I was having an argument in another forum. I just wanted to back up my information. Is the TPS Voltage proprotional to Boost. Can some one explain why or why not. Thank you.

 

I would say no, as a guess, but I am not totally familiar with it.

As far as I can tell, the TPS measures the position of the throttle. It has 2 sensors outside the TB that are triggered when the throttle moves. What level the boost is at has nothing to do with the position of those sensors...

Or thats how I see it.

 

no it is not. TPS (throttle position sensor) is proportional to throttle position. boost does not change the voltage output.

 

The reason I say that is the voltage changes with throttle position......well the throttle plate moves with the changing of the throttle. So they are kinda link together. So as the throttle plate opens voltage increase....and there is a boost change.

 

well yeah its all linked, but the TPS isnt proportional to boost.

your throttle position in 3rd gear can yield 5psi
but in 1st gear that same position will net a lower psi.

therefore theres no direct correlation between throttle position and boost...

 

OK thanks

 

it's funny how the names of things sometimes give away their function innit...

 

A (T)hrottle (P)osition (S)ensor is a linear potentiometer that changes voltage with mechanical movement. It will read the same voltage with the key 'on' but the engine not running at various throttle positions as it will with the engine actually running. It is not related to boost in any way. The manifold pressure sensor and air-flow meter will show different values for the same pedal/TPS position depending on the engine's operating condition (boost, decel, cruise, etc.). According to the logging I have done on the factory sensors, the narrow TPS gets to maximum (100%) reading when the full-range TPS is at 20% of it's full scale reading.

Hope this helps!

 

There are throttle position sensors (identical ones) on naturally aspirated cars.

You won't make positive manifold pressure at zero load, yet the TPS will still give a full range of output.

Uou are trying to form a link between two things which are indirectly related.

It's like saying that tachometer reading is proportional to boost b/c boost increases as the rpms go up... there is no real relation.

Besides, the TPS voltages are linear, whereas boost patterns are not.

Why do you think we have a pressure sensor?