More Boost for Same MPH?!?

[Big John]

The last time or two out with my trailer I have noticed that it takes more boost to run the same mph. I usually drive by boost pressure, loaded around 10 to 12( = @65mph ) and unloaded around 6 to 7. This combo has always given me great ecomomy and plenty of power in reserve.
Recently I have noticed that my boost is running in the 14 to 18 psig range to get the same mph. Trailer is the same, same tires, same basic topography. My milage has also fallen off 1 to 2 mpg while pulling, but not while empty.
Any ideas? I thought that it might be weaker fuel due to time of year, but I have not seen this in previous years. Any help or suggestions would be appreciated.
Big John ( this is the '96 5sp )
P. S. Any of you double-valved people have any thoughts?
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'94 2500 Diesel Reg. Cab
Auto 3. 54 4X4 TST 230hp
"If you can't Dodge it, Ram it!
'96 2500 diesel clubcab 4x4 5speed

 

[csutton7]

maybe you need to recalibrate your guages if possible--chris

 

[jponder]

Originally posted by Big John:
The last time or two out with my trailer I have noticed that it takes more boost to run the same mph. I usually drive by boost pressure, loaded around 10 to 12( = @65mph ) and unloaded around 6 to 7. This combo has always given me great ecomomy and plenty of power in reserve.
Recently I have noticed that my boost is running in the 14 to 18 psig range to get the same mph. Trailer is the same, same tires, same basic topography. My milage has also fallen off 1 to 2 mpg while pulling, but not while empty.
Any ideas? I thought that it might be weaker fuel due to time of year, but I have not seen this in previous years. Any help or suggestions would be appreciated.
Big John ( this is the '96 5sp )
P. S. Any of you double-valved people have any thoughts?

When you say you drive by boost do you mean you will ease off gas climbing hills and gently give going down. Your boost will drop when going downhill correct. Do you try to maintain a certain boost all the time? I think that maintaining a constant boost might be better than a constant throttle. I geus you could think of it as maintaining the same load to the engine. I would like to try this empty to see how it effects mileage. i just dont have a boost gauge yet.



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2001 ETH/DEE ST 4X4 SPACE SHUTTLE

 

[Diesel Freak]

well if weather condiions (temp, humidity, head/tail wind) and truck/trailer weight are the same, then you may have something causing extra drag. Possibly dragging trailer brakes, or some other thing that you may have added to raise wind resistance.

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http://www.mudrunner.sites.cc

 

[jponder]

Originally posted by cdaledh:
well if weather condiions (temp, humidity, head/tail wind) and truck/trailer weight are the same, then you may have something causing extra drag. Possibly dragging trailer brakes, or some other thing that you may have added to raise wind resistance.

Yes I was thinking about this too and it seems he must have more drag to increase his fueling and therefore his boost for given MPH.

 

[Big John]

JPonder, I try to set my cruise control on level ground at @6psig boost empty and @10psig loaded and let cruise maintain speed. The boost does vary considerably, up to 32 psig, when climbing hills with the trailer. My trailer weighs about 10,000 loaded. I have checked the brakes on the trailer and the truck and they are cool,no drag. The boost gauge reads the same as my test gauge, but they both could be wrong. I will check this.

Thanks for the suggestions. I will check the front and rear end for problems as a possible drag source as well.

Big John