High speed aerodynamics

[Jesda]

When traveling at 120mph+, is it better (for reducing drag) to open the vents and prop up the sunroof for better air flow through the cabin, or should they all remain closed to prevent lift?

[DrewQ45]

When traveling at 120mph+, is it better (for reducing drag) to open the vents and prop up the sunroof for better air flow through the cabin, or should they all remain closed to prevent lift?

If not too hot, I usually put the fan on manual by pressing just the fan button then change the mode to blow strictly from the front vents. Otherwise I just run the AC. I've always read that using the AC at highway speeds is more economical than opening the windows which creates serious drag.

[elwesso]

If not too hot, I usually put the fan on manual by pressing just the fan button then change the mode to blow strictly from the front vents. Otherwise I just run the AC. I've always read that using the AC at highway speeds is more economical than opening the windows which creates serious drag.

Agreed.. especially if you have tinted windows where the AC doesnt have to work as hard!

Seeing how the intake for the vents is just below the windshield wipers i dont see how that would have any effect, however opening the sunroof would liekly cause a disturbance on the roof line.....

[heywier427]

im pretty sure hes asking what will help the car stay planted at high speeds. may i suggest a 4 foot wing off of the pos honda down the street!

[elwesso]

I know.....

Actually the Q45t spoiler reduces the coefficient of lift significantly... I cant remember exactly but its significiant...

A 90-93 Q45 had the lowest CoL of any luxury car in 1990

[Q45tech]

When you are averaging 150 mph and getting 5.5-6.0 MPG not sure if the T trunk would help much.........the down force might hurt MPG?

[elwesso]

http://q45.spilky.com/rtq45m30/scan0040.jpg

Look at the last paragraph... Rear trunk spolier reduces coefficient of lift from 0.21 to 0.14

[Q45tech]

Yes the lift is reduced by applying a significant downforce on the rear wheels.....reducing ~~400 pounds of lift to maybe 250 pounds........lift transfers the CG to increase steering capacity.

Install an active suspension ride height potentiometer and measure the lift vs speed.......steady speed vs acceleration.

[DrewQ45]

I seem to remember a certain someone saying this recently....

Someone on this forum needs to go to the salt flats with a GPS.

Back at ya!