Calling all CAT techs. Answer this question.

Sorry I cant help you much,but for what its worth the new 08 engines will never make it over here.
We have just started getting the first of the twin turbo's over here this year and CAT have said they are going to be limited.
Having HUGE turbo issues already and the truck engine salesmen have already halved in numbers.
The writing's on the wall.

 

put an 18 speed gearbox,dont see the point of 10 speeds on highway truck even if you use it on flat relief

 

Like stated earlier these motors were designed to be the most effiecent (if you want to call them efficent) at around 1250rpm. Anything over that your just wasting fuel. The spped doesn't help either, especially out west with the winds. The C-15 I have hates the cold weather more than any other motor I have had. My mileage drops off at least .6 when the temps drop below 30. It sounds like there may be more going on in the motor or ecm. One reason you may not be able to get it over 1700rpm is if the progressive shifting is turned on in the ecm. Check with your mechanic or boss and see if it is turned on. If so learn how to use it and that should help some. One thing I have seen with the C-15's is the more you turn the setting up in the ecm (hp and torque) the better the mpg. CAT is trying to move so much air through the motor to cut down on the emissions that it is hurting the mpg.

 

what mpg do you get on average, what does shimmed fuel pump mean?

 

I average right now with the cold weather and pullling a 53' dry van around 5.4 to 5.6. I don't have any hard numbers what my mpg's are in the summer cause i have installed some stuff and changed programing in the ecm back in Sept. But with what I'm seeing now I'm guessing I'll be around 6.3 - 6.4 area.

The shimmed fuel pump is just putting a shim in the fuel pump to increase the fuel pressure. Which in turn puts a little extra fuel in the cylinders with every injector firing. I don't suggest that everyone (especially company driver) do this. If you don't know the motor and have the gauges to watch your fuel pressure you could push fuel past the o-rings and into the oil or coolant.

 

Stranger...I would say there is something in the motor or ecm that isn't right. The low mpg's your getting just don't seem normal. CAT did have a problem with fuel filters and bases...long story if you want to know more just ask. But I would talk to the mechanics to see if the other trucks are getting this bad mpg.

 

I had crapy fuel milage and low power with my MXS til I went back to using CAT fuel filters, the power came back but still have some what crapy fuel milage...just not as bad. In the winter my fuel milage always drops like a rock.

One thing I noticed in your post was you said you was bumping 1700 while shifting in the top gears. I never get above 1450~1500 RPM's while shifting up. But mine is set at 2150 RPM's and I'm sure my fuel settings are set higher than a company truck would be. It took me awhile to figure out that anything over 1500RPM was weasting fuel with the ACERT.
Thats one reason why I cant see spending the extra mney on turning my 475 up to a 550 because the torque falls off at about the same RPM. The 550's horsepower goes past where the 475 dose but I never run the RPM's up the high anyway.

 

where did you get ecm programing done? did you change FTS, FLS?
how much higher will fuel pressure be with a shim in a fuel pump?
i own my truck little over 2 years, my mpg rarely gets over 5.5 with very light foot on the throttle and going around 60 mph. trying to find some info how to get better mpg. not really want to increase my HP, i have 550 now.