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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@Gordon
You could try some bigger chunk sizes and see if it helps, but I'm afraid it's never going to be super-fast. By default the WiFi is connected at 115200 baud, so realistically even with zero overhead you're still looking at only around 12k/second.
By increasing the WiFi baud rate (you need to send a command to the ESP8266 to set it up) and also increasing the SD card bit rate you could improve things, but I think it may still not be as fast as you really want for a 2MB file.