Slightly disappointed with MPG's

[flagmanruss]

I'm sure someone must have compared the 12V vs 24V cams, flow & timing... enlighten me. The 24V was built from the ground up as a smogged engine. By defination almost, a less efficient engine.

[hd99fxr3]

Lets say you are idling, but moving at 70mph, would you not be getting incredible mileage? Lets say you had an unloaded truck vs. pulling a trailer, is there not a significant difference? They aren't incapable of using less fuel.. The ECM on these things can only control so much.. There are much more efficient things out there, and things that haven't even been invented. All of which can make the truck require less fuel my making the engine more efficient or other means. Stodg has got the same mileage as me using propane, so it's not like the thing is incapable of being more efficient given the means to do so. But of course propane is an additional cost of course. I'm just saying that you have to think outside the box. The RV275 injectors gain you MPG's, higher fuel pressure gain you MPG's...what else is there? Could be several things we could be doing. Nobody would care if there wasnt an identical truck like the 12V's out there saying that yes you SHOULD be getting much better mileage. What gets me is the fact that my timing is static, I have 2 less valves, so the efficiency (theoretical) loss should mean that I get less mpg's than a 24v. But the 24V has emissions but do you really mean to tell me, that a truck, with more valves for better flow and variable timing, can not only be seemingly less efficient than a 12V, but also go beyond that another couple mpgs, just because of emissions?.... I keep thinking that the emissions loss would be gained by the efficiency improvement. I know compression ratio has something to do with it because a 12V is 17 or so and a 24V is around 16 ( You see all kinds of numbers on the net so who knows what it actually is). That has something to do with it obviously but it's still missing something. Plus the ppumper 24V trucks get the same mileage as they did with the VP as far as I have read, so it's not exactly the emissions doing it. We can go over this for hours, like millions of others have since 1998... Nobody seems to do much other than ponder about it. I'm gonna get to the bottom of it. I know there is a bit of politics involved and stuff that is keeping them from getting 30+ mpg, but even so I want to weed that crap out and figure out whats holding it back.

I'm right there with your line of thinking. I know awhile back we had a discussion about adding Cetane boosters to the fuel. It was grudgingly admitted by Mike and others that adding Cetane to a '06 with the third injection event, may in fact be beneficial. I did in fact try some and gained mpgs on the 150 mile round trip I do to go to work. The problem seems to be in diesels that the milage is getting killed to meet emissions, with a multi pronged attack. First you have lowered compression to reduce heat (NoX), Then you have the piston dome redesigned to achieve, something???, Injector nozzle redesign to coinside with piston redesign, and then you have cam timing event changes to hold exhaust gases in the cylinder to again reduce heat (NoX), and finally injection timing, and added injection events to again quell heat (NoX). Oops almost for got the turbo changes. It is pretty clear as to why the 24v engines in general, and the 3rd and 4th gens in particular, don't fair as well. It's the cost to undo, the efficency killing enhancements to our engines, that will stall out any major effort to undo what .gov has foisted upon us. To get the efficency back all you have to do is, change the cam, pistons, injectors, turbo, and ECM / PCM programing to get them back to getting good efficency from a gallon of fuel. Problem is who has that kind of scratch lying around, without feeling a mortal sense of loss when it's gone. You will never get an ROI, and you can buy alot of fuel over the life time of the truck, without really making a dent, in the pile of cash you saved by not doing the mods to get the efficency back.

[SoTX]

I was driving 100 miles round trip to work and was averaging about 17 MPG, lower if I had to blow by non-driving people though.

[dorkweed]

I've had my '04.5 almost twice as long now as I had my '99. I can say for certainty that I get way better mileage on average with my current truck (Mighty Whitey) than I did with my old '99 (Mean Green). 20.7mpg was the best I could ever get out of greeny. Greeny however was religious about being consistant with mileage...............17-19mpg all the time in combo towing/empty. I've had a high of 23.2mpg a couple years ago on my '04.5......................and recently had 4 tanks in a row of 20+mpg and one of those was 21+!!!!!The aftermarket "magic" is out there to make the 3rd and 4th gens really good on fuel. But you need to live in a free state (no testing) to realize it!!!:smart:

[02cumminsdude]

Short update, I installed an AFE stage 2 intake. Noticed a slight difference in the feel of the truck since my factory filter was pretty clogged. But mostly just has deeper tone in the cab, not to mention more turbo whistle. Sounds like a damn jet at times Don't know the affect on mpgs yet, however I can say this, by changing my driving style and lowering the Juice to level 1, my overhead got up to 17.1 for the first time since I owned the truck. After a couple short miles of driving with AFE and turning the juice back up to 5, the overhead went right to 17.2 and I also have much less black smoke when accelerating hard. So all in all, the AFE is proving itself, but I look forward to the actual gains at my next fill up. On a side note, the AFE is suprisingly difficult to install for how much money you spend on it. I had to do a lot of pulling and forcing the box and the tube into place and the tube doesn't line up very well with the box. Overall I'm happy so far, but the install was not what I expected from one of the "higher end" intakes.