heat management, CF hood alternative

[Reaper]

the further back you can get the vents the better they will work. You want them close to level otherwise air will build up on the rear slat of each vent and choke off the vent in front of it since its a flat plane. Mounting over the belts works with vents that have less fins and more negative drop from the hoodline plus some ducting from the radiator up. not possible with my front mount turbo. you can see in the pictures my turbo is still pretty close.

heres some wind tunnel testing of closer spaced vents moved further forward and why i chose the current design/location. In the video you can see the front vents on the gtr dont do anything. Thats because the vent angle is too steep causing air to "pack up" on the slat behind each vent. The rear vents are at a much shallower angle. The same angle as my trackspec vents in there current location and function much better.

[#maverick#]

how are these in the rain? Do they have some sort of rain guard?

[MaximeT]

Originally Posted by Reaper

the further back you can get the vents the better they will work. You want them close to level otherwise air will build up on the rear slat of each vent and choke off the vent in front of it since its a flat plane. Mounting over the belts works with vents that have less fins and more negative drop from the hoodline plus some ducting from the radiator up. not possible with my front mount turbo. you can see in the pictures my turbo is still pretty close.

heres some wind tunnel testing of closer spaced vents moved further forward and why i chose the current design/location. In the video you can see the front vents on the gtr dont do anything. Thats because the vent angle is too steep causing air to "pack up" on the slat behind each vent. The rear vents are at a much shallower angle. The same angle as my trackspec vents in there current location and function much better.

Thanks, great video.

[Reaper]

Originally Posted by #maverick#

how are these in the rain? Do they have some sort of rain guard?

why would you use a rain guard? you do realize an engine compartment has a GIGANTIC hole in the front that water comes through at 65mph when driving in the rain right? The only drawback to a vented hood is if your coolant overflow tank burps(if its over filled) it comes out the vent.

[Draco-REX]

Originally Posted by Reaper

the further back you can get the vents the better they will work. You want them close to level otherwise air will build up on the rear slat of each vent and choke off the vent in front of it since its a flat plane. Mounting over the belts works with vents that have less fins and more negative drop from the hoodline plus some ducting from the radiator up. not possible with my front mount turbo. you can see in the pictures my turbo is still pretty close.

heres some wind tunnel testing of closer spaced vents moved further forward and why i chose the current design/location. In the video you can see the front vents on the gtr dont do anything. Thats because the vent angle is too steep causing air to "pack up" on the slat behind each vent. The rear vents are at a much shallower angle. The same angle as my trackspec vents in there current location and function much better.

I guess it's car dependent. I wish there was a pressure map for the front of the twins, but I don't think anyone who's invested the money to generate one wants to share.

The GTR as pictured in the video has a very small low-pressure area at the front of the hood, so that would explain the video.


But some cars have a larger low-pressure area at the front of the hood:


I do admit that the hood shape of the twins shares more with the GTR than the GC Impreza however.

[Kiske]

30*F ambient temp drop!?! Any difference in IAT's or fluid temps since in isn't an oven anymore? I'm all for this but, really I only think this will look good on a full track car or a twin of darker color like yours.

[Reaper]

Originally Posted by Draco-REX

I guess it's car dependent. I wish there was a pressure map for the front of the twins, but I don't think anyone who's invested the money to generate one wants to share.

The GTR as pictured in the video has a very small low-pressure area at the front of the hood, so that would explain the video.


I do admit that the hood shape of the twins shares more with the GTR than the GC Impreza however.

nice find. the video i posted is from a shop i work at. we're hopefully sending the shop brz/or my frs to the wind tunnel this fall/winter. We also have a guy that does cfd and 3d car scanning so its all only a matter of time.

[Reaper]

Originally Posted by Kiske

30*F ambient temp drop!?! Any difference in IAT's or fluid temps since in isn't an oven anymore? I'm all for this but, really I only think this will look good on a full track car or a twin of darker color like yours.

it looks pretty docile on my car. But i think any other color you might want to color match it. Either way i took the pictures in lighting and angles that made them stand out since that was the point of the picture. When the car is dirty or not under florescent lighting it looks less aggressive.

I honestly didnt log as much as i usually do last track day. its all subjective since it was a different track with different weather conditions. you would have to run back to back on the same track same day. But running a 450hp turbo frs in the south and not having cooling issues hot lapping it is doing pretty well. I have a completely stock cooling system minus the oil cooler. temps were 200 water 230 oil running 20 minute sessions hard enough to destroy a set of tires. If there's enough interest ill tape them off next test and tune day. I also have the capability to do thermal imaging but its kind of a hurdle to set it up. Ill get around to it though this winter. Also hopefully wind tunnel time soonish.

[RedFR-s]

I love this idea. Was trying to figure out a good way to vent a top mount oil cooler and this looks like it will work and far more cost effective than a CF alternative. Just need the balls to cut the OEM hood.

[Draco-REX]

Any pics of the underside? Thanks.

[Rookie84]

I like it. I was also looking to do this at some point and was looking for a manufacturer of such vents.

BTW, is a rain cover available? If it is, it would seal the deal for me. I want to leave the rain cover on for street use and take them off for track days.

[NW86]

Those look awesome and saves me some money on buying a vented carbon fiber hood. BTW the s2000 vents are on their websute now.

[Reaper]

Originally Posted by RedFR-s

I love this idea. Was trying to figure out a good way to vent a top mount oil cooler and this looks like it will work and far more cost effective than a CF alternative. Just need the balls to cut the OEM hood.

Doooo iiittt.

[plucas]

Originally Posted by Draco-REX

I guess it's car dependent. I wish there was a pressure map for the front of the twins, but I don't think anyone who's invested the money to generate one wants to share.

I do admit that the hood shape of the twins shares more with the GTR than the GC Impreza however.

Fluid flow around a vehicle is very dependent on the car's design. Just because it works for one, doesn't mean it can be used as a blanket term for all vehicles. You also cannot always trust CFD or wind tunnel testing to have real world results. One big misconceptions of wind tunnels are that they reproduce what the car will see on the road or track. However, this is false. Wind tunnels only simulate the conditions on the road or track. Simulations inherently deviate from reality and it is often hard to quantify all the sources of the error. This is not to say that using wind tunnels or CFD is wrong or isn't helpful. The complete opposite is true. CFD and wind tunnels are very useful in helping design proper parts that work. However, you need to have the experience and know the theory to really understand the reality. You need to have the proper inputs (CFD) or choose the right tunnel for your needs (wind tunnel testing).

We have done CFD testing for the FT86. We do not have the funds for proper wind tunnel testing so results have not been verified by this route. However, on the track, we have seen the real word results. Also I have backed up many CFD cases to other CFD houses and windtunnels. Three examples are the ahmed model, DrivAer models, and the Perrinn LMP1. I will now get off the boring information and get to the CFD of the FT86.

Pressure Plot on the car, specifically the hood


Pressure Cut Plot offset from the center line of the car



Iso Surface around the car showing lower pressure