CM870 Turbocharger Speed Sensor

[Rawze]

(10-10-2020 )hypoxia Wrote:  

(10-10-2020 )Rawze Wrote:  you also did not mention how much boost it was making... or if you have pressurized up the whole engine to see if there are any boost leaks.

could simply be the speed sensor but like others have said... clogged exhaust,. bad intake air filter, or actuator acting up can cause it too.

and .. if you have the mentality of trying to save money on engine sensors by going aftermarket ... or you can't afford it... ..your in the wrong business!.

Since demandate, boost will just hit 32 for a second, normally below 30. Pulls mountain grades OK, two or three MPH slower than before. Have not pressurized it yet. EGT has been good. I think exhaust and intake filter OK. I've been on the road since May & out again in a week but for a short time. I chuckled when I asked about aftermarket parts as I figured what the answer was but I had a stick and couldn't resist poking the bear. :) You guys are great!

Only 30 psi boost, there is something wrong. A CM870 should peak at about 36 psi or so (37 - 38 on a 550+ engine) and hold steady, not surge and not fall back.

you said EGT's are normal, but you did not say what they were... and is this pre-turbo or post turbo readings?

[Chamberpains]

He means 36 psi. Not 63. Its a typo.

I forgot its a cm870. Air controlled actuator. Using insite, run the actuator test (on/off) and make sure there is no actuator leaks for the actuator itself all the way back to the control module on the other side of the engine. I had an actuator that would only leak half way through its travel then would seal up at full compression. It would make the turbo surge fairly violently.

I actually caught it while I was troubleshooting another problem and was driving the truck with the dog box off and heard it leaking and skipping around.

[hypoxia]

(10-11-2020 )Chamberpains Wrote:  He means 36 psi. Not 63. Its a typo.

I forgot its a cm870. Air controlled actuator. Using insite, run the actuator test (on/off) and make sure there is no actuator leaks for the actuator itself all the way back to the control module on the other side of the engine. I had an actuator that would only leak half way through its travel then would seal up at full compression. It would make the turbo surge fairly violently.

I actually caught it while I was troubleshooting another problem and was driving the truck with the dog box off and heard it leaking and skipping around.

I tried to run the actuator test but every time I clicked "Start" it did nothing. I could click "Stop" & it stopped but never highlighted Extend or Retract or delay time.

I need to look for Rawze CAC leak test video. I haven't seen the EGT hit 500. It's a pyrometer strapped to the exhaust manifold at the turbocharger. Mostly it's in the 2 & 300's; 400's on a long climb.

[Rawze]

(10-12-2020 )hypoxia Wrote:  ...
It's a pyrometer strapped to the exhaust manifold at the turbocharger. Mostly it's in the 2 & 300's; 400's on a long climb.

Outside of manifold is only showing you the manifold temp, not the actual EGT's. .. That is fine, can be used as a reference for helping save fuel and monitoring temp of turbo under heavy loads. Just verify the temps some time with a temp gun and make sure the far end area of the probe is touching metal fairly well.

[tree98]

If the actuator is stuck and not moving it's full travel the EGT's would be high.

[Nilao]

Both my trucks idle around 280 on the pyrometer mounted to the manifold. Run 480 on flat ground with the peterbilt and 540 with the prostar. On a hill the peterbilt will hit 680ish and the prostar will go into the 800's. Has always been that way. Don't know if it's because the Pete has a larger CAC and fairly clear exhaust while the prostar has a smaller CAC and a couple screens in the exhaust I have never taken the time to remove.