JXB Audi: Is this the ultimate autocross aero setup?

By J.G. Pasterjak
Aug 23, 2022 | Audi, Autocross, Aerodynamics, audi s4, UMI, King of the Mountain

Photography by Hilary Anderson

What if we go bigger?”

Sure, why not? Lots of amazing ideas start out that way–including this one.

Jay Bullington is the owner of this particularly aggressive Audi S4, which normally competes in the SCCA’s Street Modified autocross class.

Having earned a berth in UMI’s King of the Mountain autocross competition, which puts more than $25,000 of prize money on the line in a winner-takes-all, run-what-you-brung-on-200tw-tires format, Bullington’s frequent co-driver, Hilary Anderson, began scouring UMI’s thin rule book for any advantage.

I realized that the rules governing aero mods were pretty limited, meaning we could do almost whatever we wanted to,” Anderson says. “So I suggested that we could put a front wing on it, like Dallas Reed’s RX-8.”

Reed’s time attack Mazda RX-8 runs an aggressive dual-element wing hung off the front bumper, but this idea, while appealing to Bullington, wasn’t quite there yet.

His suggestion: “What if we go bigger?”

Upon returning to his home base at JXB Performance, where he builds and sells high-performance chassis and driveline pieces for many premium German sports machines, Bullington set about designing an aero package that would raise the bar at an already loaded King of the Mountain competition.

He designed a five-element front and five-element rear wing. The former is cantilevered out in clean air in front of the car, while the latter is perched fully above the roofline on a pair of sturdy pylons.

He based the design and wing profiles off an A Modified formula car formerly driven by KJ Christopher. With less than a week before the big event, Bullington and his co-driver–multi-time SCCA Solo champ Jason Frank–have had only one weekend of testing to sort out the balance.

With all that downforce, it will take some power to push it through the air, but this already potent platform should have no trouble making that happen. In its current SCCA Street Modified trim, it produces an estimated 650-plus horsepower from its 4.0-liter, twin-turbo engine.

If you’re saying, “Wait, the 4.0TT never came in the S4,” you’re right. The engine comes courtesy of an Audi S7 and has been upgraded with RS7-spec turbos, more boost and a custom tune.

Many of the chassis parts were built by Bullington’s JXB, including the spherical bushings, strut mounts, driveshaft carriers and anti-roll bars. Reinharte three-way adjustable shocks handle damping, and a six-speed transmission directs torque to all four wheels.

And now if you’re saying, “Hey the 4.0TT never came coupled to a manual transmission,” you’re right again.

Bullington believes this is the only 4.0TT to be hooked to a manual box. He credits Oleg Popov with the hard parts swap and Nikita Lesnikov with the coding to digitally integrate the package into a working whole.

With limited time to test, the JXB team is trying to compress a lot of development and practice into a short timeline.

Anderson said the only real changes from the Street Mod setup will be the aero, the use of Falken Azenis RT660 rubber in place of Hoosiers, and likely some different spring rates to compensate for the added downforce.

But, she adds, the car is a joy to drive: “It’s super linear. Initially we were a bit concerned that the turbos would pose a lag issue, but they spool early and the V8 torque is enough to get you out of corners if you’re not on boost.”

The wings offer nearly 50 square feet of combined wing area–27 rear and 20 front–and the JXB crew is hoping that’s enough to hold Bullington and Frank on the mountain and fly them to a win on one of the most high-profile autocross stages in the country.

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GameboyRMH GRM+ Memberand MegaDork
8/23/22 8:26 a.m.

I would think making the last couple elements of the front wing out of Lexan would be worthwhile...

PMRacing GRM+ Memberand UltraDork
8/23/22 8:45 a.m.

BenB HalfDork
8/23/22 8:45 a.m.

Duke MegaDork
8/23/22 9:13 a.m.

I was wondering, since there's no way you can see cones past that thing, is the intent to yeet them into the stratosphere before the shaggers even notice you hit one?


hunter47 Reader
8/23/22 9:16 a.m.

In reply to Duke :

"hey wasn't there a slalom here?"

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
8/23/22 10:04 a.m.

That's awesome, and I hope it does well.

I've long thought that for autox, there is no such thing as too much wing!

dculberson MegaDork
8/23/22 10:12 a.m.

It's a training aid designed to force you to keep your eyes up. You should already know where the cone is by the time the car gets there, and this car makes sure you either learn that skill or take out every cone on the course.

busmech GRM+ Memberand New Reader
8/23/22 10:40 a.m.

Lets see a bigger radiator fan taking air from under the car. "but I need a 100hp engine to cool my car". Also needs the lighted rods on the front corners like a big rig has

GameboyRMH GRM+ Memberand MegaDork
8/23/22 10:42 a.m.
busmech said:

Lets see a bigger radiator fan taking air from under the car. "but I need a 100hp engine to cool my car". Also needs the lighted rods on the front corners like a big rig has

I've been thinking, when you put this much power into driving wings through the atmosphere, and that power has to go through the ground, how much forward traction could you gain by putting the same amount of power into running a sucker fan instead?

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
8/23/22 10:48 a.m.

In reply to GameboyRMH :

Which is more efficient, an airplane or a helicopter?

But it is an excellent question. 

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