Splitter for thé leading edge of a car hood? - Fuel Economy, Hypermiling, EcoModding News and Forum

67-ls1 · 10-07-2021, 06:52 PM

I’m currently fixing a rearend issue but my next project is a grill block to cut down on the air through my grill.

I already have an air dam below the bumper that is sealed back to the radiator core support.

Since my car is old, the grill is pretty vertical. And the leading edge of the hood is basically folded back at some degree less than vertical.

So I”m thinking what would be the benefit/detriment to have a small splitter like extension along the leading edge of the hood, for conversation, say 1”. Would it not affectively lengthen the hood slightly and force more air from the grill off the side of the car? And would either of these be good or bad?

Pic of the hood just FYI.

freebeard · 10-07-2021, 07:44 PM

As points of reference, I would suggest the 2nd Generation Golf, where they rounded off the earlier square edge ....just enough. And Smokey Yunick's never-raced car. motortrend.com/vehicle-genres/12q3-1966-chevrolet-chevelle-grand-national-race-car/

Quote:

Since the car was designed specifically for Daytona, Smokey lavished most of his attention on aerodynamics. The front bumper was sectioned so it could be widened by two inches and lowered by one. Fenders were reprofiled to improve airflow. The inside of the wheelwells were reworked for the same reason. The chrome supporting the windshield and back glass was made perfectly flush. He beat on the center section of the roof -- the hammer marks are still visible -- while subtly recontouring the rear lip to create what he called a vortex generator....

aerohead · 10-08-2021, 10:18 AM

The air is already displacing out ahead of the car as if it had some phantom nose. It's referred to as a Prandtl line of discontinuity.
In the Volkswagen photo link you can see this.
You need an uninterrupted pathway for these streamlines to get over the leading edge of the hood.
A splitter would look like a 'wall' to the air, with the potential to create remarkable separation and turbulence.
The air 'knows' what to do.
I recommend that you abort any attempt to direct it sideways, and just let it go where it's gonna go. That raked-back radius on top of the nose ought to be enough for attached flow.
https://ecomodder.com/forum/member-a...ing-follow.jpg

Piotrsko · 10-08-2021, 10:31 AM

Thats why it's called flat plate equivalent in aircraft circles. OTOH, trailing vortices suck and can get minimized.

freebeard · 10-08-2021, 11:42 AM

The top edge is fine. The purpose of a splitter is to provide a horizontal shelf for the air to exert downward pressure on.

kach22i · 10-08-2021, 09:28 PM

Quote:

Originally Posted by 67-ls1

Pic of the hood just FYI.

Beautiful car, not sure I would change much of anything.

freebeard · 10-08-2021, 09:49 PM

Quote:

....not sure I would change much of anything.

The fiberglass hood. The front edge is an inch low while the crown is wrong. Pie cuts, re-glass and repaint. Done.

67-ls1 · 10-09-2021, 07:03 AM

Quote:

Originally Posted by freebeard

The fiberglass hood. The front edge is an inch low while the crown is wrong. Pie cuts, re-glass and repaint. Done.

The hood is steel and they never fit well. I have been thinking about some small cuts to the structure below and rewelding once the curve is correct

freebeard · 10-09-2021, 12:55 PM

I assumed fiberglass, steel is harder to work with. But you do see the problem so that's good.

67-ls1 · 10-10-2021, 10:01 PM

Quote:

Originally Posted by freebeard

I assumed fiberglass, steel is harder to work with. But you do see the problem so that's good.

None of the repo sheetmetal available for these cars is worth a dam. They all require tweaking to get them to fit. Mine will take more then tweaking but I think I can get it there.

I also won’t extend the hood edge out any based on all your guys advice.