Custom Hood vs Hood Duct
 

Opinions on the difference between hood duct and custom hood with built in hood duct type.

I was looking at the TS- Style Siebon
http://seiboncarbon.com/tsii-style-c...ubaru-brz.html

Currently in stock

I would need to buy that, have someone paint it black OEM color for my Subaru BRZ so could see it adding up cost fast but if it is worth it and makes a difference in look compared to the hood duct I would be fine with it.

I have never had a custom hood or hood duct on a car so curious on that as well. I see several hood ducts that I assume a car shop could just add to my current hood?

Something like the following:
https://shop.namelessperformance.com...d-duct-system/


Thoughts and main differences between the two or am I way off?

Leaning towards the Siebon TS-Style hood but want to make sure when I buy it I can get someone to pain the carbon fiber and fitted and have no issues.

Well, Launcher, I must ask ....... why do you want either one ..... ??

* to make the hood lighter ..??

* to allow hot air to escape the engine compartment .. ??

* to look cool ..... cause CF ..??

* other


humfrz

From an aesthetic standpoint, I would go for the carbon variety, paint it, and leave the carbon louvres unpainted. Then again, it's always form>function for me. My two cents

If you are going to paint a carbon fiber hood it defeats the purpose to me. From what I know most consumer level carbon fiber bits are carbon fiber molded/stuck onto a hood shaped piece of fiberglass. My 2 cents

Factory hood is surprisingly light for what it is.

Unless you have other reasons for wanting to switch, or just a different look.

These look cool! About half the price of a hood.


https://i.imgflip.com/22v99o.jpgvia Imgflip Meme Generator


There are more options... Some that look sleeker...
https://i.imgflip.com/22v9ea.jpgvia Imgflip Meme Generator

https://i.imgflip.com/22v9j3.jpgvia Imgflip Meme Generator

My $0.02 I live in Oregon. My louvered hood let water sit on my engine and corroded the aluminum parts which made them look terrible. (different car)

Defeats the purpose? What is the purpose?

Has anyone drilled holes in the windshield cowl? Seems like it would be a good stealth way to vent the engine compartment.

[ame="https://www.youtube.com/watch?v=G3ja6Hn8ps4"]https://www.youtube.com/watch?v=G3ja6Hn8ps4[/ame]

:cheers:

The cowl is not a low pressure zone. That would provide no benefit. Often what "seems like" would work does not. This is especially true with aerodynamics.

This is actually a high pressure area. Ever hear of "Cowl Induction"?

I bought this Mustang hood vent off e-bay for 90 bucks.

The cowl piece is shielded from airflow, so I think that's debatable. I think it's likely a low pressure area exists in the airflow void where the vents would be. Also need to consider there is an underhood pressure component, and the underhood air is hotter. Seems you should know that once you cut a vent into something that the pressure zones can easily change and need to be reanalyzed.

Yes, but they project upwards from the rear hoodline and towards the windshield to ensure the rear opening gets into the high pressure zone, and this is typically done to cars that aren't as streamlined and have an abrupt hood to windshield transition that helps to more clearly create a high pressure area. I'm not saying it would positively work, but I don't think it can be so simply dismissed.

Here's an example of what I'm thinking about using the 2019 ZR1. Ignore for a second that its hood vent caused a dramatic change to the high pressure zone in the center of the windshield. Just look at the area I zoomed in on and notice how the high pressure area on the windshield ends at roughly the height of the back of the hood, and what's under that point is low pressure.

Don’t our cars come with rubber vents in the area you are circling?

To look like carbon fiber of course. Gotta show off that nice CF weave.

Hello OP ....... you still with us ....??


humfrz

Yep, I'm still waiting for that since post #2.

:iono:


humfrz

This was proven years ago on here, probably find the threads if you have a look about.

I see what your saying.

Believe it or not, the original purpose of carbon fiber was not to be used as automotive jewelry. I wouldn't assume everyone thinks that is of course its purpose.

I looked at it today but didn't look closely at the edges. I think I know what you're talking about but I'll have to reinspect. The cowl trim piece serves as a big inlet chamber for the HVAC, so any venting except for the very edges would get sucked into the cabin.

I searched a few variations of "windshield cowl" and couldn't find anything.

@Tcoat :thumbsup:



What about cutting the side fender open into engine bay.... I know those are not that effective but it should work to a certain point too? :threadjacked:

Cowl/base of windscreen, is a high pressure area.

Like I did.

I saw that model and I don't think it's detailed enough to check. I've already discarded the idea due to HVAC interference, but you realize the vent would be recessed under the back of the hood about 4 inches or so towards the front? And the CFD model doesn't consider the radiator airflow, which is the target of the venting. If airflow into the engine compartment is high enough, the firewall can create a high pressure zone too. I'm guessing that is what makes the hood dance at speed.

If I recall proper, that had been tried .....;)


humfrz

Gosh, the last time I saw JPS on car was way back.. a Lotus Esprit.

I styled my car in the old John Player Special F-1 livery.

Very good. It reminds of the ole Hertz Mustangs. Similar stripes.

I haven't seen CFD, or tunnel testing, that did not show the cowl area as a high pressure zone. The turning of the air from a general horizontal, to more vertical direction, causes high pressure.

Granted, there are probably cases where something else is influencing it, and making it low pressure, but i have not seen it.

This is true.

That area of the car is always higher pressure. I am sure there is a way to make it low pressure, but in general, that area is a terrible choice for evacuating air.

Right, but it's nearly always modeled as the hood running into the windshield as if it's a simple obtuse-angled corner, ignoring the void area that is recessed towards the front of the car and under the rear of the hood. And the influence of an engine bay that has trapped a lot of air that wants to escape is also generally ignored. The Corvette example I pointed to earlier, while it is a different car, demonstrates that the high pressure area doesn't necessarily have to travel below the hood line and towards the front of the car. I'm not trying to say that I'm right, because I do understand your point. I just haven't seen enough to convince me it is 100% factual in this case.

Going back to your case, I have attached the same picture with some arrows to point out areas.

https://i.imgur.com/VXhiMZI.jpg

Red Arrow: Best for evacuation, lowest pressure
Orange Arrow: Good for evacuation, low pressure
Yellow Arrow: Worst place for evacuation on the entire hood. This location has the highest pressure and would result in the least productive evacuation. Likely air would actually make its way *into* the engine bay.

People reduce complexity on CFD models to aid in solving. There are industry standards (followed by OE's, privateers, and race teams) that are accepted because they do not result in incorrect results.

Hope that helps,
Eric

I agree, but my aim wasn't to investigate this as the best option. I was looking at is as a possible way to get "some" venting without cutting the stock hood or dealing with aftermarket hoods. Also, the theoretical vent location is not on the surface of the hood, it would be on flat vertical face under the rear of the hood, and recessed about 4" toward the front of the car as measured from the vertical plane at the back edge of the hood.

I don't mind if I'm wrong. I just don't think pointing to the pressure distribution on the top surface of the hood tells the full story, or that the underhood pressure isn't a factor.

To see the carbon weave. It doesn't sound like OP is making a literal race car, so the carbon is purely cosmetic. That's why I get carbon parts for my car

May I put forward the Beatrush Underpanel. No cutting, modding or replcing of the bonnet required. Proven to work, might even add downforce if claims are correct. Pulls heat directly past and away from the manifold too. Only downside is that it's not cheap, but still cheaper than a modded or aftermarket bonnet.

I also thought that might be a good addition.

For what it's worth, carbon parts can add functionality to street cars, too. To say it is "purely cosmetic" I think is selling carbon short. Maybe that's all he cares about, but true carbon parts bring more to the table than style, regardless of implementation or appreciation.