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Woods247 BrokeFiST Build
- Thread starter Woods247
- Start date
Thread Starter
#1,182
Wonder if there’s any real ill effect caused by leaving the upper and lower cowls off during dry days. This is undoubtedly the most effective “hood vent” although I wonder if the lower cowl purposely diverts air behind the engine to aid in cooling the turbo. Probably huh?? Edit: It’s gotta let way more heat out from the back side of the engine. I’m gonna try it at Road Atlanta this week.
Thread Starter
#1,183
These are next for the build:
1) custom rear diffuser
2) convince a local member to build me a set of his rockers so I can create a flat floor 😊
3) S280, injectors and HPFP (or a WOR setup)
1) custom rear diffuser
2) convince a local member to build me a set of his rockers so I can create a flat floor 😊
3) S280, injectors and HPFP (or a WOR setup)
Disagree. Base of windshield is typically a higher-pressure zone from stagnant/unattached air. This typically promotes inward flow (Windshield forward) and screws with the under hood pressure as a whole, as you're now pressurizing it from the front and rear and creates a turbulent/stagnate air pocket. This air in turn is now all high-pressure and screws with the balance of the car front to rear in regards to lift. Remember: Neutral lift is fine front and rear, it's when one end is at an extreme when cars become unbalanced. This could also disrupt airflow through the radiator, but I don't think we have enough ducting to really cause major issues. See example:
Cowl hoods work off the same principle (Granted the old 60s muscle car hoods were more vertical. This is exactly why the fresh air vents are placed at the base of the cowl as well. It's capturing the natural high-pressure area so when the vent is opened, it naturally wants to expand (High pressure into low pressure) into the vent and provide fresh air with near zero additional drag.
If you want to cool the turbo a NACA duct similar to the Type R and Evo X would be best. Just enough to cool the turbo without disturbing most of the air. To pull air out from under the hood you need a rearward facing duct/extractor. This will allow the stagnant high pressure air to push into the fast low pressure air as it moves over the hood/past the windshield and literally flow outwards/get pulled into the outside air. you need to have this vent forward enough to be in the low-pressure fast moving air however. This is why so many race car hoods have the vents just after the radiator. Highest charged/hottest air (Wants to expand) that is in the lowest pressure zone (just rearward of the front leading edge).
Good Read:
https://themotorhood.com/themotorhood/2018/8/1/flow-form-understanding-how-aero-really-works
With that said, these are high orchistrated examples of aero-driven cars. You won't know until you try removing the set-up, but I bet a few temp. probes and some basic yarn tuft tests would tell you a lot.
Cowl hoods work off the same principle (Granted the old 60s muscle car hoods were more vertical. This is exactly why the fresh air vents are placed at the base of the cowl as well. It's capturing the natural high-pressure area so when the vent is opened, it naturally wants to expand (High pressure into low pressure) into the vent and provide fresh air with near zero additional drag.
If you want to cool the turbo a NACA duct similar to the Type R and Evo X would be best. Just enough to cool the turbo without disturbing most of the air. To pull air out from under the hood you need a rearward facing duct/extractor. This will allow the stagnant high pressure air to push into the fast low pressure air as it moves over the hood/past the windshield and literally flow outwards/get pulled into the outside air. you need to have this vent forward enough to be in the low-pressure fast moving air however. This is why so many race car hoods have the vents just after the radiator. Highest charged/hottest air (Wants to expand) that is in the lowest pressure zone (just rearward of the front leading edge).
Good Read:
https://themotorhood.com/themotorhood/2018/8/1/flow-form-understanding-how-aero-really-works
With that said, these are high orchistrated examples of aero-driven cars. You won't know until you try removing the set-up, but I bet a few temp. probes and some basic yarn tuft tests would tell you a lot.
Last edited:
I agree with @the duke: the area in front of the windshield is high pressure. The big $$$ rally guys figured out that the best place for vents is the upper corners of the hood. I haven't tuff-ed the car but I can feel plenty of heat venting out of the Verus vents in my hood. My splitter doesn't go as far back as yours and I'm not letting as much air into the front of the car. For kicks, I might have, allegedly, headed to my favorite empty stretch of highway where I could hit > 120 and I don't have the problems that you do with the rear of my FiST and I haven't opened up the rear grid (yet).
I'll bet you a case of our respective favorite that your rear aero problem will get much better if you pull the bumper cover, tape up all the gaps around the heat-exchangers to make sure that all the air that gets in passes through a heat exchanger, tape up the bottom half of the grill, returning it to stock-ish, and add hood vents, all without reducing heat-exchanger performance.
If you flat-bottom the car the rear aero problem will get much worse. Flat-bottom cars duct the air that enters the front of the air out with hood and vender vents. Only the air that makes it under the splitter charges the diffuser.
I'll bet you a case of our respective favorite that your rear aero problem will get much better if you pull the bumper cover, tape up all the gaps around the heat-exchangers to make sure that all the air that gets in passes through a heat exchanger, tape up the bottom half of the grill, returning it to stock-ish, and add hood vents, all without reducing heat-exchanger performance.
If you flat-bottom the car the rear aero problem will get much worse. Flat-bottom cars duct the air that enters the front of the air out with hood and vender vents. Only the air that makes it under the splitter charges the diffuser.
Thread Starter
#1,193
I reinstalled the cowl, driver headlight, removed my canards (for testing) and ordered a set of SICO hood vents since they’re the only ones I could find that install in roughly the correct location. Looks like everyone else it out of business.. I will build a cover/drain underneath them for rainy track days. They’re ginormous but I figured worth a shot.
Thread Starter
#1,198
They’ll have a cover underneath if it rains. It’s not a concern for me though. My car is garaged and covered at tracks. I can’t remember the last time I drove it in the rain. Definitely been awhile.
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