Did some tow testing to check EGT's, and found something that might be useful to those without gauges.

My oil pressure drops 10PSI at 1250 deg repeatably. So if you are towing uphill and see more drop than 10PSI from your cruise pressure, you are probably over 1250, and might consider backing off.

Did oi; press return to normal as soon as you backed off throttle?

Yep. Takes maybe 15 seconds to return to normal.

You hit that pulling the vette? How much did you have the TTS tweaked up?

I ran the TTS Level 2 LLY. Those EGT's were generated at 4500ft, up a 6% grade with a 14k combined weight.

1250 is not bad. Hit over 1500 on the dyno.

Just where do you think the oil went? Later! Frank

My guess:

The temperature of the return oil from the turbo is a function of the turbo temp. The hotter the turbo gets, the hotter the return oil, which lowers the viscosity of the oil.

It returns to normal pressure much quicker than you would think though. Guess the oil gets cooled pretty effectively in the Duramax.

I assume that the LLY uses the same oil/antifreeze cooler that the LB7 does. 15 sec is pretty good turn around. Is the turbo cooled with coolant.......same as LB7?

Also, the pistons have a cooling channel cast into the underside of each crown. There is a jet plumbed into the main oil passage that sprays a good volume of oil into that channel at all times. It cools the pistons, and when EGT goes up, oil gets hotter and pressure will drop as McRat has noted. This may be more of a factor than the turbo heat rejection to the oil, although I say that without any experience with the LLY.

Are you running dino oil McRat? I'd be interested to see how much difference synthetic oil makes in this situation.

Dino oil.

I change my oil too often to bother with syn.

Others have noted the pressure drop as well. I was just trying to quantify it.

mine does it too..........w/ shell full syn.............why?