c-15 no fuel mileage HELP

Just to say, not to get ya mad, but do you need the power to run in the hills? I run in the north east US and have a 2007 Freigh, Century with the Mercedes plant (not my choice, company truck ). We are obviously locked at 65 mph, and the truck is a 10 spd auto box with manual mode, would preffer your 13 though! We have dual 130 us gal. tanks and i can squeeze about 1150 miles on one load of fuel and i beleive my readout comes to about between 5.8 and 6.2 mpg. From seventh gear on my foot is to the floor, engine seems to be pretty gutless. Have you driven an auto box? If you have, at least the freight models, you will see why our foot is to the floor. (If it shows anything on a 2.5 mile 6% grade with 42 ooolbs in the box hitting the bottom at 65mph i crest the top at 35 - 38 mph in 7th, if that gives you an idea of the power). If you need the power then the fuel mileage goes with too.

 

How about running the overhead?

When was the last time it was done?

 

did your air to air lose any pressure when it was tested ?

what brand/model of tires do you have?

 

I had a friend with similar truck, 05 w9l daycab, getting 5.1 mpg with twin turbo bxs cat. We installed the M100463 Donaldson mufflers, put in good fuel #'s and good flashfile and now its 5.7 to 5.9 . Trying to get him to do a Fass style fuel system...reread the Cat post and the Acerts post. They are very informative and the trucks are strong with decent mileage with a few minor mods.

Rob

 

First off, what serial prefix is your motor and what HP/TQ ratings are in the ECM. The 25-40 PSI of boost sounds low. I suggest you krun the overhead and have the mechanics really look at the IVAs...you may have one on the verge of going out, but not throwing a code. Also build yourself a CAC checker. They are simple and very inexpensive to build. The ACERTS put out more boost than any other motor, but the shops only test them to normal specs of about 25-30 PSI. This isn't enough since you could be pushing boost past your clamps at a higher PSI than what the shops are testing at. Speaking of clamps, if yours are due for replacement I would go with the larger diameter spring clamps that Freightliner and some Mack dealerships carry.

What primary and seconday fuel filters are you running? ACERTS need fuel flow and hate water. I run a FASS system as a primary/water seperator setup and only CAT high efficency seconday filters. Also some of the stock primary filter heads are to restrictive.

Check these things out and get back to us and we can then move onto the next step.

 

Is this a 475/1650 engine ? if so your gearing is about right. if its an 1850 tq, your gearing is too high.should have 3.36. 40 psi is about right for 1650 tq. low for an 1850 tq if your gauge is right. you said fuel psi is good,what is it ?