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+--- Thread: Cm875ism turbo compressor outlet derate (/showthread.php?tid=4625)
Cm875ism turbo compressor outlet derate - wellrun - 06-01-2019
Driver complain about truck cutting back when climbing a hill.....no active faults in ecm.....but when I rev and look at data I see there's a turbo compressor outlet tempreture derate active....what could be causing that derate or temp prob?
RE: Cm875ism turbo compressor outlet derate - Rawze - 06-01-2019
the turbo has too much heat soak for one reason or another.
* bad programming?
* Excess boost?
* exhaust restriction? plugged up dpf?
* air filter restriction.
* CAC restriction? - or after-market CAC?
* CAC or EGR circuit has leak and turbo is spooling up too much to compensate for it?
is the truck de-mandated or still has EGR/DPF?
RE: Cm875ism turbo compressor outlet derate - wellrun - 06-01-2019
Still has egr....it's and cm875 no dpf..... exhaust back pressure is about 120-130 I maximum is that too high?
RE: Cm875ism turbo compressor outlet derate - Chamberpains - 06-01-2019
When are you getting that back pressure reading? Idle, high idle, first start up and warming up, pulling heavy?
RE: Cm875ism turbo compressor outlet derate - wellrun - 06-01-2019
High ilde during snap reving
RE: Cm875ism turbo compressor outlet derate - Chamberpains - 06-02-2019
Your gonna get higher readings when snap reving.
As far as what Rawze is suggesting...
We'll go down the list.
1st - ensure you have a good and current updated program from Cummins that belongs in that vehicle. If its deleted in any way get ahold of Unilevers, MommaBurt or Price diesel and see if they can help in any way. They are very trustworthy. The rest we don't know and probably have screwed things up. Programs in Cummins engine are vehicle specific and 99% of people can't get that thru their "i know everything" heads. Cummins quickserve is free and is an incredible free source of tech info from Cummins that is engine specific.
2nd - is the exhaust restricted in any way. Muffler plugged, exhaust pipe pinched or full of soot. Pull the pipe off right out of the turbo and see if your code goes away. Be sure you don't burn anything when doing this if it located in a tight place.
3rd - be sure the air filter is in good condition. Change it if you have any doubts. They're cheap.
4th - CAC and intake problems - plug off the exhaust at the turbo. Exhaust side and intake side the find a port (usually turbo temp sensor, boost sensor or even a OE empty plug for after market sensors) and rig a regulator and shop air to it and pressure test the entire engine. Fill the system up to whatever max boost psi of the system is and soak everything in soapy water. A lot of small leaks equal 1 huge leak that the ECM will try to compensate for. Fix all leaks on intake and exhaust side. This is important to do with VG turbo especially because they adjust according to intake and exhaust pressure readings.
Make sure your sensors on the engine are reading correctly and aren't all sooted up. Pull all of them out and give them an inspection. If they are old and sooted up, replace them. Simply cleaning them probably won't bring them back to 100% accurate readings.
If they are sooted up, then you can guarantee the piping going to and coming from them is sooted up. Pull these pipes off or clean them however you can. This is called an EGR tune up. When you send soot thru anything, it will build up and clog everything. Causing blockage and bad sensor reading and poor circulation of whatever these pipes circulate. Your engine will try to compensate for these readings being wrong and cause poor engine running conditions.
Lastly, make sure you don't have some dumb over hyped under engineered aftermarket CAC. Some of these companies claim the world because they can afford to by a lot of advertising and deliver a pile of high prices shi#t. Be sure you don't have 1 of these things.
After all that's done and if you have your problem still. Come on back, let us know what you've done and found (because we like to know what people run into, it helps us learn too) we'll see if we can come up with more avenues to run down with you.
RE: Cm875ism turbo compressor outlet derate - wellrun - 06-02-2019
Thanks alot guys..it's a customer truck I'm a diesel tech....I Will be checking it again to make sure....there was an inactive fault for compressor inlet tempreture and egr diff pressure sensor.... driver also says that whenever he climbing a hill the truck cut back at times
RE: Cm875ism turbo compressor outlet derate - wellrun - 06-02-2019
High ilde during snap reving