I have a logo that is over 2000px wide, but when I place it as the logo in the top left of the theme header, it gets shrunk down to barely 200px. In the style.css file I found:

.custom-logo {
    max-width: 180px;
}

and I changed that to 400px and that didn’t affect anything.

In the header.php file is the line:

<?php twentysixteen_the_custom_logo(); ?>

but I checked the functions.php and other files and I cannot find that function

However in the functions.php file on lines 74 – 86 is the function:

/*
         * Enable support for custom logo.
         *
         *  @since Twenty Sixteen 1.2
         */
        add_theme_support(
            'custom-logo',
            array(
                'height'      => 240,
                'width'       => 240,
                'flex-height' => true,
            )
        );

In that function I changed the width to 400 and that didn’t change anything on the front.

Looking at the header, you can see there is plenty of room for a wider logo:

How can I get the logo image to fill the space up to the right nav?