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Benjamin9669 · 10-28-2025, **(Subject: 870 boost issue. )**

Cm870 usually will put 36-38 psi no problem, noticed I can barely get over 30… I had a boot leaking from air compressor to intake I thought it was that, fixed that, wasn’t it, found a boot near the turbo was leaking a bit too, changed that, didn’t help, pyro doesn’t run much warmer, but a little more noticeable as usually it runs 700-800 empty and 800 loaded. What is the easiest thing to check? Would back pressure sensor the tube being plugged cause it? I’m noticing if I let it pull at 1600 on a hill and try to get it above 31 it will drop back. I know it isn’t program related because I have had 36-38 whenever it was needed. No black smoke no cel.

hookliftpete · 10-28-2025, **(Subject: 870 boost issue. )**

Try the exhaust pressure sensor, might be plugged up or sensor needing replaced

marek4792 · 10-28-2025, **(Subject: 870 boost issue. )**

I'd still get the program checked because this screams silent derate..

Benjamin9669 · 10-29-2025, **(Subject: 870 boost issue. )**

(10-28-2025 )marek4792 Wrote: I'd still get the program checked because this screams silent derate..

What part screams silent derate? The fact that it usually pulls 36-38. It’s not hitting 36/38 and dropping back down it’s just like there’s not enough air or fuel because i can barely get 30 lol. I know all about the silent derate because I use to have a program that was absolute shi#t.

marek4792 · 10-29-2025, **(Subject: 870 boost issue. )**

Just from the way your post sounds, but if you really want to be sure check what the fuel state monitor is saying. Like hookliftpete said check your exhaust /boost / fuel pressure and temperature sensors and barometric to make sure you dont have a sensor failing in range..

Rawze · 10-29-2025, **(Subject: 870 boost issue. )**

It could be a boost issue itself ... or it could be something holding the fueling back, and you end up with less boost.

monitoring the 'combustion_control_path_owner', enigne mode and other settings (via Caltrm) will tell you which one it is ... or if there is indeed a silent drerate, etc ...
https://rawze.com/forums/showthread.php?...3#pid58693

Also, if it is de-mandated,.. and it was not done by someone officially recommended on the forum here, then you seriously need to get the programming reviewed to ensure it is not harmful to the engine over time.. and so that there are no mistakes in it that can cause ghost issues.