PLEASE help me! VNL670 with an ISX CM2350 4.4 MPG!

[Rawze]

Just for reference there hammerhead, on a 2350 with egr still active, a couple psi higher than a demandated truck if it is using a lot of egr gas.


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What is the rear ratio of the truck? What is the mileage? - I did not see it mentioned.

Like hammerhead has said,.. has anyone verified that the truck has the correct program in it based on the engine ser#?. I.E.> Make sure someone did not "up the hp".

* Has anyone bothered to look at the decomp tube and verify it is not partially clogged? Reference: http://rawze.com/forums/showthread.php?t...07#pid1807

* Has anyone bothered to see if the Doser injector behind the turbo is leaking fuel?

* Has anyone bothered to pressurize the CAC and check it for leaks? -- How about pressurizing the entire engine between the intake filter and the back of the turbo and checking it for leaks as well?

* Does the truck have an after-market CAC unit on it? - Many brands of after-market CAC uints are very restrictive and cause fuel mileage losses.

* Does it have an after-market EGR cooler on it? -- Same thing, they can rob you of fuel mileage and in fact many have even caused engine damage due to excessive egr temps.

* Anyone bothered to pressurize the fuel tanks and check the lines for leaks?

* Does it pass a leak-down test? Reference: https://youtu.be/eH9GRkeozTM

* Anyone bother to flow-test or even inspect the the SCR unit for clogging?

* Anyone bothered to do valve adjustment?

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It the mean time ...

Like Hammerhead said, slowing down to 63~ish will help -- A LOT!. So will driving by your boost gauge and limiting boost to about 15 psi or so as a good start. I am not saying this as a replacement to any fuel mileage loss problems the engine or truck may have,.. but it will definitely help mitigate losses. This is especially true while you figure out how to get the fuel mileage back up to normal levels. Better driving habits always lead to higher profits and less down time.