# Hood Clearance

A discussion about the ever-popular hood scoop/grill hole modification for increasing airflow came up.

A comment was made about the benefit of this modification on account of the lack of open area between the hood and grill for air to pass through.

Although the hood rubber seal contacts the grill behind the air intake openings it is thought that there is inadequate space between the hood and grill to allow enough air into the intake after opening up the driver side of the grill to the intact duct.

Curious about how much space there is between the hood and grill I set out to investigate with the help of some Play-Doh.

The plan is simple, set a small amount of Play-Doh on the grill at four sample points and then close the hood. Then the hood is opened and each of the Play-Doh samples is evaluated to assess the deformation.

The picture above shows the first trial run setup. Results follow:

Measurement of the thickness of the Play-Doh at the thinnest point yielded results of:

1. 9.56 mm
2. Not measured
3. 11.36 mm
4. 11.4 mm

Blue wasn’t measured because it barely deformed and was visibly thicker than the other three samples. Blue is a well used ball of Play-Doh that is not as pliable as the other colors.

Roughly, the average minimum thickness was 1 cm.

The Play-Doh was formed back into cylinders and moved slightly forward relative to the initial location.

Once the Play-Doh is positioned the hood is closed. I then proceed into the cabin to unlock the hood latch and raise the hood.

Condition of each sample of Play-Doh is shown in the following pictures:

Again each of the samples was measured for thickness at the location of visually being thinnest.

At the second trial location the respective depths are:

1. 12.7 mm
2. 12.78 mm
3. 14.04 mm
4. 11.43 mm

Roughly the average minimum thickness is 12 mm.

The area of the grill to intake duct that is opened as part of the popular modification adds approximately 10 sq. in. of open area.

Measurement of the openings are: 67×30, 91×30, 65×26 mm.

The span of the hood opening is approximately 90 cm and the approximate minimum height of the opening is 1 cm, for an area of roughly 14 sq. in.

Assuming that almost no air can pass through an opening that is 14 sq. in. (roughly the area of a 4.5″ diameter circle) seems like a poor assumption.