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Ask AJ Hartman - Aero Questions

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315
369
Exp. Type
HPDE
Exp. Level
3-5 Years
Raleigh, NC
I sealed the top of the bucket with clear lexan. It was pretty simple. But also on my '16 S550 the grille were the air inlet is has a lot of the hex holes blocked off. I felt that was not good so I opened them up with a drill and a dremel grinder. I figure more air is better. I still have no idea why Ford would block that off.
I hadn't thought of that. You probably prevented me from asking another question next week. 🤪
 
You'll probably want to seal the top of the airbox but not a huge deal.

Engine perspective: Air entering the grill is ducted to the air box, at WOT the fresh air will be ingested into the engine, at idle/cruise the unused air will go out the vent, sealing the airbox will net some tiny amount of positive pressure but likely not much hp gain.

Aero perspective: the vent will be evacuating airbox air instead of air from the back of the radiator, so a tic of cooling to be had if its covered.
 
83
132
Exp. Type
HPDE
Exp. Level
Under 3 Years
West
I have the GT350 airbox currently but will be installing the closed top GT500 airbox very soon. I did not realize much change in the AIT with the open top and did have my filter get quite soaked when the car sat in a good rain storm with the front end pitched downward in my driveway. I agree that the "ram" from the front inlet with a closed box will be nothing to negligible, but I hope that I can get a few degrees less AIT since the 350 box does not seal well against the hood even with added sealing.
 
351
355
Exp. Type
Autocross
Exp. Level
20+ Years
So Cal
Hey, AJ, check this out. I think I might have a couple ideas for you. These are 350R Magneride Struts. I'm using a 3" ID spring and a shock body/perch off a King desert damper. The upper perch is a Hyperco Wobbly-top. If you Dremel the dust cover retaining ears off the bearing, this fits absolutely perfect. I've got probably 15-20k miles on it.

20211126_130658.jpg20211126_130020.jpg20211126_130035.jpg
 
Hey, AJ, check this out. I think I might have a couple ideas for you. These are 350R Magneride Struts. I'm using a 3" ID spring and a shock body/perch off a King desert damper. The upper perch is a Hyperco Wobbly-top. If you Dremel the dust cover retaining ears off the bearing, this fits absolutely perfect. I've got probably 15-20k miles on it.

View attachment 84922View attachment 84924View attachment 84923
Cool for sure. But your missing the biggest advantage of my setup in that it can be installed in about an hour or two on an unmodified strut with just basic hand tools.
 
351
355
Exp. Type
Autocross
Exp. Level
20+ Years
So Cal
You were asking about the top spring perch and the bearing. Here's the way I made it work. I did mine for me, not production, so there are obviously going to be differences in our approach. To have your initial response be an unfavorable comparison of the two is a little disappointing. When I saw your approach, I thought it was a really cool idea.

You might be better off going for springs with a shorter height to get your static ride back if you want to go much stiffer than 350#/in. That's on the low side for track duty, IMO, but it's about all you're going to be able to damp if you're on the base Magneride struts. The 350R/500 struts and shocks make significantly more force and can take more spring. You've got plenty of real-estate where you're putting your spring on the diameter, but not a lot on the length. The longer the piece of wire you can use for any spring, the better they tend to be in terms of rate consistency. 2.5/3.0 barrel or 3" OD straight spring would be easy gain if you're looking for a little extra load capacity/travel.
 
You were asking about the top spring perch and the bearing. Here's the way I made it work. I did mine for me, not production, so there are obviously going to be differences in our approach. To have your initial response be an unfavorable comparison of the two is a little disappointing. When I saw your approach, I thought it was a really cool idea.

You might be better off going for springs with a shorter height to get your static ride back if you want to go much stiffer than 350#/in. That's on the low side for track duty, IMO, but it's about all you're going to be able to damp if you're on the base Magneride struts. The 350R/500 struts and shocks make significantly more force and can take more spring. You've got plenty of real-estate where you're putting your spring on the diameter, but not a lot on the length. The longer the piece of wire you can use for any spring, the better they tend to be in terms of rate consistency. 2.5/3.0 barrel or 3" OD straight spring would be easy gain if you're looking for a little extra load capacity/travel.

I originally tried 6" springs but they would go solid like 1/4" before the internal bump stop and with the shim stack to maintain ride height (or adjustable perch like I showed in my video) there just wasn't quite enough room. I'm sure with some tinkering and what exact spring a 6" could maybe work but it would be tricky. So 7" it is and since the perches themselves are not adjustable like yours, about 400lbs is about all you'll be able to do with my kit.
 
51
43
Exp. Type
HPDE
Exp. Level
3-5 Years
California
Hey AJ,
So I started in Hondas and in the JDM side of time attack you see these "fender canards" on lots of cars. I was curious if these are simply another method for relieving fender pressure, or if they may add some downforce from the angle or mostly designed for cosmetic purposes. I see this style on lots of JDM cars at Tsukuba circuit and have yet to see it on an American car so I was wondering what your take would be.
Here is a sample of the canards:
1685647766170.png
And here is some examples of cars with this "fender canard" already molded in to it:
1685647839992.png1685647869255.png
 
Hey AJ,
So I started in Hondas and in the JDM side of time attack you see these "fender canards" on lots of cars. I was curious if these are simply another method for relieving fender pressure, or if they may add some downforce from the angle or mostly designed for cosmetic purposes. I see this style on lots of JDM cars at Tsukuba circuit and have yet to see it on an American car so I was wondering what your take would be.
Here is a sample of the canards:
View attachment 86645
And here is some examples of cars with this "fender canard" already molded in to it:
View attachment 86646View attachment 86647
Kinda tricky to say. The upper one is just more or less a "fin" to direct air. Where? I'm not sure. It looks like right at the side mirror which isn't the smartest move. Air is somewhat downwashing around that area so you'd get some result but totally depends on other factors whether thats good or not. The blue car on the other hand, I'd assume that the gap created by the trailing edge of the fender would work similar to a tire relief and helps under fender pressure evacuate. So totally different scenario than the top picture.
 
51
43
Exp. Type
HPDE
Exp. Level
3-5 Years
California
Kinda tricky to say. The upper one is just more or less a "fin" to direct air. Where? I'm not sure. It looks like right at the side mirror which isn't the smartest move. Air is somewhat downwashing around that area so you'd get some result but totally depends on other factors whether thats good or not. The blue car on the other hand, I'd assume that the gap created by the trailing edge of the fender would work similar to a tire relief and helps under fender pressure evacuate. So totally different scenario than the top picture.
Interesting, thanks for the info! I overlooked the difference in shape from both of them.
 
18
29
Exp. Type
Autocross
Exp. Level
Under 3 Years
Concord NC
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.

Cowl block off.jpg
 
558
702
Exp. Type
Time Attack
Exp. Level
3-5 Years
SoCal
Lol, me too, went through five of them suckers!! added a Setrab 915 cooler with a pump and temps went from 300 to 180-200, That was with a extra big cooling duct under the car. Finally got fed up and added a Calimer stage 3 Mt82 and temps went down to 180 with out the pump.....
Mad Hatter, are you saying the Ben Calimer trans actually runs cooler? i wonder why? i also have one..
 
51
43
Exp. Type
HPDE
Exp. Level
3-5 Years
California
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?
From my very unprofessional understanding. The smooth panel should help in reducing drag. I think it should be beneficial at any point in aerodynamics on the car. The lack of wipers and vents should help smooth out the airflow and hopefully drop the pressure on that part of the windshield.
 
I don't understand why this became a trend. If someone wants to take their sports car on a road trip and needs the extra storage space, sure, but why are people putting them on to take to a car show 🤷‍♂️

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.
 

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