722.6 blue solenoid wanted (For research)
Thread Starter
Junior Member
Joined: Sep 2019
Posts: 73
Likes: 46
From: Reading, UK
2003 E55 AMG
722.6 blue solenoid wanted (For research)
Hi everyone,
Some of you may know me as RAND_ASH, who has made a custom 722.6 TCU module.
I have made some discoveries about how the solenoids work in the 722.6, and want to test a theory for an upcoming video I am working on for my 722.6 TCU series, but i need a single blue top solenoid to test this...
In short, the 722.6 pressure solenoids (MPC and SPC), come in either 'brown' or 'blue' top configurations. Everyone has reported swapping to blue tops makes shifts feel firmer and nicer (Especially for us AMG users). But the explanation of "Blue tops makes higher pressure" does not sit well with me, here is why. MPC and SPC solenoids are linear solenoids. The electrical current being sent to them has a linear reaction on the valves position, which in tern has a linear affect on pressure in the gearbox. When the valve is off (Closed), no pressure is bled from the pressure solenoids, thus, pressure in the valve body is at its maximum. When the solenoid is fully active (Valve is fully open), the pressure is at its minimum as all the pressure is vented off. When the gearbox is in limp home mode. Both MPC and SPC are switched off, so the valves are retracted, and the pressure in the gearbox is at its self-regulated maximum (The valve body contains a regulator valve that cuts itself off when pressure reaches a defined maximum to regulate the pressure in the valve body as a fail-safe). So, if the solenoid off = max pressure, how does switching to blue tops increase pressure? You cannot increase pressure beyond the solenoid off pressure unless you change the spring in the regulator valve in the valve body.
As part of my development of my TCU, I have benched a stock TCU on a valve body test bench. I have unlocked test mode on my own OEM EGS52 module, which has let me control the solenoids directly over CAN to do some testing, and this has led to some interesting discoveries.
With brown top solenoids, asking the MPC solenoid pressure to drop from 1500mA (0 mBar pressure) to 300mA (About 5000 mbar in the valve body) instantly, results in this oscilloscope trace. Each vertical grey line represents about 20ms in time.
Here, the blue line represents current draw (measured at the shunt resistor). You can see, it takes about 65ms for the current to reduce to its target value.
Now, with a lot more compute power available on my TCU vs stock EGS, I have made a very clever current control algorithm which can perform over/undershooting of the current target to 'catch' the solenoid arm and let it retract faster, which results in the following drop in current in the same test:
The same drop only takes about 12ms now.
So, I propose the following theory, and want to borrow someones spare blue top solenoid to test it (It isn't installed in a real 722.6, just on a desk test setup).
What if, blue solenoids don't increase pressure, but they instead increase the reaction speed of the solenoid with a stiffer spring? This would still result in firmer shifting as the desired pressure the TCU wants can be achieved faster rather than lagging behind what the solenoid is being asked to do? I therefore want to see if this current control algorithm I created ends up making brown solenoids react as fast (Or faster) than the blue top solenoids!
As the project is open source (And for the curious here), this current control algorithm can be viewed here too
https://github.com/rnd-ash/ultimate-...c_solenoid.cpp
Some of you may know me as RAND_ASH, who has made a custom 722.6 TCU module.
I have made some discoveries about how the solenoids work in the 722.6, and want to test a theory for an upcoming video I am working on for my 722.6 TCU series, but i need a single blue top solenoid to test this...
In short, the 722.6 pressure solenoids (MPC and SPC), come in either 'brown' or 'blue' top configurations. Everyone has reported swapping to blue tops makes shifts feel firmer and nicer (Especially for us AMG users). But the explanation of "Blue tops makes higher pressure" does not sit well with me, here is why. MPC and SPC solenoids are linear solenoids. The electrical current being sent to them has a linear reaction on the valves position, which in tern has a linear affect on pressure in the gearbox. When the valve is off (Closed), no pressure is bled from the pressure solenoids, thus, pressure in the valve body is at its maximum. When the solenoid is fully active (Valve is fully open), the pressure is at its minimum as all the pressure is vented off. When the gearbox is in limp home mode. Both MPC and SPC are switched off, so the valves are retracted, and the pressure in the gearbox is at its self-regulated maximum (The valve body contains a regulator valve that cuts itself off when pressure reaches a defined maximum to regulate the pressure in the valve body as a fail-safe). So, if the solenoid off = max pressure, how does switching to blue tops increase pressure? You cannot increase pressure beyond the solenoid off pressure unless you change the spring in the regulator valve in the valve body.
As part of my development of my TCU, I have benched a stock TCU on a valve body test bench. I have unlocked test mode on my own OEM EGS52 module, which has let me control the solenoids directly over CAN to do some testing, and this has led to some interesting discoveries.
With brown top solenoids, asking the MPC solenoid pressure to drop from 1500mA (0 mBar pressure) to 300mA (About 5000 mbar in the valve body) instantly, results in this oscilloscope trace. Each vertical grey line represents about 20ms in time.
Here, the blue line represents current draw (measured at the shunt resistor). You can see, it takes about 65ms for the current to reduce to its target value.
Now, with a lot more compute power available on my TCU vs stock EGS, I have made a very clever current control algorithm which can perform over/undershooting of the current target to 'catch' the solenoid arm and let it retract faster, which results in the following drop in current in the same test:
The same drop only takes about 12ms now.
So, I propose the following theory, and want to borrow someones spare blue top solenoid to test it (It isn't installed in a real 722.6, just on a desk test setup).
What if, blue solenoids don't increase pressure, but they instead increase the reaction speed of the solenoid with a stiffer spring? This would still result in firmer shifting as the desired pressure the TCU wants can be achieved faster rather than lagging behind what the solenoid is being asked to do? I therefore want to see if this current control algorithm I created ends up making brown solenoids react as fast (Or faster) than the blue top solenoids!
As the project is open source (And for the curious here), this current control algorithm can be viewed here too
https://github.com/rnd-ash/ultimate-...c_solenoid.cpp
Thread Starter
Junior Member
Joined: Sep 2019
Posts: 73
Likes: 46
From: Reading, UK
2003 E55 AMG
For the curious...this is how the TCU performs right now at its limit:
This is with brown top solenoids in my 226K mile E55 AMG. I probably won't recommend driving daily like this
This is with brown top solenoids in my 226K mile E55 AMG. I probably won't recommend driving daily like this
Super Member
Joined: May 2006
Posts: 566
Likes: 21
From: Australia
03 E55 AMG
"rnd_ash: So, if the solenoid off = max pressure, how does switching to blue tops increase the pressure? You cannot increase pressure beyond the solenoid off pressure unless you change the spring in the regulator valve in the valve body."
Correct, but... The blue top has a higher flow rate, therefore 'time' is altered to exhaust oil. It just does it quicker...
Correct, but... The blue top has a higher flow rate, therefore 'time' is altered to exhaust oil. It just does it quicker...
