Aero vs. Power? What's best for Daytona?
 

Prepping for my first Daytona event in my Miata, have been enjoying discussions with my buddies and some of our venders on optimizing for this track, and wanted to get additional thoughts. The car is an NA with a BP4W Rotrex supercharged engine making 165rwhp in its current tune for the class (NASA TT5). We anticipate hitting speeds of around 145-150mph in the banking.

1. I will be adding a front air dam and giving up my OEM aero credit. So, I can either add weight to meet my power/weight target or drop power to use my current weight.
2509lbs / 165rwhp OR 2450lbs / 161rwhp?

2. With an air dam (no splitter) is there any benefit to adding a 2D wing? One school of thought is that the wing improves airflow around the car without giving up too much in drag, and helps keep the car settled. The other is that wing drag reduces speed in the long banked sections that isn't offset enough by any benefits in the infield. Another consideration is using a wide, flat spoiler at a low angle to reduce lift and make the car more aerodynamically efficient.

Adding a splitter requires an additional drop of 5 horsepower. Once I use an air dam, I can also add a wing or spoiler for no additional penalty.

I am new to aero, and read through many of the informative threads in this forum. Since this track is different from any of the others I know, it would be helpful to hear what you have to say.

Well it is one of only two circuits where pro-teams come up with low-drag packages (the other being Road America), so I'd say go with gives the lowest drag for the least hit to power.

Low drag. You spend a lot of time flat out.
The banks and straights are pure low drag high HP.
The few corners where downforce is a benefit are very much offset by top end speed.
I wouldn't bet on hitting 150 with only 165 HP.
Figure a front running Spec Miata is around 125 and in a full draft 130.

I really figured Johnny w 9 lives or another one of the aero guys would chime in.

I purchased a medium down-force kit from Johnny at 9 Lives last week and he was very helpful with suggestions. Since Daytona is so different from other tracks in the region, I was hoping for some specific insights from others into optimization. This is my first time using aero on the Miata and have read through a lot of the material on this site and on occamsracers.

The current plan is to install the front air dam with a home-fabricated undertray that does not extend forward and create a splitter. This will allow me to have another 5rwhp compared to running with a splitter under NASA TT5 rules. I have a buddy with a Blackbird Fabworx rear spoiler, and he will let me borrow his trunk for the event. It is my understanding that the wing that comes with the 9 Lives kit will not improve enough time in the infield to warrant the aero drag on the long banked portions of the track. Instead, we'll set the spoiler to a very low angle of attack to help with the aero and reduce rear lift. For tracks like Sebring, the kit undertray/splitter will be installed along with the wing.

What do you think about this plan? Suggestions and critiques appreciated!

Thanks for the suggestions. The low drag/max HP approach is what we're planning on, and hoping to hear about whether it's helpful to use a rear spoiler vs. wing vs nothing.
I've hit 134 going into turn 1 at Homestead on the Roval course (NASCAR turns 3 & 4 + half the infield) with OEM aero, so we'll see what she does at Daytona.

We ran Crusher in PTC with and airdam and 2D wing for a while. Probably the lowest drag Miata we ever built. Great for ACS (high banked roval). Prior to that we ran a splitter which was even more effective but a rules change after Mid-Ohio Nationals required we ditch a few points to stay in class.
If the wing is free with and airdam, then that's the direction I would go.

- Aim to run the airdam as close to the ground as rules allow
- Have undertray meet airdam 2-3" above bottom edge of dam. This creates downforce. Enough to buckle the undertray if its not rigid enough.
- Experiment with both zero AOA and even slightly negative AOA. We found useful downforce even with the rear APR GT250 at -5° AOA (relative to ground plane)
- I'd stick with OEM or Singular end plates. Bigger ones at downforce, which you don't really need, and add some drag, which you definitely don't need. For normal road courses, go big on the end plates, gurney and splitter for big downforce increase.

Try to match your peak power with gearing to coincide with anticipated top speed. Its easy to get a mismatch that finds you over or under geared on the top end.

Post pics of your final config

I suspect that this is not widely appreciated. Probably most relevant to 2D wings, but if you can get a lift/drag plot of your airfoil a whole new world of aero optimisation opens (at least in respect to tuning the rear wing, and implications for car balance and circuit optimisation).

Seconding the photo request!.

Air-dam is definitely worth losing the OEM aero bit. It adds quite a bit of downforce and reduces drag over the OEM body. So it will be even more beneficial at Daytona.

Going by percentages, airdam with "undertray", and 2D wing(9LR) is fairly balanced. For NASA rules the "under-tray" can be a flat surface behind the air-dam. So it's the usual splitter design but cut short.

The wing is going to reduce the lift at the back of the car enough for the small amount of drag it creates to be worth it. Not to mention the braking and min corner speeds you'll gain from it. (I swear I don't have that line ready to copy/paste!)

Do you have a rear wing now? If not, give me a PM. Happy to help MT bros out when I can.

Adds down-force, but also adds drag. As usual, there's a little trade-off going on there. I'd say minimal drag would be the goal for Daytona.

Thank you all for the advice! Emilio knows me, and I tend to be quite analytical about things I don't have direct knowledge/experience with, then execute the plan. I'm looking forward to this next step in the evolution of my car, and in learning how to drive it well.
The airdam is a given for the front, and the consensus is that, even for Daytona, running with the wing at 0 aoa is better than other aero remedies (e.g. low aoa spoiler) or nothing. Is there any empirical data comparing drag vs lift characteristics between a 2-D wing like the one in the 9-Lives kit and a spoiler like the one sold by Moti at Blackbird Fabworx? I've scoured the internet for information and found useful stuff here on MT.net, at Occamsracecar, and on the 9-Lives site, but nothing this specific. I know the proof is in the laptimes, but the data helps my brain be at ease.
I just received the 9-Lives Racing medium downforce kit, so have all the ingredients to set up the car. I will have to wait on installing the undertray/splitter that came with the kit and fabricate a splitter-less undertray so that I can run a little more power (5rwhp difference) at Daytona. I can then switch to the splitter/less power configuration for other tracks (e.g. Sebring and Homestead).
I will definitely post pictures and results.

Taken from the 9-Lives Racing website - drag and downforce values at 60, 100, and 140mph
Wang @ 0 aoa 3/42, 9/146, 17/259
Wang @ 5° aoa 5/64, 14/181, 28/357

Ah, didn't know you had a medium kit. Here's the CFD on the medium kit. So air-dam, 3" splitter, standard wing at 2* AOA

https://cimg3.ibsrv.net/gimg/www.mia...0ff381464e.png


In regards to the spoiler, I haven't found any data on that particular design myself either. But what we do know is spoilers like that are around 3-4:1 lift to drag. The data I've seen on other spoilers have lower downforce numbers vs a wing and YUGE drag numbers to go along with it.

As always, test and find out! If the car is unmanageable in the infield, then a wing at 0* could be the route to go.

Thanks again! I will do some testing at Daytona and report back. Is there an additional digit in the cell for Hardtop Wing Only / Balance?

I'm curious on your testing for sure! I won't be surprised if you're faster at Daytona without a wing, though.

And no..... that is not a typo on the number. It does need a negative in front of it, though. But 659.6% of the total down-force of the car is on the rear, so yes it causes lift on the front with a wing only. Another reason why the air-dam is critical to the aero setup on NA/NB.

Keep in mind, it's big percentages, but small raw numbers. Same goes with the run #3 balance, it's got more on the front than the rear. By the numbers you'd want to crank more AOA into the rear to balance, say ~5* instead of 0*. Well..... I tried that and I went slower :rofl: Granted I was at 135rwhp/2300lbs at Road Atlanta where every MPH helps on the straights. The min speeds went up just a hair, but vmax into every turn was down, back straight I lost 2mph(119mph at 5*, 121mph at 0*)


As promised, I pinged our lead engineer about your setup and question. Your setup is similar to mine, so this works out great :D

Question: Should you run a wing on NA miata, ~170rwhp, 2400lbs, and air-dam at Daytona?

Awesome! Thanks for the updated info from the engineer.

It HAS to be a typo. You cannot have a multiple of the whole act on a part, it is a logical absurdity.

You can have 6.6 times the front downforce acting on the rear though - and that what your table says.

I'm glad someone else caught that. Wasn't going to say anything.

Poor choice of wording on my part. Before that rabbit hole starts, I'll try to clear it up.

The math on that column is front down-force as a % of the total for the car. So the fact that the rear makes a lot of negative lift, leaves the front making (this multitude) more lift than the overall car. The wording of "The rear is making (this multitude) more down-force than the front." would be better, I think.

Big picture here, it's huge percentages but tiny raw numbers. It's not ideal to run a NA/NB with just a rear wing. :party:

Data point - stock bodied NA with GV front lip, small KG Works decklid spoiler, 2425 weight, 5in pinchweld height, 205 Hoosiers, 8in wheels, 262whp (measured on official dyno at the track that weekend), 3.63 gears, only did 150.1 mph on the front straight at Daytona with a very amateur driver (me). With 4.10 gears on a prior occasion it did 143 but pegged the limiter and I really did not want to raise the limit at that point.

I will definitely say that the small spoiler made a noticeable difference in how light the back end felt in the high speed braking and turn in off the straight in turn one.

Mounting everything up and have a question about fitment of the 9 Lives air dam and splitter with the Sturdy Bois mounts. We are finding that the height of the air dam is taller than expected. If the top of the air dam with all the nicely drilled holes is aligned just above the molded line in the front bumper cover, it puts the splitter too low. I'm running my car at 5.25" to the rocker panel pinched seam. I'm not apposed to trimming, just wanted to make sure I wasn't missing something. (edited to correct wrong rocker panel height)

Air dam and hood vents installed! I made an undertray to replace the 9-Lives splitter so as not to have to de-power the car for this event.https://cimg3.ibsrv.net/gimg/www.mia...6c36a70ee6.jpg

Missed your fitment question, but it looks like you figured it out. The go-to route is to mount the splitter and sturdy-bois first, then line up the air-dam.

Any way to add wheel spats in front of rear wheels without points being assessed? Not the most important thing, just curious.

Nah, the rules read as......

"3) Vertical front air dam (5º tolerance) that follows or extends beneath the outermost edge of the front and side bodywork/fascia."

No "spats" or whickers allowed in ST4/5/6.

2:21.7xx yesterday in the best session that day and a 2:18.9xx this morning in a much better session. Were you able to test with and without a wing yet? I'm super curious now, especially since NASA Nationals will be at Daytona in 2021.

That was fun! First time at Daytona in my car, so that's my excuse for under-driving on Saturday.

I ran the car without the wing on Saturday and for the first session on Sunday.
It rained for 2 out of the 4 sessions on both days, so I wasn't able to do as much testing as I wanted to.
Saturday fastest time was 2:21.761, leaving a LOT on the table in turns 1 and the bus stop. Winning time that day was 2:18.970 by an Integra driver. I got third.
Sunday fastest time was 2:18.760, good enough for the win and track record (first time for this class at Daytona, so likely to come down). Still left time on the table mainly in turn 1. Car felt very slightly loose in a few of the tight turns on the infield with the air dam (no splitter) and no wing.
I installed the wing set to 0°AOA for the second session and ran 2:20.435, partly due to being held up by traffic, but also from the changed balance causing more push. I had to change my line/style and didn't adapt quickly enough for a strong lap. Sessions were short, so we could only get 4 good laps each time out, It rained in the afternoon and I didn't go out again since I only had Hoosier R7s (and no wiper blades).
Fastest speed was ~140mph without the wing, and ~137.5mp with the wing (from imperfect memory).

I'll follow up with more information once I have the chance to review the videos and TrackMate data,

I figured the weather was guna be a pain this weekend. Glad you guys got some decent sessions though.

In for the data! 2.5mph isn't anything to brush off! It's probably worth not running the wing for our setups in ST5/TT5. The big disadvantage NA/NBs have is the OEM aero(no air-dam) is horrible compared to other cars in the class. Like a S2K, FRSBRZ, E36 even. Their front aero isn't horrible so they can take that OEM aero mod back :-\

@CoralDoc , I was looking at my Saturday & Sunday fastest laps. One thing I noticed, but didn't document in my notes (wind) is I had a 4 mph reduction in top speed Sunday. Looking at my speed traces, only the straights in one direction were impacted so I'm speculating that wind may have impacted top speeds on Sunday.

Glad I'm not the only 1 that never felt content with how to do Turn 1.

Interesting observation about the possible headwind. Also, it was cloudy on Saturday afternoon and cooler on the Sunday earlier run (when running no wing) compared to the warmer and sunnier Sunday later morning run with the wing.
Thanks for your help at the track!

Also, for comparison, fastest Spec Miata driver times were 2:24.xxx on each day.

After looking at the data, it is striking how similar the car's performance was in each configuration. The slower lap time with the wing was due to driver choice/error. There was a lift in the straight towards turn 4 (kink between hairpins) to facilitate a pass and under-driving turn 6. In general, minimum speeds in the infield turns were higher with the wing, however exit speeds were a little higher without the wing (I suspect due to the greater push with the wing and lack of driver familiarity). For the fastest laps in each configuration, maximum speeds heading into the bus stop and into turn 1 were nearly the same, slightly slower by a few tenths of a MPH with the wing. The maximum speed of all laps in each configuration was 139.9MPH without the wing and 137.6 with the wing. However, speed out of turns preceding banking were very close, and the early part of the banking segments showed very similar speed, with slower speed becoming evident at higher speeds towards the end of the straights.

In summary, once I learn to use the extra grip with the wing to more consistently carry speed out of the turns, it may be the faster configuration. I wish I had the opportunity to test again with a slightly negative AOA to reduce the push (and perhaps further reduce drag), but that will have to wait for someone else (or next year).

I hope to process the videos and upload them once I get unburied at work.

BTW, for some reason my fastest lap video lacks audio. All the other sessions have it. Video obtained with a GoPro Hero 2, so if anyone has any ideas to salvage the sound, let me know.

Just back from Sebring - I am very impressed with the performance of the car with aero. I set personal best times each day and the TT5 track record - 2:33.799 on Saturday and 2:33.550 today. Running with the air dam (no splitter) and wing set at slightly negative angle of attack, the car felt nicely balanced and planted in the turns.

Nicely done. It's always a revelation when you get into a well set-up Miata with some effective low-drag aero.

Nice! You likely have the TT5 record at Sebring now?

Yes, sir! 2:33.550
I am very impressed with how much more confidently I can drive the car, especially in the fast turns 1 and 17 at Sebring. The car is PLANTED in Bishop's Bend and through 15-16, the important turn that leads onto the long back straight. I saw the fastest top-end speeds I ever measured in my car of 125.6 MPH due to the faster exit speed out of 16.

9-Lives just came out with that funky "Street wang" in case you feel like spending more money. It does focus on stability improvements with minimum drag, which does seem to fit what you were trying to do at Daytona. Too bad you already did it, though!

Positive feedback is always great to hear! Maybe I'll make it down to Sebring one day!

I was watching my buddy's lap and there you were!

Also, the Street Wang is made for the street really. It's goal is to provide some help on the rear of the car, as efficiently as possible. I think for Daytona we'd come up with something a little different IF a NA/NB proves to be faster with rear aero at Daytona consistently. NASA nationals is going there for 2021 soooooo I might try to get something together.

Good timing for this thread. I have been thinking about NASA 2021 Daytona for a couple weeks, and also have an ST5/TT5 NB.
Keep in mind that an airdam is not exactly "free". You forfeit the .4 BTM credit.
Taking A-arm and Weight Factor penalties ONLY is the closest a Miata can get to class-max P:W, and therefore the most raw power.
There is a Weight Factor credit at 2450lbs, so you would want to stay equal to or greater than that if you have the capability to make that much power.
The next credit is 2550lbs, and might be worth ballasting up at the same power to get the airdam/wing for .1 less penalty at the same raw power.

2453lbs @ 168.01avg whp with BTM
2453lbs @ 163.53avg whp w/o BTM (Airdam/wing)
2453lbs @ 158.26avg whp with Splitter

2557lbs @ 166.04avg whp with Splitter/wing
2557lbs @ 171.61avg whp w/o BTM (Airdam/wing)
2557lbs @ 176.34avg whp With BTM

Goldilocks(?): 2520lbs @ 168avg whp w/o BTM(airdam/wing)
-This gets an airdam/wing paid for 'just' 67lbs of ballast at the same raw power as the BTM/2450lb build.

There is a potential 10whp spread in mod factor penalties to pay for the drag reduction.
From ~90mph to ~135mph, how much horsepower does having the airdam/wing save?

FTFY

On most tracks, the rate of acceleration between 75-100mph is most important. Daytona might be 105-125 so drag reductions that save 10-20whp in aero drag might be worth taking.
Forgive me for being lazy, but what about a big, shallow angle duck tail to reduce drag instead of a wing? Drag wise, a big, shallow duck tail and airdam with 205's on 9's would be the lowest total rolling/aero.

Talking about something like the drag-racing style "spoilers"? Like this?
https://cimg1.ibsrv.net/gimg/www.mia...433b6a935b.jpg

You probably want to test to see what the right angle is but we found that somewhere between 10 and 20 degrees works at ACS with Supermiata duck tails.

https://cimg6.ibsrv.net/gimg/www.mia...0107652ddd.jpg

Yeah, I'm going beg to run CFD on it with our NA model at least. Get some good starting points and test it on track. I figure they'll have one test event at Daytona before nationals to do that.

I'll share the CFD on this forum too, once I get it.

I was speculating about this in my first post :)

NASA Florida and Southeast are planning an event at Daytona on May 29-30, and then Nationals will be there on Sept 16-19.

Also, here's a photo of my assistant from when the 9 Lives packages arrived ... maybe good for a cat or two?
https://cimg6.ibsrv.net/gimg/www.mia...4870d83d89.jpg

Finally a video of my fastest lap at Daytona - air dam with no wing. Unfortunately, the audio did not work.

Just seeing this thread, but I have to second Emilio's post regarding a low AOA spoiler.
To me, seeing that you set your best lap w/o a wing, means that there's more to be had with the use of a spoiler.