Hood Extractor for Downforce

[The Radium King]

well, make the opening too small relative to the front opening and air will have to compress to flow through and most likely get cooling issues as you reduce airflow over the rad. not sure what the issue is with a larger opening; presume air would expand and have less force to oppose any positive pressure over the hood so perhaps again reduced airflow. w the porsche gt3 vent the output is about the same size as the input.

w the 911 rsr posted the vent is quite big - no side rads on this car so there is one big front rad and opening to match. not sure what is up here; i think the way it is set up (airflow back at an angle vs directed straight up for downforce) i think they are looking to actually shorten the travel distance of the upper airflow - for all intents the nose of the car is shorter. lots of trade-offs here that i presume they have addressed - the bigger front rad i presume creates more air resistance than a smoother shape, and the increased airflow over the top of the car (vs slamming the air straight upwards) will increase lift (although not as much as the travel distance has been shortened) but reduce air resistance.

this additional airflow over the top of the car interacts with what is hanging off the back; again downforce vs lift. a big wing hanging off the back will create downforce, while a 'spoiler' (gurney flap?) is designed to kill airflow; creates dead air in front of it which forces the airflow over the top of the car to delaminate from the car and kill the lift effect. this delamination takes work, however, too much and you increase the energy required to push the car through the air. of course a wing and a spoiler work in conjunction; spoiler has to be in clean air to work.

final thought would be to tune the car to the track you are on; are you going so fast that the aero aides are slowing you down (ie,, a rear wing takes more force to push through the air as speed increases)? or is it a more technical track with lots of turning where you want mega downforce at the expense of top speed?

regardless, i wouldn't be afraid of playing w aero; faster is faster or it isn't. and if you increase downforce on the front such that your rear now feels too loose, don't devolve, just pin the rear down better.