Veloster N Long-term (Track) Report

I’ve had my Veloster N for a year and a half, and with two track seasons finished, it’s time for a retrospective. I’m not going to get into daily driver details, just going to review the important things; race track things.

Wheels

Most people downsize the OEM wheels from 19” to 18” because aftermarket wheels are much lighter, and 18” tires are usually about 20% cheaper. The big challenge is fitting wider wheels and tires; unless you cut the fenders and install flares, the Veloster N can’t fit wide tires. When you compare the wheel and tire sizes to other cars, the Elantra N can easily fit 245 on 9”‘ wheels, while a Civic Type R can fit a 265 on 10”. It’s just not fair.

Ergo, VN track drivers typically fit a 235 tire on 18×8.5 +45. My buddy Chris was able to fit a 245 RT660 on a 8.5 +50, but he was at stock ride height. I tried the same tire on a 8.5 + 45 with 1” lowering springs, and it rubbed front and back.

On 1” lowering springs, a 245 RT660 on 18×8.5 +45 rubs front and rear. The same tire on 18×8.5 +50 will clear with stock springs.

I have three sets of wheels:

  • OEM 19×8+55 – Theres nothing to like about the stock wheel, it’s narrow and weighs over 29 lbs. When I wore out the OE Pirelli PZ4 tires, I put $65 Linglong Crosswind tires on these wheels, which is better rubber than they deserve.
  • Konig Countergram 18×8.5 +43 – I bought these because I like the black center and polished aluminum lip. They were about $300 at Fitment Industries and weigh 19 lbs. I have only used these for Kumho V730s, and they fit fine.
  • Motegi MR140 18×8.5 +45 – These are a bargain at $173 from Phil’s Tire. The only downside is the mounting holes are super narrow, and even 17mm lug nuts won’t fit, so you need to use spline (tuner) nuts, which I fucking hate. Anyway, the wheels are cheap and at 19.1 lbs, quite light. I used these for the 18” PZ4, Blu Trac Race, Pilot SS, and RT660.

I’ve read somewhere that reducing rotating weight is 3x more important than weight elsewhere on the car. So taking 10 lbs off each wheel is a huge benefit for acceleration and braking. Being unsprung weight, this also helps handling.

Tires

I put camber bolts in my Veloster N, and it maxes out at -1.8 degrees of camber. I understand that the DCTs can get more camber than the 6M versions, but I don’t exactly understand why. In any case, this doesn’t allow my car to get the most out of a proper track tire, and so the difference between an all-season and a super 200 is less what it should be. Or another way of putting that is that my car goes well on shitty tires.

At this point I’ve track tested eight different tires, from cheap all-seasons, to max performance summer tires, a few 200s, and a premium 100 treadwear. All of these were properly abused on the same race track, and I dutifully collected data for comparative analysis.

I’ll list them in the order I drove them (including two tires on a friends Veloster N), and sum it up with a report card.

  • Pirelli PZero PZ4 – I’ve had these in the OE 235/35-19 on 8” wide wheels, and 235/40-18 on 8.5”. I felt they were decent rain tires, but otherwise just average. You need to keep the pressures high to keep them from rolling over, and rotate them frequently, as they deteriorate quickly on a dry track.
  • Falken RT660 – I drove these in a wider 245/40-18 on my buddy Chris’s VN, and came away solidly impressed. On an otherwise stock VN I was only .25 seconds off Pineview’s all-time FWD record. Chris’s car doesn’t have a lot of camber, but he had the tires heat cycled before delivery, and thus experienced none of the center delamination or tread splice issues that others have reported.
  • Maxxis VR1 R2 – The Hankook RS4s used to be my favorite dual duty tire, but it’s not always available, and rarely on sale. Maxxis VR1s are pretty close in performance, and a great second choice. I used this tire on Chris’s VN and went a little slower than I did on the RT660. On the other hand, Chris didn’t like the feel of the Falken’s and went faster on Maxxis. This goes to show you that it’s not always the outright grip that matters, and you might turn a faster lap on a tire with less grip. Feel, feedback, and confidence are important.
  • Linglong Crosswind UHP All Season – I bought these because I needed something (anything) to put on my 19” OE wheels after the PZ4 wore out. At $65 on sale, I didn’t expect much more than round and black, but I took them to the track just the same. The sidewalls were mush and they howled like a chorus of tone-deaf banshees, but the performance wasn’t terrible. Three different drivers flogged them all day long, and the budget 400 TW tires earned some respect.
  • Kumho V730 – This is a good dry track tire, but worthless in the wet. It has a NT01 feel, with great feedback and grip that’s good down to the cords. While searching for more grip, I aired them down too low and corded the outside shoulder with half the tread remaining. I can’t start these at less than 32 cold, which means they’ll come up to 41 psi hot, and so I have to pit once and air them down, which is a PITA. They are cheaper than most 200s, and if the car could get more camber, I’d use nothing else.
  • Armstrong Blu-Trac Race – Armstrong left the e off of Blu and the k of off Trac and the grip off a 200 TW tire. And yet this was the most fun tire I’ve tried so far. They break away very early, but are super easy to control when sliding. You can get them with a money-back guarantee, and they go on sale a few times per year. This tire puts the E in HPDE.
  • Goodyear Eagle Supercar 3R – I admit that I often order food looking at the right side of the menu, and so it’s not surprising that I buy tires by price. But this summer I decided to spoil myself for once and get a premium tire and set some PB laps. The grip of the SC3R was incredible, if inaudible, and the turn-in was so insanely quick, it felt like I was driving a completely different car. All the ingredients were there, but the lap times never materialized. The tires made the car feel like I had all the nannies on, and took the fun out of driving. In the end, I went a second faster on V730 than I did on SC3R. I recently traded them away for a used set of RT660s. I’ve also had the devil of a time getting my rebate, which is part of why I bought them in the first place. I’m done with Goodyear.
  • Michelin Pilot Super Sport – These were the OE tire on the base Veloster N (non-Performance Pack), and came in a smaller 225/40-18 size on that version. I got them for free on Facebook Marketplace with half the tread remaining. They are easy to drive at the limit, but have an unusual sound, more of a protesting whine than a painful howl. The PSS are a generation older than most 300 TW tires, but were within a second of the V730 or SC3R. I corded the outside shoulder, just like every other tire. Man I need coilovers.

The following table is how I’d rank the tires on my Veloster N. I’ll probably get some disagreements here, but I like a playful tire that lets the car dance, and lap times matter don’t as much to me as having fun.

TireGripLongevityPriceFunGrade
SC3RA+DD- ($325)DC-
PZ4CCB ($175)CC+
RT660ACC- ($250)CC+
Crosswind DCA+ ($65)CC+
PSSCBC+ ($175)BB-
VR1BBC ($230)B+B
Blu TracDAB+ ($165)AB
V730ABB- ($200)B-B
Tires by grade.

In the future I have two choices: get coilovers so that I can use better track tires, or switch to endurance tires with a symmetrical tread pattern. RS4s are the easy button, working well with camber challenged cars, and allowing me to flip them once, after I wear the outside shoulders.

The more expensive choice is to buy coilovers, which allow more camber and corner balance the car, and that would reorder my tire list completely. The negative camber would also allow the wheels to tuck under the fenders better. With that I might be able to fit 18×9 +45 wheels and 245 tires.

But… this is still a street car and I’ve ruined other cars in the past making them too track focused. I’ll revisit this conundrum in 2025.

Brakes

Muzafar Umarov manages the N Track and Autocross group on Facebook, and is a knowledgeable source on all things N. From him I learned that the Veloster N brake bias starts at roughly 70% front, but changes dynamically based on slip. Brake bias is controlled electronically for each wheel, and can shift to as much as 93% front if the rear wheels are locking.

This is both good news and bad news. If you’re accustomed to using the rear brakes to rotate the car on corner entry, you’ll be disappointed. The system essentially prevents corner entry oversteer, intentional or not. This infuriated my brother, who swore the traction control was on, even though it was turned off in the custom settings.

This also means that putting higher friction brake pads on the rear is a waste. Just as the dynamic brake bias system won’t help you turn the car on corner entry, it also won’t stop the car any faster. The sticky rear pads will just transfer more bias to the front brakes sooner. As a result, even the very serious folks at GenRacer are still using the OE rear brake pads.

And for that reason I’m also using OE rear pads, and will be for the foreseeable future. They are inexpensive, wear is imperceptible, and there’s no reason to use anything else. Life can be just that simple.

The OE front brake pads are reported to be quite good as well, and can do autocross and light track duty as long as you use the OE tires. But they are a little expensive, and the cheap hack is to use the Elantra N pads, and reuse the Veloster N shims.

But I don’t know about that, since once you upgrade the tires, you’re going to want better than OE pads. Knowing this, I switched the front brake pads to Porterfield R4-E immediately upon delivery.

This is a pad I have racing experience with, and as someone who’s never had antilock brakes on a track car before, I typically prefer pads with a lower friction coefficient. I believe the R4-E (E is for Endurance) come in around .46 mu, which is quite a bit lower than most serious race pads. As a result, they probably require more brake pressure. But I like the way they feel as I release the brake pedal, and that’s more important to me than initial bite or maximum stopping power.

Another reason to use a less aggressive pad is that several Veloster N owners have reported getting ice mode when using higher friction track pads. This can overwhelm the stock calipers and ABS system, and send the car into a panic. And so there are at least a few reasons for me to use the R4-E (the E is also for Economy).

The pads cost $210, which is $100 less than what you’d pay for most hybrid street/track pads, and half the cost of a dedicated track/race pad. I leave the R4-E on for daily driving, and they stop fine when cold and don’t squeal annoyingly like an aggressive track pad. (Although I understand some people like that.)

The way the R4-E work on both street and track remind me of the old Stoptech 301, before they switched manufacturing plants. That was a true dual duty pad, but it lasted about half as long as a R4-E. Still, they were less than half the price, and I used them without complaint for years.

Admittedly, I don’t experiment much with brakes, but Gregg Vandivert has done a ton of brake pad testing on his Elantra N. He had a problem using the Porterfield R4 (not R4-E) compound; the pads cracked and separated from the backing plates. The reason this happens is because Hyundai uses a cheap single piston caliper, and so the backing plate needs to be ultra stiff, or it flexes.

Gregg says Porterfield has two thicknesses of backing plates available, and you can special order pads with the thicker ones. Well, my R4-E pads have not cracked or separated, and so perhaps the E pads come with thicker backing plates to begin with? I will need to ask the folks at Porterfield at some point.

In any case, the brake pads are just fine for street and track driving, and they held up for over a year of both. Eventually the brakes started to fade on track, and I figured it was time to change them out. When I pulled them off I noticed they wore evenly inside and outside, and I had used 99% of the friction material without getting into the backing plates. I got lucky there.

I got everything out of them.

Moving on from pads to rotors, I’m now just onto my second set. The service limit is 28mm and that’s where mine are at the outside edge, but down near the center they are 27.2mm.

It looks like I’ll need to replace rotors every two sets of pads, but if I get pad-curious then I’ll do both at the same time so they bed in properly. I paid $140 at Parts Geek for the front rotors, while my local Hyundai shop wanted $400 for essentially the same thing. Areyoufuckingkiddingme?

Two sets of front pads and one pair of rotors works out to $540, and that covers maybe two years. I don’t know how long the OE rear pads and rotors last, but certainly longer. That’s some serious economy, and it surprises me that Veloster brakes are as cheap as Miata brakes.

Fuel and engine modes

The Veloster manual says to use 91 octane, but I use 93 most of the time, because that’s what’s available. However, many of the pumps here only have non-ethanol 90 for Premium (lots of boats and such in this area). I don’t know what the power difference is between 90 non-ethanol, 91, and 93, but it may get more power out of 93 because of the higher octane. I don’t know if the VN has the “octane learning” feature of the EN, but I’m pretty sure the ECU will pull out timing when it senses lower octane. But then again, ethanol burns at 80k BTUs, while gasoline burns hotter with 118k BTUs, and so maybe I should be running non-ethanol?

I get exactly 7.0 mpg on track at Pineview and NYST. Every time. My friend Chris is only a couple tenths of a second slower than me on Pineview’s short track (45 second lap) and gets 2 mpg more than I do. So it’s interesting to see the diminishing returns on driving the car harder. At Watkins Glen I get a miserable 6.0 mpg. In practical terms, this means emptying a 5-gallon jug every track session.

On the highway I get mostly 32-33 mpg with the N wing, and I lose maybe 1 mpg with the ducktail spoiler. With a wing on the car, it gets just under 30 mpg, which is kind of surprising, because I thought that ducktail would have more drag. I haven’t done an accurate two-way test over a distance though.

The Veloster N has four different pre-set driving modes that change engine response, exhaust note, suspension stiffness, steering quickness, traction control, rev matching, and the electronic limited slip diff. I only use one of the pre-set modes, Normal. Economy mode doesn’t do shit, and the performance modes are a collection of settings I’d never use together.

Thankfully Hyundai made a N Custom mode that allows you to adjust each setting individually and save it as a custom setup. Mine has the suspension set to soft, and a quiet engine note with none of the pop and burble nonsense. I turn all of the nannies off, including rev matching, and max out the eLSD. I haven’t decided which of the three steering modes I like best, but I can change that on the fly using the touchscreen.

I use the Normal driving mode when I’m on the street, or when I am on track and it’s raining a shit storm. Compared to my N Custom mode, Normal is about a second faster in the wet and about 1.5 seconds slower in the dry. So I definitely appreciate having the options.

I dyno tested all the engine modes and they put out the same power. Eco mode is supposed to limit boost pressure, but it doesn’t make a difference on my car. I got 244 hp at the wheels on a Dynojet, and that’s 10 more than I expected.

Someone said the different engine modes don’t change power, they change how the engine responds. But given how the modes are identical on the dyno, I’m skeptical, I’ll A/B test engine response on track and see what the stopwatch says.

Finally, there was a recent software update that changes a bunch of things in the N Custom mode. I like the new layout, and appreciate that Hyundai is still making updates to a car they discontinued. I keep the updated software on a keychain USB drive in case I meet someone with a EN, KN, or VN that hasn’t made the update yet.

Track warranty

Arguably the best reason to buy a Hyundai is for the 10-year powertrain warranty. I bought mine as a Hyundai-certified pre-owned car, and so I’m covered until November 2032. I also upgraded to full bumper to bumper coverage, and so if anything goes wrong with my car in the next eight years, someone else is fixing it. And because this is a N car, the warranty extends to track use.

In fact, I’ve already used the warranty. The engine blew up on track at Waterford; Hyundai picked it up at the track, fixed it, and delivered it to me 500 miles away. They even paid for the rental car to get me home. I suspect in the next 8 years I will be using the warranty again.

Hatchback life

There aren’t a lot of sports cars that have enough room to transport a set of tires inside the car. Of course most 4-door sedans can do this, with two in the boot and two on the rear seats, but how many proper track cars can swallow a set of slicks? The Subaru-Toyota BRZ-86 was apparently designed to carry a set of track tires in the back, and I’ve seen four tires disappear inside a BMW 1-series. So I imagine that most BMW coupes can manage this as well.

Hatchbacks have the advantage here, and when you fold down the rear seats, even a diminutive MINI Cooper can carry four tires inside. But can you name any track car that can transport eight tires inside? With the space-saving Modern Spare in the well and one on the front seat, that’s actually nine!

Shocker! Seven in the back and one in the front.

The first time I went down to the A2 wind tunnel, I transported three splitters, five wings, two spoilers, a diffuser, boxes of tools, spares, and other parts inside the car and drove the 10 hours to Moorseville. Try that in any other car you’d actually take to a wind tunnel.

That’s a lot of junk in that trunk!

And if this wasn’t enough space already, I added a trailer hitch so that I can use a cargo tray or small trailer. The Veloster trailer hitch was designed for the base model Veloster, and required some modifications to fit my car.

Aerodynamics

My Veloster has been to the A2 wind tunnel twice, and now I know more about hatchback aerodynamics than I ever dreamed I would. The OE body has a drag of .416 and makes a tiny bit of downforce, which is pretty surprising, since most cars make lift.

Front downforce was easy to get, and even a flat splitter made 135 lbs of downforce at 100 mph. My curved splitter made 195 lbs, and coupled with upper and lower canards and hood vents, total front downforce was north of 300 lbs. And this is without cutting vents into the fenders or extracting air behind the wheels, which you would do on a proper race car, but I may never get around to on a daily.

At the other end of the car, wings didn’t perform as well as I expected, and even the Kamm-back shape is a compromise over a proper coupe or fastback. As such, most wings up to 55” span had lift-to-drag ratios less than 4:1. A 70” Wing Logic gave the best results at 7:1, which is more a function of the wingspan than the shape of the wing; it’s obviously important to get the ends of the wing into clean air where they can get away from the hatchback roofline.

If wings were disappointing, spoilers were a revelation, as they made both front and rear downforce. (Wings reduce front downforce through leverage; Spoilers aggregate pressure over the l roofline, and some of that is in front of the rear wheels.) Spoilers can’t get as much total downforce as a wing, but they work surprisingly well if you’re not going to add a splitter.

The biggest surprise was that adding a 1” Gurney flap on the OE N spoiler gave a better L/D ratio than all but the largest wing.

1” angle aluminum Gurney flap. In the wind tunnel I used duct tape, here it’s fastened with rivets, and in the future I’ll drill those out and use rivnuts for easy on/off. Notice I also added slightly taller end plates, but I didn’t do that in the wind tunnel.

At 100 mph, the OE wing makes 30.8 lbs of downforce and loses 2.5 hp due to drag. With the wicker-kicker it makes an astonishing 123.6 lbs of downforce and uses 8.3 hp. (These numbers are compared to the base model, which has a roof extension, but no wing).

Rear view of wicker, kicker, Gurney flap. I’ll probably paint it black at some point in the future.

The Gurney flap information isn’t (yet) in my wind tunnel report, but there’s over 50 pages specific to the Veloster N, going nose to tail on aerodynamic parts, simulated lap times, and a lot of discussion.

I also did some practical testing of wings and spoilers at Pineview Run and NYST. The short story is that my Veloster went 2.5 seconds faster with rear downforce alone. Given that, I wouldn’t even bother adding front downforce unless you have a really significant wing to balance it out.

Conclusion

In the past year and a half I’ve done probably 30 track days in my Veloster N; I’m still smiling. It’s got enough cargo capacity for everything I bring to the track, and a comfortable ride that makes long-distance track treks a pleasure. It has adequate power, and handles better than it should. Even on track like Pineview, which has a lot of long corners and uphill switchbacks that punish FWD cars, it’s fast and fun to drive.

As track cars go, it’s economical. It doesn’t need expensive brake pads or ultra grippy tires, and seems to work just as well with mid-performance items. If you want to keep the warranty, you can’t modify engine parts or tuning, which leaves very little to spend money on. Except gas, as it is pretty thirsty.

The funny thing is, I’m actually looking forward to when the car is out of warranty, and I can install a bigger turbo. With a larger turbo, all the bolt ons, and a ECU tune, it might get down to a 10:1 lbs/hp ratio. Then I’ll gut it, cage it, and race whatever dumb series will have me. But I’ve got 8 years of wringing the snot out the stock engine, and I’m not at all disappointed with that.

I daresay I’m forming an emotional attachment to this car! It’s the amalgamation of so many cars I wanted and never bought: It’s the Honda CRX I pined for in college, but modernized and powerful; It’s the later CR-Z with double the power and nearly the economy; It’s the 3-door cousin of a MINI Clubman JCW, but with better aerodynamics; It’s as weird as the M Coupe “clown shoe” I nearly bought, but easier to live with.

And it’s so much fun! I love tossing the car into an early apex, forcing it into a four-wheel drift, and then digging it out with the front wheels. It’s Miata like, in its combination of economy and ability to bruise egos everywhere it goes. If you have a BMW M car, Corvette, or Porsche, you’d better be a decent driver, because the hurt machine is coming though!

This is probably the last car I buy that isn’t an electric self-driving killjoy mistake, and so I’m going to continue to modify it for more fun. I’ve already removed the rear seats and put in a flat cargo floor. Next I’ll install a harness bar and race seat. Sometime this winter I’ll figure out a DRS dual wing, because hitting a button on the straights is a plus one to fun. And maybe I’ll hook that up to an adjustable splitter as well. Let’s see what happens in 2025.

As if the car needed more space.

Miata Wind Tunnel Test Ideas

I wrote this post a while ago, and since then I made it back to the wind tunnel and tested a lot of things. Sadly, Falconet wasn’t ready for that trip, and so instead I took a Miata with the full 9 Lives Racing medium downforce kit. I was able to test everything that’s been modeled in CFD, and the entire 9LR catalog, as well as many other options, such as fastback, hood and fender vents, and various things to reduce drag and add downforce.

I’m going back to the A2 wind tunnel this summer and I’ll test a bunch of stuff on my Hayabusa-swapped Miata, Falconet. Wind tunnel testing is expensive, and it’s an 11-hour drive each way, so I need to be ultra prepared so that I’m not wasting time and money.

As part of that preparation, I want to know what other people are curious about. Do you have some parts to test? Send them to me and I’ll send them back when I’m done. Do you have some ideas you want to test, but can’t implement? Maybe I can cobble something together in time. Please drop me a comment at the bottom or use my contact form to email me, and I’ll do my best to test what’s important to the Miata community.

One of the benefits to wind tunnel testing is the parts don’t have to be race spec, they just need to survive a couple runs. So a lot of parts go on with the minimum number of fasteners and the maximum amount of duct tape. This allows me to do so a lot more fabricating and testing than would normally be possible.

Anyway, here are some things I’ll be testing.

Canards

I’ll be the first to admit I was wrong about canards, and so this is one area where I’ll be spending a lot of time money. Before I tested my Veloster N in the wind tunnel, I thought canards were poseur junk, but after finding out that changing the height by 8″ made a 700% increase in downforce, I realized I knew jack shit about canards.

I’ll test height to find out the optimal position on the lower canard. I’ll also test size, shape, angle, profile (blade vs airfoil), and end treatment (wicker sizes).

I will not be testing these canards.

Splitter

On my Veloster I tested flat vs curved splitters and found massive gains (150% more downforce) using a splitter that curved upwards at the trailing edge. This is essentially that same thing as using splitter diffusers, but instead of diffusing air into the wheel wells, the air is diffused over the entire width of the car. So I’d like to test this vs a flat splitter with splitter diffusers.

Laminating a splitter with a full width diffuser on the trailing edge.

I also added vortex strakes in front of the wheels and this reduced drag quite a bit, but because those strakes were only on one splitter, I didn’t do a proper A/B test. So I’ll test these again on the same diffuser to see how worthwhile that is.

I’ve seen some online conjecture on the drag from splitter rods, and it doesn’t make a lot of sense to me. I’ll double the number of splitter rods (they’ll be fake) and see what happens.

There’s already published data on splitter length, but I might test this if enough people are hungry for that data. Likewise splitter height has been tested and published (but not on a Miata). Just the same, it’s easy enough to put blocks under the tires and test changes to height and rake, and how that affects downforce and drag.

And I might get around to testing an airdam with an undertray and no splitter lip. I think I can get the undertray to make a lot of suction, even without a splitter lip. This test isn’t a high priority for me, because I’m not personally going to set up Falconet like this, but with enough community whining, this test could go higher up the list.

Underbody

When it comes to underbody aero on touring cars (especially Miatas), I’m a confirmed naysayer. But, just like it was with canards, I might find myself eating my own words after this test!

Some of the things I’ll be testing are a flat bottom, a partial flat bottom (trans tunnel exposed), barge boards, and at least one diffuser. Falconet uses a motorcycle transmission, and so that whole transmission tunnel is open. I’ll diffuse some air into that area and see what happens.

Vents

Al at Race Louvers has some of the best wind tunnel data on the web, and I see no reason to duplicate his efforts. But I have some ideas to get more extraction out of the wheel wells, and these haven’t been tested by him yet. I’ll also be testing a hood extractor vent, which is specific to Falconet, but the data may be interesting to others.

Wings

I’ve already tested and published wind tunnel data on five wings, four end plates, and Gurney flaps, but I have a few things still to test.

I have an oddball wing I made with a short 41″ wingspan with 16″ of chord. It seems absurd, but the additional chord was shown to be very efficient in previous testing, with a clear top-speed advantage. I want to try this as a single and dual element.

There are big wings and big wings. This is the latter.

I’ll compare that wing to a Wing Logic, and that in turn to the industry standard 9 Lives Racing wing. Wing Logic appears to be a CH10, which has less camber and thickness than a Be 123-125 (which is about what the 9LR wing measures). If both wings were the same size and had the same Gurney flap, I’m fairly certain the 9LR would outperform Wing Logic. But this isn’t apples to apples, since the latter has more chord and a built-in Gurney flap. Anyway, interesting comparison.

I may also test my MSHD wing as a dual element. It’s designed as a 3D wing, but unlike many, the trailing edge is a single flat line across the span, and so I can add a second element pretty easily. And I kinda want to make a 2D MSHD, this one will be 63.5 x 11 with a built-in 1/2″ Gurney flap.

MSHD 3D 500 sq-in outperformed all other wings in my testing.

Tops

I tested the first version of my fastback at Watkins Glen, and I’d like to correlate the results from real-world track testing to wind tunnel testing. So I’ll bring an OEM roof and trunk with me and I may as well do one run without the top as well. I wish I still had a Chop Top, that would be worth testing again.

The one time I tried my race car’s fastback on my street car, the engine dropped a valve. But notice how narrow it is at the B pillar.

Open windows

Open windows add drag and reduce downforce, and so I’d like to test various things that may help. I’d like to test a wicker or vortex generator on the A pillar, smoothing airflow out the B pillar, using a longitudinal strake along the top of the window, and large NASCAR-style window nets (which are mostly fabric and not a lot of holes).

Mirrors and mirror stalks are another thing that might affect open windows, or downforce in general. By forcing air downwards, it’s possible to move air away from the windows (and wing). Conversely, moving air upwards may add downforce. And how would these trick mirrors compare to OEM mirrors or no mirrors at all? Gotta find out.

And you?

So that’s at least $4000 worth of testing and I haven’t started on your tests yet. What’s keeping you up at night?

Testing Wing End Plates in a Wind Tunnel

The following article is made up of excepts from my wind tunnel report. You’ll get a more cohesive story, and a lot more data on many more aerodynamic parts, if you buy the report and read it end to end.

End plates on wings are necessary; they separate the low-pressure region under the wing from the high-pressure area on top of the wing. The suction side of the wing is what does most of the work, so by keeping the high pressure side from bleeding into the suction side, the wing makes more downforce.

The shape of the low-pressure region under the wing is different for every airfoil. However, for most wings designed for motorsports, you’ll find that the low-pressure region is at the front of the wing and often extends ahead of the wing. The low-pressure area extends about a chord’s distance below the wing as well.

The shape of the low-pressure region below the wing depends on the airfoil. I inverted the images so that it relates to car wings. This image is from Race Car Aerodynamics, and I highly suggest you buy the book.

Given that information, and after looking at the preceding image, you might conclude that a good endplate should be shaped to exactly cover the high and low pressure regions of the wing. And from that, you might surmise that a good endplate for a 10” chord motorsports wing should extend 10” below the wing, and should have a lot of surface area concentrated at the front. And that’s how I see it as well. However, some end plates have most of the area towards the rear of the wing, and I can’t say I understand that. But aerodynamics is full of weird contradictions, and perhaps some of those end plates work.

With the amount of companies selling improved end plates with different shapes and sizes, you’d assume there was something to be gained over a plain rectangular end plate. And because some of these fancy end plates cost a couple hundred dollars, and boast CFD-designed pedigrees, they must be doing something useful, right?

CFD and wing efficiency

Some of my wind tunnel data conflicts with published CFD (computational fluid dynamics) data. This isn’t surprising, as CFD is just a computer calculation, and not real-world data. Manufacturers typically test wings in free-stream CFD, meaning that the wing is suspended in mid-air, as only a computer simulation can do. This is the best way to calculate what happens when you change wing angle, add Gurney flaps, or change the shape and size of end plates. Free stream CFD is essential, because it eliminates everything in front of the wing. This is really the only way to compare one thing to another.

But when you put a wing on a car, everything in front of the wing affects its performance. Wind speed and direction, cars in front of you, and open windows can make a huge difference. Plus there’s the shape of your car, the angle of the windshield, aerodynamic devices on your car, like splitter, canards, hood vents, vortex generators, GPS antenna, wing stands, … you name it, every single thing that’s in front of your wing changes how it performs. You’ll never get the same amount of downforce from your wing as the free stream CFD data shows. Not even close.

You can research wings on Airfoil Tools or Bigfoil, or use tools like Javafoil and CFD, and you’ll find wings that have a 14:1 L/D ratio, or better. But when you put the wing on the car and adjust the angle of attack, you’ll be stoked when your wing has half of that.

For this reason, anything you do to improve the efficiency of the wing in free-stream CFD is meaningless until you put it on the car. For example, modifications to wing end plates can reduce drag, and this shows up in CFD as a gain in wing efficiency. But when you put the wing on the car, the drag of the wing is inconsequential to the total vehicle drag. Touring cars are essentially huge rounded bricks, and wings are tiny streamlined objects by comparison, and so you can understand that the drag from the wing is essentially nothing compared to the drag of the vehicle. 

In reality, the only thing that matters is the aerodynamic efficiency of the entire vehicle, and you typically get that by going after as much wing downforce as possible. Modifications to the end plate that reduce drag might increase free stream wing efficiency, but they do that by reducing wing downforce. And this makes the L/D ratio of the car worse, and the car goes slower. Ergo, it’s utterly worthless to optimize wing efficiency in free stream CFD by reducing drag. If you use CFD for anything, it should be for optimizing the wing for maximum downforce.

Testing end plates in a wind tunnel

Before I get to the testing data, let me tell you exactly how shit stupid I am. My aerodynamics sensei Kyle Forster had these things to say about end plates:

  • Use a rectangular shape. Adding vents, cuts, and other tricks are more likely to reduce the performance of the wing than improve it.
  • Optimizing the performance of the wing end plates is the least important part of the entire vehicle’s aero package.

You might think I would take Kyle at his word. He worked for the Mercedes Formula 1 team as an aerodynamics engineer during the manufacturer’s most dominant years. But I’m also a stubborn, pig-headed ass who believes in getting his own data. So I took three end plates (four if you count that I turned one backwards) to the A2 wind tunnel and spent my hard-earned money to see if he was right.

I tested four wings in the wind tunnel, but when I got around to testing the end plates, they were all swapped onto a 55″ (1397 mm) 9 Lives Racing wing. This is the benchmark motorsports wing for many good reasons, so I figured why not go with the industry standard.

I first tested the basic rectangular end plate, which is made from an aluminum street sign that I simply cut in half, rounded the corners, and called it done.

Sorry about the image quality, these are stills from the video monitors in the wind tunnel.

I then swapped those for a popular CFD-designed end plate. I’ve always found this design to fly in the face of reason – why is there a big cut out right where the low-pressure region is?

CFD end plate with a pressure relief cut on the top, and a large radius cut into the leading edge.

I then turned the end plate backwards and tested that. From my point of view, it seems like the end plate might perform better with more surface area facing forward and less at the rear. It wasn’t a great fit, though.

The CFD end plate didn’t fit very well when I flipped it around backwards. I got two of the holes to match up and called it good enough.

Finally I tested an end plate of my own design. It’s in some ways the opposite of the CFD end plate, having a lot of surface area forward and tapering towards the rear. There’s a very small relief cut on the upper back corner that’s supposed to reduce a vortex there (er… so I’ve read). But more significantly, this end plate has a very small wicker on the trailing edge.

My Occam’s Racer end plate with more area forward and Gurney flap. This is the same end plate in the cover image.

Let’s see how the end plates performed:

End platecD cLVehicle L/D
Rectangular.467-.382.82
CFD.475-.386.81
CFD backwards.474-.385.81
Occam’s Racer.480-.398.83
Coefficients of drag and lift with various end plates. cL is a negative number because it’s showing downforce; more negative is more better.

Wind tunnel data

So let’s unpack the coefficient data and translate that into more common figures, like pounds of downforce and horsepower consumed.

  • Rectangular – Vehicle L/D ratio .82
    • Baseline to compare with other end plates
  • CFD – Vehicle L/D ratio .81
    • +1.8 lbs total downforce
    • 4.1 lbs drag = 0.4:1 L/D ratio for end plate
    • +1.1 hp used from drag
  • CFD backwards – Vehicle L/D ratio .81
    • +1.5 lbs total downforce
    • 3.5 lbs drag = 0.4:1 L/D ratio for end plate
    • +.9 hp used from drag
  • Occam’s Racer – Vehicle L/D ratio .83
    • +8.8 lbs total downforce
    • 6.9 lbs drag = 1.3:1 L/D ratio for end plate
    • +1.8 hp used from drag

The first thing you’ll notice is that the CFD end plate increased downforce by almost 2 lbs at 100 mph. That’s more than the rectangular end plate, but not much. As a consequence of that additional downforce, there’s a bit more drag.

Turning the CFD end plate backwards resulted in less downforce, but also less drag. Overall, the CFD end plate performed the same forwards as backwards. Surprising.

Another surprise was that my Occam’s Racer end plates gained 8.8 lbs of downforce over the rectangular plate. Not surprising, this also resulted in more drag. However, these end plates resulted in the best vehicle L/D ratio.

Racing simulations

Those numbers are all very close, and you might be wondering how they affect the only thing that matters: lap times!

To find out, I put the coefficient of lift and drag values into OptimumLap and ran them around two race tracks, the autocross course from 2010 SCCA Solo Nationals, and Lime Rock Park. I typically use these two tracks because they are close in lap time, but are completely different with respect to speed. I’ve also included my local track Watkins Glen, because it’s very high speed and should spread the results out more. (My wind tunnel report shows lap time comparisons for every part that I test, as well as some useful combinations.)

End platecD cLAutocrossLime RockWGI
Rectangular.467.38261.7961.03134.74
CFD.475.38661.7961.05134.81
CFD backwards.474.38561.7961.05134.81
Occam’s Racer.480.39861.7861.04134.81
Lap times

On the autocross track, my end plates won by a whopping .01 seconds. At Lime Rock, the rectangular street signs won by the same insignificant margin. At Watkins Glen, the “No Skateboarding” sign went .07 seconds faster than either of the fancy end plates.

Discussion

The CFD-designed end plates were a disappointment, and put an exclamation point on my rant at the beginning of this post about using free stream CFD. Look, I’m not at all doubting that these end plates worked better in CFD and returned exactly what they calculated. But overall performance didn’t change facing either way, and shows how useless free stream CFD can be in the real world.

The custom end plates I designed are based on a hunch that I should put most of the area low and forward. More significantly, these end plates have a small Gurney flap on the outer edge, and it’s likely that the shape of the end plate was no better than the others, and it was simply the addition of the wicker that gave this end plate the most downforce. Most downforce doesn’t mean best, as it wasn’t terribly efficient and only returned a 1.3:1 L/D ratio above and beyond the rectangular plate. Using these end plates would make the car faster on a tight track, but slower on most race tracks.

In the end, there really is nothing wrong with a rectangular end plate. If you don’t have the means of CFD testing your entire vehicle and optimizing the end plates to your entire car, then a rectangular end plate is your best bet. I make mine from street signs that I buy from my local metal recycler for $1 per pound. And so both end plates are less than $2 and come with amusing graphics. It astonishes me that people will pay much more for something that performs worse.

But let’s face it, no matter what you do to the end plate, it’s not going to make it significantly worse, either. End plates with cuts and vents are a great place for personalization, they are a source of many silly conversations, and they throw competitors off the scent. In the end, I say do whatever you want, it won’t matter much anyway.

But if you want to hedge your bets and do the least work, just stick to a rectangular end plate. Learning this lesson cost me $300 plus a lot of time and effort, and it proves I should just have just believed Kyle Forster.

But it wasn’t a total waste of time and money if that keeps other people from making the same mistake. So if this article saves you money, please consider buying me a coffee, or if you want 50+ pages of the same kind of data, then buy my wind tunnel report. It’s only through contributions that I can afford to do wind tunnel testing and continue the lord’s work. Thanks!

Postscript

After posting this article, I got a bunch of great comments on the Professional Awesome Technical Forum on Facebook. This group has a wealth of knowledge that surpasses my own, so please see this post, scroll through the comments, and benefit from the global knowledge base.