Suzuki DF200/DF225/DF250 V6 4-Stroke Outboards Service Manual, Page 93Get this manual
ENGINE CONTROL SYSTEM
SYSTEM OPERATION
This system is operated by the vacuum created during engine operation and controlled by the ECMTo operate the system (openclose the shut off valve to change the intake tract), the collector, check valve, vacuum tank, VSV and depression chamber are connected with hoses as shown in the illustrationA rod is used to connect the shut off valve and depression chamber for opening and closing the valve LOWMID SPEED RANGE When engine speed is below the preset value (), the ECM generates signal to turn the VSV ON, applying vacuum to the depression chamber which closes the shut off valveWith the valve closed during the engines low to mid speed range, intake air is supplied through the lowmid speed intake tract onlyIn this operating mode, intake air speed is boosted and, combined with the resonance effect, increases low and mid speed range engine torque: Preset value; DF225: approx4 200 rmin DF250: approx4 800 rmin HIGH SPEED RANGE When the engine speed is above the preset value (), the ECM generates signal to turn the VSV OFF, and vacuum is no longer applied to the depression chamberWithout vacuum the shut off valve return spring returns and holds the valve in its normal open positionIn this operating mode, intake air is supplied to the engine through the high speed intake tract onlyThis enlarges the intake tract volume, improves intake inertia and efficiency, which increases the engines output power