losing power on hard pull

[tdawg]

I have a 2007 cm870 that boost starts out about 30 and drops down to about 20 on a hill. I have tried two different turbos and have no leaks on intake or exhaust sides. No codes. If I come to a stop and take off again it gives me 37bls of boost through every gear and problem doesn't start till I am up to speed for a few minutes.Starting to wonder if this is fuel related?

[Waterloo]

Has the programing on the truck been messed with, like a custom tune? Are you putting the factory VGT turbos on or old school Holsets?

[tdawg]

have not messed with programing and turbos are correct cummins part

[Waterloo]

Has the actuator been inspected, they are air controlled and I know they can get buggy, have you checked the air lines etc? We need one of the neighborhood 870 guys to chime in. And you have been tightening everything up, pressure tested motor and CAC, checking for leaks?

[tdawg]

Tried different actuators and pressure tested everything. 37bls of boost from a stop through all gears getting up to 70mph then the problem starts after you let out of it and then you hit a hill and low boost. exhaust system is new with no restrictions.

[DDlighttruck]

(11-14-2019 )tdawg Wrote:  Tried different actuators and pressure tested everything. 37bls of boost from a stop through all gears getting up to 70mph then the problem starts after you let out of it and then you hit a hill and low boost. exhaust system is new with no restrictions.

My experience has been if you hit the hill at 75-85 mph you can generally keep the momentum going and pull the hill easily. If you hit it at 55-65 forget it you’re downshifting to third or fourth gear and pulling it at 10 mph

That’s just my opinion, based on sitting in the drivers seat. If the rears need to be done I’ll probably look at dropping to 3.90s or 4.10s. Trying to drive one of these motors slower is painful in hills.

[Rawze]

(11-14-2019 )tdawg Wrote:  I have a 2007 cm870 that boost starts out about 30 and drops down to about 20 on a hill. I have tried two different turbos and have no leaks on intake or exhaust sides. No codes. If I come to a stop and take off again it gives me 37bls of boost through every gear and problem doesn't start till I am up to speed for a few minutes.Starting to wonder if this is fuel related?

sounds to me like maybe its going into some kind of derate. Check engine state with insite while pulling a hill.

Does the engine have factory programming in it? - or does it have a de-mandate tune in ti? - and if so, who did it?

[Chamberpains]

Also, does this problem happen while using the high or 3rd stage Jake's for any long period of time. Does the boost cut out or drop off significantly or never reach high 20's psi?

[tdawg]

seems like a derate but a bad one. jakes jump up to 28 and then comes back to 15. I changed the exhaust pressure sensor yesterday and nothing changed. Doesn't make sense for it to have all the power you want from a stop but lose it on highway.