Lets talk "Power Adders"

[darcane]

Even though you are carrying a load, I still don't think you will gain much if any fuel economy by modifying the intake or exhaust.

When you talk about "efficiency" of an engine/vehicle, it doesn't necessarily mean fuel efficiency. Better flowing intake and exhaust will improve volumetric efficiency (engine will suck in a larger volume of air per revolution) which is not the same as fuel efficiency (traveling farther per unit of fuel). Improving volumetric efficiency won't always to an increase in fuel efficiency.

That said, there is a little room for improvement in both power and fuel economy by tweaking the computer a little. One of the things I was planning on was a Blackbear tune for my Silverado:
Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles
Which I have read can give a small boost in fuel economy. They can also enable e-fans on the older trucks like yours that don't have them.

What should I expect as far as performance/mpg difference?
Other than a pure HP gain, overall drivability will be increased. In most cases, you'll notice much less of a lag when you take off from a light or need to accelerate when getting around an obstacle. Typical mileage gains have been in the 1-2mpg range.

[SilveradoMike]

Ive also looked into black bear. I like what they do but having to use my truck daily I would have to pay the core fee to just have a programmed ecu sent to me. And my smog guy told me it may not pass smog with a reprogrammed ecu, but he isn't 100% sure.

Im still having trouble understanding how improving power (mostly low end torque) wouldn't translate to an increase in mpg. Letting the engine make the same amount of power eaiser or at a lower rpm seems to make sense in my head. My thinking is this. If you have two identical trucks with idenical loads and total weight. But one has 500hp/tq and the other has 250hp/tq. Wouldnt the one with more power be able to do the job eaiser? There for reducing load on the engine and thus decreasing throttle input/fuel usage? Both being driven same route/speed ect.

[oil pan 4]

Electric coolant pump wont help unless you have an alt delete.
I run an electric coolant pump and don't believe it did much for fuel economy.

Now, the electric cooling fan conversion was a great mod, netted up to 2mpg.

Exhaust mods typically don't offer much if any returns. While I was running my diesel suburban N/A I did a back pressure test. I didn't see much back pressure at all.
It was one of the last mods I did to my N/A configuration, when completed I didn't see any fuel economy increase.

[oil pan 4]

Putting the turbo on my diesel also netted me at least +2MPG.
(Dont expect the same result with a gasser)

[mechman600]

Don't waste your time and money on free flowing exhaust and intake because they will not make a difference in economy.

Do waste your time and money on taller gearing and aero mods because they will make a difference.

Obviously a small diesel engine swap would be great for economy, but only if you have no eco-conscience and love creating toxic pollution in the form of NOx and other nice things.

[darcane]

Originally Posted by SilveradoMike

Im still having trouble understanding how improving power (mostly low end torque) wouldn't translate to an increase in mpg. Letting the engine make the same amount of power eaiser or at a lower rpm seems to make sense in my head. My thinking is this. If you have two identical trucks with idenical loads and total weight. But one has 500hp/tq and the other has 250hp/tq. Wouldnt the one with more power be able to do the job eaiser? There for reducing load on the engine and thus decreasing throttle input/fuel usage? Both being driven same route/speed ect.

That's because you are talking peak hp rather than the hp used at that specific RPM/throttle position/load.

If you need 200hp to accelerate your loaded-up, gas-powered truck and you have one truck that makes 500 peak hp and one that makes 250 peak hp, the 250hp truck will likely be more fuel efficient. Why? The throttle will be nearly wide open on the less powerful engine, while the 500hp engine will be more closed. So, the cylinders will be acting against a significant vacuum in the intake manifold because the throttle plates are blocking air flow. It will take less of the available capacity on the 500hp engine, so there will likely be less stress on the engine and tranny (which would presumable be designed to handle higher loads), but that doesn't mean better fuel economy.

Even better for economy would be to accelerate more slowly and only need 100hp. Still run the 250 peak hp truck at nearly WOT but at lower rpms.

[Viturro]

For the money of an ecu, go with a fiberglass man and pay him for almost 4 durable aero mods.
if you want to pass the emissions test and have more power (for a less stress driving) maybe i do go for a better air filter, if i remember good ,with the K&N air filters you can clean them and use them again, they are different of the oem.

[UFO]

Originally Posted by mechman600

...

Obviously a small diesel engine swap would be great for economy, but only if you have no eco-conscience and love creating toxic pollution in the form of NOx and other nice things.

Biodiesel. Better mileage, no petroleum. That's what my eco-conscience tells me.

[cRiPpLe_rOoStEr]

If you could get a wrecked Diesel-powered Mercedes-Benz, either a Sprinter van or some sedan, to take the engine for a swap into your Silverado, that would be a good option. And I'm also favorable to aeromods with fiberglass as pointed out by Viturro. You might have already seen those fiberglass front clips widely used in race trucks, lighter than their sheetmetal counterparts and often also more aerodynamic too...

Originally Posted by UFO

Biodiesel. Better mileage, no petroleum. That's what my eco-conscience tells me.

I'm also favorable to biodiesel, and even pure vegetable oils.

As far as NOx emissions while using regular petroleum-based Diesel fuel, some newer engines get lower compression ratios in the order of 14:1, which reflect into lower NOx amounts since the combustion goes slightly colder, such as the Mazda SkyActiv-D that's gonna be released in the American market soon. Surprisingly, this same low compression ratio which is often pointed out as "revolutionary" was also used in the old Cummins NTC-400 (Big Cam) engine...

[mechman600]

Originally Posted by cRiPpLe_rOoStEr

Surprisingly, this same low compression ratio which is often pointed out as "revolutionary" was also used in the old Cummins NTC-400 (Big Cam) engine...

You are not suggesting that a Cummins Big Cam was a clean engine, are you?

I shudder to think of the amount of hydrocarbons emitted every single time one of those started up cold. So much smoke that we had the fire department show up at work one time. The later STC versions weren't as bad, but still....