This snowplow 'thingy' reduced the engine compartment pressure by....

[MetroMPG]

Originally Posted by Mandilon

The fact that I wasn't getting any bubbles at 68 MPH obviously proves that the air was flowing easier 'around' this vehicle.

Not to discourage you, but what you observed doesn't prove that air was "flowing easier". It only indicates that you reduced pressure in the engine compartment.

Note: I'm not saying that there may not be a net improvement in drag. Only that this test doesn't prove it.

Keep at it! Looks like you're motivated and having fun.

[hypermiler01]

Where's the other end of the hose? Just because you lowered the pressure in the engine bay doesn't mean it's lower in front of the van.