Low oil pressure?

yellow rose said

Interesting stuff. I hope everybody reads these threads even if they never build high a RPM engine. It's good to know that those who came before us, who didn't have computers, weren't as stupid as we thought. They had it sciences out.

I also think the guys building stuff at the time they engineered this crap never thought anyone could make power at RPM ranges where oil timing would be an issue.

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Honestly, I think this was all being figured out in the 1920's and 1930's, at least the thinking of what would happen and the math behind it. Heck, the Ford V8's started mass production in what... 1931?.... and building 1800 HP aircraft engines for WWII did not 'just happen'.

The dynamic forces get quite interesting when the RPM's get high enough. I found a rod force graph computed for a simple 1 cylinder crank. It looked normal at 4000 RPM with a single peak just after TDC. At 12,000 RPM, that peak disappeared almost completely, I suspect due to the inertial forces on the piston+rod going over the top just about equaling the compressive force from combustion.

If I had to guess, your solution to the problem worked mostly due to the fact that you put full pressure 'right at' the bearing, and skipped all the pressure losses in-between. Plus, you probably got rid of all that oil mass that has to be accelerated down that 4-5" passage from the gallery to the main bearing. The time opening for oiling to the rod gets down to 2 tenths of a millisecond at 8,000 RPM for the standard hole size... yes, that's .0002 seconds. It takes a finite amount time to accelerate any oil mass. That all has less to do with timing per se, but just plain getting the oil where you want it.