Can't see video on my phone. OP mention that similar results are observed on other convertibles.

My hypothesis: the top down does lower the center of gravity. There maybe some negative effects on aerodynamics as well. However, tsukuba isn't a very high speed track, the aerodynamics factor likely did not matter as much as the center if gravity.

 

Not buying it, CG height change should be negligible. It would not noticeably affect cornering capability.

Besides, a non-negligible drop in CG height requires a complete re-tune of the suspension in order to optimize it to the new CG.

 

Having the top down has 0 negative effects. the car creates more than enough downforce for the speed that its driven. With the top down, as said before it creates a negitive drag coefficient in the center of the car. think of it like this, what is easier to slide on a hosed down tarp or a dry tarp? the air in the middle of the car acts like a roof, but lets the air coming off the windshield pass over it easier.

 

A few things here:

1. I'm not convinced that the S2000 makes any downforce, stock. Really, few production cars actually make downforce, and even then they are likely either exotics or have some big-ol' wings on them.

2. I'm not sure what a "negitive [sic] drag coefficient" is and I'm not getting your analogy.

3. Again, data from wind tunnel testing tells the whole story. For those that want to find out, pool up some money and rent a wind tunnel for a few hours. Otherwise, all we're doing is guessing. With that said, some guesses are better than others.

 

In a drag race with 2 s2000's with equal drivers the car with the top down will lose.

 

track times arent conclusive here...a good wind tunnel drag coefficient test would be the most certain way to find some valuable data here.

It has been proven time and time again that the S2000 has less drag if the top is up vs down.

 

maybe this is because with top down there is a better visibility and better feeling which can lead to a bit of better driving.

 

Good point.

 

 

I think billios has it right (though not in the sense that "more drag => more downforce"). Spoilers on aircraft wings create drag and kill lift. IMO that's exactly the case here. Top down might be a configuration with more drag and less lift (doubt it's making downforce, but same relative effect)

I do have two degrees in aerospace engineering, FWIW (not that that makes me right).

I don't agree with the driver comfort theory. For one thing, I'm more comfortable at the track with the top up (my faster primary track cars have been coupes).

I would still bet at most tracks that top up is faster, certainly true for miatae, anyway.