Custom Hood vs Hood Duct

[gtengr]

Originally Posted by Kodename47

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.

My understanding is that nothing should be vented anywhere to the underside of the car if it can be avoided. Using low pressure under the car to extract would incrementally increase the pressure under car. That the engine bay air is heated might make it worse. If anything, I think a few holes in the stock under panel need to be patched up once venting to the top side is done. It's probably less of a factor in stock form, but I want to eventually have the bottom as flat as I can reasonably make it.

[gtengr]

Originally Posted by makinen

Under hood pressure should be counted for the venting. Pressure difference really makes air move.

I did an experiment for the vent at the cowl area on 2016. With the help of a Gurney flap, at least it blows out some air. I guess a blocking vertical barrier that divides low pressure zone and high pressure zone could help more.

I know it cannot blow out as much air that hood vent can. But could be better than nothing.

Very nice! Did you just remove that plastic end piece and replace it with a grill? Any further cutting involved?

Originally Posted by makinen

Or do make your own like this, @gtengr .

Looks functional for venting, but not the route I want to take.

[Kodename47]

Originally Posted by gtengr

My understanding is that nothing should be vented anywhere to the underside of the car if it can be avoided. Using low pressure under the car to extract would incrementally increase the pressure under car. That the engine bay air is heated might make it worse. If anything, I think a few holes in the stock under panel need to be patched up once venting to the top side is done. It's probably less of a factor in stock form, but I want to eventually have the bottom as flat as I can reasonably make it.

To quote their website:

The under panel improves the rectifying effect on the bottom surface of the body during high speed driving and generates downforce.
Also suppresses the flow of air caught in the engine room.
By installing a ventilator, it efficiently discharges the heat of the engine room and prevents heat up of the engine.
We also made use of 2.0 mm thick aluminum material for weight gain.

It's certainly smoother than the DIY posted above.
http://laile.co.jp/carparts/cooling/under_panel/

[gtengr]

Originally Posted by Kodename47

To quote their website:

It's certainly smoother than the DIY posted above.
http://laile.co.jp/carparts/cooling/under_panel/

That one is smoother a lot smoother, but still not the route I want to take. It might reduce lift on a stock car, but I'm confident it would be detrimental with a flat bottom.

[Kodename47]

Would be interesting to see if the underbody aero would be massively affected. For example blown diffusers utilise the heat and extra airflow under the car, so it's not always a bad thing. It does depend on some factors though. You might find it actually helps improve airflow coming under the front bumper for example, splitter or not. I'd imagine having no lower splitter would see the front bumper create way more of an issue than this plate.

The idea of a gurney flap at the rear of the bonnet is interesting. I wonder if it need an actual wing shaped flap or just something to kick up the airflow away from the cowl. If the latter, it would be cheap to implement with those universal spoiler lips available on eBay etc.

[Gunman]

Originally Posted by gtengr

My understanding is that nothing should be vented anywhere to the underside of the car if it can be avoided.

Agreed, you want to evacuate the underside, and keep the jet moving/accelerating, to create downforce. Front and side splitters/skirts work to keep the air out. I'd avoid any non-essential under body openings, which can cause turbulence. We used to seal around the air jack openings, on the GTLM/GTD/GT3 Viper. Flat smooth bottom is good. We did have openings under the exhaust, but also played with the location and shape to minimize the effect, and maintain the center jet.

[makinen]

Originally Posted by gtengr

Very nice! Did you just remove that plastic end piece and replace it with a grill? Any further cutting involved?

Just removed parts.



In the below pictures, I removed both parts at the ends of cowl area. But what I am actually using are only rubber parts removed from them. Those rubber parts which I colored in orange in the above diagram are for the fully opened posion of the hood.

[gtengr]

Originally Posted by Kodename47

Would be interesting to see if the underbody aero would be massively affected. For example blown diffusers utilise the heat and extra airflow under the car, so it's not always a bad thing. It does depend on some factors though. You might find it actually helps improve airflow coming under the front bumper for example, splitter or not. I'd imagine having no lower splitter would see the front bumper create way more of an issue than this plate.

Whether it's a massive effect is hard to say imo. I'm pretty sure the blown diffuser effect is more due to the exhaust gas having a higher relative velocity than the air in the diffuser than it is the heat. The engine bay heat doesn't really flow so much as it needs extracting, and in an FR layout it would have to be dumped at the front of the car. So it slows that air, which in turn means slower air through the diffuser.

[gtengr]

Originally Posted by makinen

Just removed parts.

Attachment 162124

In the below pictures, I removed both parts at the ends of cowl area. But what I am actually using are only rubber parts removed from them. Those rubber parts which I colored in orange in the above diagram are for the fully opened posion of the hood.

Cool. I think I'll drill out those plastic pieces and leave some of the material there to cover up the fender bolt and some of the hinge. I'm going to wait until I get the Edelbrock on (waiting for the 2017 kits) before doing anything so that I can check it with datalogging.

[Gunman]

Originally Posted by Kodename47

Would be interesting to see if the underbody aero would be massively affected. For example blown diffusers utilise the heat and extra airflow under the car, so it's not always a bad thing.

The exhaust was being used to deflect the rear tire wake away from the diffuser, to increase its efficiency, OR re-energize the flow at the back of the diffuser. The downside, was the on/off effect based on the engine rpm, engine mapping, or throttle control entering the corner was key, to keep from upsetting the aero balance.

Way more complicated, than what anyone would get to work on a street car.

[Launcher]

Originally Posted by humfrz

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

Sorry for the late response, this thread took off into several different ways haha

Mostly just for looks at this point. I only track my car like once or twice a year and store it in the winter like right now.

The CF hood style looks the best and was thinking about just painting it black instead since I am not sure I would like the rest of the car black and then hood only CF

[humfrz]

Originally Posted by Launcher

Sorry for the late response, this thread took off into several different ways haha

Mostly just for looks at this point. I only track my car like once or twice a year and store it in the winter like right now.

The CF hood style looks the best and was thinking about just painting it black instead since I am not sure I would like the rest of the car black and then hood only CF

....... and that is the more correct answer.

Yep, this thread, like most, has many tangents spinning off of it .....


humfrz

[norcalpb]

Originally Posted by humfrz

....... and that is the more correct answer.

Yep, this thread, like most, has many tangents spinning off of it .....


humfrz

I learned new things in this thread...

[Kiske]

Originally Posted by NRXRaptor

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

It's a wet carbon hood, most likely with a fiberglass underside or core. The point is moot unless your replacing a car make with a heavy steel hood (pre-90's.)

:/