1983 Porsche 911 SC Targa

Sunday, April 28, 2013

Throttle Position Sensor

The throttle position sensor provides a signal to the controller to determine how much voltage and current from the battery pack is passed to the motor. The sensor is an automotive grade potentiometer – a 5,000 Ohm resistor with a sliding contact that measures a variable portion of the resistance depending on position.

The sensor connects to the throttle linkage of the car with a ball joint. When you depress the accelerator pedal (I can’t call it a gas pedal anymore), the arm of the throttle position sensor rotates, sending a signal to the controller to increase the power to the motor.

The sensor needs to be mounted in the same location as the throttle body of the gas engine. The throttle linkage is routed through a bellcrank on the transmission, so I decided to mount my throttle position sensor to the transmission adaptor plate to avoid throttle surging due to torque induced twisting of the transmission during acceleration.

The adaptor plate has a cutout feature at the bolt mount that I used to key the throttle bracket.


  1. I like your solution of simply using beefier torsion bars in front to carry the weight, thus keeping attitude and altitude very close to stock. The Zuffenhausen people worked hard to get that right. Sounds like you ran through the stock gearbox. Another good solution I know a VW Type 2 that chose two direct-drive motors. Nice solution, but it added mass.
    I'll be watching for your performance reports once things get nicely seated and broken in. Be careful out there!
    Bert Knupp
    Nashville, TN

    1. Hi Bert. Adding a second motor and losing the transaxle would be a net wash for mass, but you still need some kind of gear reduction, even for fixed drive, and the complexity of installation goes up. The gear box was available with the car, and in good shape, so it made sense to keep it.

      I've set the controller to 70% and it keeps up with traffic quite nicely. If you are ever in town visiting your sister, knock on my door and you can take a ride.

      Your sister told me about your car projects and I found a few pictures of your police VW online. Wow. Nice job. Can you point me to any links where I can read more about it?