MrTomT

Looks good Greg!
I'm also pretty interessted in these ideas so can't wait to see the end result...
btw, the wheels on that Monaro concept have just about zero travel before they impact the guards
Cheers,
Tom

slate blue

I took some pics while I was trying to get an idea of placement for max aero efficiency and looks. Lucky thing the one place they fit is the best for aero and looks. Here's some of the pics I took.

In this pic you will notice that the profile of the 599 Bonnet is the same as the 928s.















It appears Aston Martin have revised their bonnet vents? I don't really follow them that closely but normally they only use mesh on their road cars, these are more like mine which are more efficient.



Greg

mark kibort

yep, that looks like the perfect place. Looks great!

blau928

Greg,

Looks great..! I would just swap the vents L/R from how you show them in the pics.. That way the vented air flows out the hood, and around the windshield instead of over it in the center as the ducts are now pointing..

Cheers,

BC

I like those alot, even if they are only somewhat functional. I think those and something for the fender pressure would really be good.

mark kibort

you want it to flow over the windshield and over the hood. it lowers the pressuer and adds to the mass flow over the car. plus adds to the effectiveness of the rear wing.

mark kibort

yes, he would need about double the size to be as effective as possible, but I would think they would be functional at most moderate track speeds.

MrTomT

Hope you are getting a 2nd bonnet for this Greg! ; )

blau928

MK,

The low pressure over the top of the car will create lift and reduce overall downforce by the additional lift created by the incremental decrease in pressure over the roof..... Maybe Greg wants this effect... I would not..

Just my $0.02,

blau928

I think these guys were thinking the same thing, as well...

Koenig-Specials 928

Those vents are similar to the ones on the front-engined V12 Ferrari 456GT

mark kibort

Thats really not true. you cant think of it like a venturi, but like a wing. venting the air flow from the high pressure side to the low pressure side, actualy reduces lift. in this case, you add air to the air stream, it doesnt go any faster, but it becomes more dense, and that air that normally would be traveling under the car, is now less dense, but at the same speed. (barring complicated venturi tunnels). this is why all the cars in the picture have the vents to go OVER the car, not to the sides. take a look at ALMS P1.P2 and many other cars today. This is what you want.


QUOTE=blau928;7223709]MK,

The low pressure over the top of the car will create lift and reduce overall downforce by the additional lift created by the incremental decrease in pressure over the roof..... Maybe Greg wants this effect... I would not..

Just my $0.02,[/QUOTE]

blau928

[/QUOTE]

Hi MK,

I wasn't thinking of it as a venturi, but the principle is the same.. Especially as a wing.. The air going over the longer side creates lift, not the air going under the shorter side of the wing. The air being directed from the high pressure zone in the nose to go over the top of the roof will increase density of the total air mass, but because of the long shape of the passage the air has to take over the roof, it will increase in speed, and decrease in pressure. It has to, as this is basic physics... Same with any wing, aircraft, or racecar.. (Venturi shape is just two long sides of a wing anyway)

I looked at the cars, the Alpina clearly is rounting the airflow along the bonnet, and around the side of the A pillar, as well as the Audis, and the other cars in the ADAC cup pixx. Even the F599X has a slight angle towards the A pillars... Most of the cars do, with the exception of the Volvo from K Pax you posted earlier.. But, even that bonnet vent is horseshoe shaped to vent some air to the sides so it goes around the A pillar..

Either way it is looked at, the air flowing over a long side of a wing will increase in speed and be lower in pressure than the air flowing over the short side of the wing. this is true for all wing shapes, and unless some new/recent discovery in physics, I don't recall it changing.

Maybe I don't get it, and you can explain a bit more how the increase in air density over the roof will increase the presure going over an airfoil shape (the roof).. BC, to me, it seems that the dense air mass would have to decrease in pressure and increase in speed to go over the roof... Not increase in pressure as it went over the roof, as this contradicts the bernoulli principle.. The air will slow down as it gets more dense, which will be just aft of the bonnet vent where it will merge with the air coning over the nose along the bonnet.

The venting of the air that would have gone under the car to the hood vent, decreases the amount of air going under the car, and will (depending on shape fo floor etc) help to have less turbulent airflow under the car. However, the air that went from that place, now going over the roof means more air going over the roof... The roof is curved, and this will decrease the pressure of the air going over roof, as a result of the increased speed of the airflow, and cause lift..

If it goes around the A pillar, you will not have the effect of lower pressure over the roof, but around the A pillar instead. In addition, the former low pressure where the hood vents are will have a higher pressure from the air coming up and merging with the air going over the bonnet, and slow down... However, this total mass of air, now denser, still needs to get from the bonnet to over the roof.... So, the cycle has to start all over again, and as the air mets the roof, it will increase in speed, and decrease in pressure....

Again, maybe I'm missing something....?

blau928

The ALMS P1/2 car, similar to the maserati you posted, has the vents angled going over the inner side of the front fenders, and then over the side frontal area of the windsccreen. On a normal car, this is where the A pillar would be....

I spent a bit of time with the Lowes team at the ALMS race as a guest, and the P1/P2 cars are designed very differently that a sports car. The air seems to go over the top, but in fact you have to look closer, as it does not go over the tallest part of the car, which would be over the driver's head... It goes over the shorter section, which is between the cockpit tub, and the outboard pods containing fuel tanks, and radiators etc...

You can see it in this pic of the Acura LMP2.. The nose is pointed, and the air channels direct the air around the center pod, very little over it..

slate blue

By Mark Kibort

Thanks!

By Mark Kibort

Agreed, although I don't have a rear wing, this is the principle of what I am applying, the 599 has a spoiler like the 928S.

By Mark Kibort

Yes, bigger would be better but this is the trade off between street and track, just like a big splitter would be better for average race speeds but impossible to use on the street but the 599 GTB still has impressive downforce figures albeit at fairly high speeds. I think what must be considered is the canceling of the lift the 928 has as stock, noted that this is minimal for an older design.

Greg