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Streachy · 12-10-2017, **(Subject: Fuel mileage. )**

CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

yamajason · 12-10-2017, **(Subject: Fuel mileage. )**

(12-10-2017 )Streachy Wrote: CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

Burning more fuel...sounds like a bad tune

scottydogtruck · 12-10-2017, **(Subject: Fuel mileage. )**

Who did the tune?

Rawze · 12-10-2017, **(Subject: Fuel mileage. )**

(12-10-2017 )Streachy Wrote: CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

Could be tuning, but could also be something else. Some history and background??

Streachy · 12-11-2017, **(Subject: Fuel mileage. )**

(12-10-2017 )Rawze Wrote:
(12-10-2017 )Streachy Wrote: CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

Could be tuning, but could also be something else. Some history and background??

Was rebuilt about 344000 kms ago. Replaced the exhaust pressure sensor since the tune and the IMAP was changed within the year. CAC is perfect. 35-38pSI boost on average. EGT’s run normally between 800-900 degrees. While pulling a hill and rpm’s reach 1800 the turbo might hit 950. We are hauling logs, so the truck is grossing 63,500 kgs. And works pretty hard. As well, from the factory it was a 550 hp, 1850 torque. Had KW turn it up to a 600, 2050. Now it’s MM’d at the same 600/2050. Runs way cooler than stock. Pulls a little better than stock as well.

Rawze · 12-11-2017, **(Subject: Fuel mileage. )**

(12-11-2017 )Streachy Wrote: ...
As well, from the factory it was a 550 hp, 1850 torque. Had KW turn it up to a 600, 2050. Now it’s MM’d at the same 600/2050. Runs way cooler than stock. Pulls a little better than stock as well.

What brand and model truck? rear ratios? terrain? climate? etc. Also, unless the trucks are identical in every way, you can't compare one truck against another. The driver and his/her driving habits come into play as much as anything else too.

Are you driving it by the boost gauge?, keeping down as much as possible at all times? - that is where your fuel mileage goes,.. whenever it is above 15-18 lbs boost, that extra power costs you extra fuel.

You did not mention who did the tuning on it, curious on that one. Maybe PM me with their name if you don't want to post it public?. Maybe also check with them and let them know what your are observing and see if there are updates and/or if some adjustments can be made for it. If you have a means to pull the program out of it and e-mail it, I can look it over for you as well and give some opinion/suggestions.

38 psi boost is a bit high on the boost for the 2250's by my experiences. Peaking at 34-36 is more like where it should be peaking when they are at their most efficient at 600HP. Too much boost and it runs lean + fuel mileage drops off quickly.

Also you need to consider that more power = more fuel consumption. You mentioned you had it turned up + it is pulling harder than ever. -- That power has to come from somewhere. Maybe turn it back down to the original 1850 and see if the fuel mileage comes back up in it if that is more important. Personally, I don't like 2050 torque in them... Not even from the factory. It is hard on those engines and only serves to make guys want to drive them harder and shift less often leading to bad/lazy driving habits and ultimately lower fuel mileage. All the extra torque is in the lower RPM ranges where it is the hardest on the engine. I would much rather see one set at 1850 than 2050, even at 600HP if someone wanted that much out of it.

You should do other tests like injector leak test and other things. You should also have the fuel pump pulled apart and inspected if it has more than 400k miles on it to ensure the rollers are not going bad in it (assuming you have the updated fuel pump) and to ensure all the components are up to date. I know a lot of guys had the ceramic plungers updated to the newer style hard steel, but what people are now seeing is that the rollers int the bottom of the pump go bad and it fails with a slow silent death, taking the engine with it along the way.

There is also the "what was done to the engine" factor. If you have block plates installed, make sure they have not burned/corroded through and that they are of really high quality. Also on those 2250 and 2350's you must!!! make all the cans 100% hollow and only the metal left including removing the inner insulation. This includes the SCR can as well. It has been seen at least a dozen times where people only drill holes, or leave material on the outer edges, or much worse, don't bother with the SCR can,.. only to end up with a partially clogged exhaust because what is left in the DOC/DPF breaks apart after a few months and gets caught up in the elbow joints, decomp tube screen, or other places.

I have also seen this trend of people saying you don't need to hollow out the SCR can. Some BS claims about it being as "passive device" and other lame excuses they have no clue about. They are absolutely 500% DEAD WRONG!. It IS going to clog up after a while!. That filter eventually clogs up, causes power and fuel mileage losses and destroys the engine when it gets bad enough. Whoever the idiot bad delete shop that came up with that bad excuse because they were simply too damn lazy to do the right thing should be taken out to the wood shed and shot!.

I have also seen decomp tube injector get leaky and clog up the exhaust after a while too. IF fluid is left in the SCR tank, this can easily happen unless the line is blocked off.

- I.E.> Just because you have disabled those systems (hopefully you live in a foreign country where that is legal) does not mean you will never have trouble with any of them ever again. If they are still mounted to the truck, harnesses plugged in, etc. then something can still short out and cause a fault, cause a leak, or clog up the exhaust if not dealt with properly and/or inspected once in a while.

trucklogger2 · 12-11-2017, **(Subject: Fuel mileage. )**

(12-10-2017 )Rawze Wrote:
(12-10-2017 )Streachy Wrote: CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

Could be tuning, but could also be something else. Some history and background??

Can you plug in insite and see where the actuator position is at idle?

Streachy · 12-12-2017, **(Subject: Fuel mileage. )**

(12-11-2017 )trucklogger2 Wrote:
(12-10-2017 )Rawze Wrote:
(12-10-2017 )Streachy Wrote: CM2250. Recently MM’d. Comparing my fuel mileage to trucks with the same engine on the same haul and our truck seems to be burning more fuel than the trucks that aren’t demandated. Any thoughts?

Could be tuning, but could also be something else. Some history and background??

Can you plug in insite and see where the actuator position is at idle?

Where should it be at at idle

Rawze · 12-12-2017, **(Subject: Fuel mileage. )**

(12-12-2017 )Streachy Wrote: ...
Where should it be at at idle

Depends on how it was demandated. An MM'd truck, the turbo is usually only set just high enough for it to make slight positive pressure at the intake if someone has taken the time to set the idle region on it. You can look at tis position and see what it is with insite, and also you can remove the IMAP sensor from its mounting hole at the intake and see if there is a slight positive pressure coming from the mounting hole.