optimal MPG mods

[K15 Blazer]

The topic is:
WHAT'S THINGS YOU PERSONALLY HAVE DONE THAT HELPED OR HURT YOUR MPG

 

[K15 Blazer]

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[ccreddell]

The science behind it is true, but on our pigs, I've never seen it make difference.

Any time you get the air dam more than 8" off the ground (and probably less), any aerodynamic benefit goes out the window. On a lowered truck where the air dam is within 1-2" of the ground, then yes, it does deflect air around the vehicle instead of under.

 

[ccreddell]

Thats what im saying. a lowered truck gets better mileage because its less air between the pavement and the top of the cab that has to get out of the way. Not because it is actually closer to the ground... I mean, airplanes get decent mpg right??

Yes, there is a correlation to the overall height and MPG, but theres way less wind resistance on a smooth hood and cab than there is on all the suspension and frame surfaces that find themselves in the wind. Thats why race cars try to use belly pans-to present a smooth surface for the air to move over. So, when you lower a vehicle, you not only lessen the frontal area, you make less space for air to get under it. If you then put an air dam under the bumper, the air has to go around on the the (mostly) smooth parts of the truck and the wind resistance caused by the 4" air dam is still way less than all the rough parts under the truck. It also causes a vacuum under the truck which aids in pulling air out of the engine compartment which aid cooling. That air isnt enough volume to cause too much wind resistance though.

 

[98_k1500]

^^ this guy has got it lol

 

[df2x4]

I personally gained 1-2MPG from my tune in my V6 truck, not that it was bad to begin with. Also tuned for 91 octane so MPG is kind of outweighed by gas price.

(I believe in the power of the front valence but I'm not going to start sh*t over it, especially on a lifted truck.)

 

[sewlow]

Wide tires take a bite out of fuel mileage, more rotating mass (weight) to spin

I think the best, most cost effective mpg increase would come from your right foot. In other words, driving like a granny.

AIR D.A.M. (Directional Airflow Modulators)
On taller vehicles an air dam won't have as much of an effect as something where the valance can be close to the ground.
Guys on Ecomodder have proven pretty substantial gains in mileage with improved air dams.
Keeping air from going under the vehicle helps reduce aerodynamic drag by keeping the amount of air traveling under the "dirty" (aerodynamically) underside of the vehicle.
Why aren't vehicles engineered with these larger air dams? Hard to make them aesthetically pleasing, and it's hard to sell a car that can't clear a speed bump without body damage, let alone survive winter roads.

On taller vehicles the aerodynamic advantages will be less dramatic in terms of drag savings, but there are still other benefits.
An air dam creates a low pressure area behind it, which in turn lets more air be drawn through the grill/radiator.
Sounds weird, but it works. Most air that flows through the radiator is expelled out the bottom of the engine compartment, so creating a lower pressure creates higher flow.
Trying to funnel more air into the radiator isn't very effective, it's very hard to create much pressure increase at road speeds (even "ram air" is rarely good for much more than a few tenths of a single psi). However, an air dam can create a pressure drop close to a full psi behind it. Greater pressure differential means greater air flow.
IF it didn't do anything the manufacturer wouldn't have spent the money designing, testing having them made and then mounting it. The reason for the dam is to prevent too much air from traveling under the vehicle which causes uplift of the vehicle which results in lesser mpg and poorer handling.

I doubt there's anyone on here that could tell you how much mpg you'd gain if you were to install one. You may have to visit some technical forums for that.

Will the original poster see a noticeable mpg or temp change installing an air dam? Probably nothing he'd notice. But the engineers aren't just wasting time and money designing air dams, they serve purposes.

Vacuum gauge.
The lowly vacuum gauge is the grand-daddy of fuel economy instrumentation.
Installing and using one remains a cost effective way to help a driver fine tune certain driving tasks for better efficiency, particularly "driving with load"
As well as aiding efficiency, adding a vacuum gauge is useful as an indicator of the general health of an engine, as well as indicate any improvements or losses from various modifications.

 

[Birchyboy]

Yes you will have less drag and better MPG, think about how that air is turbulent under the truck, it isn't completely smooth. Why don't you use your noggin' first.

The valence not only keeps air from under teh truck but diverts to the sides so it goes around the truck easier. Has anyone here gone to college?



Now you are being a ridiculous liberal, the difference is quantifiable and will make a difference, but changing tire size is a much different force than the air. No you won't envy a Prius' owner's MPG, but you are envying their brillance right now with your post

Liberal? yes. Ridiculous? No. Sarcastic? Definitely!

Now, where did I put that darn throttle body spacer, intake tornado thingamajug and painters tape for all of my seams?

 

[K15 Blazer]

Yeah wind resistance is a joke. Most people drive 70 to 80 mph anyway.
You might as well get out the tape and seal up your grill and hood gaps and add a boat tail on the rear to end.......

I think gas also makes a huge difference. Chevron actually got me 4MPG better over arco a couple times...

 

[df2x4]

Gas does make a difference. I've also noticed a difference between gas stations in both of my trucks. Took a few tanks to confirm it wasn't just my driving, but it's there.