Grill block failure
 

So while I'm up at the shack for a grand week of fishing and drinking adult beverages I decided to finish up some aero work on Stinker. Where the original lower grill blocks were, I replaced them with plexiglas that wraps around to the driving lights. Then I made another that would fit in the center of the lower grill so I could take it off as needed.

With the entire lower grill blocked off:

28 miles (to town and back), speeds from 30 mph to 55 mph, mileage 21.5.

With the center opened again:

28 miles (to town and back), speeds from 30 mph to 55 mph, mileage 25.6.

From what I'm seeing here is that this part of the bumper is basically straight up and down with little angle. Blocking the entire area seems, in hindsight, to have increased the pressure on the front of the truck. I also wonder if the air dam has something to do with this since it's right below this area.

Maybe I'll make a camera mount for the front of the thing and do some tuft testing. That'll get the neighbors talking.

so have you been driveing like this the entrire time or was this justs a quick test?

What's the route altitude like?

What were the wind conditions ? same/same for each trip?

Isn't the lower grill area also part of the air intake for the Weber-nator ? That may 'splain it ! :D

Did you block off the source of combustion air for intake?
Sorry I don't remember your intake setup but if it's pulling from the engine bay then ... you get my drift.

iirc Bruce his air intake is coming from the passenger side fenderwell which is behind the headlight . Hey kitcar ? do you still have the clear tape on the body seams ? Bruce may be on to something ...

you have a scan gauge right?

More data:

Approx. 1400 feet above sea level
Air Temp, 87 degrees
Humidity 57%
Barometric pressure was 1013.9 mb
Winds 10 mph SSW, variable
Coolant temp, 201 degrees (both tests)
Timing, 6 to -2 degrees (both tests)
Engine load with entire lower grill blocked, 23% @ 55 mph, level
Engine load with partial block, 20% @ 55 mph, level

Intake is through the passenger side fender via the wheel well; air flow and intake pressure unchanged as was the coolant temp. Vehicle closed loop for entire test.

Maximum speed, 55 mph