4 replies to this topic

[endura]

Not a specific spec miata question as I know this is not legal in SM,  figured the knowledge base here would have some insight. 

Caged '90,  220 whp, TT & W2W.  Bolted hardtop.  Main track for one of the series is Mosport,  extremely high speeds.  Vmax 130 mph and average is 93 mph.  No restrictions on aero, allowed to run windows up or down.  Gave up on controlling cockpit temps. windows up, committing to running windows down.  

Question is should I remove the hardtop glass?  

From what I've found, it does seem to be better for aero.  Found an instance from the 2007 runoffs when someone ran with no rear glass and, due to their straightline speed, was immediately told to put it back on.  Some other comments here and there from people with soft tops who ran with rear window unzipped and claimed increased straight line speed,  but nothing definitive.

Any insight would be appreciated before I send a perfectly good hardtop window into the scrap bin.  

[Bench Racer]

Did you gain any straight line speed with ALL windows up?

[endura]

Yes.  Windows up gained consistent 4-5 mph on the back straight at Mosport.  

[Bench Racer]

Ok, thinking about your 4-5 mph gain and viewing these pictures should confirm, windows up and condition the driver or cool the driver. There is cheating done in the U.S. so that driving with windows down per rules, gaping the bottom of the rear of hard top and or removing the rubber gasket allows the wind from open windows to escape works to some degree.

 

https://www.google.c...-BWePS-75aytPM:

[endura]

yup, read up on the ''floating hardtop''.  until I can do a back to back test this spring, this is all anectodal.  However, everything I've read leads to cockpit air evacuation from the rear reducing drag.    options are,

-glass removal, leave open.

-replace with vented plexi.

-lift up rear of hardtop somehow.  (probably way more complicated than it sounds)

-cut off hardtop rear bottom piece (section between two frankenstein bolts).  

 

lifting up rear temporarily for back to back testing is easiest way to confirm whether it works or not.  Once I have the data, can move forward with more permanent options.