Low mount turbo control

[Log lugger]

Hello all could anyone tell me what the output pressure should be on a low mount turbo controller?

[Rawze]

(08-13-2023 )Log lugger Wrote:  Hello all could anyone tell me what the output pressure should be on a low mount turbo controller?

For all anyone knows, you could be referring to your turbocharged lawn mower... (some satire lol).

what kind of engine?.. truck?... year.make, etc.?.

Maybe some background on what issues it may have?.. and if it is de-mandated (deleted), who done it?.

[Log lugger]

Ah yes cm870 07 379 still has all it's working egr components with new egr cooler piping all recently removed and cleaned .all new sensors and holset turbo.getting the chuffing and black smoke until fuel pedal backed off a little then can go again usually happens around 1500 rpm.installed a remote air pressure gauge in the cab to read delivery pressure to the actuator it runs at 90 psi idling then 45 to 50 going along on the road and back to 90 for engine braking.i have not found anything yet in quickserve for operating pressures. But did find an old post on here between rawze and chamber pains about the subject but I believe they were dealing with the older hi mount version. I wasn't sure if the parameters were the same or not...

[marek4792]

Does the actuator arm move freely? Meaning if you put a 10mm to the bolt on the end of the rod, can you overpower the spring force and move it down with ease or does fight you all the way, and/ or end up loosening said bolt in the process?

During a long stay at Rawze's we have stumbled onto this after getting my turbo rebuilt by YTS later to find out the exhaust housing had a "fixed" VG ring which if the center housing wasn't clocked properly the VG vaines would actually hang up and in turn create this exact issue you're experiencing. It's simple as unclamping the exhaust housing and reclocking the turbo until you get no resistance in travel on the little arm where your actuator rod bolts to and tightening it back up. Better to remove the actuator rod when testing this.

[Log lugger]

Yes I did remove actuator and check movement of the arm.it goes quite easily.

[Andre_The_Giant]

Have you done injectors tests? Not just the computer ones, but actual leak tests where you remove the fuel solenoid's and put a tool & hose on it? Rawze has video on YouTube for Procedure, can be found on quick serve also

[Rawze]

just some related info...

There is an inline air filter on some of those older CM870's going to that turbo air controller. They do clog up as the truck gets old.

Also you should be getting a regulated 90 PSI to the supply hose and it should not drop in pressure. If it does then you have a problem in the air system somewhere.. usually the air-dryer unit going bad. .. or the engine fan is leaking air only when it is engaged. It is on the same circuit as the engine fan for most CM870 trucks.

- Build air up all the way 100% .. ensure the A/C system is switched off.. ensure the engine fan is not engaged (is free-spinning) ,... shut the key off, turn it right back on as soon as the engine stops turning. Get out ans see if the engine fan free-spins (it should).. and check it, and the rest of the truck for air leaks while the pressure is ABOVE 90 psi in the dash gauges.

I.E> Anything pulling that 90-psi line down coming from the air-dryer directly effects that turbo arm. Hence, why the red engine maker made the actuator electronic on the CM871's and newer model engines.


If the air supply is not restricted and is steady 90-psi going TO the controller ... and the arm does not have any spots that have higher resistance during its travel range (testing it with plunger removed) .. then it may be the controller itself.

The controller you are describing is notorious for going bad on the CM870's when they get old. If it is more than 5+ years old, investing in a new one is not a bad idea. If it does not clear up the issue, then clean up and keep the old one as a spare for testing.

If moisture or oil intrusion gets into the controller valve, it will make it go bad... so ensure the air compressor is not worn out and putting oil into the air system.. and ensure the air-dryer desiccant filter is not more than a couple years old + check air tanks for moisture at their relief valves regularly (which everyone should be doing any ways as a trucker and your regular inspections. Its called a 112-pint inspection for a d#m,n reason!).

[Log lugger]

Yes I do have the injection leak plates and I do that test periodically it has proven to be a valuable tool.also,that controller supply line comes directly out of the tank with no other draws off it.and no filter in line.i also checked the inlet screen on the controller it was clear.im just curious about the max pressure on the actuator side of the controller.

[JimT]

(08-14-2023 )Rawze Wrote:  Its called a 112-pint inspection for a d#m,n reason!).

Can that 112-pint inspection be performed at beer-o-clock or is it reserved for Octoberfest?