CM2250 Poor fuel mileage

[Truckdriven]

(02-10-2022 )JMBT Wrote:  This may be a long shot, but what about a rolling resistance problem? A sticking brake or something from sitting so long? Could be on the truck or trailer. What about drive axle alignment? Maybe scrubbing a bit to much. Or even trailer alignment? Does the trailer pull straight and easy??

Just thoughts…

Yea I thought of those things as well... it has all disc brakes which is new for me , are they as likely to stick/drag as drum brakes? I will say I noticed the one front wheel brake had a slight drag in the beginning but after running it a short time that disappeared entirely. I had a full alignment done on all tractor axles a month ago.

I wouldn't have any reason to doubt the trailer cause it trails nicely and has new slack adjusters and chambers and they seem to be adjusted properly. Also I had pulled a lightly loaded amazon trailer 900 miles and had the same low mpg the trailer was 1 month old so should be aligned properly?

[JMBT]

Well I am glad you had thought of those things, it sounds like you have covered all the bases. It was just a thought, sometime the simplest stuff is the root of the evil…lol!

I don’t know on the Amazon trailer. I have seen some of their “drivers” smack a curb like it wasn’t there…. Of course I am the guy that gets out and lays down lumber if I have to climb a curb, ha!! But seriously!

[Truckdriven]

(02-10-2022 )Rawze Wrote:  in CT. the setting is actually 'CBL_Fuel_State'
Everything about the engine and what it is doing is mentioned on pages 53 - 57 in this document. Page 57 shows the outcomes of this fuel state setting in detail:: http://rawze.com/forums/showthread.php?tid=7677

So I checked and under full accelerator position fuel state goes 47, I recorded it along with a number of other things, do you want me to send it to you??

[Rawze]

(02-10-2022 )Truckdriven Wrote:  ...
So I checked and under full accelerator position fuel state goes 47, I recorded it along with a number of other things, do you want me to send it to you??

that is not a derate, but a common code to see. Code 47 means that the engine mode fuel limiter is active for whatever engine mode it is running in. I.E.> it has reached its max allowed power for that particular engine mode.

how many mg/stroke and what engine mode is being applied when that code is showing?.

mg/stroke Can be monitored by watching 'Total_fueling'

and active engine mode can be seen via 'CBR_Chi_Table_Mask' and 'Chi_Mode_Status'.

turbo position can be seen at '_VGT_Actuator_Position'

[Truckdriven]

(02-11-2022 )Rawze Wrote:  that is not a derate, but a common code to see. Code 47 means that the engine mode fuel limiter is active for whatever engine mode it is running in. I.E.> it has reached its max allowed power for that particular engine mode.

how many mg/stroke and what engine mode is being applied when that code is showing?.

mg/stroke Can be monitored by watching 'Total_fueling'

and active engine mode can be seen via 'CBR_Chi_Table_Mask' and 'Chi_Mode_Status'.

turbo position can be seen at '_VGT_Actuator_Position'

I recorded a data log with most of that in but to be honest I don't know how to review it. I will Email the files to you.

[Rawze]

(02-11-2022 )Truckdriven Wrote:  

(02-11-2022 )Rawze Wrote:  that is not a derate...

I recorded a data log with most of that in but to be honest I don't know how to review it. I will Email the files to you.

best thing to do is get some (usually free) desktop recording software and record what is going on that way.

[Truckdriven]

(02-11-2022 )Rawze Wrote:  that is not a derate, but a common code to see. Code 47 means that the engine mode fuel limiter is active for whatever engine mode it is running in. I.E.> it has reached its max allowed power for that particular engine mode.

how many mg/stroke and what engine mode is being applied when that code is showing?.

mg/stroke Can be monitored by watching 'Total_fueling'

and active engine mode can be seen via 'CBR_Chi_Table_Mask' and 'Chi_Mode_Status'.

turbo position can be seen at '_VGT_Actuator_Position'

At 1612 rpm 100% throttle I have
_Intsantaneous_percent_load~ 91.016
Total_fueling~ 264.16 m/g stroke
_VGT_Actuator_Position~ 22.09
_exhaust_pressure2~ 383.55
CBR_Base_Chi_Low_Index and CBR_Base_Chi_High_Index always stays at 4

[Rawze]

(02-11-2022 )Truckdriven Wrote:  ...Total_fueling~ 264.16 m/g stroke
...

264 mg/stroke is roughly about 440-460~ish HP or so worth of fuel.

Since your program (that you sent me a while back for review) shows it is a 450HP/1750trq program, this is about right. This means that the ECM is at least doing what it is told and that it "thinks" it is making full power etc.

The turbo only being at 22% sounds a touch low, 32-33% would be more like what is typically needed for a W900 truck at that RPM/Power level ... but it being a W900, they are known for requiring lower positions than other trucks, simply because the larger 4" intake piping + CAC is very large, have almost no restrictions in them. Raising it a bit could be done.. but you also complain about massive fuel mileage losses too though. - This would not be caused by turbo programming alone. - This implies that there has to be an air(or exhaust) related issue somewhere with the truck/engine.

This means that if your getting the fuel.. and the boost is lower than expected, ... it sounds exactly like maybe an air (or exhaust) related issue to me so far. Perhaps a boost leak somewhere that only happens under load?, or perhaps maybe a clogged up air filter?, clogged up exhaust?... damaged turbo turbine blades?, something... - At least that is what you posted so far.. but it literally anyone's guess. Engine problems that are not obvious are impossible to troubleshoot via "texting" and "forums" alone.

I.E.> It is all just blind guessing.


In any event, the boost (turbo programming) should likely be corrected so that it makes more like 34-35 psi under full max loads, and not only 28-30 like you described above.

Maybe a trip to Mr. Hags with it? if no one can find it?.

[FnG92]

I'm in a similar boat myself, reading this has given me a couple ideas. Just wanted to say thanks