Parse long CSV file with esp8266
Instead od the SD card you can use the esp8266 file system SPIFFS. It uses the flash of the esp8266, which is connected at 40MHz as Quad I/O on newer systems.

To use SPIFFS you create a folder named data in your esp8266 sketch folder. You put the files in that folder and then you use the SPIFFS upload plugin. 

In runtime use the SPIFFS library. It is similar to SD library.