ISR Performance Thermostat - Nissan VQ35DE - 68 DegreeIS 21200 31U13 ISR Performance Thermostat Nissan VQ35DE with water port 68 Degree ISR Performance colder thermostat for VQ35DE Engines. Good upgrade for High performance engines, The ISR units opens at 68 deg celsius compared to factory 78 deg celsius. Cool down your motor before heat builds up! Once the engine is fully warmed up the ISR thermostat will open up at a lower temperature than standard thermostats, also allowing the coolant to flow through