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Old 04-01-2020, 08:11 AM   #21 (permalink)
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My understanding with wheel spats/deflectors is that much more drag occurs on the upper half of the wheel is moving against the wind at twice the speed of the vehicle. This is what mine shipped with:



This is what some ecomodders have done:




As for the sides, even a tiny spat at the top of the wheel arch is going to give most of the benefit, since that's where the tire is moving most rapidly against the wind.


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Old 04-01-2020, 12:11 PM   #22 (permalink)
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40-45 mpg

Quote:
Originally Posted by Tahoe_Hybrid View Post
I'd really like to increase the MPG to 40-45MPG on this V8 6.0L Engine..


we had a 7mph tailwind the other day
it was reporting 40 to 45MPG on the instant gauge @ 60MPH steady speed..

flat land i think getting down to 0.28 from 0.34 will get me that 40ish at 60mph...

this is not about the MPG it's about improving the emissions output


that would cut the emissions output by 50% over EPA ratings

is it possible on a budget? say $200?


this would put my MPG right there with the Geo Metro
1.0L L3 GAS..



Hypermiling gets me about 31.5MPG (95% highway only) currently
On three occasions I've seen 39.9 mpg @ 60-mph,steady,interstate cruising,Texas to California and back .That's with 4,220-lbs all up weight, around 29-sq-ft frontal area,Cd 0.2675,and REGULAR UNLEADED.With a direct-injection turbo-diesel we'd be looking at 51.87 mpg at the same velocity.
The Tahoe is heavier and of larger frontal area.Your V-engine has higher internal friction.Your drive-line has higher internal friction.
In materials,$200 is quite reasonable,but you might be looking at 800-1200 man-hours in fabrication time to create a low enough drag,requiring the most difficult to achieve compound curves,everywhere.
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Old 04-01-2020, 12:19 PM   #23 (permalink)
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V-4 mode

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Originally Posted by Tahoe_Hybrid View Post
the next update was 2015 which the front end changed 0.34 and smaller mirrors (these mirrors can be modified to fit on mine) but it's pricey at about 350$ for just that the 2019 might be slightly lower as they added air ducts

the biggest drag in the front is the mirrors, because of the size of them.



you can hear the wind dragging on them at about 75 or so


the only reason i'm able to get the good mpg is because i use 91oct as it's able to keep it in V4 mode much longer then 87oct ( it hyper switches from v8v4v8 i'm pretty sure that is bad for the engine i.e wear and tear wise to the AFM system )
GM chose the V-8 for the Corvette to allow it to remain in the V-4 mode as well.A V-6 wouldn't cut it.I can see the octane issue.Ford's EcoBoost engines require premium when towing or heavy load.
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Old 04-01-2020, 12:26 PM   #24 (permalink)
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airdam

Quote:
Originally Posted by Tahoe_Hybrid View Post
I did some clearance checks

and the front has

8 inches

sides have 10 inches

the rear at the muffler is 13 inches



would a bigger airdam help?
Hucho warns that a deeper airdam can increase drag.Extremely low dams can cut drag,but without being 'active' they're torn off on the first driveway ramp.
Brett Herndon,of Aerolid fame,constructed an absolutely fabulous airdam for his F-150,but was forced to modify it,as it's extended depth cut into fuel economy,just as predicted by Hucho.Active aerodynamics is the solution,but adds a couple orders magnitude to build complication.
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Old 04-01-2020, 12:31 PM   #25 (permalink)
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parachute

Quote:
Originally Posted by Tahoe_Hybrid View Post
but it does look like it has some Parachutes type items under it, especially the rear bumper..



how about wheel splats? I was thinking of using 18 wheeler mud flaps(cutting them though) it's 33.30$ for a pair to do all 4 tires

the 2015+ has built in wheel splats to the front air dam..
.



but i think might be able to do a Vent duct where those plastic covers are ?
Technically,the rear bumper fascia cannot 'parachute' unless you've got a belly pan all the way to it,and fully attached flow.Subaru lowered the drag of their 1985 XT by 'adding' a parachute rear bumper.Drag went up without it.
If you're going to the trouble of doing a belly pan,you'd want to do a diffuser,to wring out all the drag reduction possible.
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Old 04-01-2020, 02:02 PM   #26 (permalink)
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If it has not been mentioned, consider a rear diffuser. That space in front of the rear bumper cover is awful.
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Old 04-02-2020, 01:34 PM   #27 (permalink)
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Quote:
Originally Posted by aerohead View Post
On three occasions I've seen 39.9 mpg @ 60-mph,steady,interstate cruising,Texas to California and back .That's with 4,220-lbs all up weight, around 29-sq-ft frontal area,Cd 0.2675,and REGULAR UNLEADED.With a direct-injection turbo-diesel we'd be looking at 51.87 mpg at the same velocity.
The Tahoe is heavier and of larger frontal area.Your V-engine has higher internal friction.Your drive-line has higher internal friction.
In materials,$200 is quite reasonable,but you might be looking at 800-1200 man-hours in fabrication time to create a low enough drag,requiring the most difficult to achieve compound curves,everywhere.
It has very aggressive DFCO. That is how i'm able to get that many mpg in the first place..

I suspect the Electrical motor is spinning the engine in DFCO... with a OBD reader you can see 0.00v on the upstream o2 sensor. that mean no fuel to air ratio.


when i first saw that i thought my sensor was broken or some other issue..


since there is no "engine braking"
it feels like it's in "neutral gear"

if I shift it into Manual Mode it has "engine braking" and you stop pretty quickly
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Old 04-04-2020, 05:19 AM   #28 (permalink)
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i pumped up the 4 tires to 44PSI
i think a good mod would be for the hood gap stripping it tends to flap around in the wind... you can see the hood get a little bit of lift and flex i'd assume this is causing drag...

seems to keep in auto stop much longer with it pumped to 44psi i had them at 40psi before

should i block off the lower or upper portion of the grille (have to be careful as i have an aluminum block)
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Old 04-04-2020, 09:10 AM   #29 (permalink)
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Quote:
Originally Posted by Tahoe_Hybrid View Post
should i block off the lower or upper portion of the grille (have to be careful as i have an aluminum block)
If you don't have one already, you can get a Bluetooth OBD II dongle from Amazon/eBay for around $5 which will let you monitor engine temps exactly. Just need to run it long enough to know if your grille block is too much or not.

Can't wait to see how it improves!
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Old 04-04-2020, 09:32 AM   #30 (permalink)
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The only problem with putting max air pressure especially in newish tires is the center of the tire wears out faster.
I air up old tires to higher pressure that have been properly rotated front to back and they look like they are going to wear out on the shoulder first.
Also better tires help. The new energy saver tires with normal 34 to 36psi get the same milage as the warn out ecopia tires with 44psi.

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Last edited by oil pan 4; 04-04-2020 at 12:10 PM..
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