When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
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 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!
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.
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.
- 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 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).
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.
Originally Posted by emilio700
- Have undertray meet airdam 2-3" above bottom edge of dam. This creates downforce. Enough to buckle the undertray if its not rigid enough.
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
**** @ 0 aoa 3/42, 9/146, 17/259
**** @ 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
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 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
Question: Should you run a wing on NA miata, ~170rwhp, 2400lbs, and air-dam at Daytona?
Originally Posted by Morlind Engineering
It all depends on whether you need it or not. If it's all squirrely around the infield then you kind of have to run it. But if you don't need it then I would think seriously about taking it off. If you run the standard aluminum section with no wicker at about 0° then it's making very little drag anyway so it's probably not hurting much. But you are also at top speed something like half the lap so it will affect lap time. I know in big boy cars you frequently set the thing up to where you can barely handle it on the infield there just because of the percentage of time you're at top speed.
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.
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.
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.
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)
09-03-2020, 12:37 PM
Aero vs. Power? What's best for Daytona?
0
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*)
