Want to build a variable line pressure controller

[94awdcoupe]

I have't seen a thread on this so i have been going over this in my head. There are are a ton of threads on the line pressure mod. How and when to do it. I want to build a street car with about 450/450 power. I plan to keep the trans side of things as simple as possible. Out of all the a/t car builds i have seen the most impressive is the Lucus budget track 1g auto. I want to somewhat duplicate what he has done by my main focus will be 100% street fun daily. What I like about the Lucas build was the fact they used stock trans /converter and a very fast spooling setup. 2.3/hta68
The only thing about that setup that wouldnt work for me is the line mod. A 2.3/small turbo makes huge torque at part throttle openings. The line pressure on street car would need to be torque biased if you want smooth shifts in all conditions. Not sure a flashed stock tcu would be capable of this. And a simple full line pressure switch would fall far short of being smooth shifting under all conditions.

So I want to build a variable controller that would be simple and reliable and most important tunable. My thoughts are always along mechanical lines to keep it simple. I was thinking use a variable pot that was mechanically controlled by a waste gate actuator. A gate that starts to open at 16psi and is fully open at 25psi would give the torque range that I think would be appropriate. The gate would simply be attached to a pot. The arm on the pot adjustable in length.

Anyone think this wouldnt work? share thoughts

 

[ramsack]

The solenoid that controls line pressure needs a PWM signal. This would be easiest to do by all solid-state. A MAP sensor, connected to a pulse generator. But smooth shifts mean slipping, which means less trans life, and slower.

 

[thiazole]

Just do the blue wire mod in parallel with the normal blue wire and put a boost switch to break the blue wire at 5psi (forcing the circuit through the resistor).

Edit: or use multiple resistors like IPT's boost controller and use more than one boost switch.

 

[HighPSI TSi Guy]

Resistors do not properly modify a PWM signal.

I don't think the OP really understands how line pressure is controlled in the transmission. A chipped TCU will do exactly what he wants. TCU dictates line pressure based on current gear and TPS.

 

[94awdcoupe]

I understood that the pressure is controlled by PWM. I also understood by adding a resistor you are lowering PWM speed. This would be no different than lowering a fuel pump ouput by reducing voltage. I assumed the IPT controller has what looks like 3-4 switch points. And again assumed those switch points were just different resistors.

 

[ramsack]

A resistor won't alter a PWM signal other than lower its amplitude. People put the resistor in there to fake the TCU into thinking the solenoid is there to achieve full line pressure. You can't control the PWM signal any way other than having an EEPROM TCU or making something to take the PWM signal, turn it into a voltage, alter the voltage, and turn it back into a PWM signal. Just get a shift kit and crank up the line pressure. It will only shift hard when you are on the throttle more. Driving around normal it will still shift harder than stock, but there is less load on everything, likely to not do damage.

 

[94awdcoupe]

how does the IPT controller work then? it looks like there is 3 or 4 switch position to adjust firmness. is that changing the PW directly or indirectly by changing resistance?

 

[ramsack]

It probably has something to do reading the TPS signal and altering what the TCU sees. I really don't know. BUT, you simply can't alter a PWM signal via resistor.