I am looking to find out if anyone has info on if the high pressure zone a tthe front of a truck has an impact on mpg's... meaning (forget engine cooling for this discussion), if its 100% blocked off, most of the airflow goes over and under the truck.
Is there any value in letting that high pressure bleed off into the engine compartment? ...effectively reducing some of the high pressure areas at the front grill...
The reason I ask is I had previously installed a grill insert that was behind the grill at the top, blocking the top half of the grill. What I immediately noticed on the freeway was improved front end stability. To me that equaled more downforce on the front of the truck. I have to assume that comes at a mpg cost. I left it there for 2+ years and removed it last summer when doing an aero before & after test (before had all aero in place, after removed it all). And... no ABA test, did not have the bandwidth to get that done. What ended up happening, and the details are fuzzy but its all documented on Cumminsforum.com... is mpg's took a good jump w/o some of those mods in place. I ultimately reinstalled 2 mods, the 2nd lower air dam and the bed seals between the cab & the bed. With how I left it (and other things going on with the truck last summer) I ended up getting ~12-15 tanks of 23.0 mpg or better. That was a shocker to me as the only other time I'd done anything over 23 was during the year of a bet with a co-worker back in 2018... had 5 tanks over 23 that year... ugh, I think I squirreled with my thoughts... sorry.
One of the things I'd considered trying to do was the front air curtains for the front wheels, taping into some of the high pressure off the front and use it to come out the sides.
could also use that front airflow bled into the engine compartment in other ways below the truck, the goal being to control it and not let it flow as it wants to into the engine compartment.
Anyways, thoughts?