13 year old son asked if my 2000 NB Miata had better aerodynamics with the top up, or down. Now, how awesome is my son for even caring, and does anyone know how dropping the convertible top affects lap times and such?
PS, my answer was "more power with the top down because I can turn the AC off" I was more amused with my answer than he was.
Miatas are faster in track with a hard top due to aero. I suspect that the soft top provides similar aero benefits.
At the (now defunct but still missed) Phoenix International Raceway a Spec Miata went 115 on the oval with the hard top and 105 without.
My impression is that, as far as drag is concerned, hard top better than soft top better than top down.
I will tell him the answers when I take him to school in the morning. Top up until we get off the interstate, top down a few blocks before we get there. He likes to make an entrance but doesn't want to mess up his hair. I just like to finish my commute topless as it gets too dang hot during the day.
Thanks yall
Top down gets the drag advantage if you also remove the windshield. 
Autobild (German rag) did independent testing and came up with the followind COD.
Top down .45
Top up .39
Hard top .37
And your son is a fine young man.
Not a NB, but still relevant...
In reply to DaewooOfDeath :
Right?!?
Time for a coast-down experiment. 
You'll need to log in to post.
