Quote:
Originally Posted by b3lha
Yes. I read that. But it is not a complete explanation. I was hoping that Harvey would provide some further clarification.
How does the QC knows when the change to the torque control and line pressure operation is needed. How does it know when a gear change is taking place, or about to take place? Where is the threshold of throttle position that causes the QC to activate?
What is the relationship between throttle pressure and the duty cycle applied by the QC? Does the QC actually apply an increase the pulse width, or just force the solenoid open with DC?
I am not asking WHAT it does, I am asking HOW it does it.
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Sorry Phil, I wanted to get a photo of the circuit board up, to explain its operation, but I am not having a lot of luck.
When I design something I subscribe to the "KISS" principal, so it is pretty simple.
It uses a LM741 Op-Amp configured as a comparator, comparing a regulated set voltage to the Throttle Position Sensors voltage. When the TP voltage reaches 1.8 V the Op-Amp sets to turn on a transistor to operate a DP/DT relay. One half turns the TCUs Torque Control line off the ECU and on to a regulated 4.5V, that it can pull up and down happily. The other side of the relay inserts a resistor in the A solenoids control line to limit its signal to 5%. This action keeps both the ECU/TCU from posting trouble codes.
The Op-Amp has some negative feed back to allow some hysteresis to give a good snap-on, and to prevent a noisy TPS from spurious triggering.
The line pressure is normally controlled by the throttle position, more throttle more line pressure, this is the normal way Autos do it. In our box there is another feed to the A solenoid that is used to reduce the line pressure for a number of reasons, cold oil, starter cranking, gear changing. So it can't be turned off all the time.
The circuit looks like this, the Throttle pressure signal is a 12V duty cycle that is run through the dropping resistor to reduce the signal to a 5V signal to mix with the 5V shift signal. The inclusion of the resistor to allow the two signals to drive the solenoid even though they may be opposite. This happens when the throttle is wide open its duty cycle signal is 5%, when the shift is to operate the shift voltage is increased to about 80% to soften the engagement, if the resistor was not used one line would short out the other line, so it acts as an isolator, or voltage divider.
When the Small Cars Shift Kit is used, the reduced resistance in the Throttle line causes a higher line pressure that would normally be used, but even with this in place, a full throttle change still has the line pressure reduced through the shift line, so it really does nothing but fool the driver into thinking it is producing a solid change.
The other thing that the SCSK can't do, that the Quick Change achieves is that because the Pilot pressure that the A solenoid regulates, is also used to set the pressure behind the shift accumulators, by keeping this pressure from reducing, it reduces any chance of slip due to the longer engagement time, that the softer accumulator gives, so its action is set in line with the throttle pressure as the whole operation is.
The Quick Changes action is progressive to the throttle position, no change at all on a light throttle, progressively getting firmer with the throttle position.
I'll get a photo up eventually.
Harvey.