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Front grill/fascia mod

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Getting further along . Today I cut another hole - for the inlet . It seems small- maybe too small. I meant to make it 4” tall and it’s more like 3.25” . 
I also think where the  fascia has landed I might actually be able to fasten the grill on top of it to keep it stick looking . I planned on blacking out the fascia to make it disappear in the background , but hard to say what it will look like once done . All I know is that no air is getting anywhere I don’t want - lol


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I built something similar for my race Z. I used .050” aluminum on the sides, and for the top and bottom the material is about the thickness of a beer can, about .010”. I used the lower right and left areas to funnel air for a second brake cooling duct on each side. 

Originally I had a sheet of lexan across the upper half, to block off the right and left upper half, and perforated the center for the radiator duct. After a bit of vigorous bump drafting the front got messed up a bit so the lexan went away.


I really should replace it, the appearance was much better.







Edited by Racer X 69
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When I first put the car on track, I removed the inner structure from the hood, with only the outer skin. At that point the ducting wasn't in place. It was obvious there was plenty of air getting into the engine bay.




The hood looked like it was going to be ripped off at speed (about 110 in this shot). I solved that problem by adding a 5th hood pin at the center of the rear edge, where the stock hood latch is, and adding two short bits of aluminum angle where it was buckling at the sides.

Last Novice Race SIR.jpg

Edited by Racer X 69
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Looking great, and we are looking forward to how it performs! 


A little bit of a nerd sesh...feel free to skip but if you are curious about the reason:


There is a direct relationship between flow velocity and pressure. The hood bulging is because you have low pressure on the top of the hood because of high flow velocity over the hood at speed. Meanwhile, you have very low air velocity on the underside of the hood. Its not a huge pressure difference but when applied on the whole surface of the hood, you get some big forces. It is how an airfoil (airplane wing) works. lets just say the hood is 4'X5'. That is 2880 square inches. Therefore, to get just 29lbs of uplift on the hood, it only takes 0.01psi of difference in pressure. 


When we design fueling facilities, the number-one stress on the canopy structure (that cover over the pumps) is uplift from wind speed. This shocks most people when I explain the uplift can be so high, it can pull the footing right from the ground if it is not designed correctly.


one thing you could do is add reliefs/vents to the hood or surrounding surfaces. Air under the hood will rush to the relief because of the difference in pressure and some of the uplift will be relieved. 


I have two latches in the front of my hood, one in the rear center, and two bump-stops midway down the length of the RFP hood. My plan is to replace the bumpstops with latches if the hood bulges too much, but that may not be enough. Trial and error! Greg Ira has 5 or 6 latch points on his EP car. 

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The exit strategy will be the most challenging to implement - especially if you don’t want to alter the looks of your car . 
No ready to put a vent in the middle of my hood . I might consider vented access doors , but really not a fan of that look either . 

I think I might increase entry size by having a second inlet above the bumper. This would give a more direct shot of air to the top of the radiator . 

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I opened up the hole . I like the fact that the upper radiator will get air this way for sure . I tried to make a smooth transition top and bottom . I’ll close up any crevices when final  version is done . Still plan on running the grill right on top of this . I want this to blend in 







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On 3/18/2022 at 1:35 PM, AydinZ71 said:

really looks great! I like the attention to detail. Consider cutting off the ends of those sheet metal screws. They will snag you good if you forget they are there! ask me how I know 🤣

I’m using them temporarily before I install rivnuts . It’s just easier to take apart with the sheet metal screws . I might keep some in areas I’m not putting my hands . 

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