11 replies to this topic

[LarryKing]

I see a lot of STL Miatas sporting rear wings that would look at home on an Indycar. They seem to be hugely popular with the track day crowd too.

 

My question: Do they make any difference in performance? How do you know? Has anyone booked wind tunnel time to measure/adjust downforce? How much faster is a dedicated STL Miata than an SM and does it really need a wing? Is it simply because it looks cool and/or chicks dig'em?

[Danica Davison]

They have a wing because when you put the car cover on it over night ... it looks like someone stole your car and replaced it with a Ferrari.

[Ron Alan]

Without a doubt these wings affect the car! I have an endurance car(170/170) that we run at the 25HR in which I have front aero and a very efficient rear wing. First time on track it had so much rear grip it made it undrivable. With some time and testing and removing some of the down force we have found a balance. It is about impossible to get the rear of the car to step out except under power in low speed corners. Zero fear of stepping out at 100mph!

[LarryKing]

Ron, is your enduro car a Miata? Why doesn't an SM step-out at 100mph? Would you have a higher top speed without the wing?

[Danny Steyn]

WV - here is what I know after 2 years of running the fast wingy thing STL and the SM in the same weekend.

 

Based on how many 5th gear straights there are the DELTA between SM and STL (my MX-5 NC car setting lots of track records) varies from a 3.5% to 6.0% time advantage over SM time. The greater the number of long straights the greater the Delta. At NOLA  I ran 1:52.8 in STL for new track record and ran an SM time to win 1:59.636

 

However at tracks that feature long sustained cornering at higher speeds (think T9 carousel at Road America) the more this Delta increases.

 

Depending on the rear wing angle and whether you run a Wicker bar or not, you can feel the drag on the straights and the downforce in the corners. getting rid of the wicker and the attack angle greatly improves straight line speed at the expense of cornering speed. Getting the right balance of rear end and front end grip takes a lot of experimentation with different diffusers and splitters. At Road Atlanta T1 I am almost 9mph faster in the STL. I suspect that the wings and tires obviously assist and the extra 400lbs obviously detract.

 

In slower corners like Road Atlanta T7 the mid corner speeds are almost identical. Tires advantage overcoming weight disadvantage.  

 

Hope this helps

[davew]

We did this experiment at Thunderhill, granted with a Mustang but the physics are all the same. For a midpack driver, the aero was a minor help. For a front line driver the car was undrivable without the aero.

 

I spent a fair amount of time playing with aero back in my Trans-Am days. A true race wing is an airfoil. Its shape is very precise. They also only work in a very limited attack angle. The wing we used worked from 3* to 9* Anything below did not create any downforce. And anything above just added drag and no additional downforce. You have to know what you have and then work within that box.

 

Wicker bills, also called Gurney lips are huge. At Mid Ohio, not a really fast track, we went from a 3/8" tall wicker (normal for us was 1/8-3/8") to a 3/4" and the car was unsafe at speed.

 

I built some crude front under trays with venturi tunnels. We could not get the car balanced at all, I think they may still be floating around the shop somewhere.

 

I have some really interesting stories about aero stuff from my T/A and IMSA days.

 

Dave

[LarryKing]

Has anyone racing an STL Miata experimented with no wing versus wing to see which produces lower laptimes?

[Jim Drago]

WV - here is what I know after 2 years of running the fast wingy thing STL and the SM in the same weekend.

 

Based on how many 5th gear straights there are the DELTA between SM and STL (my MX-5 NC car setting lots of track records) varies from a 3.5% to 6.0% time advantage over SM time. The greater the number of long straights the greater the Delta. At NOLA  I ran 1:52.8 in STL for new track record and ran an SM time to win 1:59.636

 

However at tracks that feature long sustained cornering at higher speeds (think T9 carousel at Road America) the more this Delta increases.

 

Depending on the rear wing angle and whether you run a Wicker bar or not, you can feel the drag on the straights and the downforce in the corners. getting rid of the wicker and the attack angle greatly improves straight line speed at the expense of cornering speed. Getting the right balance of rear end and front end grip takes a lot of experimentation with different diffusers and splitters. At Road Atlanta T1 I am almost 9mph faster in the STL. I suspect that the wings and tires obviously assist and the extra 400lbs obviously detract.

 

In slower corners like Road Atlanta T7 the mid corner speeds are almost identical. Tires advantage overcoming weight disadvantage.  

 

Hope this helps

Danny

Do you run Hoosier A's primarily?

[Danny Steyn]

Danny

Do you run Hoosier A's primarily?

 

Yes

[Danny Steyn]

Has anyone racing an STL Miata experimented with no wing versus wing to see which produces lower laptimes?

 

Read Dave's comments above - the faster the driver the more aero helps. For a slow driver he will see very little time advantage. For a fast driver with large-attachments, the aero advantage, and lap time improvement, is significant

[Ron Alan]

Ron, is your enduro car a Miata? Why doesn't an SM step-out at 100mph? Would you have a higher top speed without the wing?

99 Miata.  As Danny and Dave have said above there are many factors...and every car is specific. But I will speak to what I have and what little I know about it

 

In its base state a NB Miata is pretty well balanced and will tend to lean toward the tight side with no mods. If you were to just add a wing and 25HP and nothing else the benefits of the wing may not be noticeable. In a Miata you need to add front down force along with your wing. Low HP cars need a very efficient wing...maximum down force to drag ratio. You can stick a duck bill on a high HP car and create lots of rear down force and not worry to much about the huge drag that is created.

 

So my car in its first 25HR race was basically a SM car with 170HP. We were 4 seconds faster than my SM car. This year I had the same power but added better suspension, aero front and rear, and 225 tires vs 205. We went 7 seconds faster than my SM car! What i need now is better front down force(grip)...this is the car limitation. The adjustable rear wing does its job very well...and it wants to do more!

[davew]

How I always approached aero tuning: On a sedan car, STL or a Trans Am car, your front aero is pretty much set and non adjustable. On the TA cars we used tape on the radiator screen to adjust down force. As much tape, as long as the car did not overheat. Watch a NAPCAR qualifying session with the entire grill taped off. Then balanced the handling with wing angle/wicker.

 

Too much rear wing will cause the car to push like a dump truck. The back end is planted so hard, the front wheels have no weight on them to get traction. The car just goes straight.

A piece of plywood screwed to a couple of uprights is technically a wing. But a true race wing has a very precise airfoil shape, designed to create down force without creating excessive drag. Only buy a real wing, these street tuner things usually induce so much drag for very little down force.