CM870

[Big_Rig_99]

Hi All, Just want to say thanks in advance for anybody that can help me.

I have a CM870 that has been de-mandated and is running a fixed non vgt turbo.

The issue I am having is that the truck de-rates itself on long hills when it gets hot (Boast stays constant but feels like fuel is being cut). Its a 565 but has a signature 600 turbo on it. It makes good power and the boast gets up to about 34-35. No check engine light comes on and the oil and coolant temp are in line.

Any Ideas?

Quick Update; Using Insite. Looking at the User Fueling State: The sequence that comes up in "Altitude Derate"

[Chamberpains]

Is your barometric pressure sensor reading correctly? They are quite accurate down to maybe 10 or so feet in altitude when they're reading correctly.
Was your Demandate done by someone reputable? Hopefully you don't have some crap calibration in your ECM where they cut a whole bunch of sensor readings out. If you have any doubt if it's a good calibration or not I would definitely have it checked out by Unilevers, Mommaburt, or gearhead.

[DLC]

From what I've heard some of the poor demadates have very few if any derates. If you had a ScangaugeD or something similar you could view the actual Barometric Pressure, intake air temp etc, I'm not sure the levels that it derates at. I like to monitor all the values my engines can see. Some bad demadates unplugging oil pressure sender doesn't yield a check engine light.

You can get a program to see the engine file and the proper changes are out there somewhere. You could check that yourself or get a professional to check it.

[Chamberpains]

DLC i'm sorry to say your words are comforting but completely wrong. There are many demandates that cause silent derates, simply have the check engine light shut off (not the actual code, which is also wrong), and a plethora of other horrible calibration changes that work against the engine running properly under all conditions it can be presented with or conditions which it was originally designed to handle.
There are very few people out there that have and use the knowledge to properly program a CM870. How do I know? I was one of the blind fools that let someone do there quote unquote professional Delete. Which sent me down a 4 year path of learning everything and anything I could on these engines. I have seen 1st hand some of the lame demandates that companies and individual on the web recommend and they're all half @$$ and will cause very poor running and eventually a premature destruction of the engine because it's blindly working against itself.
Just because you don't have a check engine light or a noticeable derate doesn't mean the engine is running anywhere close to peak performance. Mine ran for 3 years with a crap Demandate. Now that I've had it corrected properly I can now see exactly where the wrong Calibration made things run poorly and under what conditions they occurred.

I can tell you also that Scanguage isn't all the parameters you can monitor on your engine and is definitely not accurate to what the ECM is seeing. A lot of Scanguage's number are of it's own calculations. Such as Torque load, Horsepower, Boost pressure, MPG and GPH of fuel use. If you want more acurate monitoring, you will need other software such as Insite or more effectively C@1t3rm.

I'm not trying to Sh1t on your parade. I'm just trying to keep a very real knowledge based view in the conversation for this guy to make accurate decisions. I also use a Scanguage KR (which I think is crap but good for some things) to monitor a few parameters to keep me under control for maximum fuel mileage for my operation.

[Chamberpains]

Big_Rig_99 did you follow the troubleshooting guide (tree) in Insite for Altitude Derate?

[MommaBurt]

Sounds like a density based fuel limit. Could be the truck but most likely was missed/not adjusted in the tune.

[ynot]

I know this is an old thread but for anyone that stumbles upon this in the future it may help them.

The truck is derating from the compressor outlet temps getting outta range, too high in other words. So its cutting back the fuel leading too lower boost too get the temperature estimates back in line.

The problem is the ecm can't estimate the COT anymore using the CIT, IMT an turbo efficiency tables in the ecm for the vgt while using the hx60. depending on the hx60 used a lot of them dont even have the bung too install the compressor inlet temp sensor so tuners just disable it an lock the CIT temp at a global valve of like 70F, which compounds the problem further when I the ECM trying too estimate the COT based off the CIT of 70F.

Installing the compressor inlet temp senior in the intake piping as close too the turbo as possible helps but the derate will still happen occasionally, really the limits on the COT derate need too be increased, or the derate just turned off.

EDIT:

I just noticed the type of turbo wasn't mentioned so it most definitely doesn't have the compressor inlet sensor, too help with the COT calculations.