher downforce circuits. At LM, Audi usually uses different louvre panels(they are removable/interchangable), as did Bentley, to reduce drag, and reduce the chances of doing damage to them with tire pick up.

And this was an effort at increasing front downforce. This is why Audi had such an advantage in the aero department at LM 2000-Panoz and almost everyone else tried to convert their cars to this spec(often with negative results in the high speed handling department). Meanwhile, with the R8 being a all new car, Audi built their car to the specs. However, this seemingly went kinda out the window when the ACO and IMSA approved rear wing endplate extensions like those on the R8 and Pescarolo in '02.

None the less for Audi at LM, the louvre deal meant little at LM, as they wouldn't run the high downforce louvres at LM except in heavy rain.

[canam]

Although louvre damage has an effect, it is generally small. Additionally, it is an effect on most of the P-cars--as they tend to have damage through the race from the pick-up problem. Some teams will put a metal screen under the louvre to protect it.

A diveplane on the other hand is very critical and can make the car's handling change dramatically as they can add a lot of downforce. As damage also tends to result from contact, it, therefore, does not affect necessarily all cars. More understeer overall or the car's right/left front balance can change. On many tracks (and most in the US) diveplanes are a must.

[AU N EGL]

Originally Posted by broadrun96

I had heard on speed that the damage usually resulted in better front downforce and removal of broken and/or loose fins in the pits would result in time/stop and go penalties. Not sure the exact specifics of how the opening of the vents would help but I'm sure allowing the air out has got to help front downforce and thus turn-in. Also no idea how the damage would be harder on the car on sprint races, except they could be running a softer tire and thus more marbles coming off. Only really noticed it alot on the Audis, but really can't remember alot of onboards from the Dyson Lolas.

The tire wheel wheels are high pressure air zones, without the louvers there would be undesirable aero lift in that region. The louvers are too allow the high pressure air to escape from the wheel well.

When the louvers are broken from road clagg being tossed up from the tires that is OK. as long as the carbon fiber louvers dont shread and cut tires.

Any car that is enclosed body will have aerolift in the wheel wells. and almost all race cars have some sort way for the air to escape.

[I love 04s]

I think too much is being read into this. The difference in aero performance is probably equal to having more bugs on the headlights at night! Anyone remember Mid Ohio 2005 when Zytek lost a front left diveplane (pretty substantial piece of aero on the 04s) as well as an entire wing end plate - both on the same side of the car???!!! When asked over the radio whether he had any handling problems - Shimoda reported that he had noticed anything was missing....

I can perhaps believe it gives you tiny fractions when the drivers are on the edge in qualy....but in the circus of a race scenario when traffic is left, right and center a damaged/broken dive plane is the last thing teams would worry about.

[chernaudi]

Why not-Audi didn't seem to care, and other than looking, the drivers probably didn't notice the difference. Also, when you have so much downforce dialed in to a car, it takes longer for the damage to become noticeable. For instance, when you're at a track like Lime Rock, Mid Ohio, etc., you'd run a lot of downforce. At LM, you want to run as little downforce as you can get away with. In other words, damage that's of little to no consequence at downforce circuits can cause handling issues at faster tracks.

[MulsanneMike]

Originally Posted by AU N EGL

The tire wheel wheels are high pressure air zones, without the louvers there would be undesirable aero lift in that region. The louvers are too allow the high pressure air to escape from the wheel well.

When the louvers are broken from road clagg being tossed up from the tires that is OK. as long as the carbon fiber louvers dont shread and cut tires.

Any car that is enclosed body will have aerolift in the wheel wells. and almost all race cars have some sort way for the air to escape.

The louvers are solving two issues...first as you mention there is the high pressure build up within the wheel well. This air has a tendancy to want to migrate to the underside of the car reducing the effectivness of the underfloor. Remember that pressure moves from concetrations of high towards concentrations of low. That's the reason for all the intricate ducting exiting the wheel well, so that you can bleed off some of that pressure to discourage it from going to areas you don't want it. And that's where the fender comes into play. Typically the top surface of the fender generates lift, so it becomes a natural area to place a louver to vent off some of that wheel well high pressure area. You reduce the top side fender lift while also reducing the wheel well pressure build up. I'd suggest that there's also a happy median between louver size (area) and performance gain. You make your louver too big (say like when tire debris punches out the louver panel as we've seen on the Audi) and it becomes so draggy to not be viable for what it does. And at places like Le Mans the overriding concern is drag, therefore you run as little louver as you can (up to the regulations minumum 25 sq in).