Posted 13 August 2012 - 08:01 PM
You need to split your original image into 4 different ones (see Image/Transform/Guillotine) and print each image separately.
Just use "Image/Print size" on the sub-images to increase thjeir print size (this decreases their print resolution, but this is expected)
Most consumer printers won't print an image border-to-border, there is usually a margin a top and bottom. Since the image is resized to fit the available print area and keep its aspect ratio, this also produces margins on the sides.
Gimp's design objective isn't to print images, you may find more specialized apps that will take you original image and split/print it automatically.