As most of you know, the way a turbo works and, registers PSI on the gauge is, when higher VOLUME of exhaust if flowing. So, when you step on the throttle pedal, as in accelerating, you get a ton of exhaust FLOWING, into and out of, the turbo. In lower RPMs, the turbo gauge registers lower pressure but, as you throttle up, and, you're at peak RPM during a grade climb, you're at peak turbo pressure. For mine, that's between 26-27 psi. that's on our C-7 330HP CAT, with 63K on the clock.
But, in a basic CLOSED THROTTLE operation, there is no high flow exhaust. Therefore, the turbo is close to a an idle position. I'm pretty sure that I've looked at my turbo pressure gauge when descending some grades and, I've seen nothing on there. But, I could be wrong so, I too might have to check this to be completely positive. That's if I remember to check it on the next down grade.
Scott
