optimal MPG mods

[98_k1500]

Yah I think I'll just bolt a piece of plywood to the front of my trucks

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??

 

[GMRedline]

delete catt.convO2 sensor now calls for rich mode

Not really. The rear O2 doesn't control fueling. It is only there to check to make sure the cat is operating properly. The front O2 (pre cat) controls the fueling.

This is all true. And a low thermostat will not allow the engine to get to proper temp [also if the computer is still hooked up, it won't stay in closed loop] and will cause it to run richer, using more fuel.

It looks like the closed loop thresholds are much lower then expected. Tune file from a 1999 Suburban k1500

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Closed Loop is enable at 133* and LTFTs are enabled at 140*.

I was also surprised to see no spark modifiers to help the engine get up to temp faster.

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The Spark adders stop at 25* and the spark retard doesn't start until 208* under heavy load.

I agree with you that it is not good to take the vehicle out of it's optimal operating range. Apparently GM relies heavily on mechanical devices like a thremostat and clutch fan to determine exactly what the optimal operating range is....

 

[Blue95]

I am not understanding how air hitting a vertical piece of plastic is going to increase MPG. By his reasoning, if i extended my valence all the way to the ground, it would get better mileage.

Yes you would, again physics is always in play.

I guess too much science makes me the idiot, typical on here.

 

[Blue95]

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??

Air flows smoothly over the top of a vehicle, not underneath it, it hits suspension parts, cross members, etc. Turbulent air causes resistance thus causing a higher drag coefficient. Air will always go under the truck, but how much and how it travels under is the whole point here.

Yes lowered is less of a footprint in the air, but also less air under the truck.

 

[thz71]

Yes you would, again physics is always in play.

I guess too much science makes me the idiot, typical on here.

You keep saying physics but no examples or facts if your just trying to sound smart it's not working. And feel free to leave

 

[polar]

I'm not gonna argue on here but the valence is there to reduce airflow under the truck because it creates drag. Drag will create resistance that will make the truck work harder to achieve the rpms needed. When you work harder it decreases mpg. Yes it will make a minimal difference on mpg but the OP should be worry about his valence. His lift and offset rims/tires are causing more of a drag than the valence

 

[thz71]

I'm not gonna argue on here but the valence is there to reduce airflow under the truck because it creates drag. Drag will create resistance that will make the truck work harder to achieve the rpms needed. When you work harder it decreases mpg. Yes it will make a minimal difference on mpg but the OP should be worry about his valence. His lift and offset rims/tires are causing more of a drag than the valence

So you're saying if i put a valence on my truck it'll make a measurable difference in mpg? You're a smart guy you can't honestly believe that.

 

[polar]

Read it again. It will make a difference but it is minimal.

 

[polar]

IMO it's not worth worrying about it on a lifted truck. They look a lot better without the valence. You don't lift a truck when you are trying to achieve mpg.

 

[thz71]

Read it again. It will make a difference but it is minimal.

Exactly my point this thread is about how he lost 6 mpg! Not .06 mpg. Hence why I said the valence made no difference then the blue 95 guy got all butt hurt.