Archive for category j. Throttle body

Throttle body

The other half of the fuel system starts into the control systems on the bike. Key to a fuel injection system is the fuel injector, allowing computer control of a pressurized fuel stream into the motor. This fuel injector and the throttle body that houses it replaces the original carburetor. It also offers host to a variety of sensors needed for the computer control system.

The throttle body being used here is from a 2003 Suzuki SV650. This includes a 19 lb/hour fuel injector and an appropriately sized opening for the air flow needed. Unfortunately, this throttle body set up is set up for running dual throttle plates, a feature I do not need, and has the valves and sensors needed spread across two throttle bodies. The SV650 is a V twin motor, so it utilizes two connected throttle bodies.

Figure TB1: Stock SV650 throttle bodies

The SV650 throttle bodies were separate with all connecting linkages removed. The secondary throttle plates were removed. On the SV650, one throttle body houses the throttle position sensor(TPS) and the other houses the idle air control valve(IACV). Both of these assemblies are needed on the bike, so IACV was removed from the unused throttle body and adapted to work on the used throttle body.

Figure TB2: Isolated throttle body

When the secondary throttle plates are removed, holes are left in the throttle body. These holes must be plugged to allow for positive air pressure to be achieved. Additionally, the throttle body has castings that can be used to mount the IACV, however, spacers need to be fabricated to properly position it relative to the throttle.

Figure TB3: Throttle body plugs and spacers

Plugs and spacers were machined for the throttle body from aluminum stock on the lathe. This was done manually, unlike the valve housings which were done with CNC capabilities.

Figure TB4: Throttle body plug in place, mounts for the spacers circled

Figure TB5: Spacers in place, IACV linkage circled

The IACV is an idle control valve. It does this by slightly opening the throttle as the bike warms up to raise the idle. An actuator attached to the throttle plate is pressed by the IACV, limiting how far the throttle can close. In figure TB5, the fabricated linkage is circled. This linkage is normally found mounted to the unused throttle body.

Figure TB6: Throttle body with IACV mounted

In figure TB6, the throttle body is shown with IACV spaced and mounted. Also seen is the orange fuel injector. At this point, the throttle body is ready for use on the motorcycle.




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