Cm870 low boost high egt

[Oilysnowman]

(02-13-2026 )tree98 Wrote:  I've never seen a turbo test in insite that gives a percentage like your saying.

I see. Mine has turbocharger and egr functionality test, then I can select both or either or. Select just the turbo, and it revs itself up to 1200 rpm and changes the turbo between 5% and 95%. Once it’s done it shows % changed and pass or fail. My old turbo showed fail at somewhere close to 75% change. Not long after that the vanes got completely stuck.

[Benjamin9669]

Cm870 kinda same thing here, seems to pull pretty decent when it’s warm outside, colder outside boost is laggy and hard to get over 20 sometimes, once warm it’ll help try to get it to 30 when it use to be 36-37psi. Me don’t know lol.

[tree98]

(02-14-2026 )Oilysnowman Wrote:  

(02-13-2026 )tree98 Wrote:  I've never seen a turbo test in insite that gives a percentage like your saying.

I see. Mine has turbocharger and egr functionality test, then I can select both or either or. Select just the turbo, and it revs itself up to 1200 rpm and changes the turbo between 5% and 95%. Once it’s done it shows % changed and pass or fail. My old turbo showed fail at somewhere close to 75% change. Not long after that the vanes got completely stuck.

Must be a test specifically for the 870 air actuated turbo. Sticky vanes will definitely cause high EGT and low boost.

[Wesoja2]

Has this issue ever been solved? I have the same thing going on with mine. Does it with EGR intact or demandated. RR also tuned my truck and we had this same exact issue that still has never went away

[Rawze]

(09-03-2026 )Wesoja2 Wrote:  Has this issue ever been solved? I have the same thing going on with mine. Does it with EGR intact or demandated. RR also tuned my truck and we had this same exact issue that still has never went away

What are the EGT's, boost, etc?.

also maybe this post helps...
https://rawze.com/forums/showthread.php?...9#pid85889

[Wesoja2]

(09-03-2026 )Rawze Wrote:  

(09-03-2026 )Wesoja2 Wrote:  Has this issue ever been solved? I have the same thing going on with mine. Does it with EGR intact or demandated. RR also tuned my truck and we had this same exact issue that still has never went away

What are the EGT's, boost, etc?.

also maybe this post helps...
https://rawze.com/forums/showthread.php?...9#pid85889

EGR is intact and functioning. New turbo (OEM) not aftermarket less then a week ago, new cooler, all new sensors, motor harness and RR flashed factory file in it 2 weeks ago cause I wanted to try diff ECM. Only aftermarket part is a {big-name trash tuning} intake pipe. It will not make more then 32-33psi above 1500 rpm’s and 1000-1100 degrees in a hard pull. If you pull it down around 1400 it’ll go up to 37ish and egts will come back down into 800-900ish. EGR flow derate kicks in above 1500 or so. I’ve confirmed no leaks in system and feed tubes to egr diff pressure are clear and flowing. I do notice a bit of moisture around the diff pressure sensor orings when I’ve pulled in off, almost looks like condensation as it’s not sticky. Mufflers are less then 6 months old and egr valve is exactly 1 year old. It does seem to run “better” the warmer the outside temp is.

[Rawze]

(09-03-2026 )Wesoja2 Wrote:  

(09-03-2026 )Rawze Wrote:  

(09-03-2026 )Wesoja2 Wrote:  Has this issue ever been solved? I have the same thing going on with mine. Does it with EGR intact or demandated. RR also tuned my truck and we had this same exact issue that still has never went away

What are the EGT's, boost, etc?.

also maybe this post helps...
https://rawze.com/forums/showthread.php?...9#pid85889

...will not make more then 32-33psi above 1500 rpm’s and 1000-1100 degrees in a hard pull. If you pull it down around 1400 it’ll go up to 37ish and egts will come back down into 800-900ish.
...

1050 - 1100 F is not excessive actually... but the boost only going to 33 and holding is a bit low. Should be in the 36-37 range.

Most of the time when the boost does this (assuming for a moment there is nothing mechanically wrong) and the ecu is dropping boost, it is due to the auxiliary emissions systems being unhappy with the engine exhaust NOx levels, etc. - The reason for the boost or other derates/dropouts can be found by monitoring things via CT software on a test drive + recording the laptop screen as it is acting up.

[Wesoja2]

(09-04-2026 )Rawze Wrote:  

(09-03-2026 )Wesoja2 Wrote:  

(09-03-2026 )Rawze Wrote:  

(09-03-2026 )Wesoja2 Wrote:  Has this issue ever been solved? I have the same thing going on with mine. Does it with EGR intact or demandated. RR also tuned my truck and we had this same exact issue that still has never went away

What are the EGT's, boost, etc?.

also maybe this post helps...
https://rawze.com/forums/showthread.php?...9#pid85889

...will not make more then 32-33psi above 1500 rpm’s and 1000-1100 degrees in a hard pull. If you pull it down around 1400 it’ll go up to 37ish and egts will come back down into 800-900ish.
...

1050 - 1100 F is not excessive actually... but the boost only going to 33 and holding is a bit low. Should be in the 36-37 range.

Most of the time when the boost does this (assuming for a moment there is nothing mechanically wrong) and the ecu is dropping boost, it is due to the auxiliary emissions systems being unhappy with the engine exhaust NOx levels, etc. - The reason for the boost or other derates/dropouts can be found by monitoring things via CT software on a test drive + recording the laptop screen as it is acting up.

What parameters should I be watching in CT to figure it out?

[Rawze]

(09-04-2026 )Wesoja2 Wrote:  ...
What parameters should I be watching in CT to figure it out?

https://rawze.com/forums/showthread.php?...6#pid28636