New hood design, want feedback.

[whatmaycome14]

I had a thought earlier today about a "slip-on" hood modification. It wouldn't be attached to the car except to slide onto and under the edges of the existing stock hood. The idea would be to create a raised surface for airflow that would smooth the transition from hood to windshield, ideally reducing the high pressure zone at the center of the base of the windshield.

Further thoughts:

1) The "double hood" idea would not do anything for air flow itself in the engine bay. The ONLY reason to consider this would be to keep the stock hood in place so that the addition would not have to be bolted on at all.

2) The primary goal would be to:
Minimize the high pressure area at the base of the center of the hood as much as possible while maintaining a reasonable view out of the front of the car

Other things to consider with the use of vents in strategic locations:
b) improve air flow through the radiator

c) improve air flow through the engine bay and prevent air from going underneath the car

Here are a few photos from google sketch-up. (Photos deleted, sorry, but I reorganized my photo bucket account and they got trashed)

[Frank Lee]

Can't hurt- looks like you've hit all the buttons we intuitively think are right. Might make for a more gradual pressure rise but then doesn't the bubble at the base of most windshields do that automatically? Would it make crosswind flow across the hood and off the leeward fender better? On the other hand I suspect flow towards the rear would be basically unaffected thus the wake zone- biggest source of drag- unaffected as well.

[freebeard]

I'm skeptical about the double-layering. It will make the hood twice as heavy. Passing air through the middle would have so much interference drag there would be no appreciable airflow.


For a duct to have any chance at success it should be short, un-convoluted and filleted. Here's an example on a Ferarri that addresses that area of the car. The double walled section is short, but there is structure along the hood edge and across the doors to make it work.

[jedi_sol]

http://ecomodder.com/forum/showthrea...rse-29359.html


The biggest gains are in the rear

[whatmaycome14]

Originally Posted by jedi_sol

The biggest gains are in the rear

Yes, I know that. However, I would like to explore this idea, and feedback related to improving this design would be greatly appreciated.

[whatmaycome14]

Originally Posted by freebeard

I'm skeptical about the double-layering. It will make the hood twice as heavy. Passing air through the middle would have so much interference drag there would be no appreciable airflow.


For a duct to have any chance at success it should be short, un-convoluted and filleted. Here's an example on a Ferarri that addresses that area of the car. The double walled section is short, but there is structure along the hood edge and across the doors to make it work.

The hood would be heavier, yes, but I don't think it would be double the weight. Even then, once you're at speed that doesn't make as much of a difference.

I started to also think about the reason hood extractors just behind the radiator work, and I agree that the double layer would probably not be helpful in this aspect. Perhaps removing the stock hood and replacing with this shape, sealing the rear (so the high pressure doesn't push air back into the engine bay) and venting the engine bay over the rear corners (where the fenders are, also a lower pressure zone) would help?

Do you think that by raising the trailing edge and reducing the extremity of the angle at the windshield would have a measurable effect?

[serialk11r]

I think Camaros or something have something like this nowadays, a bump in the hood that extends a lot closer to the windshield. I would guess it's good for a very tiny gain, because no one is bothering to do this.

[Frank Lee]

Do you think that by raising the trailing edge and reducing the extremity of the angle at the windshield would have a measurable effect?

No. Have you seen the discussions on the high pressure bubble at the base of the windshields of 2 and 3 box cars?

[whatmaycome14]

Originally Posted by Frank Lee

No. Have you seen the discussions on the high pressure bubble at the base of the windshields of 2 and 3 box cars?

Not to the extent that I think I need to apparently. However, the high pressure zone would only have an impact if the rear of the hood was not sealed. I'm thinking that if it were sealed against the glass, then the air would have no choice but to continue to flow over or around the car, no?

[tvbd56]

One thing that I see is that it would act as a windshield wiper deflector. Instead on the air hitting every single part of the windshield wipers, the air should travel above the wipers.