Question... when you are just cruising at 70mph at level grade, and not accelerating what are you seeing your boost at? My boost at that speed is generally 4-8psi. If you have 30psi of boost under no load or elevation change... then there is definitely an issue here.

 

I think mine is in that range too, but soon as I encounter even a bit of a grade the boost climbs like crazy without any extra throttle input. I will verify the boost numbers tomorrow in the conditions you asked about - they seem normal until a slight load is encountered or a bit of extra throttle is applied.

 

Laredo, your truck sounds normal to me. Increased output requires increased boost. This is even more true on modern emissions controlled engines because for some reason higher boost pressures help produce less harmful emissions.

Not too sure why this works the way it does, but my work truck's engine is produced by the only company that made a 2004 EPA compliant heavy duty diesel engine without having to use an EGR system. In their explanation of their emissions control devices, the fact that the engine has two turbos and uses higher boost pressures than the competition is mentioned as one of the reasons they don't need EGR.

Your PSD seems to act in exactly the same manner as mine does.

 

I ran 70 mph yesterday on level pavement. Boost was about 20 all the time.

 

I'm reminded of a funny story. Last summer I was sitting at a rest area somewhere up north. A guy pulls in and parks behind me with a DRW 6.4 pulling a camping trailer that might have weighed 3500lbs if the water tanks were full. i ask how he liked the truck and eventually about MPG. He says he gets 15 to 16 towing and that the secret is to keep the boost under 10. I just smiled and bid him good day, knowing that at 10 on the boost I'd never get my 17,000lb 5er out of the rest area.

 

StanleyZ, Ive seen just a few of your posts lately with the pics, and thats one beautiful 350 you have there

 

I did some towing and found something wierd (IMHO). When towing my boost actually appears normal, with around 38 as the max but when empty, the boost is actually higher at part throttle, and I still see 40+ for boost at WOT

 

Laredo, I've noticed the same thing. I think it's perfectly normal in a modern emissions controlled engine. It certainly behaves different than the boost gauge on my work truck does! But then again, my work truck isn't EPA 2007 complaint!

My mileage has been above average, the thing runs like a dream and tows even better. I don't think anything's wrong with the boost gauge acting a bit funny; I just think it's one of the interesting things about such a complex engine.

You do know that the PCM controls the high pressure turbo, right? The boost is where it is because the computer wants it there!

Enjoy your truck!

 

Well, thank you very much, how about my H model Huey? Ain't that a beaut. What is the chopper in your pic?

 

One of 2 American Eurocopter BK-117's we use. Im a Flight Nurse/Paramedic. Its my home away from home. Love those Huey's. They are the s*#t!

 

Are you stock? I forgot that I am running a 250hp spartan tune, cat and dfp delete. That could def make a difference. But for me, just cruising on level ground with no throttle increase the boost stays steady under 10psi. As soon as I lay into the throttle though it def gets up there but I dont remember seeing in the mid 30's unless I was WOT. I will pay closer attention today. How does the truck feel? Like it builds the boost and power smoothly and evenly? This 6.4 is so different from my 6.0. The 6.0 felt like a brute, the power came on all of a sudden and it came on strong. The 6.4 is much smoother, builds smoother and doesnt hit you as hard, but its going much much faster than the 6.0 haha.

 

Thanks for raising the fuel issue! New 2010 and hauling a huge load on the interstate for 1400 miles. Noiticed the truck not catching the over drive gear very well at all on part of the trip and boost being too high ('bout 24 PSI running 63 MPH on flat ground.)

Opposite trip on exact same road with fuel from different source, the truck easily caught overdrive and boost pressures remained below 20 PSI easily. Much better milage and obviously less engine work.

This was our first trip and we used no cetaine bost. Bought fuel from several branded stations and other non-branded as well just off the interstate. Can't remeber the station where things seemed screwed up.

Winter fuel should have had nothing to do with this, since we traveled the carolina's, GA and FL. (The issue was actually with Florida bought fuel.)

Back to Silver Diesel Kleen on each tank I guess????

 

Were you towing an enclosed trailer, or an open one?

Because it sounds like you were driving in wind. A headwind or tailwind can have a huge effect on fuel economy because your engine has to provide a significant increase in power to push your truck and trailer through the wind.

Never tracked it on my pickup, but on flat ground I've seen as low as 5 MPG in a headwind and as high as 8.5 MPG with a tailwind. This from a loaded tractor trailer weighing between 60-80,000 lbs. Wind makes a HUGE difference!

 

The only way to make boost is to burn fuel with air producing exhaust gases powering the turbo which compress intake air which is your boost pressure.
Low turbo inlet pressure from clogged air filters reduce the horsepower capability of the engine. This is the reason for low restriction intake and filter systems. (CAI)
At 70 mph you are pushing a huge frontal truck area through the air. Lots of drag that requires lots of horsepower.

 

Truck is stock but has levelling kit and 35" tires. The truck feels good (for stock power), like you commented, its smooth, refined power. I cant wait to do the tuner/DPF delete because I miss the power that my Innovative tuned 6.0 produced!!!