*Correcting the sec pressure with a fixed linear offset will be incorrect as the solenoid pressure vs current profile is not linear
"No, the pressure vs signal output is linear, I have the map. I'm also not using a fixed linear offset, it's a scaling factor using a voltage trigger value to activate the circuit. Hopefully that's clear, I used a comparator to analyze the input signal."
*The maximum clamping is indeed still limited by the system pressure, a stiffer spring will not bring anything as the spring force can be neglected compared to the hydraulic clamping force, however the system might still have some margin.
"I have sufficient oil pump pressure available anyway (4-5.5 Mpa). I rarely operate above 3-3.5 Mpa at the Secondary Pulley, thus there is sufficient pressure available to still drive all hydraulic circuits.
Not sure I fully understand you, but the stiffer spring within the valve body is to increase the pulley pressure. I have never done the modification so I can't verify exactly what spring and what metering orifice in the valve body sealing plates were modified. Normally I'd say the ECM/TCM would simply compensate for the increased spring rate by altering the control solenoids duty cycle, but I can't comment beyond that. Somehow Level10 made a CVT hold some pretty serious torque.
*Overwriting the sec pressure will potentially decrease ratio stability as the primary pressure should follow the higher secondary pressure, but the system does not know this hence it will need to rely on the ratio PID to compensate for this ratio as well but only very limited.
"Not sure I agree with this. Without the PID control, the car won't get out of park. It's continuously relying on feedback control. The only thing I'm doing differently is forcing the ECM/TCM to trim another 5-7% from it's expected settings, most likely it won't throw a TCM code and trim the solenoids accordingly.
*Increasing the input torque and compensating the sec pulley pressure for this might maybe work, but will you do the same for the drive/reverse clutch and TC? Probably the TC control both controls the switching from TC mode to lockup mode and hence simply increase or decreasing the current is unlikely to work. I also assume the adaptive control on the TC only works for the lockup clutch biting point and does not impact the TC switching current.
"Good questions. No, I'm not modifying the drive/reverse clutch pressures or TC. There is nothing to be gained on the Torque converter if a good CVT fluid like AMSOIL is used, it has a generous sized clutch. If you read my build, I modified the forward clutch packs to handle something like 320 lb-ft of torque with the same clamping pressure. I'm good to go."
*fatigue of the pushbelt and variator shafts might become a problem due to the higher clamping.
True. The higher clamping is a necessary evil. Without it, the belts would slip and wear out rapidly. Did you know the factory already adds 20% safety margin on pulley pressure to account for pulley wear? I'm simply adding another 5-7% pressure on top of that and only at WOT or a certain torque value where I would expect some slippage might occur.
*Increasing the rev limit will lead to higher centrifugal forces on the prim cylinder parts, this in combination with higher clamping pressure as a result from the reaction (through PID) on the increased sec pressure might overload the pulley pressure cilinder parts.
"Yes, increased RPMs tends to make the belt slip. Increased torque breaks parts.......and increases slippage. Which is better? This is precisely why I designed my CVT to be prevent slippage, because higher rpms doesn't break rotating parts like torque does.
I came accros this thread by accident, nice project! Would you happen to have a re-build manual which you constructed yourself or a mapping of system pressures vs solenoid currents? Basically any information would be of interest to me. What oil do you use? Where do you source parts, website?
Thanks. I do have a couple rebuild manuals I can point you to. Yes, the Pressure vs sensor output maps exist, I'll look for it. I use AMSOIL CVT fluid. I have too many sources to list here. I'll see if I can dig up all the vendors I used.