" I thought the engine could only be more fuel efficient because they were able to get better emmissions with no EGR"

What is the rationale for that?

 

I'm certainly no expert, but it could be that:

Better emissions = less unburned fuel = more fuel efficient

Of course, we must remember as well that more power (325/600) often takes more fuel to obtain, so there you go.

Neil

 

Your close, but less unburned fuel may have been achieved by retarding the timing, which gives less power. So to get to the same power as you would have had without worrying about emissions you have to add more fuel. Also, the post injection event adds to the increased fuel used. A small amount of fuel is added at the beginining of the exhaust stroke that burns off the hydrocarbons. No more power, but you used more fuel.

Unfortunately, there is more to emissions than just unburned fuel. Some emissions (NOx and Sulfer particulates) are a "byproduct" of the combustion process. If you completely burned all the fuel, you would still have emissions. What you said, however, does apply to unburned hydrocarbons.

 

What would be nice is if a box would become available that would re-tune these engines to what they are ment to do....hugh amounts of torque with excellent mileage! Screw emissions!!

Just my opinion....

 

I have a 93' and get in between 22-25 mpg on highway, about 18-20 mpg in the city. Get around the same when towing something.

 

I'm with you NJTackle...I want better economy not better emissions...I love everything about my truck except the mileage but I still think I would swap for a 305/555 HO.
I am thinking about trying a box and seeing what happens. At least it would be MY fault if I kept my foot in and got poor MPG.

 

With the emissions now in place on the 4.5 trucks I dont see how Banks or any of the aftermarket companys can legally produce a box that does to much of anything unless they list it as "for off road use only". Seems to be the trick thats worked in the past anyway!