Throttle-by-Wire

[Will McGonegal]

We have tested heavy duty diesel truck engines on one of our dynos here.
Many are fly-by-wire style accelerator controls.  They do have logic to detect 
when the accelerator pedal system is not working correctly.  For example, the 
Detroit Diesels we've tested use a 0 to 5 volt accelerator signal.  It's really 
more like a 0.5 to 4.0 volt command signal.  The breakout control box we use 
here has a potentiometer supply this accelerator signal.  The ground and 5 volt 
power are not simply across the ends of the potentiometer.  The circuit is 
connected such that the potentiometer is hooked through a resistor to ground, 
and through another resistor to 5 volts.  This allows the pot to sweep between a 
voltage that is slightly above ground to slightly below 5 volts.  If the engine 
control module detects this voltage to be out of this range (wire fell off from 
hitting a pothole?), a fault code is generated.  Then the engine just idles.

Will McGonegal


 > Date: Mon, 21 Jan 2002 12:09:08 -0800 (PST) From: Phil Hunter
 > <ilphayunterhay at yahoo.com> Subject: Re: Throttle-by-Wire
 >
<snip>


 > Simple scenario: twisty mountain road, nighttime, foggy, slick. Few drivers
 > in the world would be using cruise control. The TBW controller sees full
 > voltage from the throttle potentiometer, did the driver floor it, or did
 > the ground wire fall off from hitting a pothole?


<snip>
 >
 > rgds, philh (digest)

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