by stuie0786 on Sun, 15 Apr 2012 6:55 +0000
On a tilt tray fuso turck i worked on the other day, it has a seperate knob that allows the driver to adjust the idle up and down. it can adjust from idle to 3000 or so rpm. the tilt tray had a switch at the rear tray controls which when turned on would put a resistor inline to the idle up knob causing the engine to idle up to 1400 rpm. this idle knob is a seperat input to the engine ecu and works the same as the fly by wire throttle. the knob has an earth a 5Volt referance voltage (from the ecu) and a return signal to the ecu. as the knob is turned it changes its resistance and by doing so it varies the voltage signal from (earth)0volts (idle) to 5Volts (3000rpm) back to the ecu. putting the resistor inline by the rear switch, being the correct rating for adjusting the idle to 1400 rpm it sends a voltage signal back to the ecu and causes the idle to idle up. now if that makes sense?????? heres some more info. hope this makes sense?????
on your hilux's i have the older shape and am in the same issue too with fly by wire throttle and putting an idle up or adjuster on it. the foot throttle has not one earth, a referance voltage supply and a return signal but two seperate earths two seperate supplys and two seperate return signals. so to trick it you have to trick both return signals at the same time to get the idle to adjust up and down , if it dosnt see the correct signals, it will know that there is something wrong with the foot throttle. it will sense this bring on the check engine light and electronically discarnect the throttle not allow the throttle to work and therefore the car wont rev. some throttles dont use a 2nd 5volts supply as the second referance voltage. now this is where it is hard to do....
they may use depending on the car
example 1 double 5volts as explained above
example 2 one 5volt supply and a 10volt supply for the second signal.
example 3 run the signals in reverse to each other.
Example 1:
if it runs the two 5 volt supplys then you need 2 exactly the same resistors to trick the ecu. if they arnt the same and if its out buy 0.01 of a volt difference (depending on the ecu and how accurate it is) the ecu may sense this and think there is something wrong with the throttle and the throttle wont work.
0 volts ant idle 2.50volts at half throttle and 5 volts at full throttle. this is on both throttle circuits.
Example 2:
some cars run two seperate and different supplys so the resistors will need to be different rating to trick the ecu. working out this rating isnt that easy and getting it exact so the ecu is happy is the hardest part. It is hard for the diy home guy to do or even some auto electrictions. (if they take the job on)
Input 1: 0 volts ant idle 2.50volts at half throttle and 5 volts at full throttle.part throttle could be 1.50volts.
Input 2: 0 volts ant idle 5 volts at half throttle and 10 volts at full throttle.part throttle could be 2.80volts.
Example 3: this is the same as example 2 but the supplys are the same but the signals run in reverse to each other.
Input 1: 0 volts ant idle 2.50volts at half throttle and 5 volts at full throttle. part throttle could be 1.50volts
Input 2: 5 volts ant idle 2.50volts at half throttle and 0 volts at full throttle.part throttle could be 3.50volts
so depends on the fly by wire will depend on ifs its easy to do. to put in a variable one would need two potentiometers at the correct ratings to do this and both be turned at the exact same time to trick the ecu.
On cruise control this is all done electronicly and worked out by the manufacture in the factory, the ones we do at work from what i can work out without modifying wont do what i want and i havent been down that path as of yet.
im looking at a hand throttle and moding the pedal to fit but when engine cold and hot, at 1/4 throttle they are different rpms when cold 900rpm and hot 1400 rpm. found this when start in mornin with flat battery and put a stick on the throttle and 10 min later the idle climbed up by its self.
hope this helps anyone and sorry for the long post.