Originally Posted By: Gene K
Thanks Shannow. Interesting that its a 1:1 relationship as I really didnt expect that.
Peak torque is up 43% at approximately the same rpm (maybe 100 rpm less) and peak horsepower is up by 60% at 700 rpm higher. Guess I better reconsider my 20% increase in viscosity.
It's not linear, just the first approximation gets you that result. Design is an iterative process, as the thicker oil will generate some amount of additional heat and become slightly thinner as a result.
Here's a bearing design curve...you can see the bearing characterist number that I used on the bottom axis, and the vertical axis is MOFT/clearance.
minf is minimum friction, Max W is the maximum power consumption. L/D is the ratio of bearing length to diameter.
You don'tknow where your engine designer put it ON a curve, so making everything else equal gets you nearly there...good enough to first do no harm.
If you just increased the load (torque), and changed nothing else, you could drop the MOFT by 25%...maybe not an issue, and certainly maybe an issue...thickening up makes sense.