JXB Audi: Is this the ultimate autocross aero setup?

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

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

Duke
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
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
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
busmech 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
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. 

GameboyRMH
GameboyRMH GRM+ Memberand MegaDork
8/23/22 10:51 a.m.

^Good point. Putting the same amount of power into the sucker fan wouldn't result in as much downforce. It would also be interesting to produce the same amount of downforce with a sucker fan (however much power that takes) and compare forward traction, acceleration and top speed.

Mugenlude
Mugenlude
8/23/22 12:33 p.m.

In reply to Duke :

I can confirm from driving the car, there is no issue seeing over the front wing or driving through slaloms.... the things that people seem to doubt most (we had doubts too)  =)

nocones
nocones GRM+ Memberand PowerDork
8/23/22 12:42 p.m.
Robbie (Forum Supporter) said:

In reply to GameboyRMH :

Which is more efficient, an airplane or a helicopter?

But it is an excellent question. 

An airplane is more efficient but wings require airspeed to create lift.  Your delta P on a wing is limited by the wings velocity.  

Helicopters turn HP into noise and as a consequence generate lift.   A sucker car can make theoretically up to ~14psi of delta P on the floorpan at 0 speed assuming enough HP is thrown at it.  

If you have limited HP or weight there are potentially cross over points where the HP required to drive a sucker mechanism or the weight penalty of said sucker mechanism would be detrimental, but if everything was unlimited big active wings combined with a sucker floor would be the ultimate. 

nocones
nocones GRM+ Memberand PowerDork
8/23/22 12:45 p.m.

In reply to Mugenlude :

Have you ran any back to back wings on/wings off testing?  I understand that you probably can't do it before the big event but it would be interesting after.  

When we were testing out FSAE car the wings where worth 2-4% on a cornering intensive course, however there was substantial driving technique change required to extract that.  Shortest distance gave way to highest possible cornering velocity on all but the tightest corners.  

ProDarwin
ProDarwin MegaDork
8/23/22 1:04 p.m.

Jupiter Gravity!

Duke
Duke MegaDork
8/23/22 1:29 p.m.
Mugenlude said:

In reply to Duke :

I can confirm from driving the car, there is no issue seeing over the front wing or driving through slaloms.... the things that people seem to doubt most (we had doubts too)  =)

Cool!

 

Mugenlude
Mugenlude New Reader
8/23/22 1:55 p.m.

In reply to nocones :

We tested with the new front aero and normal SM rear wing setup (2-element Ciro) - it resulted in me spinning the car for the first time ever turning in the first brake zone.

Javelin
Javelin GRM+ Memberand MegaDork
8/23/22 2:14 p.m.
GameboyRMH said:
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?

The cooling is all on the rear with a huge fan. It's blown over the rear spoiler!

engineered
engineered New Reader
8/23/22 2:29 p.m.

Impressive setup.  Was CFD analysis done to design this? 

Front wing looks extremely steep, does it not stall?  And looks like it might feed tons of dirty air to the rear wing.  If the car if front limited then this might be OK.

Certainly tons of drag with this setup, so I assume they have gobs of power. (can't see the full article yet)

CrustyRedXpress
CrustyRedXpress GRM+ Memberand HalfDork
8/23/22 4:26 p.m.

This is the ideal racecar body. You may not like it, but this is what peak autocross looks like.

msterbeau
msterbeau New Reader
8/23/22 4:33 p.m.
BenB said:

This.

hilary_anderson_racing
hilary_anderson_racing
8/23/22 7:39 p.m.
Javelin said:
GameboyRMH said:
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?

The cooling is all on the rear with a huge fan. It's blown over the rear spoiler!

The rear cooling is just the heat exchanger for the air to water cooler for the turbos.

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand PowerDork
8/23/22 8:00 p.m.

I see I'm not the only person that has questions about heat control. 

759NRNG
759NRNG UberDork
8/23/22 9:14 p.m.

R    U    effen     kidding  ME  what are y'all on CRACK????  enough already 

Javelin
Javelin GRM+ Memberand MegaDork
8/23/22 10:11 p.m.
Floating Doc (Forum Supporter) said:

I see I'm not the only person that has questions about heat control. 

Javelin
Javelin GRM+ Memberand MegaDork
8/23/22 10:13 p.m.
759NRNG said:

R    U    effen     kidding  ME  what are y'all on CRACK????  enough already 

It's a purpose built autocross only car competing at the no-rules UMI King of the Mountain this weekend, where it has a legitimate shot at winning. It's an A-Mod with a body conceptually, and nobody laughs at them.

JG Pasterjak
JG Pasterjak Production/Art Director
8/23/22 10:40 p.m.
Javelin said:
It's an A-Mod with a body conceptually, and nobody laughs at them.

I mean, I'm laughing, but I think that's more of a fear response.

Someone on Facebook tried to be king of the snarkmsters and posted something like "All this just to chase cones?"

And my response to that is "YES. OF COURSE. WHY ELSE WOULD YOU DO IT. ALL OF THIS STUFF WE DO IS MADE UP ANYWAY SO WHY NOT DO THE MOST AMAZING AND EXTREME VERSION OF EVERYTHING." God some people wouldn't know a party if they had a lampshade on their heads. Maybe try appreciating the willingness of smart and creative people to do cool stuff like this and you might actually experience joy for once in your life.

nealt
nealt GRM+ Memberand New Reader
8/24/22 12:24 a.m.

In reply to JG Pasterjak :

I'd do something this crazy for the fun of it. But in this case, there's not just a bowling trophy or an embroidered jacket on the line...there's twenty-five-effen-k to be won!

loosecannon
loosecannon SuperDork
8/24/22 7:30 a.m.

I can't wait to see some video of it on track. 

te72
te72 HalfDork
8/24/22 10:22 a.m.

Still has better visibility lines than an S550 Mustang...

stonebreaker
stonebreaker New Reader
8/24/22 11:31 a.m.

That's so cool!! Plus, you can earn extra money in the winter snowplowing!

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
8/24/22 11:31 a.m.
JG Pasterjak said:
Javelin said:
It's an A-Mod with a body conceptually, and nobody laughs at them.

I mean, I'm laughing, but I think that's more of a fear response.

Someone on Facebook tried to be king of the snarkmsters and posted something like "All this just to chase cones?"

And my response to that is "YES. OF COURSE. WHY ELSE WOULD YOU DO IT. ALL OF THIS STUFF WE DO IS MADE UP ANYWAY SO WHY NOT DO THE MOST AMAZING AND EXTREME VERSION OF EVERYTHING." God some people wouldn't know a party if they had a lampshade on their heads. Maybe try appreciating the willingness of smart and creative people to do cool stuff like this and you might actually experience joy for once in your life.

Can you engrave this with a head shot (and maybe a dragon or a wolf and moon) on the challenge trophies this year?

CrustyRedXpress
CrustyRedXpress GRM+ Memberand HalfDork
8/24/22 5:29 p.m.

In reply to Robbie (Forum Supporter) :

I think this is probably the forum's first copypasta. It's brilliant. 

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand PowerDork
8/26/22 1:39 p.m.
CrustyRedXpress said:

In reply to Robbie (Forum Supporter) :

I think this is probably the forum's first copypasta. It's brilliant. 

Yes, I've met that guy, and he's actually a really good writer. 

ojannen
ojannen Reader
8/26/22 2:20 p.m.

It is sitting in 9th after the first heat in the fastest class.

The top 10 has 2 teslas, 4 evos, 2 corvettes, a viper, and this S4.  The top 3 are way ahead with 4-10 separated by about 4 tenths.  There are lots of awd cars there.  I wonder if it is course based or weather based or the good drivers in good awd cars having a good morning.

loosecannon
loosecannon SuperDork
8/27/22 11:34 a.m.

I wonder what happened that the car is not even in the trophies? I'm guessing there are set up issues because throwing giant wings on a car tends to change spring rates and such.

JG Pasterjak
JG Pasterjak Production/Art Director
8/27/22 2:24 p.m.
loosecannon said:

I wonder what happened that the car is not even in the trophies? I'm guessing there are set up issues because throwing giant wings on a car tends to change spring rates and such.

This afternoon's runs have been better for Jason in particular, but early on they were having real trouble with porpoising coming out of slower corners. To the point they were having to back out of the throttle to control the osciallations. I know they added a lot of spring to deal with the wings, and it may not be agreeing with UMIs bumps.

Javelin
Javelin GRM+ Memberand MegaDork
8/27/22 9:32 p.m.
loosecannon said:

I wonder what happened that the car is not even in the trophies? I'm guessing there are set up issues because throwing giant wings on a car tends to change spring rates and such.

They made the challenge for the 25k tonight and solved the porpoising with softer springs. 

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand PowerDork
8/27/22 11:29 p.m.

they made it through the first round of 6, right?  But missed out in the move from 24 to 8?  I know times crept down as the night wore on... but I'm not sure they had the pace for it?

 

in a completely unrelated note... anyone remember where the ChEaparral's C4 happens to be?

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/28/22 8:10 a.m.
GameboyRMH said:
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?

About 10% of the downforce from a Top Fuel dragster is from the headers.

 

They used to point the headers at the rear tires to blow them clean, in the days when they spun the tires down the track and had no aero to speak of.  Someone tried pointing them up and instantly had a lot more traction.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
8/28/22 8:16 a.m.

In reply to sleepyhead the buffalo :

Corvette museum, IIRC.

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand PowerDork
8/28/22 11:47 a.m.

I've been thinking about it since posting last night... and I reckon the 'surface undulations' that were upsetting the JXB car, probably means that a suction system is probably of limited advantageous use at UMI

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