Ask AJ Hartman - Aero Questions

[mavisky]

I'm looking to start working on some aero on my 93 Fox body. I am looking at this cowl block off panel and am wondering if it will cause issues later when I add a hood vent, rear wing and front splitter. I know the lower windshield is a trouble area for turbulence if I remember correctly. Currently I have the stock cowl vent on the car. What is the thoughts for adding this panel whether it be now, before I have any of the others or later after I have some?

Also while I am asking question. I have a 93 Notchback. What is the proper height and width I should look at for the rear wing? I thought I had heard before that most wings should be no taller than the roof. I am going to be running NASA TT & ST in the future and rules state it can be no taller than 8.0" above the roof line or width greater than the vehicles body width, or end plates with area greater than 144 square inches each, or 12.0" protrusion from the rear of the vehicle.

I can't imagine any negatives from that air panel being in place over the stock setup.

In regards to the Wing, AJ just posted a video discussing height and setback on his Youtube Channel. The general consensus is that there's generally no need to mount the wing as high as the roof unless you're dealign with a short decklid like your notchback. In that scenario, the harsh drop off can make it hard to get clean air anywhere near the actual decklid. In your scenario mounting it approximately as high as the roof or just a little below would probably be best.

 

[Ewheels]

Because they spent hundreds if not thousands to get this trick setup and it's unique I guess. I don't know why people have little stuffed dolls of children hiding their eyes leaned against their classic street cars, but they do sometimes. I don't understand why car show people do much of what they do.

They're an interesting breed, that's for certain.

 

[Mad Hatter]

Mad Hatter, are you saying the Ben Calimer trans actually runs cooler? i wonder why? i also have one..

I think its about the improved bearings and the semisquare cut gears. Its Definity much cooler..... Sorry about being off topic.

 

[Mistaricky]

Hey AJ,

I'm not sure if this has been asked already. but on the 992 gt3rs. they have some sort of air guide on the roof. I know our cars can benefit from vortex generators based on verus engineerings research. But could our cars benefit in any way from these guides? I imagine rear aero would be necessary to see an actual benefit.

 

[Fabman]

Because they spent hundreds if not thousands to get this trick setup and it's unique I guess. I don't know why people have little stuffed dolls of children hiding their eyes leaned against their classic street cars, but they do sometimes. I don't understand why car show people do much of what they do.

I was in that show car crowd for a minute....all the fake wannabe race car sh!t and dumb looky lou stuff with no purpose was nauseating enough that I turned my show car into a race car after 30 years away from track life.
Now I look back and think: "Man, I really effed up a nice car". LOL.

 

[flyhalf]

Hey AJ,

I'm not sure if this has been asked already. but on the 992 gt3rs. they have some sort of air guide on the roof. I know our cars can benefit from vortex generators based on verus engineerings research. But could our cars benefit in any way from these guides? I imagine rear aero would be necessary to see an actual benefit.
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Fyi.. i believe AJ tested vortex generators on wind tunnel and didnt find any real benefit.

 

[flyhalf]

Fyi.. i believe AJ tested vortex generators on wind tunnel and didnt find any real benefit.

Just found it.
It wasnt a 350.

 

[Mistaricky]

Just found it.
It wasnt a 350.

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Verus must be milking the advertising on those vortex generators. Thank you for the info!

 

[flyhalf]

Verus must be milking the advertising on those vortex generators. Thank you for the info!

They did CFD on 350. so maybe there is a benefit for the car? Also their wing is different than AJ (less DF) so maybe could help?

 

[Mad Hatter]

Saw this pic today of the NASCAR trip to Le Mans, I guess they went for more downforce, maybe a wing was not allowed? In any case it was fast.

 

[flyhalf]

Saw this pic today of the NASCAR trip to Le Mans, I guess they went for more downforce, maybe a wing was not allowed? In any case it was fast.

View attachment 90142

It was allowed .but they did that on purpose to keep the "NASCAR" STYLE. LOVE IT

 

[Mad Hatter]

It was a very cool idea and wish I could have seen it. But that rear duck tail must have had massive drag?? Love the idea of a lump of "NASCAR American Muscle" shaking the leaves off the trees a Le Mans.

 

[Dave_W]

I haven't kept up with the rules and changes between the old GTE and GT3, but the GT classes used to use air inlet restrictors to reduce power for Balance of Performance. I don't think the Garage 56 car was subject to the BoP rules, so it probably could make way more power than the GT3 cars. The main concern that the ACO (group that runs LM24) had was the NASCAR entry would be a moving chicane in the Porsche curves. Before practice, they actually came up with a system that dictated flag stations in the area show a mandatory white flag for a slow vehicle whenever the Camaro was in the esses. All the extra (not NASCAR legal) aero on the Chevy meant it was able to maintain pretty good speed through that section, so they dropped the white flag mandate after the first couple practice sessions.

 

[mikeD4V]

Hey AJ,

I'm not sure if this has been asked already. but on the 992 gt3rs. they have some sort of air guide on the roof. I know our cars can benefit from vortex generators based on verus engineerings research. But could our cars benefit in any way from these guides? I imagine rear aero would be necessary to see an actual benefit.
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The fins on the GT3RS roof are designed to deflect warm air, from the front heat exchanger, outward in an attempt to get cooler air into the engine's intake over the trunk lid.

There are a few videos from Porsche circulating about how the aero works on this car but here's the p-car media article regarding its aero:

Aerodynamics

media.porsche.com

• Air from the centrally positioned radiator flows out via large openings and air deflectors (nostrils) on the bonnet and is directed to the left and right. Additionally, fins on the roof direct the air outwards, ensuring cooler intake temperatures in the rear.

 

[twistedneck]

Does anyone make a ready to bolt on big huge racing front splitter for S197 with mini diffusers on it and side skirts or is that always DIY?

 

[Fabman]

Does anyone make a ready to bolt on big huge racing front splitter for S197 with mini diffusers on it and side skirts or is that always DIY?

DIY.
@AJ Hartman has all the parts but you’ll need to assemble them and make the bracketry yourself. He has the pattern for mine so you could purchase an exact copy of what I’m running if you find that interesting at all.

 

[Egparson202]

Nice car @Fabman ! Lotta work went into that piece.

 

[AJ Hartman]

Another question...I have a CAI which "seals" up against the hood to (as y'all know) keep the hot stuff hot and the cool stuff cool (as the MC DLT tried to do years ago...hahahaha). The stock hood vent is right over the CAI, about where I marked in red. Since the CAI has an air inlet that allows air in through the front grill, I'm curious if the hood vent should be sealed up? My completely unqualified theories:
1. Is the hood vent pulling air out of the CAI bucket, making it hard for the throttle body to breathe?
2. Is the hood vent helping to pull air into the bucket, allowing ample air for the throttle body?

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I developed these for my GT350 air box. The air box on the GT's looks really close but not 100% sure how close it is to fitting. https://ajhartmanaero.com/gt350-airbox-lid/

 

[Arscca#27]

AJ,
has there been any wind tunnel testing for the Fox body Mustang between the GT and LX front bumpers that I could see? This winter I want to add a splitter and I'm curious which, if either front bumper is better. I already have the lower grill opening ducted to the radiator and I'm planning on adding a hood vent this winter as well. I'm curious though if I should change to a GT bumper over the current LX front bumper to help with aero or leave it as it is?

 

[Arscca#27]

I can't imagine any negatives from that air panel being in place over the stock setup.

In regards to the Wing, AJ just posted a video discussing height and setback on his Youtube Channel. The general consensus is that there's generally no need to mount the wing as high as the roof unless you're dealign with a short decklid like your notchback. In that scenario, the harsh drop off can make it hard to get clean air anywhere near the actual decklid. In your scenario mounting it approximately as high as the roof or just a little below would probably be best.

Thanks for your advice and AJ's video. It was a big help. I forgot to respond earlier. I currently have it roughly 2 1/2" below the roof and it seems to be working great in the one track outing I did at VIR. Now I'm going to build a splitter and add a hood vent.