New lower air dam for 2017 Chevy Full size van

[EcoVan]

Yes, rule of thumbs are usually bad for scientific advancement. However, as you said, when you get to know your field intimately, patterns emerge and recognizing those patterns often leads to significant advancement in a field. I am one of those that tends to pick up on patterns in many things in the world. My specialty is working with steam space heating systems and general energy conservation for buildings. My degree is in Architecture from IIT-Chicago with a specialty in City and Regional Planning. Spending 6 years with some of the sharpest and most expansive minds on the planet tends to rub off good things.
From my specialty, the knowledge in fluid dynamics tends to filter in aerodynamics...so I find aero quite interesting and easy to see in the "mind's eye".

I am itching to get some testing done with the van, but in the meantime I've got brakes to fix and upgrade the single pintle injectors in my 1998 Ford Zetec Escort to new 4 holes for better atomization.

Just had the O2 sensors changed on our 2007 Jeep GC v-6 4wd and went from 21.2 highway to a little over 24 on initial tests... a nice 13% increase on a vehicle only rated at 19MPG Highway.

[freebeard]

I am one of those that tends to pick up on patterns in many things in the world. My specialty is working with steam space heating systems and general energy conservation for buildings. My degree is in Architecture from IIT-Chicago with a specialty in City and Regional Planning. Spending 6 years with some of the sharpest and most expansive minds on the planet tends to rub off good things.

I would participate in a thread in the https://ecomodder.com/forum/saving-home.html subforum.

My entire work career my resume targeted low-cost energy efficient housing. Now I can't find anyone who wants to talk about it.

Maybe a wood-and-brass steampunk solar powered and heated house?

IIT-Chicago

What do you think of Stewart Hicks? www.youtube.com/user/stewarthicks

[EcoVan]

The van is in need of alignment and maybe a front end part and we need a new NOX #1 sensor, but I did have a chance to run a few miles with the new airdam/valance in place. I appear to have gained about .75 to 1 mpg @ 68 mph in 8th gear from 33.3 to 34+. What was more interesting is at about 62 MPG in 7th gear I used to run about 31 to 32 mpg and now was running 34mpg. I think at least the change did no harm. I would expect the factory air dam to be higher than optimum ( it has steadily gotten lower over the years), since GM wouldn't want it getting ripped off on jobsites. I've still got 7 1/2 inch clearance with the van loaded. I suspect getting the front belly pan in place and tied and sealed to the back of the airdam will cut the vacuum drag behind the dam and I should see further gains with increased cooling air flow through the grill... allowing for some grill block. ( the van comes with a factory grill cover for winter use).
It's a couple weeks before the repairs get done, so further testing then.

[aerohead]

Originally Posted by EcoVan

The van is in need of alignment and maybe a front end part and we need a new NOX #1 sensor, but I did have a chance to run a few miles with the new airdam/valance in place. I appear to have gained about .75 to 1 mpg @ 68 mph in 8th gear from 33.3 to 34+. What was more interesting is at about 62 MPG in 7th gear I used to run about 31 to 32 mpg and now was running 34mpg. I think at least the change did no harm. I would expect the factory air dam to be higher than optimum ( it has steadily gotten lower over the years), since GM wouldn't want it getting ripped off on jobsites. I've still got 7 1/2 inch clearance with the van loaded. I suspect getting the front belly pan in place and tied and sealed to the back of the airdam will cut the vacuum drag behind the dam and I should see further gains with increased cooling air flow through the grill... allowing for some grill block. ( the van comes with a factory grill cover for winter use).
It's a couple weeks before the repairs get done, so further testing then.

On the 2015 F-150, and on a CdA-basis, Ford measured the drag minimum with about one-inch of the bottom of the differential's 'pumpkin' still exposed to the airstream.
This suggests an initial belly pan test at this elevation, with a small blister fairing behind the exposed portion of the pumpkin, mounted, or integrated into the diffuser.
BamZipPow's Toyota T-100 diffuser floats with the rear axle, with the trailing edge captured within a transverse slot below the tailgate area, acting as a 'hinge.' It's very clever!

[aerohead]

Ford published a -0.1825 pressure coefficient behind the tailgate.
Test conditions were:
117.333 ft/second
29.92-" Hg
14.7-psi
1500- pressure samples, @ eight different yaw conditions, six different frontal areas, ten samples/second, ten seconds/ configuration, @ fifteen simultaneous sampling locations
From the Cp formula, local flow velocity average mean @ the tailgate separation line was 127.59 ft/second
From the Cp formula, average mean base pressure was 26.936" Hg, 13.142-psi.
If Wolf Heinrich Hucho's neighborhood metric for a Cp = -0.20 'squareback' ( Ford Expedition ), then, the F-150's Cd 0.1825 indicates for a degree of pressure recovery, lacking in a generic squareback.
The Rivian R1, @ Cd 0.30, might illustrate pressure recovery due to a captured vortex over it's OEM bedcover, it's boat-tailed rear fenders, and full belly pan ( I've no details about any 'diffuser' ).
If CYBERTRUCK makes it to production next year, it will be interesting to see any actual test results. Theoretically, the Tesla will have the highest pressure recovery of any pickup ever offered. And would 'show', by default, with respect to highway range, on a pack size, frontal area, travel weight basis.
Owners, never interested in off-roading, could easily aero-mod CYBERTRUCK into the low Cd 0.20s. Lower with a trailer.

[EcoVan]

was heavy traffic, which seems to help MPG on the van. I needed to get the alignment corrected and that was taken care of. AT 62 MPH in 7th gear ( of 8) was getting about 33 to 34. At 55MPH was getting an incredible 35 to 36mpg. I picked up 2 mpg at 62 MPH and I never checked it before at 55, but I never saw this kind of MPG.

I haven't been able to check MPG at 68MPH, which used to be the best MPG speed because I couldn't duplicate the conditions.

The van does seem to roll much easier at highway speeds and my employee that drives it regularly said it seemed to be doing better too.

I'd say the deeper air dam was a definite improvement. Its depth matches most on road SUVs. Front belly pan is next, maybe with front tire spats. Might be able to hit 40 MPG with this full size van with 2500 lbs in the back. Gotta love this 2.8 Diesel!

[E.Roy]

Cool discussion on this topic. I have a theory that older fullsize vans are likely more susceptible to underbody drag without a deep valence because of their flatter face causing the underbody air path to become a path of less resistance, and thus forcing air underneath and increasing drag. This theory would mean vans might benefit from a deep valence more than other body styles.

Also, I wonder if this played into Ford's Econoline redesign in 2008 where they elongated and stretched the grill 5" forward from the windshield

[EcoVan]

but that does make a lot of sense. I should look back at the NASA studies to see if there is a pattern there.

[Piotrsko]

Whole lot of stuff hanging on full size vans frame rails causing bunches of drag, axles and their suspension being worst offenders. If you stop it from going under there and creating eddies, significant drag savings

[freebeard]

I have a theory that older fullsize vans are likely more susceptible to underbody drag without a deep valence because of their flatter face causing the underbody air path to become a path of less resistance, and thus forcing air underneath and increasing drag.

My preference is shifting from air dam to splitter. An example from Singer:


https://external-content.duckduckgo....8d9&ipo=images

It trades overall length for airflow around the wheels, but leaves a central jet.