The long knurled knob is the load control valve. It is pre-set before the beginning of the dyno pull. The two smaller black knobs control incomming water to the engine & incomming water to the dyno reservoir. Incomming water to the engine is metered at the outlet to control engine temperature. Incomming water to the dyno reservoir is adjusted to maintain a completely full reservoir during dyno pulls. This ensures that there is no change in the pre-set load amount due to a change in the water height in the reservoir.
