I was wondering about the difference in oil pressure behavior between a gas engined car and the turbodiesels. (I know we are talking apples & oranges here, but bear with me).
On the 300D (1984, 198,000 miles) the pressure gauge is pegged when at a cold idle, just like the V-8. Once fully warmed up, the oil pressure will be at about 1.5 – 1.7 bar at idle, again just like the V-8. On a fully warmed up engine, my 450 engine will peg the oil pressure at just barely above idle. However, it takes about 1300-1400 RPMs to get the needle all the way up to 3 on the turbodiesel when it is good & hot.
My hypothesis is that the additional flow requirements from the oil jets under the pistons, as well as the oil feed for the turbo take up a lot of flow, and the oil pump just needs a little more speed to increase the volumetric displacement enough to compensate.
Am I on the right track here, or am I just rationalizing an inherent problem with my new baby? (YIKES!)