COBB Custom Features: GT-R Increased Clutch Pressure (20+ Bar)

COBB Custom Features: Nissan 20+ Bar Clutch Pressure




The dual clutch (GR6) transmission in the R35 GTR utilizes two multi-disc clutch packs for power transfer to each of the gear shafts. One gear shaft drives even gears while the other drives odd, the clutches alternate engagement to select which shaft to send power through thus allowing the non-powered shaft to select a new gear. This alternating engagement allows the transmission to very quickly and sequentially upshift and downshift by routing power from one shaft to the next as gear engagement is incremented or decremented. A limitation of this system is that a clutch pack must couple all engine torque to its gear shaft, this torque can sometimes exceed the capacity of the clutch for a given lockup pressure. The clutch pressure is TCM controlled by a hydroelectric solenoid, low pressures and ramp rates allow for comfortable engagement while high pressures and ramp rates maintain low slip angles at high load. Although typical maximum clutch pressure for a stock TCM calibration is around 16.5bar, it has been discovered that 20bar is a reasonable increase in pressure that allows for greater clamping force while maintaining mechanical integrity of the transmission seals and otherwise.




Applicable Transmission ROM:

  • Gen 1 TCM
    • Nissan GT-R TCM LC4 KB51A
    • Nissan GT-R TCM LC4 KB51B
    • Nissan GT-R TCM LC5 38B0A
    • Nissan GT-R TCM LC5 38B0B
    • Nissan GT-R TCM LC5 KJ10A
    • Nissan GT-R TCM LC5 KJ10B

  • Gen 2 TCM
    • Nissan GT-R TCM Gen2. LC1 62B1A
    • Nissan GT-R TCM Gen2. LC1 62B1B
    • Nissan GT-R TCM Gen2. LC2 NISMO 89S0B
    • Nissan GT-R TCM Gen2. LC3 80B0A
    • Nissan GT-R TCM Gen2. LC3 80B0B
    • Nissan GT-R TCM Gen2. LC4 6AV0A





How To Enable:

This feature must be tuned using AccessTuner software.





Available Adjustments and How to Make them:


When tuning this feature it's advisable to creep up on your target as the clutch sensor is incapable of reading over 20 bar of pressure.  This means if you go anything over that limit you could be making any unknown amount of pressure higher than 20 bar, potentially causing damage to your vehicle.  As such we typically recommend sticking with a value slightly under the sensor limit.





Clutch A & B Solenoid Current (Max)

Two clutch solenoid current maximums exist in the software.  The base value is typically 1.5 amps. By increasing the current value can change the pressures slightly differently depending on the transmission.  Raising the current values alone is enough to increase the clutch pressure.


Stock values are shown and will need to be tuned appropriately per car in order to achieve desired clutch pressure



    


Clutch A/B Target Pressure

When increasing the clutch pressure you'll need to increase this value in order to avoid throwing a clutch pressure dtc.


Stock values are shown and will need to be tuned appropriately per car in order to achieve desired clutch pressure




ECM Side

You'll also need to go into the engine tune and adjust the maximum torque values in the area you want maximum clutch pressure in the Clutch Torque and Clutch Torque - Extended TPW engine tables.


Stock values are shown and will need to be tuned appropriately per car in order to achieve desired clutch pressure

    





Things To Look Out For:

The amount of pressure increased per current increase can and will vary based on the age of the transmission.  Additionally built transmissions with upgraded clutches or solenoids will respond differently from a standard transmission in terms of how much amperage is required to achieve your pressure goals.  No matter the transmission's condition, We recommend small changes starting at a known safe value for your setup rather than skipping immediately to a higher value, as this could potentially cause damage to the existing seals.





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