515 detroit, fuel ecconomy/ turbo questions

I recently bought an '05 classic, with the 515 detroit.
13 double over,
3:58 gears
Running 24.5 low pros
This is the first 515 for me, and I have little experience w an egr engine. I've not run it enough to have an accurate fuel mpgs yet, but my feeling is so far, low 5s. I pull a 53 van, and am usually grossed between 50 and 80. I also, try to keep my weight loaded forward to decrease heavy tandem drag, and air flow turbulence behind the fairings. I'm from the old school, where you ran detroits at 1700, cats @ 2000... I've been reading about the 1200 to 1500 rpms on the newer engines, which I plan to try out. I usually run @ speed limit, or just above, so, 60 to 75 mph. Something I've noticed however, is in the top hole, at 70 mph, I'm taching just above 15, but my boost pressure runs high, and sometimes, never falls off at all, even on flat ground. I can drop to 12th tho, and run 1700, and the boost pressure is much less. This "seems" to do a little better on fuel, from what I can tell so far. I'm wondering if anyone has any experience with this. I'm thinking of getting it in to someone to get tuned, thinking mabey its something in the ecm settings? The last 13 double over I had was behind a 3406e, and it didn't do that..

Otherwise, any advice re improving fuel mileage for this application will be appreciated.
Be it mechanical, or adjustments to driving habits. Thanks, and happy to meet everyone.

 

I should add that the instance I mentioned was on more or less level ground, running on cruise. My boost pressure however even has a slight reading (according to my gauge) at idle, showing 2-3 lbs... Wondering if i have a sticky waste gate or something.. Idk even if this turbo has a waste gate.

 

Well, I know slower speeds can certainly make a difference. Sometimes a huge one. But that's part of the reason I went with this particular spec, to be able to run at lower rpms. Fuel savings are key, but time is also money. As little as 5 to 6 mph makes a huge difference on a log page. I'm not above pencil stroking logs here and there, but no matter how I log it, 2 extra hours on the road, means less time in the sleeper. Or 100 miles less per day, means less completed loads every week. I want my cake, and eat it too. I used to run my little century, 470 balls to the wall all the time, and did 6, with it wrapped out. I "think" I should be able to haul the same trailer, same speed, at less rpms and do the same, or better on fuel. At least, I would think so? Aerodynamics not withstanding.

 

I guess its the over fueling that I'm thinking of. Mind you, the turbo/rpms I'm mentioning are only in top hole/od. But top hole, the boost jumps to 40 lbs, a lot! And 12th it stays around 30, or less, but higher rpms. This truck is equipped with an air ride steer axle too. I'm not discounting it may have been set up for some kind of oversized hauling, and perhaps I need to have the computer settings checked out. I gotta get some trailer tires, and get my air-weigh hooked up in here, but getting it scoped out is my next priority after that.

 

I will say, I love having air in the front. This is the best riding truck since my '00 w9 back in the day. Now that was a nice truck!

 

Thanks guys, I'm trying the progressive shifting. So far, no real issues there. Elroy, re driving slower. It's very true that it can save fuel. But its also very true that its a sacrifice on time. You said you were 1/2 hour behind after only 105 km.. I'm not looking @ my speedo right now. What is that, about 80 miles? Multiply that by 10, which is my average day. Yes, it makes a HUGE difference on time. In real world numbers, I started out back when driving a 57 mph swift truck. Now, I drive as fast as I want. It's the difference in a 3000 or 5000 mile week. I don't do 5000 always,cuz its tough to log. But close. Depends on the runs and the roads. Say, between 4 and up to 5 per week. I get flat rate on my loads. So, the more I do, the more i earn. If I cud double my mpgs, that would be one thing. But 1 mpg, give or take isn't enough to justify giving up that much work. I do want the best mileage I can get, but at the same time, I have a job to get done. I can't sacrifice the job for sake of minor fuel savings.
It's like generators. Yeah, they're great, and they do save fuel, and some wear and tear. But at 12000$ ea, its a luxury I just can't afford. There are a lot of old sayings that people use, ie idleing burns 1 gallon per hour. I have never found this to be true. The reality, in my experience is more like .25% of that. And, when the weather is nice, I shutter down. There is also something to be said however for starter wear, and the fact that a cold engine burns more fuel than one that's warm. Also, team trucks get better road mileage than solo trucks, because all the axles are warmed up, and roll a little easier. Tire pressure, fifth wheel placement, weight distribution. They all contribute.
I'm not saying you're wrong, I'm just saying there are other factors to consider. I'm working on a happy medium. I need the best mileage I can get, without sacrificing productivity.