The initial figures don't add up...

100 BAR @ 2.5 LPM = 0.416kW and that's at 100% efficiency.

If you take the standard 85% overall efficiency that most systems have, then your motor power would need to be 0.49kW. This suggests that the original 0.37kW motor is too small, or your figures for the flow and/or pressure are not right.

Where is the pressure measured and where is the relief valve in relation to the pump? The relief valve may be positioned to limit the system pressure rather than to limit the pump pressure.

If you measure the pressure at the pump, the relief valve is far away from the pump, possibly at the end of a branch line, then your pump pressure will always be high and backing the relief valve off may not have the effect you were hoping for.

A simple hand sketch will suffice...

What did you do to adjust the relief valve?

Correct me if I'm wrong, but can't electrical motors be scaled down by reducing the amount of current supplied? IIRC, you don't want to operate below 30% capacity, because that can cause damage to the motor. Still, you should be able to reduce your current input to the motor, which will reduce the power output of the pump. Just make sure that you still supply the recommended voltage.

HPost, I think OP listed the max pressure (at minimum RPM) and max flowrate (at minimum operating pressure) - you wouldn't run under these conditions siumltaneously, since your max flowrate will always be at minimum pressure. Realistically, I'd expect something closer to 0.8LPM at 100 bar operating pressure.

You need to call in a tradesman who understands how the lube system is supposed to work, before you hack it any more.

Mike Halloran
Pembroke Pines, FL, USA