My thoughts on eCVT temperatures.
First the facts:
- Conventional manual transmissions don't need coolers because they have minimal friction surfaces / clutches inside the transmission, they use gears that generate very little heat
- Conventional automatic transmissions do need fluid coolers because they use friction surfaces / clutches that generate heat every time they change gears
- Automatic transmissions also use a torque converter which generates heat whenever it is slipping. The fluid in the torque converter is shared with the fluid in the automatic transmission.
- eCVT have less gears than even a manual transmission and do not have clutches or torque converters like an automatic transmission
- The FFH motor and generator are inside the eCVT and integral to the transmission shafts.
- Scan gauges consistently show the eCVT motor and generator are at a higher temperature than the transmission fluid temperature
- Motors/Generators, wiring and electronics all have higher electrical losses at higher temperatures because the resistance is higher at higher temperatures.
- Transmission components (seals, bearings, motors) generally last longer at lower temperatures
- The lower the transmission fluid temperature the higher the viscosity or resistance to movement.
Based upon the above facts here are my conclusions / recommendations:
- The primary purpose of the FFH transmission fluid cooler is to remove the heat generated by the motor and generator
- Although high viscosity of the transmission fluid at lower temperature effects fuel economy (FE), the higher temperature of the motor / generator has a bigger effect on FE.
- At very low temperature (maybe less than freezing) a transmission heater may help FE but at normal operating temperatures a cooler eCVT will result in better FE.
- Once up to operating temperatures the eCVT should be kept as cool as possible for better FE and motor/generator/transmission life
Interested in your comments.
Edited by Automate, 30 May 2015 - 10:06 AM.